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This section is non-normative.
It must be admitted that many aspects of HTML appear at first glance to be nonsensical and inconsistent.
HTML, its supporting DOM APIs, as well as many of its supporting technologies, have been developed over a period of several decades by a wide array of people with different priorities who, in many cases, did not know of each other's existence.
Features have thus arisen from many sources, and have not always been designed in especially consistent ways. Furthermore, because of the unique characteristics of the Web, implementation bugs have often become de-facto, and now de-jure, standards, as content
is often unintentionally written in ways that rely on them before they can be fixed.
Despite all this, efforts have been made to adhere to certain design goals. These are described in the next few subsections.
1.5.1 Serializability of script execution
This section is non-normative.
To avoid exposing Web authors to the complexities of multithreading, the HTML and DOM APIs are designed such that no script can ever detect the simultaneous execution of other scripts. Even with workers, the intent is that the behavior of implementations can be
thought of as completely serialising the execution of all scripts in all browsing contexts.
The navigator.getStorageUpdates() method, in this model, is equivalent to allowing other scripts to run while the calling script is blocked.
1.5.2 Compliance with other specifications
This section is non-normative.
This specification interacts with and relies on a wide variety of other specifications. In certain circumstances, unfortunately, the desire to be compatible with legacy content has led to this specification violating the requirements of these other specifications. Whenever
this has occurred, the transgressions have been noted as "willful violations".
1.6 Relationships to other specifications
1.6.1 Relationship to HTML 4.01 and DOM2 HTML
This section is non-normative.
This specification describes a new revision of the HTML language and its associated DOM API.
The requirements in this specification for features that were already in HTML 4 and DOM2 HTML are based primarily on the implementation and deployment experience collected over the past ten years. Some features have been removed from the language, based on
best current practices; implementation requirements for some of these, as well as for non-standard features that have nonetheless garnered wide use, are still included in this specification to allow implementations to continue supporting legacy content. [HTML4]
[DOM2HTML]
A separate document has been published by the W3C HTML working group to provide a more detailed reference of the differences between this specification and the language described in the HTML 4 specification. [HTMLDIFF]
1.6.2 Relationship to XHTML 1.x
This section is non-normative.
This specification is intended to replace XHTML 1.0 as the normative definition of the XML serialization of the HTML vocabulary. [XHTML10]
While this specification updates the semantics and requirements of the vocabulary defined by XHTML Modularization 1.1 and used by XHTML 1.1, it does not attempt to provide a replacement for the modularization scheme defined and used by those (and other)
specifications, and therefore cannot be considered a complete replacement for them. [XHTMLMOD] [XHTML11]
Thus, authors and implementors who do not need such a modularization scheme can consider this specification a replacement for XHTML 1.x, but those who do need such a mechanism are encouraged to continue using the XHTML 1.1 line of specifications.
1.7 HTML vs XHTML
This section is non-normative.
This specification defines an abstract language for describing documents and applications, and some APIs for interacting with in-memory representations of resources that use this language.
The in-memory representation is known as "DOM5 HTML", or "the DOM" for short.
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variable = object . method( [ optionalArgument ] )
This is a note to authors describing the usage of an interface.
/* this is a CSS fragment */
The defining instance of a term is marked up like this. Uses of that term are marked up like this or like this.
The defining instance of an element, attribute, or API is marked up like this. References to that element, attribute, or API are marked up like this.
Other code fragments are marked up like this.
Variables are marked up like this.
This is an implementation requirement.
1.9 A quick introduction to HTML
This section is non-normative.
A basic HTML document looks like this:
<!DOCTYPE HTML>
<html>
<head>
<title>Sample page</title>
</head>
<body>
<h1>Sample page</h1>
<p>This is a <a href="demo.html">simple</a> sample.</p>
<!-- this is a comment -->
</body>
</html>
HTML documents consist of a tree of elements and text. Each element is denoted in the source by a start tag, such as "<body>", and an end tag, such as "</body>". (Certain start tags and end tags can in certain cases be omitted and are implied by other tags.)
Tags have to be nested such that elements are all completely within each other, without overlapping:
<p>This is <em>very <strong>wrong</em>!</strong></p>
<p>This <em>is <strong>correct</strong>.</em></p>
This specification defines a set of elements that can be used in HTML, along with rules about the ways in which the elements can be nested.
Elements can have attributes, which control how the elements work. In the example above, there is a hyperlink, formed using the a element and its href attribute:
<a href="demo.html">simple</a>
Attributes are placed inside the start tag, and consist of a name and a value, separated by an "=" character. The attribute value can be left unquoted if it doesn't contain any special characters. Otherwise, it has to be quoted using either single or double quotes. The
value, along with the "=" character, can be omitted altogether if the value is the empty string.
<!-- empty attributes -->
<input name=address disabled>
<input name=address disabled="">
<!-- attributes with a value -->
<input name=address maxlength=200>
<input name=address maxlength='200'>
<input name=address maxlength="200">
HTML user agents (e.g. Web browsers) then parse this markup, turning it into a DOM (Document Object Model) tree. A DOM tree is an in-memory representation of a document.
DOM trees contain several kinds of nodes, in particular a DOCTYPE node, elements, text nodes, and comment nodes.
The markup snippet at the top of this section would be turned into the following DOM tree:
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q DOCTYPE: html
q html
r head
s #text: •••
s title
s #text: Sample page
s #text: ••
r #text: ••
r body
s #text: •••
s h1
s #text: Sample page
s #text: •••
s p
s #text: This is a
s a href="demo.html"
s #text: simple
s #text: sample.
s #text: •••
s #comment: this is a comment
s #text: •••
The root element of this tree is the html element, which is the element always found at the root of HTML documents. It contains two elements, head and body, as well as a text node between them.
There are many more text nodes in the DOM tree than one would initially expect, because the source contains a number of spaces (presented by "•") and line breaks ("•") that all end up as text nodes in the DOM.
The head element contains a title element, which itself contains a text node with the text "Sample page". Similarly, the body element contains an h1 element, a p element, and a comment.
This DOM tree can be manipulated from scripts in the page. Scripts (typically in JavaScript) are small programs that can be embedded using the script element or using event handler content attributes. For example, here is a form with a script that sets the value of
the form's output element to say "Hello World":
<form name="main">
Result: <output name="result"></output>
<script>
document.forms.main.elements.result.value = 'Hello World';
</script>
</form>
Each element in the DOM tree is represented by an object, and these objects have APIs so that they can be manipulated. For instance, a link (e.g. the a element in the tree above) can have its "href" attributed changed in several ways:
var a = document.links[0]; // obtain the first link in the document
a.href = 'sample.html'; // change the destination URL of the link
a.protocol = 'https'; // change just the scheme part of the URL
a.setAttribute('href', 'http://example.com/'); // change the content attribute directly
Since DOM trees are used as the way to represent HTML documents when they are processed and presented by implementations (especially interactive implementations like Web browsers), this specification is mostly phrased in terms of DOM trees, instead of the
markup described above.
HTML documents represent a media-independent description of interactive content. HTML documents might be rendered to a screen, or through a speech synthesizer, or on a braille display. To influence exactly how such rendering takes place, authors can use a
styling language such as CSS.
In the following example, the page has been made yellow-on-blue using CSS.
<!DOCTYPE HTML>
<html>
<head>
<title>Sample styled page</title>
<style>
body { background: navy; color: yellow; }
</style>
</head>
<body>
<h1>Sample styled page</h1>
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2 Common infrastructure
2.1 Terminology
This specification refers to both HTML and XML attributes and DOM attributes, often in the same context. When it is not clear which is being referred to, they are referred to as content attributes for HTML and XML attributes, and DOM attributes for those from the
DOM. Similarly, the term "properties" is used for both JavaScript object properties and CSS properties. When these are ambiguous they are qualified as object properties and CSS properties respectively.
Generally, when the specification states that a feature applies to the HTML syntax or the XHTML syntax, it also includes the other. When a feature specifically only applies to one of the two languages, it is called out by explicitly stating that it does not apply to the other
format, as in "for HTML, ... (this does not apply to XHTML)".
This specification uses the term document to refer to any use of HTML, ranging from short static documents to long essays or reports with rich multimedia, as well as to fully-fledged interactive applications.
For simplicity, terms such as shown, displayed, and visible might sometimes be used when referring to the way a document is rendered to the user. These terms are not meant to imply a visual medium; they must be considered to apply to other media in equivalent
ways.
When an algorithm B says to return to another algorithm A, it implies that A called B. Upon returning to A, the implementation must continue from where it left off in calling B.
2.1.1 XML
To ease migration from HTML to XHTML, UAs conforming to this specification will place elements in HTML in the http://www.w3.org/1999/xhtml namespace, at least for the purposes of the DOM and CSS. The term "elements in the HTML namespace", or
"HTML elements" for short, when used in this specification, thus refers to both HTML and XHTML elements.
Unless otherwise stated, all elements defined or mentioned in this specification are in the http://www.w3.org/1999/xhtml namespace, and all attributes defined or mentioned in this specification have no namespace (they are in the per-element partition).
When an XML name, such as an attribute or element name, is referred to in the form prefix:localName, as in xml:id or svg:rect, it refers to a name with the local name localName and the namespace given by the prefix, as defined by the following table:
xml
http://www.w3.org/XML/1998/namespace
html
http://www.w3.org/1999/xhtml
svg
http://www.w3.org/2000/svg
Attribute names are said to be XML-compatible if they match the Name production defined in XML, they contain no U+003A COLON (:) characters, and their first three characters are not an ASCII case-insensitive match for the string "xml". [XML]
The term XML MIME type is used to refer to the MIME types text/xml, application/xml, and any MIME type ending with the four characters "+xml". [RFC3023]
2.1.2 DOM trees
The term root element, when not explicitly qualified as referring to the document's root element, means the furthest ancestor element node of whatever node is being discussed, or the node itself if it has no ancestors. When the node is a part of the document, then that
is indeed the document's root element; however, if the node is not currently part of the document tree, the root element will be an orphaned node.
A node's home subtree is the subtree rooted at that node's root element.
The Document of a Node (such as an element) is the Document that the Node's ownerDocument DOM attribute returns.
When an element's root element is the root element of a Document, it is said to be in a Document. An element is said to have been inserted into a document when its root element changes and is now the document's root element. Analogously, an element is said to
have been removed from a document when its root element changes from being the document's root element to being another element.
If a Node is in a Document then that Document is always the Node's Document, and the Node's ownerDocument DOM attribute thus always returns that Document.
The term tree order means a pre-order, depth-first traversal of DOM nodes involved (through the parentNode/childNodes relationship).
When it is stated that some element or attribute is ignored, or treated as some other value, or handled as if it was something else, this refers only to the processing of the node after it is in the DOM. A user agent must not mutate the DOM in such situations.
The term text node refers to any Text node, including CDATASection nodes; specifically, any Node with node type TEXT_NODE (3) or CDATA_SECTION_NODE (4). [DOM3CORE]
A content attribute is said to change value only if its new value is different than its previous value; setting an attribute to a value it already has does not change it.
2.1.3 Scripting
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The construction "a Foo object", where Foo is actually an interface, is sometimes used instead of the more accurate "an object implementing the interface Foo".
A DOM attribute is said to be getting when its value is being retrieved (e.g. by author script), and is said to be setting when a new value is assigned to it.
If a DOM object is said to be live, then that means that any attributes returning that object must always return the same object (not a new object each time), and the attributes and methods on that object must operate on the actual underlying data, not a snapshot of the
data.
The terms fire and dispatch are used interchangeably in the context of events, as in the DOM Events specifications. [DOM3EVENTS]
2.1.4 Plugins
The term plugin is used to mean any content handler for Web content types that are either not supported by the user agent natively or that do not expose a DOM, which supports rendering the content as part of the user agent's interface.
Typically such content handlers are provided by third parties.
One example of a plugin would be a PDF viewer that is instantiated in a browsing context when the user navigates to a PDF file. This would count as a plugin regardless of whether the party that implemented the PDF viewer component was the same as that
which implemented the user agent itself. However, a PDF viewer application that launches separate from the user agent (as opposed to using the same interface) is not a plugin by this definition.
This specification does not define a mechanism for interacting with plugins, as it is expected to be user-agent- and platform-specific. Some UAs might opt to support a plugin mechanism such as the Netscape Plugin API; others might use remote content
converters or have built-in support for certain types. [NPAPI]
Browsers should take extreme care when interacting with external content intended for plugins. When third-party software is run with the same privileges as the user agent itself, vulnerabilities in the third-party software become as dangerous as those in the user agent.
2.1.5 Character encodings
An ASCII-compatible character encoding is a single-byte or variable-length encoding in which the bytes 0x09, 0x0A, 0x0C, 0x0D, 0x20 - 0x22, 0x26, 0x27, 0x2C - 0x3F, 0x41 - 0x5A, and 0x61 - 0x7A, ignoring bytes that are the second and later bytes of multibyte
sequences, all correspond to single-byte sequences that map to the same Unicode characters as those bytes in ANSI_X3.4-1968 (US-ASCII). [RFC1345]
This includes such encodings as Shift_JIS and variants of ISO-2022, even though it is possible in these encodings for bytes like 0x70 to be part of longer sequences that are unrelated to their interpretation as ASCII. It excludes such encodings as UTF-7,
UTF-16, HZ-GB-2312, GSM03.38, and EBCDIC variants.
2.1.6 Resources
The specification uses the term supported when referring to whether a user agent has an implementation capable of decoding the semantics of an external resource. A format or type is said to be supported if the implementation can process an external resource of
that format or type without critical aspects of the resource being ignored. Whether a specific resource is supported can depend on what features of the resource's format are in use.
For example, a PNG image would be considered to be in a supported format if its pixel data could be decoded and rendered, even if, unbeknownst to the implementation, the image actually also contained animation data.
A MPEG4 video file would not be considered to be in a supported format if the compression format used was not supported, even if the implementation could determine the dimensions of the movie from the file's metadata.
The term MIME type is used to refer to what is sometimes called an Internet media type in protocol literature. The term media type in this specification is used to refer to the type of media intended for presentation, as used by the CSS specifications. [RFC2046] [MQ]
2.2 Conformance requirements
All diagrams, examples, and notes in this specification are non-normative, as are all sections explicitly marked non-normative. Everything else in this specification is normative.
The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this document are to be interpreted as described in RFC2119. For readability, these words do not appear in all
uppercase letters in this specification. [RFC2119]
Requirements phrased in the imperative as part of algorithms (such as "strip any leading space characters" or "return false and abort these steps") are to be interpreted with the meaning of the key word ("must", "should", "may", etc) used in introducing the algorithm.
This specification describes the conformance criteria for user agents (relevant to implementors) and documents (relevant to authors and authoring tool implementors).
There is no implied relationship between document conformance requirements and implementation conformance requirements. User agents are not free to handle non-conformant documents as they please; the processing model described in this
specification applies to implementations regardless of the conformity of the input documents.
User agents fall into several (overlapping) categories with different conformance requirements.
Web browsers and other interactive user agents
Web browsers that support the XHTML syntax must process elements and attributes from the HTML namespace found in XML documents as described in this specification, so that users can interact with them, unless the semantics of those elements have been
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overridden by other specifications.
A conforming XHTML processor would, upon finding an XHTML script element in an XML document, execute the script contained in that element. However, if the element is found within a transformation expressed in XSLT (assuming the user agent
also supports XSLT), then the processor would instead treat the script element as an opaque element that forms part of the transform.
Web browsers that support the HTML syntax must process documents labeled as text/html as described in this specification, so that users can interact with them.
User agents that support scripting must also be conforming implementations of the IDL fragments in this specification, as described in the Web IDL specification. [WEBIDL]
Non-interactive presentation user agents
User agents that process HTML and XHTML documents purely to render non-interactive versions of them must comply to the same conformance criteria as Web browsers, except that they are exempt from requirements regarding user interaction.
Typical examples of non-interactive presentation user agents are printers (static UAs) and overhead displays (dynamic UAs). It is expected that most static non-interactive presentation user agents will also opt to lack scripting support.
A non-interactive but dynamic presentation UA would still execute scripts, allowing forms to be dynamically submitted, and so forth. However, since the concept of "focus" is irrelevant when the user cannot interact with the document, the UA would not
need to support any of the focus-related DOM APIs.
User agents with no scripting support
Implementations that do not support scripting (or which have their scripting features disabled entirely) are exempt from supporting the events and DOM interfaces mentioned in this specification. For the parts of this specification that are defined in terms of an
events model or in terms of the DOM, such user agents must still act as if events and the DOM were supported.
Scripting can form an integral part of an application. Web browsers that do not support scripting, or that have scripting disabled, might be unable to fully convey the author's intent.
Conformance checkers
Conformance checkers must verify that a document conforms to the applicable conformance criteria described in this specification. Automated conformance checkers are exempt from detecting errors that require interpretation of the author's intent (for example,
while a document is non-conforming if the content of a blockquote element is not a quote, conformance checkers running without the input of human judgement do not have to check that blockquote elements only contain quoted material).
Conformance checkers must check that the input document conforms when parsed without a browsing context (meaning that no scripts are run, and that the parser's scripting flag is disabled), and should also check that the input document conforms when parsed
with a browsing context in which scripts execute, and that the scripts never cause non-conforming states to occur other than transiently during script execution itself. (This is only a "SHOULD" and not a "MUST" requirement because it has been proven to be
impossible. [COMPUTABLE])
The term "HTML5 validator" can be used to refer to a conformance checker that itself conforms to the applicable requirements of this specification.
XML DTDs cannot express all the conformance requirements of this specification. Therefore, a validating XML processor and a DTD cannot constitute a conformance checker. Also, since neither of the two authoring formats defined in this specification are
applications of SGML, a validating SGML system cannot constitute a conformance checker either.
To put it another way, there are three types of conformance criteria:
1. Criteria that can be expressed in a DTD.
2. Criteria that cannot be expressed by a DTD, but can still be checked by a machine.
3. Criteria that can only be checked by a human.
A conformance checker must check for the first two. A simple DTD-based validator only checks for the first class of errors and is therefore not a conforming conformance checker according to this specification.
Data mining tools
Applications and tools that process HTML and XHTML documents for reasons other than to either render the documents or check them for conformance should act in accordance to the semantics of the documents that they process.
A tool that generates document outlines but increases the nesting level for each paragraph and does not increase the nesting level for each section would not be conforming.
Authoring tools and markup generators
Authoring tools and markup generators must generate conforming documents. Conformance criteria that apply to authors also apply to authoring tools, where appropriate.
Authoring tools are exempt from the strict requirements of using elements only for their specified purpose, but only to the extent that authoring tools are not yet able to determine author intent.
For example, it is not conforming to use an address element for arbitrary contact information; that element can only be used for marking up contact information for the author of the document or section. However, since an authoring tool is likely unable
to determine the difference, an authoring tool is exempt from that requirement.
In terms of conformance checking, an editor is therefore required to output documents that conform to the same extent that a conformance checker will verify.
When an authoring tool is used to edit a non-conforming document, it may preserve the conformance errors in sections of the document that were not edited during the editing session (i.e. an editing tool is allowed to round-trip erroneous content). However, an
authoring tool must not claim that the output is conformant if errors have been so preserved.
Authoring tools are expected to come in two broad varieties: tools that work from structure or semantic data, and tools that work on a What-You-See-Is-What-You-Get media-specific editing basis (WYSIWYG).
The former is the preferred mechanism for tools that author HTML, since the structure in the source information can be used to make informed choices regarding which HTML elements and attributes are most appropriate.
However, WYSIWYG tools are legitimate. WYSIWYG tools should use elements they know are appropriate, and should not use elements that they do not know to be appropriate. This might in certain extreme cases mean limiting the use of flow elements to just a
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few elements, like div, b, i, and span and making liberal use of the style attribute.
All authoring tools, whether WYSIWYG or not, should make a best effort attempt at enabling users to create well-structured, semantically rich, media-independent content.
Some conformance requirements are phrased as requirements on elements, attributes, methods or objects. Such requirements fall into two categories: those describing content model restrictions, and those describing implementation behavior. Those in the former
category are requirements on documents and authoring tools. Those in the second category are requirements on user agents.
Conformance requirements phrased as algorithms or specific steps may be implemented in any manner, so long as the end result is equivalent. (In particular, the algorithms defined in this specification are intended to be easy to follow, and not intended to be
performant.)
User agents may impose implementation-specific limits on otherwise unconstrained inputs, e.g. to prevent denial of service attacks, to guard against running out of memory, or to work around platform-specific limitations.
For compatibility with existing content and prior specifications, this specification describes two authoring formats: one based on XML (referred to as the XHTML syntax), and one using a custom format inspired by SGML (referred to as the HTML syntax).
Implementations may support only one of these two formats, although supporting both is encouraged.
XML documents that use elements or attributes from the HTML namespace and that are served over the wire (e.g. by HTTP) must be sent using an XML MIME type such as application/xml or application/xhtml+xml and must not be served as text/html.
[RFC3023]
Documents that use the HTML syntax, if they are served over the wire (e.g. by HTTP) must be labeled with the text/html MIME type.
The language in this specification assumes that the user agent expands all entity references, and therefore does not include entity reference nodes in the DOM. If user agents do include entity reference nodes in the DOM, then user agents must handle them as if they
were fully expanded when implementing this specification. For example, if a requirement talks about an element's child text nodes, then any text nodes that are children of an entity reference that is a child of that element would be used as well. Entity references to
unknown entities must be treated as if they contained just an empty text node for the purposes of the algorithms defined in this specification.
2.2.1 Dependencies
This specification relies on several other underlying specifications.
XML
Implementations that support the XHTML syntax must support some version of XML, as well as its corresponding namespaces specification, because that syntax uses an XML serialization with namespaces. [XML] [XMLNAMES]
DOM
The Document Object Model (DOM) is a representation — a model — of a document and its content. The DOM is not just an API; the conformance criteria of HTML implementations are defined, in this specification, in terms of operations on the DOM.
[DOM3CORE]
Implementations must support some version of DOM Core and DOM Events, because this specification is defined in terms of the DOM, and some of the features are defined as extensions to the DOM Core interfaces. [DOM3CORE] [DOM3EVENTS]
Web IDL
The IDL fragments in this specification must be interpreted as required for conforming IDL fragments, as described in the Web IDL specification. [WEBIDL]
Unless otherwise specified, if a DOM attribute that is a floating point number type (float) is assigned an Infinity or Not-a-Number value, a NOT_SUPPORTED_ERR exception must be raised.
Unless otherwise specified, if a method with an argument that is a floating point number type (float) is passed an Infinity or Not-a-Number value, a NOT_SUPPORTED_ERR exception must be raised.
JavaScript
Some parts of the language described by this specification only support JavaScript as the underlying scripting language. [ECMA262]
The term "JavaScript" is used to refer to ECMA262, rather than the official term ECMAScript, since the term JavaScript is more widely known. Similarly, the MIME type used to refer to JavaScript in this specification is text/javascript, since that is
the most commonly used type, despite it being an officially obsoleted type according to RFC 4329. [RFC4329]
Media Queries
Implementations must support some version of the Media Queries language. [MQ]
This specification does not require support of any particular network transport protocols, style sheet language, scripting language, or any of the DOM and WebAPI specifications beyond those described above. However, the language described by this specification is
biased towards CSS as the styling language, JavaScript as the scripting language, and HTTP as the network protocol, and several features assume that those languages and protocols are in use.
This specification might have certain additional requirements on character encodings, image formats, audio formats, and video formats in the respective sections.
2.2.2 Extensibility
Vendor-specific proprietary extensions to this specification are strongly discouraged. Documents must not use such extensions, as doing so reduces interoperability and fragments the user base, allowing only users of specific user agents to access the content in
question.
If markup extensions are needed, they should be done using XML, with elements or attributes from custom namespaces. If DOM extensions are needed, the members should be prefixed by vendor-specific strings to prevent clashes with future versions of this
specification. Extensions must be defined so that the use of extensions does not contradict nor cause the non-conformance of functionality defined in the specification.
For example, while strongly discouraged to do so, an implementation "Foo Browser" could add a new DOM attribute "fooTypeTime" to a control's DOM interface that returned the time it took the user to select the current value of a control (say). On the other
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hand, defining a new control that appears in a form's elements array would be in violation of the above requirement, as it would violate the definition of elements given in this specification.
User agents must treat elements and attributes that they do not understand as semantically neutral; leaving them in the DOM (for DOM processors), and styling them according to CSS (for CSS processors), but not inferring any meaning from them.
2.3 Case-sensitivity and string comparison
This specification defines several comparison operators for strings.
Comparing two strings in a case-sensitive manner means comparing them exactly, code point for code point.
Comparing two strings in an ASCII case-insensitive manner means comparing them exactly, code point for code point, except that the characters in the range U+0041 .. U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) and the corresponding
characters in the range U+0061 .. U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z) are considered to also match.
Comparing two strings in a compatibility caseless manner means using the Unicode compatibility caseless match operation to compare the two strings. [UNICODECASE]
Converting a string to ASCII uppercase means replacing all characters in the range U+0061 .. U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z) with the corresponding characters in the range U+0041 .. U+005A (i.e. LATIN CAPITAL LETTER A to
LATIN CAPITAL LETTER Z).
Converting a string to ASCII lowercase means replacing all characters in the range U+0041 .. U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) with the corresponding characters in the range U+0061 .. U+007A (i.e. LATIN SMALL LETTER A
to LATIN SMALL LETTER Z).
A string pattern is a prefix match for a string s when pattern is not longer than s and truncating s to pattern's length leaves the two strings as matches of each other.
2.4 Common microsyntaxes
There are various places in HTML that accept particular data types, such as dates or numbers. This section describes what the conformance criteria for content in those formats is, and how to parse them.
Implementors are strongly urged to carefully examine any third-party libraries they might consider using to implement the parsing of syntaxes described below. For example, date libraries are likely to implement error handling behavior that differs from what is
required in this specification, since error-handling behavior is often not defined in specifications that describe date syntaxes similar to those used in this specification, and thus implementations tend to vary greatly in how they handle errors.
2.4.1 Common parser idioms
The space characters, for the purposes of this specification, are U+0020 SPACE, U+0009 CHARACTER TABULATION (tab), U+000A LINE FEED (LF), U+000C FORM FEED (FF), and U+000D CARRIAGE RETURN (CR).
The White_Space characters are those that have the Unicode property "White_Space". [UNICODE]
The alphanumeric ASCII characters are those in the ranges U+0030 DIGIT ZERO .. U+0039 DIGIT NINE, U+0041 LATIN CAPITAL LETTER A .. U+005A LATIN CAPITAL LETTER Z, U+0061 LATIN SMALL LETTER A .. U+007A LATIN SMALL LETTER Z.
Some of the micro-parsers described below follow the pattern of having an input variable that holds the string being parsed, and having a position variable pointing at the next character to parse in input.
For parsers based on this pattern, a step that requires the user agent to collect a sequence of characters means that the following algorithm must be run, with characters being the set of characters that can be collected:
1. Let input and position be the same variables as those of the same name in the algorithm that invoked these steps.
2. Let result be the empty string.
3. While position doesn't point past the end of input and the character at position is one of the characters, append that character to the end of result and advance position to the next character in input.
4. Return result.
The step skip whitespace means that the user agent must collect a sequence of characters that are space characters. The step skip White_Space characters means that the user agent must collect a sequence of characters that are White_Space characters. In both
cases, the collected characters are not used. [UNICODE]
When a user agent is to strip line breaks from a string, the user agent must remove any U+000A LINE FEED (LF) and U+000D CARRIAGE RETURN (CR) characters from that string.
The code-point length of a string is the number of Unicode code points in that string.
2.4.2 Boolean attributes
A number of attributes are boolean attributes. The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.
If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace.
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17. If got number is true, then append value to the numbers list.
18. Return the numbers list and abort.
2.4.4.7 Lists of dimensions
The rules for parsing a list of dimensions are as follows. These rules return a list of zero or more pairs consisting of a number and a unit, the unit being one of percentage, relative, and absolute.
1. Let raw input be the string being parsed.
2. If the last character in raw input is a U+002C COMMA character (","), then remove that character from raw input.
3. Split the string raw input on commas. Let raw tokens be the resulting list of tokens.
4. Let result be an empty list of number/unit pairs.
5. For each token in raw tokens, run the following substeps:
1. Let input be the token.
2. Let position be a pointer into input, initially pointing at the start of the string.
3. Let value be the number 0.
4. Let unit be absolute.
5. If position is past the end of input, set unit to relative and jump to the last substep.
6. If the character at position is a character in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), interpret the resulting sequence as an integer in
base ten, and increment value by that integer.
7. If the character at position is a U+002E FULL STOP character (.), run these substeps:
1. Collect a sequence of characters consisting of space characters and characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). Let s be the resulting sequence.
2. Remove all space characters in s.
3. If s is not the empty string, run these subsubsteps:
1. Let length be the number of characters in s (after the spaces were removed).
length
2. Let fraction be the result of interpreting s as a base-ten integer, and then dividing that number by 10 .
3. Increment value by fraction.
8. Skip whitespace.
9. If the character at position is a U+0025 PERCENT SIGN (%) character, then set unit to percentage.
Otherwise, if the character at position is a U+002A ASTERISK character (*), then set unit to relative.
10. Add an entry to result consisting of the number given by value and the unit given by unit.
6. Return the list result.
2.4.5 Dates and times
In the algorithms below, the number of days in month month of year year is: 31 if month is 1, 3, 5, 7, 8, 10, or 12; 30 if month is 4, 6, 9, or 11; 29 if month is 2 and year is a number divisible by 400, or if year is a number divisible by 4 but not by 100; and 28 otherwise.
This takes into account leap years in the Gregorian calendar. [GREGORIAN]
The digits in the date and time syntaxes defined in this section must be characters in the range U+0030 DIGIT ZERO to U+0039 DIGIT NINE, used to express numbers in base ten.
While the formats described here are intended to be subsets of the corresponding ISO8601 formats, this specification defines parsing rules in much more detail than ISO8601. Implementators are therefore encouraged to carefully examine any date parsing
libraries before using them to implement the parsing rules described below; ISO8601 libraries might not parse dates and times exactly the same manner. [ISO8601]
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2.4.5.1 Months
A month consists of a specific proleptic Gregorian date with no time-zone information and no date information beyond a year and a month. [GREGORIAN]
A string is a valid month string representing a year year and month month if it consists of the following components in the given order:
1. Four or more digits, representing year, where year > 0
2. A U+002D HYPHEN-MINUS character (-)
3. Two digits, representing the month month, in the range 1 ≤ month ≤ 12
The rules to parse a month string are as follows. This will either return a year and month, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
1. Let input be the string being parsed.
2. Let position be a pointer into input, initially pointing at the start of the string.
3. Parse a month component to obtain year and month. If this returns nothing, then fail.
4. If position is not beyond the end of input, then fail.
5. Return year and month.
The rules to parse a month component, given an input string and a position, are as follows. This will either return a year and a month, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
1. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not at least four characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the
year.
2. If year is not a number greater than zero, then fail.
3. If position is beyond the end of input or if the character at position is not a U+002D HYPHEN-MINUS character, then fail. Otherwise, move position forwards one character.
4. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the
month.
5. If month is not a number in the range 1 ≤ month ≤ 12, then fail.
6. Return year and month.
2.4.5.2 Dates
A date consists of a specific proleptic Gregorian date with no time-zone information, consisting of a year, a month, and a day. [GREGORIAN]
A string is a valid date string representing a year year, month month, and day day if it consists of the following components in the given order:
1. A valid month string, representing year and month
2. A U+002D HYPHEN-MINUS character (-)
3. Two digits, representing day, in the range 1 ≤ day ≤ maxday where maxday is the number of days in the month month and year year
The rules to parse a date string are as follows. This will either return a date, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
1. Let input be the string being parsed.
2. Let position be a pointer into input, initially pointing at the start of the string.
3. Parse a date component to obtain year, month, and day. If this returns nothing, then fail.
4. If position is not beyond the end of input, then fail.
5. Let date be the date with year year, month month, and day day.
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6. Let second be a string with the value "0".
7. If position is not beyond the end of input and the character at position is a U+003A COLON, then run these substeps:
1. Advance position to the next character in input.
2. If position is beyond the end of input, or at the last character in input, or if the next two characters in input starting at position are not two characters both in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), then fail.
3. Collect a sequence of characters that are either characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9) or U+002E FULL STOP characters. If the collected sequence has more than one U+002E FULL STOP characters, or if the last
character in the sequence is a U+002E FULL STOP character, then fail. Otherwise, let the collected string be second instead of its previous value.
8. Interpret second as a base-ten number (possibly with a fractional part). Let second be that number instead of the string version.
9. If second is not a number in the range 0 ≤ second < 60, then fail.
10. Return hour, minute, and second.
2.4.5.4 Local dates and times
A local date and time consists of a specific proleptic Gregorian date, consisting of a year, a month, and a day, and a time, consisting of an hour, a minute, a second, and a fraction of a second, but expressed without a time zone. [GREGORIAN]
A string is a valid local date and time string representing a date and time if it consists of the following components in the given order:
1. A valid date string representing the date.
2. A U+0054 LATIN CAPITAL LETTER T character.
3. A valid time string representing the time.
The rules to parse a local date and time string are as follows. This will either return a date and time, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
1. Let input be the string being parsed.
2. Let position be a pointer into input, initially pointing at the start of the string.
3. Parse a date component to obtain year, month, and day. If this returns nothing, then fail.
4. If position is beyond the end of input or if the character at position is not a U+0054 LATIN CAPITAL LETTER T character then fail. Otherwise, move position forwards one character.
5. Parse a time component to obtain hour, minute, and second. If this returns nothing, then fail.
6. If position is not beyond the end of input, then fail.
7. Let date be the date with year year, month month, and day day.
8. Let time be the time with hour hour, minute minute, and second second.
9. Return date and time.
2.4.5.5 Global dates and times
A global date and time consists of a specific proleptic Gregorian date, consisting of a year, a month, and a day, and a time, consisting of an hour, a minute, a second, and a fraction of a second, expressed with a time zone, consisting of a number of hours and
minutes. [GREGORIAN]
A string is a valid global date and time string representing a date, time, and a time-zone offset if it consists of the following components in the given order:
1. A valid date string representing the date
2. A U+0054 LATIN CAPITAL LETTER T character
3. A valid time string representing the time
4. Either:
r A U+005A LATIN CAPITAL LETTER Z character, allowed only if the time zone is UTC
r Or:
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2. Advance position to the next character in input.
3. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be
the timezonehours.
4. If timezonehours is not a number in the range 0 ≤ timezonehours ≤ 23, then fail.
5. If sign is "negative", then negate timezonehours.
6. If position is beyond the end of input or if the character at position is not a U+003A COLON character, then fail. Otherwise, move position forwards one character.
7. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be
the timezoneminutes.
8. If timezoneminutes is not a number in the range 0 ≤ timezoneminutes ≤ 59, then fail.
9. If sign is "negative", then negate timezoneminutes.
2. Return timezonehours and timezoneminutes.
2.4.5.6 Weeks
A week consists of a week-year number and a week number representing a seven day period. Each week-year in this calendaring system has either 52 weeks or 53 weeks, as defined below. A week is a seven-day period. The week starting on the Gregorian date
Monday December 29th 1969 (1969-12-29) is defined as week number 1 in week-year 1970. Consecutive weeks are numbered sequentially. The week before the number 1 week in a week-year is the last week in the previous week-year, and vice versa. [GREGORIAN]
A week-year with a number year has 53 weeks if it corresponds to either a year year in the proleptic Gregorian calendar that has a Thursday as its first day (January 1st), or a year year in the proleptic Gregorian calendar that has a Wednesday as its first day (January
1st) and where year is a number divisible by 400, or a number divisible by 4 but not by 100. All other week-years have 52 weeks.
The week number of the last day of a week-year with 53 weeks is 53; the week number of the last day of a week-year with 52 weeks is 52.
The week-year number of a particular day can be different than the number of the year that contains that day in the proleptic Gregorian calendar. The first week in a week-year y is the week that contains the first Thursday of the Gregorian year y.
A string is a valid week string representing a week-year year and week week if it consists of the following components in the given order:
1. Four or more digits, representing year, where year > 0
2. A U+002D HYPHEN-MINUS character (-)
3. A U+0057 LATIN CAPITAL LETTER W character
4. Two digits, representing the week week, in the range 1 ≤ week ≤ maxweek, where maxweek is the week number of the last day of week-year year
The rules to parse a week string are as follows. This will either return a week-year number and week number, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
1. Let input be the string being parsed.
2. Let position be a pointer into input, initially pointing at the start of the string.
3. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not at least four characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the
year.
4. If year is not a number greater than zero, then fail.
5. If position is beyond the end of input or if the character at position is not a U+002D HYPHEN-MINUS character, then fail. Otherwise, move position forwards one character.
6. If position is beyond the end of input or if the character at position is not a U+0057 LATIN CAPITAL LETTER W character, then fail. Otherwise, move position forwards one character.
7. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the
week.
8. Let maxweek be the week number of the last day of year year.
9. If week is not a number in the range 1 ≤ week ≤ maxweek, then fail.
10. If position is not beyond the end of input, then fail.
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11. Return the week-year number year and the week number week.
2.4.5.7 Vaguer moments in time
A date or time string consists of either a date, a time, or a global date and time.
A string is a valid date or time string if it is also one of the following:
q A valid date string.
q A valid time string.
q A valid global date and time string.
A string is a valid date or time string in content if it consists of zero or more White_Space characters, followed by a valid date or time string, followed by zero or more further White_Space characters.
The rules to parse a date or time string are as follows. The algorithm is invoked with a flag indicating if the in attribute variant or the in content variant is to be used. The algorithm will either return a date, a time, a global date and time, or nothing. If at any point the
algorithm says that it "fails", this means that it is aborted at that point and returns nothing.
1. Let input be the string being parsed.
2. Let position be a pointer into input, initially pointing at the start of the string.
3. For the in content variant: skip White_Space characters.
4. Set start position to the same position as position.
5. Set the date present and time present flags to true.
6. Parse a date component to obtain year, month, and day. If this fails, then set the date present flag to false.
7. If date present is true, and position is not beyond the end of input, and the character at position is a U+0054 LATIN CAPITAL LETTER T character, then advance position to the next character in input.
Otherwise, if date present is true, and either position is beyond the end of input or the character at position is not a U+0054 LATIN CAPITAL LETTER T character, then set time present to false.
Otherwise, if date present is false, set position back to the same position as start position.
8. If the time present flag is true, then parse a time component to obtain hour, minute, and second. If this returns nothing, then set the time present flag to false.
9. If both the date present and time present flags are false, then fail.
10. If the date present and time present flags are both true, but position is beyond the end of input, then fail.
11. If the date present and time present flags are both true, parse a time-zone component to obtain timezonehours and timezoneminutes. If this returns nothing, then fail.
12. For the in content variant: skip White_Space characters.
13. If position is not beyond the end of input, then fail.
14. If the date present flag is true and the time present flag is false, then let date be the date with year year, month month, and day day, and return date.
Otherwise, if the time present flag is true and the date present flag is false, then let time be the time with hour hour, minute minute, and second second, and return time.
Otherwise, let time be the moment in time at year year, month month, day day, hours hour, minute minute, second second, subtracting timezonehours hours and timezoneminutes minutes, that moment in time being a moment in the UTC time zone; let timezone be
timezonehours hours and timezoneminutes minutes from UTC; and return time and timezone.
2.4.6 Colors
A simple color consists of three 8-bit numbers in the range 0..255, representing the red, green, and blue components of the color respectively, in the sRGB color space. [SRGB]
A string is a valid simple color if it is exactly seven characters long, and the first character is a U+0023 NUMBER SIGN (#) character, and the remaining six characters are all in the range U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), U+0041 LATIN CAPITAL
LETTER A .. U+0046 LATIN CAPITAL LETTER F, U+0061 LATIN SMALL LETTER A .. U+0066 LATIN SMALL LETTER F, with the first two digits representing the red component, the middle two digits representing the green component, and the last two digits
representing the blue component, in hexadecimal.
A string is a valid lowercase simple color if it is a valid simple color and doesn't use any characters in the range U+0041 LATIN CAPITAL LETTER A .. U+0046 LATIN CAPITAL LETTER F.
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The rules for parsing simple color values are as given in the following algorithm. When invoked, the steps must be followed in the order given, aborting at the first step that returns a value. This algorithm will either return a simple color or an error.
1. Let input be the string being parsed.
2. If input is not exactly seven characters long, then return an error.
3. If the first character in input is not a U+0023 NUMBER SIGN (#) character, then return an error.
4. If the last six characters of input are not all in the range U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), U+0041 LATIN CAPITAL LETTER A .. U+0046 LATIN CAPITAL LETTER F, U+0061 LATIN SMALL LETTER A .. U+0066 LATIN SMALL LETTER F,
then return an error.
5. Let result be a simple color.
6. Interpret the second and third characters as a hexadecimal number and let the result be the red component of result.
7. Interpret the fourth and fifth characters as a hexadecimal number and let the result be the green component of result.
8. Interpret the sixth and seventh characters as a hexadecimal number and let the result be the blue component of result.
9. Return result.
The rules for serializing simple color values given a simple color are as given in the following algorithm:
1. Let result be a string consisting of a single U+0023 NUMBER SIGN (#) character.
2. Convert the red, green, and blue components in turn to two-digit hexadecimal numbers using the digits U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9) and U+0061 LATIN SMALL LETTER A .. U+0066 LATIN SMALL LETTER F, zero-padding if necessary,
and append these numbers to result, in the order red, green, blue.
3. Return result, which will be a valid lowercase simple color.
Some obsolete legacy attributes parse colors in a more complicated manner, using the rules for parsing a legacy color value, which are given in the following algorithm. When invoked, the steps must be followed in the order given, aborting at the first step that
returns a value. This algorithm will either return a simple color or an error.
1. Let input be the string being parsed.
2. If input is the empty string, then return an error.
3. If input is an ASCII case-insensitive match for the string "transparent", then return an error.
4. If input is an ASCII case-insensitive match for one of the keywords listed in the SVG color keywords or CSS2 System Colors sections of the CSS3 Color specification, then return the simple color corresponding to that keyword. [CSSCOLOR]
5. If input is four characters long, and the first character in input is a U+0023 NUMBER SIGN (#) character, and the last three characters of input are all in the range U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), U+0041 LATIN CAPITAL LETTER A .. U+0046
LATIN CAPITAL LETTER F, and U+0061 LATIN SMALL LETTER A .. U+0066 LATIN SMALL LETTER F, then run these substeps:
1. Let result be a simple color.
2. Interpret the second character of input as a hexadecimal digit; let the red component of result be the resulting number multiplied by 17.
3. Interpret the third character of input as a hexadecimal digit; let the green component of result be the resulting number multiplied by 17.
4. Interpret the fourth character of input as a hexadecimal digit; let the blue component of result be the resulting number multiplied by 17.
5. Return result.
6. Replace any characters in input that have a Unicode code point greater than U+FFFF (i.e. any characters that are not in the basic multilingual plane) with the two-character string "00".
7. If input is longer than 128 characters, truncate input, leaving only the first 128 characters.
8. If the first character in input is a U+0023 NUMBER SIGN character (#), remove it.
9. Replace any character in input that is not in the range U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), U+0041 LATIN CAPITAL LETTER A .. U+0046 LATIN CAPITAL LETTER F, and U+0061 LATIN SMALL LETTER A .. U+0066 LATIN SMALL LETTER F
with the character U+0030 DIGIT ZERO (0).
10. While input's length is zero or not a multiple of three, append a U+0030 DIGIT ZERO (0) character to input.
11. Split input into three strings of equal length, to obtain three components. Let length be the length of those components (one third the length of input).
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1. Apply the IDNA ToASCII algorithm to the string, with both the AllowUnassigned and UseSTD3ASCIIRules flags set, but between steps 2 and 3 of the general ToASCII/ToUnicode algorithm (i.e. after splitting the domain name into individual labels), reverse the
order of the labels.
If ToASCII fails to convert one of the components of the string, e.g. because it is too long or because it contains invalid characters, then the string is not valid; abort these steps. [RFC3490]
2. Check that the end of the resulting string matches a suffix in the Public Suffix List, and that there is at least one domain label before the matching substring. If it does not, or if there is not, then the string is not valid; abort these steps. [PSL]
3. Check that the domain name up to the label before the prefix that was matched in the previous string is a registered domain name.
2.4.10 References
A valid hash-name reference to an element of type type is a string consisting of a U+0023 NUMBER SIGN (#) character followed by a string which exactly matches the value of the name attribute of an element in the document with type type.
The rules for parsing a hash-name reference to an element of type type are as follows:
1. If the string being parsed does not contain a U+0023 NUMBER SIGN character, or if the first such character in the string is the last character in the string, then return null and abort these steps.
2. Let s be the string from the character immediately after the first U+0023 NUMBER SIGN character in the string being parsed up to the end of that string.
3. Return the first element of type type that has an id attribute whose value is a case-sensitive match for s or a name attribute whose value is a compatibility caseless match for s.
2.5 URLs
2.5.1 Terminology
A URL is a string used to identify a resource.
A URL is a valid URL if it is a valid Web address as defined by the Web addresses specification. [WEBADDRESSES]
A URL is an absolute URL if it is an absolute Web address as defined by the Web addresses specification. [WEBADDRESSES]
To parse a URL url into its component parts, the user agent must use the parse a Web address algorithm defined by the Web addresses specification. [WEBADDRESSES]
Parsing a URL results in the following components, again as defined by the Web addresses specification:
q <scheme>
q <host>
q <port>
q <hostport>
q <path>
q <query>
q <fragment>
q <host-specific>
To resolve a URL to an absolute URL relative to either another absolute URL or an element, the user agent must use the resolve a Web address algorithm defined by the Web addresses specification. [WEBADDRESSES]
The document base URL of a Document object is the document base Web address as defined by the Web addresses specification. [WEBADDRESSES]
The term "URL" in this specification is used in a manner distinct from the precise technical meaning it is given in RFC 3986. Readers familiar with that RFC will find it easier to read this specification if they pretend the term "URL" as used herein is really
called something else altogether. This is a willful violation of RFC 3986. [RFC3986]
2.5.2 Dynamic changes to base URLs
When an xml:base attribute changes, the attribute's element, and all descendant elements, are affected by a base URL change.
When a document's document base URL changes, all elements in that document are affected by a base URL change.
When an element is moved from one document to another, if the two documents have different base URLs, then that element and all its descendants are affected by a base URL change.
When an element is affected by a base URL change, it must act as described in the following list:
If the element is a hyperlink element
If the absolute URL identified by the hyperlink is being shown to the user, or if any data derived from that URL is affecting the display, then the href attribute should be re-resolved relative to the element and the UI updated appropriately.
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For example, the CSS :link/:visited pseudo-classes might have been affected.
If the hyperlink has a ping attribute and its absolute URL(s) are being shown to the user, then the ping attribute's tokens should be re-resolved relative to the element and the UI updated appropriately.
If the element is a q, blockquote, section, article, ins, or del element with a cite attribute
If the absolute URL identified by the cite attribute is being shown to the user, or if any data derived from that URL is affecting the display, then the URL should be re-resolved relative to the element and the UI updated appropriately.
Otherwise
The element is not directly affected.
Changing the base URL doesn't affect the image displayed by img elements, although subsequent accesses of the src DOM attribute from script will return a new absolute URL that might no longer correspond to the image being shown.
2.5.3 Interfaces for URL manipulation
An interface that has a complement of URL decomposition attributes will have seven attributes with the following definitions:
attribute DOMString protocol;
attribute DOMString host;
attribute DOMString hostname;
attribute DOMString port;
attribute DOMString pathname;
attribute DOMString search;
attribute DOMString hash;
o . protocol [ = value ]
Returns the current scheme of the underlying URL.
Can be set, to change the underlying URL's scheme.
o . host [ = value ]
Returns the current host and port (if it's not the default port) in the underlying URL.
Can be set, to change the underlying URL's host and port.
The host and the port are separated by a colon. The port part, if omitted, will be assumed to be the current scheme's default port.
o . hostname [ = value ]
Returns the current host in the underlying URL.
Can be set, to change the underlying URL's host.
o . port [ = value ]
Returns the current port in the underlying URL.
Can be set, to change the underlying URL's port.
o . pathname [ = value ]
Returns the current path in the underlying URL.
Can be set, to change the underlying URL's path.
o . search [ = value ]
Returns the current query component in the underlying URL.
Can be set, to change the underlying URL's query component.
o . hash [ = value ]
Returns the current fragment identifier in the underlying URL.
Can be set, to change the underlying URL's fragment identifier.
The attributes defined to be URL decomposition attributes must act as described for the attributes with the same corresponding names in this section.
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In addition, an interface with a complement of URL decomposition attributes will define an input, which is a URL that the attributes act on, and a common setter action, which is a set of steps invoked when any of the attributes' setters are invoked.
The seven URL decomposition attributes have similar requirements.
On getting, if the input is an absolute URL that fulfills the condition given in the "getter condition" column corresponding to the attribute in the table below, the user agent must return the part of the input URL given in the "component" column, with any prefixes specified
in the "prefix" column appropriately added to the start of the string and any suffixes specified in the "suffix" column appropriately added to the end of the string. Otherwise, the attribute must return the empty string.
On setting, the new value must first be mutated as described by the "setter preprocessor" column, then mutated by %-escaping any characters in the new value that are not valid in the relevant component as given by the "component" column. Then, if the input is an
absolute URL and the resulting new value fulfills the condition given in the "setter condition" column, the user agent must make a new string output by replacing the component of the URL given by the "component" column in the input URL with the new value; otherwise,
the user agent must let output be equal to the input. Finally, the user agent must invoke the common setter action with the value of output.
When replacing a component in the URL, if the component is part of an optional group in the URL syntax consisting of a character followed by the component, the component (including its prefix character) must be included even if the new value is the empty string.
The previous paragraph applies in particular to the ":" before a <port> component, the "?" before a <query> component, and the "#" before a <fragment> component.
For the purposes of the above definitions, URLs must be parsed using the URL parsing rules defined in this specification.
Attribute Component Getter Condition Prefix Suffix Setter Preprocessor Setter Condition
protocol <scheme> — — U+003A COLON (":") Remove all trailing U+003A COLON (":") characters The new value is not the empty string
host <hostport> input is hierarchical and uses a server-based naming — — — The new value is not the empty string and input is
authority hierarchical and uses a server-based naming
authority
hostname <host> input is hierarchical and uses a server-based naming — — Remove all leading U+002F SOLIDUS ("/") characters The new value is not the empty string and input is
authority hierarchical and uses a server-based naming
authority
port <port> input is hierarchical, uses a server-based naming — — Remove any characters in the new value that are not in the input is hierarchical and uses a server-based naming
authority, and contained a <port> component (possibly range U+0030 DIGIT ZERO .. U+0039 DIGIT NINE. If the authority
an empty one) resulting string is empty, set it to a single U+0030 DIGIT ZERO
character ('0').
pathname <path> input is hierarchical — — If it has no leading U+002F SOLIDUS ("/") character, prepend a —
U+002F SOLIDUS ("/") character to the new value
search <query> input is hierarchical, and contained a <query> U+003F QUESTION MARK ("?") — Remove one leading U+003F QUESTION MARK ("?") —
component (possibly an empty one) character, if any
hash <fragment> input contained a <fragment> component (possibly an U+0023 NUMBER SIGN ("#") — Remove one leading U+0023 NUMBER SIGN ("#") character, if —
empty one) any
The table below demonstrates how the getter condition for search results in different results depending on the exact original syntax of the URL:
Input URL search value Explanation
http://example.com/ empty string No <query> component in input URL.
http://example.com/? ? There is a <query> component, but it is empty. The question mark in the resulting value is the prefix.
http://example.com/?test ?test The <query> component has the value "test".
http://example.com/?test# ?test The (empty) <fragment> component is not part of the <query> component.
2.6 Fetching resources
When a user agent is to fetch a resource, the following steps must be run:
1. If the resource is identified by the URL about:blank, then return the empty string and abort these steps.
2. Perform the remaining steps asynchronously.
3. If the resource is identified by an absolute URL, and the resource is to be obtained using a idempotent action (such as an HTTP GET or equivalent), and it is already being downloaded for other reasons (e.g. another invocation of this algorithm), and the user
agent is configured such that it is to reuse the data from the existing download instead of initiating a new one, then use the results of the existing download instead of starting a new one.
Otherwise, at a time convenient to the user and the user agent, download (or otherwise obtain) the resource, applying the semantics of the relevant specifications (e.g. performing an HTTP GET or POST operation, or reading the file from disk, following redirects,
dereferencing javascript: URLs, etc).
For purposes of generating the address of the resource from which Request-URIs are obtained as required by HTTP for the Referer (sic) header, the user agent must use the document's current address of the appropriate Document as given by this list. [HTTP]
When navigating
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The active document of the source browsing context.
When fetching resources for an element
The element's Document.
When fetching resources in response to a call to an API
The active document of the browsing context of the first script.
4. If there are cookies to be set, then the user agent must run the following substeps:
1. Wait until ownership of the storage mutex can be taken by this instance of the fetching algorithm.
2. Take ownership of the storage mutex.
3. Update the cookies. [COOKIES]
4. Release the storage mutex so that it is once again free.
5. When the resource is available, or if there is an error of some description, queue a task that uses the resource as appropriate. If the resource can be processed incrementally, as, for instance, with a progressively interlaced JPEG or an HTML file, additional tasks
may be queued to process the data as it is downloaded. The task source for these tasks is the networking task source.
The application cache processing model introduces some changes to the networking model to handle the returning of cached resources.
The navigation processing model handles redirects itself, overriding the redirection handling that would be done by the fetching algorithm.
Whether the type sniffing rules apply to the fetched resource depends on the algorithm that invokes the rules — they are not always applicable.
2.6.1 Protocol concepts
User agents can implement a variety of transfer protocols, but this specification mostly defines behavior in terms of HTTP. [HTTP]
The HTTP GET method is equivalent to the default retrieval action of the protocol. For example, RETR in FTP. Such actions are idempotent and safe, in HTTP terms.
The HTTP response codes are equivalent to statuses in other protocols that have the same basic meanings. For example, a "file not found" error is equivalent to a 404 code, a server error is equivalent to a 5xx code, and so on.
The HTTP headers are equivalent to fields in other protocols that have the same basic meaning. For example, the HTTP authentication headers are equivalent to the authentication aspects of the FTP protocol.
2.6.2 Encrypted HTTP and related security concerns
Anything in this specification that refers to HTTP also applies to HTTP-over-TLS, as represented by URLs representing the https scheme.
User agents should report certificate errors to the user and must either refuse to download resources sent with erroneous certificates or must act as if such resources were in fact served with no encryption.
User agents should warn the user that there is a potential problem whenever the user visits a page that the user has previously visited, if the page uses less secure encryption on the second visit.
Not doing so can result in users not noticing man-in-the-middle attacks.
If a user connects to a server with a self-signed certificate, the user agent could allow the connection but just act as if there had been no encryption. If the user agent instead allowed the user to override the problem and then displayed the page as if it was fully
and safely encrypted, the user could be easily tricked into accepting man-in-the-middle connections.
If a user connects to a server with full encryption, but the page then refers to an external resource that has an expired certificate, then the user agent will act as if the resource was unavailable, possibly also reporting the problem to the user. If the user agent
instead allowed the resource to be used, then an attacker could just look for "secure" sites that used resources from a different host and only apply man-in-the-middle attacks to that host, for example taking over scripts in the page.
If a user bookmarks a site that uses a CA-signed certificate, and then later revisits that site directly but the site has started using a self-signed certificate, the user agent could warn the user that a man-in-the-middle attack is likely underway, instead of simply
acting as if the page was not encrypted.
2.6.3 Determining the type of a resource
The Content-Type metadata of a resource must be obtained and interpreted in a manner consistent with the requirements of the Content-Type Processing Model specification. [MIMESNIFF]
The algorithm for extracting an encoding from a Content-Type, given a string s, is given in the Content-Type Processing Model specification. It either returns an encoding or nothing. [MIMESNIFF]
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The sniffed type of a resource must be found in a manner consistent with the requirements given in the Content-Type Processing Model specification for finding that sniffed type. [MIMESNIFF]
The rules for sniffing images specifically are also defined in the Content-Type Processing Model specification. [MIMESNIFF]
It is imperative that the rules in the Content-Type Processing Model specification be followed exactly. When a user agent uses different heuristics for content type detection than the server expects, security problems can occur. For more details, see the Content-Type
Processing Model specification. [MIMESNIFF]
2.7 Character encodings
User agents must at a minimum support the UTF-8 and Windows-1252 encodings, but may support more.
It is not unusual for Web browsers to support dozens if not upwards of a hundred distinct character encodings.
User agents must support the preferred MIME name of every character encoding they support that has a preferred MIME name, and should support all the IANA-registered aliases. [IANACHARSET]
When comparing a string specifying a character encoding with the name or alias of a character encoding to determine if they are equal, user agents must use the Charset Alias Matching rules defined in Unicode Technical Standard #22. [UTS22]
For instance, "GB_2312-80" and "g.b.2312(80)" are considered equivalent names.
In addition, user agents must support the aliases given in the following table, so that labels from the first column are treated as equivalent to the labels given in the corresponding cell from the second column on the same row.
Additional character encoding aliases
Alias Corresponding encoding References
x-sjis windows-31J [SHIFTJIS] [WIN31J]
windows-932 windows-31J [WIN31J]
x-x-big5 Big5 [BIG5]
When a user agent would otherwise use an encoding given in the first column of the following table to either convert content to Unicode characters or convert Unicode characters to bytes, it must instead use the encoding given in the cell in the second column of the
same row. When a byte or sequence of bytes is treated differently due to this encoding aliasing, it is said to have been misinterpreted for compatibility.
Character encoding overrides
Input encoding Replacement encoding References
EUC-KR windows-949 [EUCKR] [WIN949]
GB2312 GBK [RFC1345] [GBK]
GB_2312-80 GBK [RFC1345] [GBK]
ISO-8859-1 windows-1252 [RFC1345] [WIN1252]
ISO-8859-9 windows-1254 [RFC1345] [WIN1254]
ISO-8859-11 windows-874 [ISO885911] [WIN874]
KS_C_5601-1987 windows-949 [RFC1345] [WIN949]
Shift_JIS windows-31J [SHIFTJIS] [WIN31J]
TIS-620 windows-874 [TIS620] [WIN874]
US-ASCII windows-1252 [RFC1345] [WIN1252]
The requirement to treat certain encodings as other encodings according to the table above is a willful violation of the W3C Character Model specification, motivated by a desire for compatibility with legacy content. [CHARMOD]
When a user agent is to use the UTF-16 encoding but no BOM has been found, user agents must default to UTF-16LE.
The requirement to default UTF-16 to LE rather than BE is a willful violation of RFC 2781, motivated by a desire for compatibility with legacy content. [CHARMOD]
User agents must not support the CESU-8, UTF-7, BOCU-1 and SCSU encodings. [CESU8] [UTF7] [BOCU1] [SCSU]
Support for encodings based on EBCDIC is not recommended. This encoding is rarely used for publicly-facing Web content.
Support for UTF-32 is not recommended. This encoding is rarely used, and frequently implemented incorrectly.
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This specification does not make any attempt to support EBCDIC-based encodings and UTF-32 in its algorithms; support and use of these encodings can thus lead to unexpected behavior in implementations of this specification.
2.8 Common DOM interfaces
2.8.1 Reflecting content attributes in DOM attributes
Some DOM attributes are defined to reflect a particular content attribute. This means that on getting, the DOM attribute returns the current value of the content attribute, and on setting, the DOM attribute changes the value of the content attribute to the given value.
A list of reflecting DOM attributes and their corresponding content attributes is given in the index.
In general, on getting, if the content attribute is not present, the DOM attribute must act as if the content attribute's value is the empty string; and on setting, if the content attribute is not present, it must first be added.
If a reflecting DOM attribute is a DOMString attribute whose content attribute is defined to contain a URL, then on getting, the DOM attribute must resolve the value of the content attribute relative to the element and return the resulting absolute URL if that was
successful, or the empty string otherwise; and on setting, must set the content attribute to the specified literal value. If the content attribute is absent, the DOM attribute must return the default value, if the content attribute has one, or else the empty string.
If a reflecting DOM attribute is a DOMString attribute whose content attribute is defined to contain one or more URLs, then on getting, the DOM attribute must split the content attribute on spaces and return the concatenation of resolving each token URL to an absolute
URL relative to the element, with a single U+0020 SPACE character between each URL, ignoring any tokens that did not resolve successfully. If the content attribute is absent, the DOM attribute must return the default value, if the content attribute has one, or else the
empty string. On setting, the DOM attribute must set the content attribute to the specified literal value.
If a reflecting DOM attribute is a DOMString whose content attribute is an enumerated attribute, and the DOM attribute is limited to only known values, then, on getting, the DOM attribute must return the conforming value associated with the state the attribute is in (in
its canonical case), or the empty string if the attribute is in a state that has no associated keyword value; and on setting, if the new value is an ASCII case-insensitive match for one of the keywords given for that attribute, then the content attribute must be set to the
conforming value associated with the state that the attribute would be in if set to the given new value, otherwise, if the new value is the empty string, then the content attribute must be removed, otherwise, the setter must raise a SYNTAX_ERR exception.
If a reflecting DOM attribute is a DOMString but doesn't fall into any of the above categories, then the getting and setting must be done in a transparent, case-preserving manner.
If a reflecting DOM attribute is a boolean attribute, then on getting the DOM attribute must return true if the attribute is set, and false if it is absent. On setting, the content attribute must be removed if the DOM attribute is set to false, and must be set to have the same
value as its name if the DOM attribute is set to true. (This corresponds to the rules for boolean content attributes.)
If a reflecting DOM attribute is a signed integer type (long) then, on getting, the content attribute must be parsed according to the rules for parsing signed integers, and if that is successful, and the value is in the range of the DOM attribute's type, the resulting value
must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, then the default value must be returned instead, or 0 if there is no default value. On setting, the given value must be converted to the shortest possible string
representing the number as a valid integer and then that string must be used as the new content attribute value.
If a reflecting DOM attribute is an unsigned integer type (unsigned long) then, on getting, the content attribute must be parsed according to the rules for parsing non-negative integers, and if that is successful, and the value is in the range of the DOM attribute's type,
the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, the default value must be returned instead, or 0 if there is no default value. On setting, the given value must be converted to the shortest
possible string representing the number as a valid non-negative integer and then that string must be used as the new content attribute value.
If a reflecting DOM attribute is an unsigned integer type (unsigned long) that is limited to only positive non-zero numbers, then the behavior is similar to the previous case, but zero is not allowed. On getting, the content attribute must first be parsed according to
the rules for parsing non-negative integers, and if that is successful, and the value is in the range of the DOM attribute's type, the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, the default value
must be returned instead, or 1 if there is no default value. On setting, if the value is zero, the user agent must fire an INDEX_SIZE_ERR exception. Otherwise, the given value must be converted to the shortest possible string representing the number as a valid non-
negative integer and then that string must be used as the new content attribute value.
If a reflecting DOM attribute is a floating point number type (float) and it doesn't fall into one of the earlier categories, then, on getting, the content attribute must be parsed according to the rules for parsing floating point number values, and if that is successful, and the
value is in the range of the DOM attribute's type, the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, the default value must be returned instead, or 0.0 if there is no default value. On setting, the
given value must be converted to the best representation of the floating point number and then that string must be used as the new content attribute value.
The values ±Infinity and NaN throw an exception on setting, as defined by Web IDL. [WEBIDL]
If a reflecting DOM attribute is of the type DOMTokenList or DOMSettableTokenList, then on getting it must return a DOMTokenList or DOMSettableTokenList object (as appropriate) whose underlying string is the element's corresponding content attribute.
When the object mutates its underlying string, the content attribute must itself be immediately mutated. When the attribute is absent, then the string represented by the object is the empty string; when the object mutates this empty string, the user agent must first add
the corresponding content attribute, and then mutate that attribute instead. The same DOMTokenList object must be returned every time for each attribute.
If a reflecting DOM attribute has the type HTMLElement, or an interface that descends from HTMLElement, then, on getting, it must run the following algorithm (stopping at the first point where a value is returned):
1. If the corresponding content attribute is absent, then the DOM attribute must return null.
2. Let candidate be the element that the document.getElementById() method would find if it was passed as its argument the current value of the corresponding content attribute.
3. If candidate is null, or if it is not type-compatible with the DOM attribute, then the DOM attribute must return null.
4. Otherwise, it must return candidate.
On setting, if the given element has an id attribute, then the content attribute must be set to the value of that id attribute. Otherwise, the DOM attribute must be set to the empty string.
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2.8.2 Collections
The HTMLCollection, HTMLAllCollection, HTMLFormControlsCollection, HTMLOptionsCollection, and HTMLPropertyCollection interfaces represent various lists of DOM nodes. Collectively, objects implementing these interfaces are called
collections.
When a collection is created, a filter and a root are associated with the collection.
For example, when the HTMLCollection object for the document.images attribute is created, it is associated with a filter that selects only img elements, and rooted at the root of the document.
The collection then represents a live view of the subtree rooted at the collection's root, containing only nodes that match the given filter. The view is linear. In the absence of specific requirements to the contrary, the nodes within the collection must be sorted in tree
order.
The rows list is not in tree order.
An attribute that returns a collection must return the same object every time it is retrieved.
2.8.2.1 HTMLCollection
The HTMLCollection interface represents a generic collection of elements.
[Callable=namedItem]
interface HTMLCollection {
readonly attribute unsigned long length;
[IndexGetter] Element item(in unsigned long index);
[NameGetter] Element namedItem(in DOMString name);
HTMLAllCollection tags(in DOMString tagName);
};
collection . length
Returns the number of elements in the collection.
element = collection . item(index)
collection[index]
Returns the item with index index from the collection. The items are sorted in tree order.
Returns null if index is out of range.
element = collection . namedItem(name)
collection[name]
collection(name)
Returns the first item with ID or name name from the collection.
Returns null if no element with that ID or name could be found.
Only a, applet, area, embed, form, frame, frameset, iframe, img, and object elements can have a name for the purpose of this method; their name is given by the value of their name attribute.
collection = collection . tags(tagName)
Returns a collection that is a filtered view of the current collection, containing only elements with the given tag name.
The object's indices of the supported indexed properties are the numbers in the range zero to one less than the number of nodes represented by the collection. If there are no such elements, then there are no supported indexed properties.
The length attribute must return the number of nodes represented by the collection.
The item(index) method must return the indexth node in the collection. If there is no indexth node in the collection, then the method must return null.
The names of the supported named properties consist of the values of the name attributes of each a, applet, area, embed, form, frame, frameset, iframe, img, and object element represented by the collection with a name attribute, plus the list of IDs that the
elements represented by the collection have.
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The namedItem(key) method must return the first node in the collection that matches the following requirements:
q It is an a, applet, area, embed, form, frame, frameset, iframe, img, or object element with a name attribute equal to key, or,
q It is an element with an ID key.
If no such elements are found, then the method must return null.
The tags(tagName) method must return an HTMLAllCollection rooted at the same node as the HTMLCollection object on which the method was invoked, whose filter matches only HTML elements whose local name is the tagName argument and that already
match the filter of the HTMLCollection object on which the method was invoked. In HTML documents, the argument must first be converted to ASCII lowercase.
2.8.2.2 HTMLAllCollection
The HTMLAllCollection interface represents a generic collection of elements just like HTMLCollection, with the exception that its namedItem() method returns an HTMLCollection object when there are multiple matching elements.
[Callable=namedItem]
interface HTMLAllCollection {
readonly attribute unsigned long length;
[IndexGetter] Element item(in unsigned long index);
[NameGetter] Object namedItem(in DOMString name);
HTMLAllCollection tags(in DOMString tagName);
};
collection . length
Returns the number of elements in the collection.
element = collection . item(index)
collection[index]
Returns the item with index index from the collection. The items are sorted in tree order.
Returns null if index is out of range.
element = collection . namedItem(name)
collection = collection . namedItem(name)
collection[name]
collection(name)
Returns the item with ID or name name from the collection.
If there are multiple matching items, then an HTMLAllCollection object containing all those elements is returned.
Returns null if no element with that ID or name could be found.
Only a, applet, area, embed, form, frame, frameset, iframe, img, and object elements can have a name for the purpose of this method; their name is given by the value of their name attribute.
collection = collection . tags(tagName)
Returns a collection that is a filtered view of the current collection, containing only elements with the given tag name.
The object's indices of the supported indexed properties are the numbers in the range zero to one less than the number of nodes represented by the collection. If there are no such elements, then there are no supported indexed properties.
The length attribute must return the number of nodes represented by the collection.
The item(index) method must return the indexth node in the collection. If there is no indexth node in the collection, then the method must return null.
The names of the supported named properties consist of the values of the name attributes of each a, applet, area, embed, form, frame, frameset, iframe, img, and object element represented by the collection with a name attribute, plus the list of IDs that the
elements represented by the collection have.
The namedItem(key) method must act according to the following algorithm:
1. Let collection be an HTMLAllCollection object rooted at the same node as the HTMLAllCollection object on which the method was invoked, whose filter matches only only elements that already match the filter of the HTMLAllCollection object on
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which the method was invoked and that are either:
r a, applet, area, embed, form, frame, frameset, iframe, img, or object elements with a name attribute equal to key, or,
r elements with an ID key.
2. If, at the time the method is called, there is exactly one node in collection, then return that node and stop the algorithm.
3. Otherwise, if, at the time the method is called, collection is empty, return null and stop the algorithm.
4. Otherwise, return collection.
The tags(tagName) method must return an HTMLAllCollection rooted at the same node as the HTMLAllCollection object on which the method was invoked, whose filter matches only HTML elements whose local name is the tagName argument and that
already match the filter of the HTMLAllCollection object on which the method was invoked. In HTML documents, the argument must first be converted to ASCII lowercase.
2.8.2.3 HTMLFormControlsCollection
The HTMLFormControlsCollection interface represents a collection of listed elements in form and fieldset elements.
[Callable=namedItem]
interface HTMLFormControlsCollection {
readonly attribute unsigned long length;
[IndexGetter] HTMLElement item(in unsigned long index);
[NameGetter] Object namedItem(in DOMString name);
};
interface RadioNodeList : NodeList {
attribute DOMString value;
};
collection . length
Returns the number of elements in the collection.
element = collection . item(index)
collection[index]
Returns the item with index index from the collection. The items are sorted in tree order.
Returns null if index is out of range.
element = collection . namedItem(name)
radioNodeList = collection . namedItem(name)
collection[name]
collection(name)
Returns the item with ID or name name from the collection.
If there are multiple matching items, then a RadioNodeList object containing all those elements is returned.
Returns null if no element with that ID or name could be found.
radioNodeList . value [ = value ]
Returns the value of the first checked radio button represented by the object.
Can be set, to check the first radio button with the given value represented by the object.
The object's indices of the supported indexed properties are the numbers in the range zero to one less than the number of nodes represented by the collection. If there are no such elements, then there are no supported indexed properties.
The length attribute must return the number of nodes represented by the collection.
The item(index) method must return the indexth node in the collection. If there is no indexth node in the collection, then the method must return null.
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The names of the supported named properties consist of the values of all the id and name attributes of all the elements represented by the collection.
The namedItem(name) method must act according to the following algorithm:
1. If, at the time the method is called, there is exactly one node in the collection that has either an id attribute or a name attribute equal to name, then return that node and stop the algorithm.
2. Otherwise, if there are no nodes in the collection that have either an id attribute or a name attribute equal to name, then return null and stop the algorithm.
3. Otherwise, create a RadioNodeList object representing a live view of the HTMLFormControlsCollection object, further filtered so that the only nodes in the RadioNodeList object are those that have either an id attribute or a name attribute equal to
name. The nodes in the RadioNodeList object must be sorted in tree order.
4. Return that RadioNodeList object.
A members of the RadioNodeList interface inherited from the NodeList interface must behave as they would on a NodeList object.
The value DOM attribute on the RadioNodeList object, on getting, must return the value returned by running the following steps:
1. Let element be the first element in tree order represented by the RadioNodeList object that is an input element whose type attribute is in the Radio Button state and whose checkedness is true. Otherwise, let it be null.
2. If element is null, or if it is an element with no value attribute, return the empty string.
3. Otherwise, return the value of element's value attribute.
On setting, the value DOM attribute must run the following steps:
1. Let element be the first element in tree order represented by the RadioNodeList object that is an input element whose type attribute is in the Radio Button state and whose value content attribute is present and equal to the new value, if any. Otherwise, let
it be null.
2. If element is not null, then set its checkedness to true.
2.8.2.4 HTMLOptionsCollection
The HTMLOptionsCollection interface represents a list of option elements. It is always rooted on a select element and has attributes and methods that manipulate that element's descendants.
[Callable=namedItem]
interface HTMLOptionsCollection {
attribute unsigned long length;
[IndexGetter] HTMLOptionElement item(in unsigned long index);
[NameGetter] Object namedItem(in DOMString name);
void add(in HTMLElement element, [Optional] in HTMLElement before);
void add(in HTMLElement element, in long before);
void remove(in long index);
};
collection . length [ = value ]
Returns the number of elements in the collection.
When set to a smaller number, truncates the number of option elements in the corresponding container.
When set to a greater number, adds new blank option elements to that container.
element = collection . item(index)
collection[index]
Returns the item with index index from the collection. The items are sorted in tree order.
Returns null if index is out of range.
element = collection . namedItem(name)
nodeList = collection . namedItem(name)
collection[name]
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collection(name)
Returns the item with ID or name name from the collection.
If there are multiple matching items, then a NodeList object containing all those elements is returned.
Returns null if no element with that ID could be found.
collection . add(element [, before ] )
Inserts element before the node given by before.
The before argument can be a number, in which case element is inserted before the item with that number, or an element from the collection, in which case element is inserted before that element.
If before is omitted, null, or a number out of range, then element will be added at the end of the list.
This method will throw a HIERARCHY_REQUEST_ERR exception if element is an ancestor of the element into which it is to be inserted. If element is not an option or optgroup element, then the method does nothing.
The object's indices of the supported indexed properties are the numbers in the range zero to one less than the number of nodes represented by the collection. If there are no such elements, then there are no supported indexed properties.
On getting, the length attribute must return the number of nodes represented by the collection.
On setting, the behavior depends on whether the new value is equal to, greater than, or less than the number of nodes represented by the collection at that time. If the number is the same, then setting the attribute must do nothing. If the new value is greater, then n
new option elements with no attributes and no child nodes must be appended to the select element on which the HTMLOptionsCollection is rooted, where n is the difference between the two numbers (new value minus old value). If the new value is lower, then
the last n nodes in the collection must be removed from their parent nodes, where n is the difference between the two numbers (old value minus new value).
Setting length never removes or adds any optgroup elements, and never adds new children to existing optgroup elements (though it can remove children from them).
The item(index) method must return the indexth node in the collection. If there is no indexth node in the collection, then the method must return null.
The names of the supported named properties consist of the values of all the id and name attributes of all the elements represented by the collection.
The namedItem(name) method must act according to the following algorithm:
1. If, at the time the method is called, there is exactly one node in the collection that has either an id attribute or a name attribute equal to name, then return that node and stop the algorithm.
2. Otherwise, if there are no nodes in the collection that have either an id attribute or a name attribute equal to name, then return null and stop the algorithm.
3. Otherwise, create a NodeList object representing a live view of the HTMLOptionsCollection object, further filtered so that the only nodes in the NodeList object are those that have either an id attribute or a name attribute equal to name. The nodes in the
NodeList object must be sorted in tree order.
4. Return that NodeList object.
The add(element, before) method must act according to the following algorithm:
1. If element is not an option or optgroup element, then return and abort these steps.
2. If element is an ancestor of the select element on which the HTMLOptionsCollection is rooted, then throw a HIERARCHY_REQUEST_ERR exception.
3. If before is an element, but that element isn't a descendant of the select element on which the HTMLOptionsCollection is rooted, then throw a NOT_FOUND_ERR exception.
4. If element and before are the same element, then return and abort these steps.
5. If before is a node, then let reference be that node. Otherwise, if before is an integer, and there is a beforeth node in the collection, let reference be that node. Otherwise, let reference be null.
6. If reference is not null, let parent be the parent node of reference. Otherwise, let parent be the select element on which the HTMLOptionsCollection is rooted.
7. Act as if the DOM Core insertBefore() method was invoked on the parent node, with element as the first argument and reference as the second argument.
The remove(index) method must act according to the following algorithm:
1. If the number of nodes represented by the collection is zero, abort these steps.
2. If index is not a number greater than or equal to 0 and less than the number of nodes represented by the collection, let element be the first element in the collection. Otherwise, let element be the indexth element in the collection.
3. Remove element from its parent node.
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2.8.2.5 HTMLPropertyCollection
The HTMLPropertyCollection interface represents a collection of elements that add name-value pairs to a particular item in the microdata model.
[Callable=namedItem]
interface HTMLPropertyCollection {
readonly attribute unsigned long length;
[IndexGetter] HTMLElement item(in unsigned long index);
readonly attribute DOMStringList names;
[NameGetter] PropertyNodeList namedItem(in DOMString name);
};
typedef sequence<any> PropertyValueArray;
interface PropertyNodeList : NodeList {
attribute PropertyValueArray contents;
};
collection . length
Returns the number of elements in the collection.
collection . names
Returns a DOMStringList with the property names of the elements in the collection.
element = collection . item(index)
collection[index]
Returns the element with index index from the collection. The items are sorted in tree order.
Returns null if index is out of range.
propertyNodeList = collection . namedItem(name)
collection[name]
collection(name)
Returns a PropertyNodeList object containing any elements that add a property named name.
propertyNodeList . contents
Returns an array of the various values that the relevant elements have.
The object's indices of the supported indexed properties are the numbers in the range zero to one less than the number of nodes represented by the collection. If there are no such elements, then there are no supported indexed properties.
The length attribute must return the number of nodes represented by the collection.
The item(index) method must return the indexth node in the collection. If there is no indexth node in the collection, then the method must return null.
The names of the supported named properties consist of the property names of all the elements represented by the collection.
The names attribute must return a live DOMStringList object giving the property names of all the elements represented by the collection, listed in tree order, but with duplicates removed, leaving only the first occurrence of each name. The same object must be
returned each time.
The namedItem(name) method must return a PropertyNodeList object representing a live view of the HTMLPropertyCollection object, further filtered so that the only nodes in the RadioNodeList object are those that have a property name equal to name.
The nodes in the PropertyNodeList object must be sorted in tree order, and the same object must be returned each time a particular name is queried.
A members of the PropertyNodeList interface inherited from the NodeList interface must behave as they would on a NodeList object.
The contents DOM attribute on the PropertyNodeList object, on getting, must return a newly constructed DOMStringArray whose values are the values obtained from the content DOM property of each of the elements represented by the object, in tree order.
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2.8.3 DOMTokenList
The DOMTokenList interface represents an interface to an underlying string that consists of a set of space-separated tokens.
DOMTokenList objects are always case-sensitive, even when the underlying string might ordinarily be treated in a case-insensitive manner.
[Stringifies] interface DOMTokenList {
readonly attribute unsigned long length;
[IndexGetter] DOMString item(in unsigned long index);
boolean contains(in DOMString token);
void add(in DOMString token);
void remove(in DOMString token);
boolean toggle(in DOMString token);
};
tokenlist . length
Returns the number of tokens in the string.
element = tokenlist . item(index)
tokenlist[index]
Returns the token with index index. The tokens are returned in the order they are found in the underlying string.
Returns null if index is out of range.
hastoken = tokenlist . contains(token)
Returns true if the token is present; false otherwise.
Throws a SYNTAX_ERR exception if token is empty.
Throws an INVALID_CHARACTER_ERR exception if token contains any spaces.
tokenlist . add(token)
Adds token, unless it is already present.
Throws a SYNTAX_ERR exception if token is empty.
Throws an INVALID_CHARACTER_ERR exception if token contains any spaces.
tokenlist . remove(token)
Removes token if it is present.
Throws a SYNTAX_ERR exception if token is empty.
Throws an INVALID_CHARACTER_ERR exception if token contains any spaces.
hastoken = tokenlist . toggle(token)
Adds token if it is not present, or removes it if it is.
Throws a SYNTAX_ERR exception if token is empty.
Throws an INVALID_CHARACTER_ERR exception if token contains any spaces.
The length attribute must return the number of tokens that result from splitting the underlying string on spaces. This is the length.
The object's indices of the supported indexed properties are the numbers in the range zero to length-1, unless the length is zero, in which case there are no supported indexed properties.
The item(index) method must split the underlying string on spaces, preserving the order of the tokens as found in the underlying string, and then return the indexth item in this list. If index is equal to or greater than the number of tokens, then the method must return
null.
For example, if the string is "a b a c" then there are four tokens: the token with index 0 is "a", the token with index 1 is "b", the token with index 2 is "a", and the token with index 3 is "c".
The contains(token) method must run the following algorithm:
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1. If the token argument is the empty string, then raise a SYNTAX_ERR exception and stop the algorithm.
2. If the token argument contains any space characters, then raise an INVALID_CHARACTER_ERR exception and stop the algorithm.
3. Otherwise, split the underlying string on spaces to get the list of tokens in the object's underlying string.
4. If the token indicated by token is a case-sensitive match for one of the tokens in the object's underlying string then return true and stop this algorithm.
5. Otherwise, return false.
The add(token) method must run the following algorithm:
1. If the token argument is the empty string, then raise a SYNTAX_ERR exception and stop the algorithm.
2. If the token argument contains any space characters, then raise an INVALID_CHARACTER_ERR exception and stop the algorithm.
3. Otherwise, split the underlying string on spaces to get the list of tokens in the object's underlying string.
4. If the given token is a case-sensitive match for one of the tokens in the DOMTokenList object's underlying string then stop the algorithm.
5. Otherwise, if the DOMTokenList object's underlying string is not the empty string and the last character of that string is not a space character, then append a U+0020 SPACE character to the end of that string.
6. Append the value of token to the end of the DOMTokenList object's underlying string.
The remove(token) method must run the following algorithm:
1. If the token argument is the empty string, then raise a SYNTAX_ERR exception and stop the algorithm.
2. If the token argument contains any space characters, then raise an INVALID_CHARACTER_ERR exception and stop the algorithm.
3. Otherwise, remove the given token from the underlying string.
The toggle(token) method must run the following algorithm:
1. If the token argument is the empty string, then raise a SYNTAX_ERR exception and stop the algorithm.
2. If the token argument contains any space characters, then raise an INVALID_CHARACTER_ERR exception and stop the algorithm.
3. Otherwise, split the underlying string on spaces to get the list of tokens in the object's underlying string.
4. If the given token is a case-sensitive match for one of the tokens in the DOMTokenList object's underlying string then remove the given token from the underlying string and stop the algorithm, returning false.
5. Otherwise, if the DOMTokenList object's underlying string is not the empty string and the last character of that string is not a space character, then append a U+0020 SPACE character to the end of that string.
6. Append the value of token to the end of the DOMTokenList object's underlying string.
7. Return true.
Objects implementing the DOMTokenList interface must stringify to the object's underlying string representation.
2.8.4 DOMSettableTokenList
The DOMSettableTokenList interface is the same as the DOMTokenList interface, except that it allows the underlying string to be directly changed.
[Stringifies] interface DOMSettableTokenList : DOMTokenList {
attribute DOMString value;
};
tokenlist . value
Returns the underlying string.
Can be set, to change the underlying string.
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When a DOMStringMap object is instantiated, it is associated with three algorithms, one for getting the list of name-value pairs, one for setting names to certain values, and one for deleting names.
[NameCreator, NameDeleter, NameGetter, NameSetter]
interface DOMStringMap {};
The names of the supported named properties on a DOMStringMap object at any instant are the names of each pair returned from the algorithm for getting the list of name-value pairs at that instant.
When a DOMStringMap object is indexed to retrieve a named property name, the value returned must be the value component of the name-value pair whose name component is name in the list returned by the algorithm for getting the list of name-value pairs.
When a DOMStringMap object is indexed to create or modify a named property name with value value, the algorithm for setting names to certain values must be run, passing name as the name and the result of converting value to a DOMString as the value.
When a DOMStringMap object is indexed to delete a named property named name, the algorithm for deleting names must be run, passing name as the name.
The DOMStringMap interface definition here is only intended for JavaScript environments. Other language bindings will need to define how DOMStringMap is to be implemented for those languages.
The dataset attribute on elements exposes the data-* attributes on the element.
Given the following fragment and elements with similar constructions:
<img class="tower" id="tower5" data-x="12" data-y="5"
data-ai="robotarget" data-hp="46" data-ability="flames"
src="towers/rocket.png alt="Rocket Tower">
...one could imagine a function splashDamage() that takes some arguments, the first of which is the element to process:
function splashDamage(node, x, y, damage) {
if (node.classList.contains('tower') && // checking the 'class' attribute
node.dataset.x == x && // reading the 'data-x' attribute
node.dataset.y == y) { // reading the 'data-y' attribute
var hp = parseInt(node.dataset.hp); // reading the 'data-hp' attribute
hp = hp - damage;
if (hp < 0) {
hp = 0;
node.dataset.ai = 'dead'; // setting the 'data-ai' attribute
delete node.dataset.ability; // removing the 'data-ability' attribute
}
node.dataset.hp = hp; // setting the 'data-hp' attribute
}
}
2.8.7 DOM feature strings
DOM3 Core defines mechanisms for checking for interface support, and for obtaining implementations of interfaces, using feature strings. [DOM3CORE]
Authors are strongly discouraged from using these, as they are notoriously unreliable and imprecise. Authors are encouraged to rely on explicit feature testing or the graceful degradation behavior intrinsic to some of the features in this specification.
For historical reasons, user agents should return the true value when the hasFeature(feature, version) method of the DOMImplementation interface is invoked with feature set to either "HTML" or "XHTML" and version set to either "1.0" or "2.0".
2.8.8 Exceptions
The following DOMException codes are defined in DOM Core. [DOMCORE]
1. INDEX_SIZE_ERR
2. DOMSTRING_SIZE_ERR
3. HIERARCHY_REQUEST_ERR
4. WRONG_DOCUMENT_ERR
5. INVALID_CHARACTER_ERR
6. NO_DATA_ALLOWED_ERR
7. NO_MODIFICATION_ALLOWED_ERR
8. NOT_FOUND_ERR
9. NOT_SUPPORTED_ERR
10. INUSE_ATTRIBUTE_ERR
11. INVALID_STATE_ERR
12. SYNTAX_ERR
13. INVALID_MODIFICATION_ERR
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3 Semantics, structure, and APIs of HTML documents
3.1 Introduction
This section is non-normative.
An introduction to marking up a document.
3.2 Documents
Every XML and HTML document in an HTML UA is represented by a Document object. [DOM3CORE]
The document's address is an absolute URL that is set when the Document is created. The document's current address is an absolute URL that can change during the lifetime of the Document, for example when the user navigates to a fragment identifier on the
page. The document's current address must be set to the document's address when the Document is created.
When a Document is created by a script using the createDocument() API, the document's address is the same as the document's address of the active document of the script's browsing context.
Document objects are assumed to be XML documents unless they are flagged as being HTML documents when they are created. Whether a document is an HTML document or an XML document affects the behavior of certain APIs, as well as a few CSS rendering
rules. [CSS]
A Document object created by the createDocument() API on the DOMImplementation object is initially an XML document, but can be made into an HTML document by calling document.open() on it.
3.2.1 Documents in the DOM
All Document objects (in user agents implementing this specification) must also implement the HTMLDocument interface, available using binding-specific methods. (This is the case whether or not the document in question is an HTML document or indeed whether it
contains any HTML elements at all.) Document objects must also implement the document-level interface of any other namespaces found in the document that the UA supports.
For example, if an HTML implementation also supports SVG, then the Document object implements both HTMLDocument and SVGDocument.
Because the HTMLDocument interface is now obtained using binding-specific casting methods instead of simply being the primary interface of the document object, it is no longer defined as inheriting from Document.
[NameGetter=OverrideBuiltins, ImplementedOn=Document]
interface HTMLDocument {
// resource metadata management
[PutForwards=href] readonly attribute Location location;
readonly attribute DOMString URL;
attribute DOMString domain;
readonly attribute DOMString referrer;
attribute DOMString cookie;
readonly attribute DOMString lastModified;
readonly attribute DOMString compatMode;
attribute DOMString charset;
readonly attribute DOMString characterSet;
readonly attribute DOMString defaultCharset;
readonly attribute DOMString readyState;
// DOM tree accessors
attribute DOMString title;
attribute DOMString dir;
attribute HTMLElement body;
readonly attribute HTMLCollection images;
readonly attribute HTMLCollection embeds;
readonly attribute HTMLCollection plugins;
readonly attribute HTMLCollection links;
readonly attribute HTMLCollection forms;
readonly attribute HTMLCollection scripts;
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NodeList getElementsByName(in DOMString elementName);
NodeList getElementsByClassName(in DOMString classNames);
NodeList getItems([Optional] in DOMString typeNames);
// dynamic markup insertion
attribute DOMString innerHTML;
HTMLDocument open([Optional] in DOMString type, [Optional] in DOMString replace);
WindowProxy open(in DOMString url, in DOMString name, in DOMString features, [Optional] in boolean replace);
void close();
void write([Variadic] in DOMString text);
void writeln([Variadic] in DOMString text);
// user interaction
Selection getSelection();
readonly attribute Element activeElement;
boolean hasFocus();
attribute DOMString designMode;
boolean execCommand(in DOMString commandId);
boolean execCommand(in DOMString commandId, in boolean showUI);
boolean execCommand(in DOMString commandId, in boolean showUI, in DOMString value);
boolean queryCommandEnabled(in DOMString commandId);
boolean queryCommandIndeterm(in DOMString commandId);
boolean queryCommandState(in DOMString commandId);
boolean queryCommandSupported(in DOMString commandId);
DOMString queryCommandValue(in DOMString commandId);
readonly attribute HTMLCollection commands;
// event handler DOM attributes
attribute Function onabort;
attribute Function onblur;
attribute Function oncanplay;
attribute Function oncanplaythrough;
attribute Function onchange;
attribute Function onclick;
attribute Function oncontextmenu;
attribute Function ondblclick;
attribute Function ondrag;
attribute Function ondragend;
attribute Function ondragenter;
attribute Function ondragleave;
attribute Function ondragover;
attribute Function ondragstart;
attribute Function ondrop;
attribute Function ondurationchange;
attribute Function onemptied;
attribute Function onended;
attribute Function onerror;
attribute Function onfocus;
attribute Function onformchange;
attribute Function onforminput;
attribute Function oninput;
attribute Function oninvalid;
attribute Function onkeydown;
attribute Function onkeypress;
attribute Function onkeyup;
attribute Function onload;
attribute Function onloadeddata;
attribute Function onloadedmetadata;
attribute Function onloadstart;
attribute Function onmousedown;
attribute Function onmousemove;
attribute Function onmouseout;
attribute Function onmouseover;
attribute Function onmouseup;
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attribute Function onmousewheel;
attribute Function onpause;
attribute Function onplay;
attribute Function onplaying;
attribute Function onprogress;
attribute Function onratechange;
attribute Function onreadystatechange;
attribute Function onscroll;
attribute Function onseeked;
attribute Function onseeking;
attribute Function onselect;
attribute Function onshow;
attribute Function onstalled;
attribute Function onsubmit;
attribute Function onsuspend;
attribute Function ontimeupdate;
attribute Function onvolumechange;
attribute Function onwaiting;
};
Since the HTMLDocument interface holds methods and attributes related to a number of disparate features, the members of this interface are described in various different sections.
3.2.2 Security
User agents must raise a SECURITY_ERR exception whenever any of the members of an HTMLDocument object are accessed by scripts whose effective script origin is not the same as the Document's effective script origin.
3.2.3 Resource metadata management
document . URL
Returns the document's address.
document . referrer
Returns the address of the Document from which the user navigated to this one, unless it was blocked or there was no such document, in which case it returns the empty string.
The noreferrer link type can be used to block the referrer.
The URL attribute must return the document's address.
The referrer attribute must return either the current address of the active document of the source browsing context at the time the navigation was started (that is, the page which navigated the browsing context to the current document), or the empty string if there is
no such originating page, or if the UA has been configured not to report referrers in this case, or if the navigation was initiated for a hyperlink with a noreferrer keyword.
In the case of HTTP, the referrer DOM attribute will match the Referer (sic) header that was sent when fetching the current page.
Typically user agents are configured to not report referrers in the case where the referrer uses an encrypted protocol and the current page does not (e.g. when navigating from an https: page to an http: page).
document . cookie [ = value ]
Returns the HTTP cookies that apply to the Document. If there are no cookies or cookies can't be applied to this resource, the empty string will be returned.
Can be set, to add a new cookie to the element's set of HTTP cookies.
If the Document has no browsing context an INVALID_STATE_ERR exception will be thrown. If the contents are sandboxed into a unique origin, a SECURITY_ERR exception will be thrown.
The cookie attribute represents the cookies of the resource.
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On getting, if the document is not associated with a browsing context then the user agent must raise an INVALID_STATE_ERR exception. Otherwise, if the sandboxed origin browsing context flag was set on the browsing context of the Document when the Document
was created, the user agent must raise a SECURITY_ERR exception. Otherwise, if the document's address does not use a server-based naming authority, it must return the empty string. Otherwise, it must first obtain the storage mutex and then return the same string
as the value of the Cookie HTTP header it would include if fetching the resource indicated by the document's address over HTTP, as per RFC 2109 section 4.3.4 or later specifications, excluding HTTP-only cookies. [RFC2109] [RFC2965]
On setting, if the document is not associated with a browsing context then the user agent must raise an INVALID_STATE_ERR exception. Otherwise, if the sandboxed origin browsing context flag was set on the browsing context of the Document when the Document
was created, the user agent must raise a SECURITY_ERR exception. Otherwise, if the document's address does not use a server-based naming authority, it must do nothing. Otherwise, the user agent must obtain the storage mutex and then act as it would when
processing cookies if it had just attempted to fetch the document's address over HTTP, and had received a response with a Set-Cookie header whose value was the specified value, as per RFC 2109 sections 4.3.1, 4.3.2, and 4.3.3 or later specifications, but without
overwriting the values of HTTP-only cookies. [RFC2109] [RFC2965]
This specification does not define what makes an HTTP-only cookie, and at the time of publication the editor is not aware of any reference for HTTP-only cookies. They are a feature supported by some Web browsers wherein an "httponly" parameter
added to the cookie string causes the cookie to be hidden from script.
Since the cookie attribute is accessible across frames, the path restrictions on cookies are only a tool to help manage which cookies are sent to which parts of the site, and are not in any way a security feature.
document . lastModified
Returns the date of the last modification to the document, as reported by the server, in the form "MM/DD/YYYY hh:mm:ss".
If the last modification date is not known, the current time is returned instead.
The lastModified attribute, on getting, must return the date and time of the Document's source file's last modification, in the user's local time zone, in the following format:
1. The month component of the date.
2. A U+002F SOLIDUS character ('/').
3. The day component of the date.
4. A U+002F SOLIDUS character ('/').
5. The year component of the date.
6. A U+0020 SPACE character.
7. The hours component of the time.
8. A U+003A COLON character (':').
9. The minutes component of the time.
10. A U+003A COLON character (':').
11. The seconds component of the time.
All the numeric components above, other than the year, must be given as two digits in the range U+0030 DIGIT ZERO to U+0039 DIGIT NINE representing the number in base ten, zero-padded if necessary. The year must be given as four or more digits in the range U
+0030 DIGIT ZERO to U+0039 DIGIT NINE representing the number in base ten, zero-padded if necessary.
The Document's source file's last modification date and time must be derived from relevant features of the networking protocols used, e.g. from the value of the HTTP Last-Modified header of the document, or from metadata in the file system for local files. If the
last modification date and time are not known, the attribute must return the current date and time in the above format.
document . compatMode
In a conforming document, returns the string "CSS1Compat". (In quirks mode documents, returns the string "BackCompat", but a conforming document can never trigger quirks mode.)
A Document is always set to one of three modes: no quirks mode, the default; quirks mode, used typically for legacy documents; and limited quirks mode, also known as "almost standards" mode. The mode is only ever changed from the default by the HTML
parser, based on the presence, absence, or value of the DOCTYPE string.
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The compatMode DOM attribute must return the literal string "CSS1Compat" unless the document has been set to quirks mode by the HTML parser, in which case it must instead return the literal string "BackCompat".
document . charset [ = value ]
Returns the document's character encoding.
Can be set, to dynamically change the document's character encoding.
New values that are not IANA-registered aliases supported by the user agent are ignored.
document . characterSet
Returns the document's character encoding.
document . defaultCharset
Returns what might be the user agent's default character encoding.
Documents have an associated character encoding. When a Document object is created, the document's character encoding must be initialized to UTF-16. Various algorithms during page loading affect this value, as does the charset setter. [IANACHARSET]
The charset DOM attribute must, on getting, return the preferred MIME name of the document's character encoding. On setting, if the new value is an IANA-registered alias for a character encoding supported by the user agent, the document's character encoding
must be set to that character encoding. (Otherwise, nothing happens.)
The characterSet DOM attribute must, on getting, return the preferred MIME name of the document's character encoding.
The defaultCharset DOM attribute must, on getting, return the preferred MIME name of a character encoding, possibly the user's default encoding, or an encoding associated with the user's current geographical location, or any arbitrary encoding name.
document . readyState
Returns "loading" while the Document is loading, and "complete" once it has loaded.
The readystatechange event fires on the Document object when this value changes.
Each document has a current document readiness. When a Document object is created, it must have its current document readiness set to the string "loading" if the document is associated with an HTML parser or an XML parser, or to the string "complete"
otherwise. Various algorithms during page loading affect this value. When the value is set, the user agent must fire a simple event called readystatechange at the Document object.
A Document is said to have an active parser if it is associated with an HTML parser or an XML parser that has not yet been stopped or aborted.
The readyState DOM attribute must, on getting, return the current document readiness.
3.2.4 DOM tree accessors
The html element of a document is the document's root element, if there is one and it's an html element, or null otherwise.
The head element of a document is the first head element that is a child of the html element, if there is one, or null otherwise.
document . title [ = value ]
Returns the document's title, as given by the title element.
Can be set, to update the document's title. If there is no head element, the new value is ignored.
In SVG documents, the SVGDocument interface's title attribute takes precedence.
The title element of a document is the first title element in the document (in tree order), if there is one, or null otherwise.
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The title attribute must, on getting, run the following algorithm:
1. If the root element is an svg element in the "http://www.w3.org/2000/svg" namespace, and the user agent supports SVG, then return the value that would have been returned by the DOM attribute of the same name on the SVGDocument interface. [SVG]
2. Otherwise, let value be a concatenation of the data of all the child text nodes of the title element, in tree order, or the empty string if the title element is null.
3. Replace any sequence of two or more consecutive space characters in value with a single U+0020 SPACE character.
4. Remove any leading or trailing space characters in value.
5. Return value.
On setting, the following algorithm must be run. Mutation events must be fired as appropriate.
1. If the root element is an svg element in the "http://www.w3.org/2000/svg" namespace, and the user agent supports SVG, then the setter must defer to the setter for the DOM attribute of the same name on the SVGDocument interface (if it is readonly, then
this will raise an exception). Stop the algorithm here. [SVG]
2. If the title element is null and the head element is null, then the attribute must do nothing. Stop the algorithm here.
3. If the title element is null, then a new title element must be created and appended to the head element.
4. The children of the title element (if any) must all be removed.
5. A single Text node whose data is the new value being assigned must be appended to the title element.
The title attribute on the HTMLDocument interface should shadow the attribute of the same name on the SVGDocument interface when the user agent supports both HTML and SVG. [SVG]
document . body [ = value ]
Returns the body element.
Can be set, to replace the body element.
If the new value is not a body or frameset element, this will throw a HIERARCHY_REQUEST_ERR exception.
The body element of a document is the first child of the html element that is either a body element or a frameset element. If there is no such element, it is null. If the body element is null, then when the specification requires that events be fired at "the body
element", they must instead be fired at the Document object.
The body attribute, on getting, must return the body element of the document (either a body element, a frameset element, or null). On setting, the following algorithm must be run:
1. If the new value is not a body or frameset element, then raise a HIERARCHY_REQUEST_ERR exception and abort these steps.
2. Otherwise, if the new value is the same as the body element, do nothing. Abort these steps.
3. Otherwise, if the body element is not null, then replace that element with the new value in the DOM, as if the root element's replaceChild() method had been called with the new value and the incumbent body element as its two arguments respectively, then
abort these steps.
4. Otherwise, the the body element is null. Append the new value to the root element.
document . images
Returns an HTMLCollection of the img elements in the Document.
document . embeds
document . plugins
Return an HTMLCollection of the embed elements in the Document.
document . links
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[PutForwards=value] readonly attribute DOMSettableTokenList item;
[PutForwards=value] readonly attribute DOMSettableTokenList itemprop;
readonly attribute HTMLPropertyCollection properties;
attribute DOMString content;
attribute HTMLElement subject;
// user interaction
attribute boolean hidden;
void click();
void scrollIntoView();
void scrollIntoView(in boolean top);
attribute long tabIndex;
void focus();
void blur();
attribute DOMString accessKey;
readonly attribute DOMString accessKeyLabel;
attribute boolean draggable;
attribute DOMString contentEditable;
readonly attribute boolean isContentEditable;
attribute HTMLMenuElement contextMenu;
attribute DOMString spellcheck;
// command API
readonly attribute DOMString commandType;
readonly attribute DOMString label;
readonly attribute DOMString icon;
readonly attribute boolean disabled;
readonly attribute boolean checked;
// styling
readonly attribute CSSStyleDeclaration style;
// event handler DOM attributes
attribute Function onabort;
attribute Function onblur;
attribute Function oncanplay;
attribute Function oncanplaythrough;
attribute Function onchange;
attribute Function onclick;
attribute Function oncontextmenu;
attribute Function ondblclick;
attribute Function ondrag;
attribute Function ondragend;
attribute Function ondragenter;
attribute Function ondragleave;
attribute Function ondragover;
attribute Function ondragstart;
attribute Function ondrop;
attribute Function ondurationchange;
attribute Function onemptied;
attribute Function onended;
attribute Function onerror;
attribute Function onfocus;
attribute Function onformchange;
attribute Function onforminput;
attribute Function oninput;
attribute Function oninvalid;
attribute Function onkeydown;
attribute Function onkeypress;
attribute Function onkeyup;
attribute Function onload;
attribute Function onloadeddata;
attribute Function onloadedmetadata;
attribute Function onloadstart;
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This specification doesn't preclude an element having multiple IDs, if other mechanisms (e.g. DOM Core methods) can set an element's ID in a way that doesn't conflict with the id attribute.
The id DOM attribute must reflect the id content attribute.
3.3.3.2 The title attribute
The title attribute represents advisory information for the element, such as would be appropriate for a tooltip. On a link, this could be the title or a description of the target resource; on an image, it could be the image credit or a description of the image; on a
paragraph, it could be a footnote or commentary on the text; on a citation, it could be further information about the source; and so forth. The value is text.
If this attribute is omitted from an element, then it implies that the title attribute of the nearest ancestor HTML element with a title attribute set is also relevant to this element. Setting the attribute overrides this, explicitly stating that the advisory information of any
ancestors is not relevant to this element. Setting the attribute to the empty string indicates that the element has no advisory information.
If the title attribute's value contains U+000A LINE FEED (LF) characters, the content is split into multiple lines. Each U+000A LINE FEED (LF) character represents a line break.
Caution is advised with respect to the use of newlines in title attributes.
For instance, the following snippet actually defines an abbreviation's expansion with a line break in it:
<p>My logs show that there was some interest in <abbr title="Hypertext
Transport Protocol">HTTP</abbr> today.</p>
Some elements, such as link, abbr, and input, define additional semantics for the title attribute beyond the semantics described above.
The title DOM attribute must reflect the title content attribute.
3.3.3.3 The lang and xml:lang attributes
The lang attribute (in no namespace) specifies the primary language for the element's contents and for any of the element's attributes that contain text. Its value must be a valid RFC 3066 language code, or the empty string. [RFC3066]
The lang attribute in the XML namespace is defined in XML. [XML]
If these attributes are omitted from an element, then the language of this element is the same as the language of its parent element, if any. Setting the attribute to the empty string indicates that the primary language is unknown.
The lang attribute in no namespace may be used on any HTML element.
The lang attribute in the XML namespace may be used on HTML elements in XML documents, as well as elements in other namespaces if the relevant specifications allow it (in particular, MathML and SVG allow lang attributes in the XML namespace to be specified
on their elements). If both the lang attribute in no namespace and the lang attribute in the XML namespace are specified on the same element, they must have exactly the same value when compared in an ASCII case-insensitive manner.
Authors must not use the lang attribute in the XML namespace in HTML documents. To ease migration to and from XHTML, authors may specify an attribute in no namespace with no prefix and with the literal localname "xml:lang" on HTML elements in HTML
documents, but such attributes must only be specified if a lang attribute in no namespace is also specified, and both attributes must have the same value when compared in an ASCII case-insensitive manner.
To determine the language of a node, user agents must look at the nearest ancestor element (including the element itself if the node is an element) that has a lang attribute in the XML namespace set or is an HTML element and has a lang in no namespace attribute
set. That attribute specifies the language of the node.
If both the lang attribute in no namespace and the lang attribute in the XML namespace are set on an element, user agents must use the lang attribute in the XML namespace, and the lang attribute in no namespace must be ignored for the purposes of determining
the element's language.
If no explicit language is given for the root element, but there is a document-wide default language set, then that is the language of the node.
If there is no document-wide default language, then language information from a higher-level protocol (such as HTTP), if any, must be used as the final fallback language. In the absence of any language information, the default value is unknown (the empty string).
If the resulting value is not a recognized language code, then it must be treated as an unknown language (as if the value was the empty string).
User agents may use the element's language to determine proper processing or rendering (e.g. in the selection of appropriate fonts or pronunciations, or for dictionary selection).
The lang DOM attribute must reflect the lang content attribute in no namespace.
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3.3.3.4 The xml:base attribute (XML only)
The xml:base attribute is defined in XML Base. [XMLBASE]
The xml:base attribute may be used on elements of XML documents. Authors must not use the xml:base attribute in HTML documents.
3.3.3.5 The dir attribute
The dir attribute specifies the element's text directionality. The attribute is an enumerated attribute with the keyword ltr mapping to the state ltr, and the keyword rtl mapping to the state rtl. The attribute has no defaults.
The processing of this attribute is primarily performed by the presentation layer. For example, the rendering section in this specification defines a mapping from this attribute to the CSS 'direction' and 'unicode-bidi' properties, and CSS defines rendering in terms of those
properties.
The directionality of an element, which is used in particular by the canvas element's text rendering API, is either 'ltr' or 'rtl'. If the user agent supports CSS and the 'direction' property on this element has a computed value of either 'ltr' or 'rtl', then that is the
directionality of the element. Otherwise, if the element is being rendered, then the directionality of the element is the directionality used by the presentation layer, potentially determined from the value of the dir attribute on the element. Otherwise, if the element's dir
attribute has the state ltr, the element's directionality is 'ltr' (left-to-right); if the attribute has the state rtl, the element's directionality is 'rtl' (right-to-left); and otherwise, the element's directionality is the same as its parent element, or 'ltr' if there is no parent element.
document . dir [ = value ]
Returns the html element's dir attribute's value, if any.
Can be set, to either "ltr" or "rtl", to replace the html element's dir attribute's value.
If there is no html element, returns the empty string and ignores new values.
The dir DOM attribute on an element must reflect the dir content attribute of that element, limited to only known values.
The dir DOM attribute on HTMLDocument objects must reflect the dir content attribute of the html element, if any, limited to only known values. If there is no such element, then the attribute must return the empty string and do nothing on setting.
Authors are strongly encouraged to use the dir attribute to indicate text direction rather than using CSS, since that way their documents will continue to render correctly even in the absence of CSS (e.g. as interpreted by search engines).
3.3.3.6 The class attribute
Every HTML element may have a class attribute specified.
The attribute, if specified, must have a value that is an unordered set of unique space-separated tokens representing the various classes that the element belongs to.
The classes that an HTML element has assigned to it consists of all the classes returned when the value of the class attribute is split on spaces.
Assigning classes to an element affects class matching in selectors in CSS, the getElementsByClassName() method in the DOM, and other such features.
Authors may use any value in the class attribute, but are encouraged to use the values that describe the nature of the content, rather than values that describe the desired presentation of the content.
The className and classList DOM attributes must both reflect the class content attribute.
3.3.3.7 The style attribute
All HTML elements may have the style content attribute set. If specified, the attribute must contain only a list of zero or more semicolon-separated (;) CSS declarations. [CSS]
In user agents that support CSS, the attribute's value must be parsed when the attribute is added or has its value changed, with its value treated as the body (the part inside the curly brackets) of a declaration block in a rule whose selector matches just the element on
which the attribute is set. All URLs in the value must be resolved relative to the element when the attribute is parsed. For the purposes of the CSS cascade, the attribute must be considered to be a 'style' attribute at the author level.
Documents that use style attributes on any of their elements must still be comprehensible and usable if those attributes were removed.
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In particular, using the style attribute to hide and show content, or to convey meaning that is otherwise not included in the document, is non-conforming. (To hide and show content, use the hidden attribute.)
element . style
Returns a CSSStyleDeclaration object for the element's style attribute.
The style DOM attribute must return a CSSStyleDeclaration whose value represents the declarations specified in the attribute, if present. Mutating the CSSStyleDeclaration object must create a style attribute on the element (if there isn't one already) and
then change its value to be a value representing the serialized form of the CSSStyleDeclaration object. [CSSOM]
In the following example, the words that refer to colors are marked up using the span element and the style attribute to make those words show up in the relevant colors in visual media.
<p>My sweat suit is <span style="color: green; background:
transparent">green</span> and my eyes are <span style="color: blue;
background: transparent">blue</span>.</p>
3.3.3.8 Embedding custom non-visible data
A custom data attribute is an attribute in no namespace whose name starts with the string "data-", has at least one character after the hyphen, is XML-compatible, and contains no characters in the range U+0041 .. U+005A (LATIN CAPITAL LETTER A .. LATIN
CAPITAL LETTER Z).
All attributes in HTML documents get lowercased automatically, so the restriction on uppercase letters doesn't affect such documents.
Custom data attributes are intended to store custom data private to the page or application, for which there are no more appropriate attributes or elements.
These attributes are not intended for use by software that is independent of the site that uses the attributes.
For instance, a site about music could annotate list items representing tracks in an album with custom data attributes containing the length of each track. This information could then be used by the site itself to allow the user to sort the list by track length, or to
filter the list for tracks of certain lengths.
<ol>
<li data-length="2m11s">Beyond The Sea</li>
...
</ol>
It would be inappropriate, however, for the user to use generic software not associated with that music site to search for tracks of a certain length by looking at this data.
This is because these attributes are intended for use by the site's own scripts, and are not a generic extension mechanism for publicly-usable metadata.
Every HTML element may have any number of custom data attributes specified, with any value.
element . dataset
Returns a DOMStringMap object for the element's data-* attributes.
The dataset DOM attribute provides convenient accessors for all the data-* attributes on an element. On getting, the dataset DOM attribute must return a DOMStringMap object, associated with the following algorithms, which expose these attributes on their
element:
The algorithm for getting the list of name-value pairs
1. Let list be an empty list of name-value pairs.
2. For each content attribute on the element whose first five characters are the string "data-", add a name-value pair to list whose name is the attribute's name with the first five character removed and whose value is the attribute's value.
3. Return list.
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The algorithm for setting names to certain values
1. Let name be the concatenation of the string data- and the name passed to the algorithm.
2. Let value be the value passed to the algorithm.
3. Set the value of the attribute with the name name, to the value value, replacing any previous value if the attribute already existed. If setAttribute() would have raised an exception when setting an attribute with the name name, then this must raise the
same exception.
The algorithm for deleting names
1. Let name be the concatenation of the string data- and the name passed to the algorithm.
2. Remove the attribute with the name name, if such an attribute exists. Do nothing otherwise.
If a Web page wanted an element to represent a space ship, e.g. as part of a game, it would have to use the class attribute along with data-* attributes:
<div class="spaceship" data-id="92432"
data-weapons="laser 2" data-shields="50%"
data-x="30" data-y="10" data-z="90">
<button class="fire"
onclick="spaceships[this.parentNode.dataset.id].fire()">
Fire
</button>
</div>
Authors should carefully design such extensions so that when the attributes are ignored and any associated CSS dropped, the page is still usable.
User agents must not derive any implementation behavior from these attributes or values. Specifications intended for user agents must not define these attributes to have any meaningful values.
3.4 Content models
All the elements in this specification have a defined content model, which describes what nodes are allowed inside the elements, and thus what the structure of an HTML document or fragment must look like.
As noted in the conformance and terminology sections, for the purposes of determining if an element matches its content model or not, CDATASection nodes in the DOM are treated as equivalent to Text nodes, and entity reference nodes are treated as if
they were expanded in place.
The space characters are always allowed between elements. User agents represent these characters between elements in the source markup as text nodes in the DOM. Empty text nodes and text nodes consisting of just sequences of those characters are considered
inter-element whitespace.
Inter-element whitespace, comment nodes, and processing instruction nodes must be ignored when establishing whether an element matches its content model or not, and must be ignored when following algorithms that define document and element semantics.
An element A is said to be preceded or followed by a second element B if A and B have the same parent node and there are no other element nodes or text nodes (other than inter-element whitespace) between them.
Authors must not use elements in the HTML namespace anywhere except where they are explicitly allowed, as defined for each element, or as explicitly required by other specifications. For XML compound documents, these contexts could be inside elements from
other namespaces, if those elements are defined as providing the relevant contexts.
The Atom specification defines the Atom content element, when its type attribute has the value xhtml, as requiring that it contains a single HTML div element. Thus, a div element is allowed in that context, even though this is not explicitly normatively
stated by this specification. [ATOM]
In addition, elements in the HTML namespace may be orphan nodes (i.e. without a parent node).
For example, creating a td element and storing it in a global variable in a script is conforming, even though td elements are otherwise only supposed to be used inside tr elements.
var data = {
name: "Banana",
cell: document.createElement('td'),
};
3.4.1 Kinds of content
Each element in HTML falls into zero or more categories that group elements with similar characteristics together. The following broad categories are used in this specification:
q Metadata content
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1. The paragraph that says "You can play with my cat simulator. object I'm quite proud of it.", where object is the object element.
2. The paragraph that says "To see the cat simulator, use one of the following links:".
3. The paragraph that says "Download simulator file".
4. The paragraph that says "Use online simulator".
5. The paragraph that says "Alternatively, upgrade to the Mellblom Browser.".
The first paragraph is overlapped by the other four. A user agent that supports the "cats.sim" resource will only show the first one, but a user agent that shows the fallback will confusingly show the first sentence of the first paragraph as if it was in the same
paragraph as the second one, and will show the last paragraph as if it was at the start of the second sentence of the first paragraph.
To avoid this confusion, explicit p elements can be used.
3.6 APIs in HTML documents
For HTML documents, and for HTML elements in HTML documents, certain APIs defined in DOM3 Core become case-insensitive or case-changing, as sometimes defined in DOM3 Core, and as summarized or required below. [DOM3CORE].
This does not apply to XML documents or to elements that are not in the HTML namespace despite being in HTML documents.
Element.tagName and Node.nodeName
These attributes must return element names converted to ASCII uppercase, regardless of the case with which they were created.
Document.createElement()
The canonical form of HTML markup is all-lowercase; thus, this method will lowercase the argument before creating the requisite element. Also, the element created must be in the HTML namespace.
This doesn't apply to Document.createElementNS(). Thus, it is possible, by passing this last method a tag name in the wrong case, to create an element that claims to have the tag name of an element defined in this specification, but doesn't
support its interfaces, because it really has another tag name not accessible from the DOM APIs.
Element.setAttribute()
Element.setAttributeNode()
Attribute names are converted to ASCII lowercase.
Specifically: when an attribute is set on an HTML element using Element.setAttribute(), the name argument must be converted to ASCII lowercase before the element is affected; and when an Attr node is set on an HTML element using Element.
setAttributeNode(), it must have its name converted to ASCII lowercase before the element is affected.
This doesn't apply to Document.setAttributeNS() and Document.setAttributeNodeNS().
Element.getAttribute()
Element.getAttributeNode()
Attribute names are converted to ASCII lowercase.
Specifically: When the Element.getAttribute() method or the Element.getAttributeNode() method is invoked on an HTML element, the name argument must be converted to ASCII lowercase before the element's attributes are examined.
This doesn't apply to Document.getAttributeNS() and Document.getAttributeNodeNS().
Document.getElementsByTagName()
Element.getElementsByTagName()
HTML elements match by lower-casing the argument before comparison, elements from other namespaces are treated as in XML (case-sensitively).
Specifically, these methods (but not their namespaced counterparts) must compare the given argument in a case-sensitive manner, but when looking at HTML elements, the argument must first be converted to ASCII lowercase.
Thus, in an HTML document with nodes in multiple namespaces, these methods will effectively be both case-sensitive and case-insensitive at the same time.
3.7 Interactions with XPath and XSLT
Implementations of XPath 1.0 that operate on HTML documents parsed or created in the manners described in this specification (e.g. as part of the document.evaluate() API) are affected as follows:
In addition to the cases where a name expression would match a node per XPath 1.0, a name expression must evaluate to matching a node when all the following conditions are also met:
q The name expression has no namespace.
q The name expression has local name that is a match for local.
q The expression is being tested against an element node.
q The element has local name local.
q The element is in the HTML namespace.
q The element's document is an HTML document.
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These requirements are a willful violation of the XPath 1.0 specification, motivated by desire to have implementations be compatible with legacy content while still supporting the changes that this specification introduces to HTML regarding which namespace
is used for HTML elements. [XPATH10]
XSLT 1.0 processors outputting to a DOM when the output method is "html" (either explicitly or via the defaulting rule in XSLT 1.0) are affected as follows:
If the transformation program outputs an element in no namespace, the processor must, prior to constructing the corresponding DOM element node, change the namespace of the element to the HTML namespace, ASCII-lowercase the element's local name, and ASCII-
lowercase the names of any non-namespaced attributes on the element.
This requirement is a willful violation of the XSLT 1.0 specification, required because this specification changes the namespaces and case-sensitivity rules of HTML in a manner that would otherwise be incompatible with DOM-based XSLT transformations.
(Processors that serialize the output are unaffected.) [XSLT10]
3.8 Dynamic markup insertion
APIs for dynamically inserting markup into the document interact with the parser, and thus their behavior, varies depending on whether they are used with HTML documents (and the HTML parser) or XHTML in XML documents (and the XML parser).
3.8.1 Controlling the input stream
The open() method comes in several variants with different numbers of arguments.
document = document . open( [ type [, replace ] ] )
Causes the Document to be replaced in-place, as if it was a new Document object, but reusing the previous object, which is then returned.
If the type argument is omitted or has the value "text/html", then the resulting Document has an HTML parser associated with it, which can be given data to parse using document.write(). Otherwise, all content passed to document.write()
will be parsed as plain text.
If the replace argument is absent or false, a new entry is added to the session history to represent this entry, and the previous entries for this Document are all collapsed into one entry with a new Document object.
The method has no effect if the Document is still being parsed.
window = document . open( url, name, features [, replace ] )
Works like the window.open() method.
document . close()
Closes the input stream that was opened by the document.open() method.
When called with two or fewer arguments, the method must act as follows:
1. Let type be the value of the first argument, if there is one, or "text/html" otherwise.
2. Let replace be true if there is a second argument and it is an ASCII case-insensitive match for the value "replace", and false otherwise.
3. If the document has an active parser that isn't a script-created parser, and the insertion point associated with that parser's input stream is not undefined (that is, it does point to somewhere in the input stream), then the method does nothing. Abort these steps and
return the Document object on which the method was invoked.
This basically causes document.open() to be ignored when it's called in an inline script found during the parsing of data sent over the network, while still letting it have an effect when called asynchronously or on a document that is itself being spoon-
fed using these APIs.
4. Unload the Document object, with the recycle parameter set to true. If the user refused to allow the document to be unloaded, then these steps must be aborted.
5. If the document has an active parser, then abort that parser, and throw away any pending content in the input stream.
6. Unregister all event listeners registered on the Document node and its descendants.
7. Remove any tasks associated with the Document in any task source.
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6. Finally, the method must return.
3.8.3 document.writeln()
document . writeln(text...)
Adds the given string(s) to the Document's input stream, followed by a newline character. If necessary, calls the open() method implicitly first.
This method throws an INVALID_ACCESS_ERR exception when invoked on XML documents.
The document.writeln(...) method, when invoked, must act as if the document.write() method had been invoked with the same argument(s), plus an extra argument consisting of a string containing a single line feed character (U+000A).
3.8.4 innerHTML
The innerHTML DOM attribute represents the markup of the node's contents.
document . innerHTML [ = value ]
Returns a fragment of HTML or XML that represents the Document.
Can be set, to replace the Document's contents with the result of parsing the given string.
In the case of XML documents, will throw a SYNTAX_ERR if the Document cannot be serialized to XML, or if the given string is not well-formed.
element . innerHTML [ = value ]
Returns a fragment of HTML or XML that represents the element's contents.
Can be set, to replace the contents of the element with nodes parsed from the given string.
In the case of XML documents, will throw a SYNTAX_ERR if the element cannot be serialized to XML, or if the given string is not well-formed.
On getting, if the node's document is an HTML document, then the attribute must return the result of running the HTML fragment serialization algorithm on the node; otherwise, the node's document is an XML document, and the attribute must return the result of running
the XML fragment serialization algorithm on the node instead (this might raise an exception instead of returning a string).
On setting, the following steps must be run:
1. If the node is an Element node, and the node's document is an HTML document, and the node is in a Document, and the node's document has an active parser, and the insertion point associated with that parser's input stream is not undefined (that is, it does
point to somewhere in the input stream), and the list of scripts that will execute when the document has finished parsing is not empty, then run the following substeps:
1. Let the script be the first element in the list of scripts that will execute when the document has finished parsing.
2. Loop: If the script is a script element without a src attribute, then execute the script.
3. If the script is not the last script in the list of scripts that will execute when the document has finished parsing, then let the script be the next script in that list, and return to the step marked loop.
4. Remove any scripts that were executed as part of this algorithm from the list of scripts that will execute when the document has finished parsing.
2. If the node's document is an HTML document: Invoke the HTML fragment parsing algorithm.
If the node's document is an XML document: Invoke the XML fragment parsing algorithm.
In either case, the algorithm must be invoked with the string being assigned into the innerHTML attribute as the input. If the node is an Element node, then, in addition, that element must be passed as the context element.
If this raises an exception, then abort these steps.
Otherwise, let new children be the nodes returned.
3. If the attribute is being set on a Document node, and that document has an active parser, then abort that parser.
4. Remove the child nodes of the node whose innerHTML attribute is being set, firing appropriate mutation events.
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5. If the attribute is being set on a Document node, let target document be that Document node. Otherwise, the attribute is being set on an Element node; let target document be the ownerDocument of that Element.
6. Set the ownerDocument of all the nodes in new children to the target document.
7. Append all the new children nodes to the node whose innerHTML attribute is being set, preserving their order, and firing mutation events as appropriate.
3.8.5 outerHTML
The outerHTML DOM attribute represents the markup of the element and its contents.
element . outerHTML [ = value ]
Returns a fragment of HTML or XML that represents the element and its contents.
Can be set, to replace the element with nodes parsed from the given string.
In the case of XML documents, will throw a SYNTAX_ERR if the element cannot be serialized to XML, or if the given string is not well-formed.
On getting, if the node's document is an HTML document, then the attribute must return the result of running the HTML fragment serialization algorithm on a fictional node whose only child is the node on which the attribute was invoked; otherwise, the node's document
is an XML document, and the attribute must return the result of running the XML fragment serialization algorithm on that fictional node instead (this might raise an exception instead of returning a string).
On setting, the following steps must be run:
1. Let target be the element whose outerHTML attribute is being set.
2. If target has no parent node, then abort these steps. There would be no way to obtain a reference to the nodes created even if the remaining steps were run.
3. If target's parent node is a Document object, throw a NO_MODIFICATION_ALLOWED_ERR exception and abort these steps.
4. Let parent be target's parent node, unless that is a DocumentFragment node, in which case let parent be an arbitrary body element.
5. If target's document is an HTML document: Invoke the HTML fragment parsing algorithm.
If target's document is an XML document: Invoke the XML fragment parsing algorithm.
In either case, the algorithm must be invoked with the string being assigned into the outerHTML attribute as the input, and parent as the context element.
If this raises an exception, then abort these steps.
Otherwise, let new children be targets returned.
6. Set the ownerDocument of all the nodes in new children to target's document.
7. Remove target from its parent node, firing mutation events as appropriate, and then insert in its place all the new children nodes, preserving their order, and again firing mutation events as appropriate.
3.8.6 insertAdjacentHTML()
element . insertAdjacentHTML(position, text)
Parsed the given string text as HTML or XML and inserts the resulting nodes into the tree in the position given by the position argument, as follows:
"beforebegin"
Before the element itself.
"afterbegin"
Just inside the element, before its first child.
"beforeend"
Just inside the element, after its last child.
"afterend"
After the element itself.
Throws a SYNTAX_ERR exception the arguments have invalid values (e.g., in the case of XML documents, if the given string is not well-formed).
Throws a NO_MODIFICATION_ALLOWED_ERR exception if the given position isn't possible (e.g. inserting elements after the root element of a Document).
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The href content attribute, if specified, must contain a valid URL.
A base element, if it has an href attribute, must come before any other elements in the tree that have attributes defined as taking URLs, except the html element (its manifest attribute isn't affected by base elements).
If there are multiple base elements with href attributes, all but the first are ignored.
The target attribute, if specified, must contain a valid browsing context name or keyword, which specifies which browsing context is to be used as the default when hyperlinks and forms in the Document cause navigation.
A base element, if it has a target attribute, must come before any elements in the tree that represent hyperlinks.
If there are multiple base elements with target attributes, all but the first are ignored.
The href and target DOM attributes must reflect the respective content attributes of the same name.
4.2.4 The link element
Categories
Metadata content.
If the itemprop attribute is present: flow content.
If the itemprop attribute is present: phrasing content.
Contexts in which this element may be used:
Where metadata content is expected.
In a noscript element that is a child of a head element.
If the itemprop attribute is present: where phrasing content is expected.
Content model:
Empty.
Content attributes:
Global attributes
href
rel
media
hreflang
type
sizes
Also, the title attribute has special semantics on this element.
DOM interface:
interface HTMLLinkElement : HTMLElement {
attribute boolean disabled;
attribute DOMString href;
attribute DOMString rel;
readonly attribute DOMTokenList relList;
attribute DOMString media;
attribute DOMString hreflang;
attribute DOMString type;
attribute DOMString sizes;
};
The LinkStyle interface must also be implemented by this element; the styling processing model defines how. [CSSOM]
The link element allows authors to link their document to other resources.
The destination of the link(s) is given by the href attribute, which must be present and must contain a valid URL. If the href attribute is absent, then the element does not define a link.
The types of link indicated (the relationships) are given by the value of the rel attribute, which must be present, and must have a value that is a set of space-separated tokens. The allowed values and their meanings are defined in a later section. If the rel attribute is
absent, or if the values used are not allowed according to the definitions in this specification, then the element does not define a link.
Two categories of links can be created using the link element. Links to external resources are links to resources that are to be used to augment the current document, and hyperlink links are links to other documents. The link types section defines whether a
particular link type is an external resource or a hyperlink. One element can create multiple links (of which some might be external resource links and some might be hyperlinks); exactly which and how many links are created depends on the keywords given in the rel
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attribute. User agents must process the links on a per-link basis, not a per-element basis.
Each link is handled separately. For instance, if there are two link elements with rel="stylesheet", they each count as a separate external resource, and each is affected by its own attributes independently.
The exact behavior for links to external resources depends on the exact relationship, as defined for the relevant link type. Some of the attributes control whether or not the external resource is to be applied (as defined below). For external resources that are represented
in the DOM (for example, style sheets), the DOM representation must be made available even if the resource is not applied. To obtain the resource, the user agent must resolve the URL given by the href attribute, relative to the element, and then fetch the resulting
absolute URL. User agents may opt to only fetch such resources when they are needed, instead of pro-actively fetching all the external resources that are not applied.
The semantics of the protocol used (e.g. HTTP) must be followed when fetching external resources. (For example, redirects must be followed and 404 responses must cause the external resource to not be applied.)
Fetching external resources must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined below) has been run.
The task that is queued by the networking task source once the resource has been fetched must, if the loads were successful, queue a task to fire a simple event called load at the link element; otherwise, if the resource or one of its subresources failed to completely
load for any reason (e.g. DNS error, HTTP 404 response, a connection being prematurely closed, unsupported Content-Type), it must instead queue a task to fire a simple event called error at the link element. Non-network errors in processing the resource or its
subresources (e.g. CSS parse errors, PNG decoding errors) are not failures for the purposes of this paragraph.
The task source for these tasks is the DOM manipulation task source.
Interactive user agents should provide users with a means to follow the hyperlinks created using the link element, somewhere within their user interface. The exact interface is not defined by this specification, but it should include the following information (obtained
from the element's attributes, again as defined below), in some form or another (possibly simplified), for each hyperlink created with each link element in the document:
q The relationship between this document and the resource (given by the rel attribute)
q The title of the resource (given by the title attribute).
q The address of the resource (given by the href attribute).
q The language of the resource (given by the hreflang attribute).
q The optimum media for the resource (given by the media attribute).
User agents may also include other information, such as the type of the resource (as given by the type attribute).
Hyperlinks created with the link element and its rel attribute apply to the whole page. This contrasts with the rel attribute of a and area elements, which indicates the type of a link whose context is given by the link's location within the document.
The media attribute says which media the resource applies to. The value must be a valid media query. [MQ]
If the link is a hyperlink then the media attribute is purely advisory, and describes for which media the document in question was designed.
However, if the link is an external resource link, then the media attribute is prescriptive. The user agent must apply the external resource to views while their state match the listed media and the other relevant conditions apply, and must not apply them otherwise.
The external resource might have further restrictions defined within that limit its applicability. For example, a CSS style sheet might have some @media blocks. This specification does not override such further restrictions or requirements.
The default, if the media attribute is omitted, is all, meaning that by default links apply to all media.
The hreflang attribute on the link element has the same semantics as the hreflang attribute on hyperlink elements.
The type attribute gives the MIME type of the linked resource. It is purely advisory. The value must be a valid MIME type, optionally with parameters. [RFC2046]
For external resource links, the type attribute is used as a hint to user agents so that they can avoid fetching resources they do not support. If the attribute is present, then the user agent must assume that the resource is of the given type. If the attribute is omitted, but
the external resource link type has a default type defined, then the user agent must assume that the resource is of that type. If the UA does not support the given MIME type for the given link relationship, then the UA should not fetch the resource; if the UA does support
the given MIME type for the given link relationship, then the UA should fetch the resource. If the attribute is omitted, and the external resource link type does not have a default type defined, but the user agent would fetch the resource if the type was known and
supported, then the user agent should fetch the resource under the assumption that it will be supported.
User agents must not consider the type attribute authoritative — upon fetching the resource, user agents must not use the type attribute to determine its actual type. Only the actual type (as defined in the next paragraph) is used to determine whether to apply the
resource, not the aforementioned assumed type.
If the external resource link type defines rules for processing the resource's Content-Type metadata, then those rules apply. Otherwise, if the resource is expected to be an image, user agents may apply the image sniffing rules, with the official type being the type
determined from the resource's Content-Type metadata, and use the resulting sniffed type of the resource as if it was the actual type. Otherwise, if neither of these conditions apply or if the user agent opts not to apply the image sniffing rules, then the user agent must
use the resource's Content-Type metadata to determine the type of the resource. If there is no type metadata, but the external resource link type has a default type defined, then the user agent must assume that the resource is of that type.
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The stylesheet link type defines rules for processing the resource's Content-Type metadata.
Once the user agent has established the type of the resource, the user agent must apply the resource if it is of a supported type and the other relevant conditions apply, and must ignore the resource otherwise.
If a document contains style sheet links labeled as follows:
<link rel="stylesheet" href="A" type="text/plain">
<link rel="stylesheet" href="B" type="text/css">
<link rel="stylesheet" href="C">
...then a compliant UA that supported only CSS style sheets would fetch the B and C files, and skip the A file (since text/plain is not the MIME type for CSS style sheets).
For files B and C, it would then check the actual types returned by the server. For those that are sent as text/css, it would apply the styles, but for those labeled as text/plain, or any other type, it would not.
If one the two files was returned without a Content-Type metadata, or with a syntactically incorrect type like Content-Type: "null", then the default type for stylesheet links would kick in. Since that default type is text/css, the style sheet would
nonetheless be applied.
The title attribute gives the title of the link. With one exception, it is purely advisory. The value is text. The exception is for style sheet links, where the title attribute defines alternative style sheet sets.
The title attribute on link elements differs from the global title attribute of most other elements in that a link without a title does not inherit the title of the parent element: it merely has no title.
The sizes attribute is used with the icon link type. The attribute must not be specified on link elements that do not have a rel attribute that specifies the icon keyword.
Some versions of HTTP defined a Link: header, to be processed like a series of link elements. If supported, for the purposes of ordering links defined by HTTP headers must be assumed to come before any links in the document, in the order that they were given in
the HTTP entity header. (URIs in these headers are to be processed and resolved according to the rules given in HTTP; the rules of this specification don't apply.) [HTTP] [RFC2068]
The DOM attributes href, rel, media, hreflang, and type, and sizes each must reflect the respective content attributes of the same name.
The DOM attribute relList must reflect the rel content attribute.
The DOM attribute disabled only applies to style sheet links. When the link element defines a style sheet link, then the disabled attribute behaves as defined for the alternative style sheets DOM. For all other link elements it always return false and does nothing
on setting.
4.2.5 The meta element
Categories
Metadata content.
If the itemprop attribute is present: flow content.
If the itemprop attribute is present: phrasing content.
Contexts in which this element may be used:
If the charset attribute is present, or if the element's http-equiv attribute is in the Encoding declaration state: in a head element.
If the http-equiv attribute is present and in the Encoding declaration state: in a head element.
If the http-equiv attribute is present but not in the Encoding declaration state: in a noscript element that is a child of a head element.
If the name attribute is present: where metadata content is expected.
If the itemprop attribute is present: where phrasing content is expected.
Content model:
Empty.
Content attributes:
Global attributes
name
http-equiv
content
charset
DOM interface:
interface HTMLMetaElement : HTMLElement {
attribute DOMString name;
attribute DOMString httpEquiv;
};
The meta element represents various kinds of metadata that cannot be expressed using the title, base, link, style, and script elements.
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When an author uses a new type not defined by either this specification or the Wiki page, conformance checkers should offer to add the value to the Wiki, with the details described above, with the "proposal" status.
This specification does not define how new values will get approved. It is expected that the Wiki will have a community that addresses this.
Metadata names whose values are to be URLs must not be proposed or accepted. Links must be represented using the link element, not the meta element.
4.2.5.3 Pragma directives
When the http-equiv attribute is specified on a meta element, the element is a pragma directive.
The http-equiv attribute is an enumerated attribute. The following table lists the keywords defined for this attribute. The states given in the first cell of the rows with keywords give the states to which those keywords map. Some of the keywords are non-conforming,
as noted in the last column.
State Keywords Notes
Content Language content-language Non-conforming
Encoding declaration content-type
Default style default-style
Refresh refresh
When a meta element is inserted into the document, if its http-equiv attribute is present and represents one of the above states, then the user agent must run the algorithm appropriate for that state, as described in the following list:
Content language state (http-equiv="content-language")
This non-conforming pragma sets the document-wide default language. Until the pragma is successfully processed, there is no document-wide default language.
1. If another meta element with an http-equiv attribute in the Content Language state has already been successfully processed (i.e. when it was inserted the user agent processed it and reached the last step of this list of steps), then abort these steps.
2. If the meta element has no content attribute, or if that attribute's value is the empty string, then abort these steps.
3. Let input be the value of the element's content attribute.
4. Let position point at the first character of input.
5. Skip whitespace.
6. Collect a sequence of characters that are neither space characters nor a U+002C COMMA character (",").
7. Let the document-wide default language be the string that resulted from the previous step.
For meta elements with an http-equiv attribute in the Content Language state, the content attribute must have a value consisting of a valid RFC 3066 language code. [RFC3066]
This pragma is not exactly equivalent to the HTTP Content-Language header, for instance it only supports one language. [HTTP]
Encoding declaration state (http-equiv="content-type")
The Encoding declaration state is just an alternative form of setting the charset attribute: it is a character encoding declaration. This state's user agent requirements are all handled by the parsing section of the specification.
For meta elements with an http-equiv attribute in the Encoding declaration state, the content attribute must have a value that is an ASCII case-insensitive match for a string that consists of: the literal string "text/html;", optionally followed by any number
of space characters, followed by the literal string "charset=", followed by the character encoding name of the character encoding declaration.
If the document contains a meta element with an http-equiv attribute in the Encoding declaration state, then the document must not contain a meta element with the charset attribute present.
The Encoding declaration state may be used in HTML documents, but elements with an http-equiv attribute in that state must not be used in XML documents.
Default style state (http-equiv="default-style")
This pragma sets the name of the default alternative style sheet set.
1. If the meta element has no content attribute, or if that attribute's value is the empty string, then abort these steps.
2. Set the preferred style sheet set to the value of the element's content attribute. [CSSOM]
Refresh state (http-equiv="refresh")
This pragma acts as timed redirect.
1. If another meta element with an http-equiv attribute in the Refresh state has already been successfully processed (i.e. when it was inserted the user agent processed it and reached the last step of this list of steps), then abort these steps.
2. If the meta element has no content attribute, or if that attribute's value is the empty string, then abort these steps.
3. Let input be the value of the element's content attribute.
4. Let position point at the first character of input.
5. Skip whitespace.
6. Collect a sequence of characters in the range U+0030 DIGIT ZERO to U+0039 DIGIT NINE, and parse the resulting string using the rules for parsing non-negative integers. If the sequence of characters collected is the empty string, then no number will have
been parsed; abort these steps. Otherwise, let time be the parsed number.
7. Collect a sequence of characters in the range U+0030 DIGIT ZERO to U+0039 DIGIT NINE and U+002E FULL STOP ("."). Ignore any collected characters.
8. Skip whitespace.
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q The value must be a valid character encoding name, and must be the preferred name for that encoding. [IANACHARSET]
q The character encoding declaration must be serialized without the use of character references or character escapes of any kind.
q The element containing the character encoding declaration must be serialized completely within the first 512 bytes of the document.
q There can only be one character encoding declaration in the document.
If an HTML document does not start with a BOM, and if its encoding is not explicitly given by Content-Type metadata, then the character encoding used must be an ASCII-compatible character encoding, and, in addition, if that encoding isn't US-ASCII itself, then the
encoding must be specified using a meta element with a charset attribute or a meta element with an http-equiv attribute in the Encoding declaration state.
If an HTML document contains a meta element with a charset attribute or a meta element with an http-equiv attribute in the Encoding declaration state, then the character encoding used must be an ASCII-compatible character encoding.
Authors should not use JIS-X-0208 (JIS_C6226-1983), JIS-X-0212 (JIS_X0212-1990), encodings based on ISO-2022, and encodings based on EBCDIC. Authors should not use UTF-32. Authors must not use the CESU-8, UTF-7, BOCU-1 and SCSU encodings.
[RFC1345] [RFC1468] [RFC2237] [RFC1554] [RFC1922] [RFC1557] [UTF32] [CESU8] [UTF7] [BOCU1] [SCSU]
Authors are encouraged to use UTF-8. Conformance checkers may advise against authors using legacy encodings.
Authoring tools should default to using UTF-8 for newly-created documents.
Using non-UTF-8 encodings can have unexpected results on form submission and URL encodings, which use the document's character encoding by default.
In XHTML, the XML declaration should be used for inline character encoding information, if necessary.
4.2.6 The style element
Categories
Metadata content.
If the scoped attribute is present: flow content.
Contexts in which this element may be used:
If the scoped attribute is absent: where metadata content is expected.
If the scoped attribute is absent: in a noscript element that is a child of a head element.
If the scoped attribute is present: where flow content is expected, but before any other flow content other than other style elements and inter-element whitespace.
Content model:
Depends on the value of the type attribute.
Content attributes:
Global attributes
media
type
scoped
Also, the title attribute has special semantics on this element.
DOM interface:
interface HTMLStyleElement : HTMLElement {
attribute boolean disabled;
attribute DOMString media;
attribute DOMString type;
attribute boolean scoped;
};
The LinkStyle interface must also be implemented by this element; the styling processing model defines how. [CSSOM]
The style element allows authors to embed style information in their documents. The style element is one of several inputs to the styling processing model. The element does not represent content for the user.
If the type attribute is given, it must contain a valid MIME type, optionally with parameters, that designates a styling language. [RFC2046] If the attribute is absent, the type defaults to text/css. [RFC2138]
When examining types to determine if they support the language, user agents must not ignore unknown MIME parameters — types with unknown parameters must be assumed to be unsupported.
The media attribute says which media the styles apply to. The value must be a valid media query. [MQ] User agents must apply the styles to views while their state match the listed media, and must not apply them otherwise.
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The styles might be further limited in scope, e.g. in CSS with the use of @media blocks. This specification does not override such further restrictions or requirements.
The default, if the media attribute is omitted, is all, meaning that by default styles apply to all media.
The scoped attribute is a boolean attribute. If set, it indicates that the styles are intended just for the subtree rooted at the style element's parent element, as opposed to the whole Document.
If the scoped attribute is present, then the user agent must apply the specified style information only to the style element's parent element (if any), and that element's child nodes. Otherwise, the specified styles must, if applied, be applied to the entire document.
The title attribute on style elements defines alternative style sheet sets. If the style element has no title attribute, then it has no title; the title attribute of ancestors does not apply to the style element. [CSSOM]
The title attribute on style elements, like the title attribute on link elements, differs from the global title attribute in that a style block without a title does not inherit the title of the parent element: it merely has no title.
All descendant elements must be processed, according to their semantics, before the style element itself is evaluated. For styling languages that consist of pure text, user agents must evaluate style elements by passing the concatenation of the contents of all the
text nodes that are direct children of the style element (not any other nodes such as comments or elements), in tree order, to the style system. For XML-based styling languages, user agents must pass all the child nodes of the style element to the style system.
All URLs found by the styling language's processor must be resolved, relative to the element (or as defined by the styling language), when the processor is invoked.
Once the element has been evaluated, if it had no subresources or once all the subresources it uses have been fetched, the user agent must queue a task to fire a simple event called load at the style element. If the resource has a subresource that fails to
completely load for any reason (e.g. DNS error, HTTP 404 response, the connection being prematurely closed, unsupported Content-Type), the user agent must instead queue a task to fire a simple event called error at the style element. Non-network errors in the
processing of the element's contents or its subresources (e.g. CSS parse errors) are not failures for the purposes of this paragraph. The style element must delay the load event of the element's document until one of these tasks has been queued.
The task source for these tasks is the DOM manipulation task source.
This specification does not specify a style system, but CSS is expected to be supported by most Web browsers. [CSS]
The media, type and scoped DOM attributes must reflect the respective content attributes of the same name.
The DOM disabled attribute behaves as defined for the alternative style sheets DOM.
4.2.7 Styling
The link and style elements can provide styling information for the user agent to use when rendering the document. The DOM Styling specification specifies what styling information is to be used by the user agent and how it is to be used. [CSSOM]
The style and link elements implement the LinkStyle interface. [CSSOM]
For style elements, if the user agent does not support the specified styling language, then the sheet attribute of the element's LinkStyle interface must return null. Similarly, link elements that do not represent external resource links that contribute to the styling
processing model (i.e. that do not have a stylesheet keyword in their rel attribute), and link elements whose specified resource has not yet been fetched, or is not in a supported styling language, must have their LinkStyle interface's sheet attribute return null.
Otherwise, the LinkStyle interface's sheet attribute must return a StyleSheet object with the following properties: [CSSOM]
The style sheet type
The style sheet type must be the same as the style's specified type. For style elements, this is the same as the type content attribute's value, or text/css if that is omitted. For link elements, this is the Content-Type metadata of the specified resource.
The style sheet location
For link elements, the location must be the result of resolving the URL given by the element's href content attribute, relative to the element, or the empty string if that fails. For style elements, there is no location.
The style sheet media
The media must be the same as the value of the element's media content attribute, or the empty string, if the attribute is omitted.
The style sheet title
The title must be the same as the value of the element's title content attribute, if the attribute is present and has a non-empty value. If the attribute is absent or its value is the empty string, then the style sheet does not have a title (it is the empty string). The
title is used for defining alternative style sheet sets.
The style sheet alternate flag
For link elements, true if the link is an alternative stylesheet. In all other cases, false.
The disabled DOM attribute on link and style elements must return false and do nothing on setting, if the sheet attribute of their LinkStyle interface is null. Otherwise, it must return the value of the StyleSheet interface's disabled attribute on getting, and
forward the new value to that same attribute on setting.
The rules for handling alternative style sheets are defined in the CSS object model specification. [CSSOM]
4.3 Scripting
Scripts allow authors to add interactivity to their documents.
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Authors are encouraged to use declarative alternatives to scripting where possible, as declarative mechanisms are often more maintainable, and many users disable scripting.
For example, instead of using script to show or hide a section to show more details, the details element could be used.
Authors are also encouraged to make their applications degrade gracefully in the absence of scripting support.
For example, if an author provides a link in a table header to dynamically resort the table, the link could also be made to function without scripts by requesting the sorted table from the server.
4.3.1 The script element
Categories
Metadata content.
Flow content.
Phrasing content.
Contexts in which this element may be used:
Where metadata content is expected.
Where phrasing content is expected.
Content model:
If there is no src attribute, depends on the value of the type attribute.
If there is a src attribute, the element must be either empty or contain only script documentation.
Content attributes:
Global attributes
src
async
defer
type
charset
DOM interface:
interface HTMLScriptElement : HTMLElement {
attribute DOMString src;
attribute boolean async;
attribute boolean defer;
attribute DOMString type;
attribute DOMString charset;
attribute DOMString text;
};
The script element allows authors to include dynamic script and data blocks in their documents. The element does not represent content for the user.
When used to include dynamic scripts, the scripts may either be embedded inline or may be imported from an external file using the src attribute. If the language is not that described by "text/javascript", then the type attribute must be present. If the type
attribute is present, its value must be the type of the script's language.
When used to include data blocks, the data must be embedded inline, the format of the data must be given using the type attribute, and the src attribute must not be specified.
The type attribute gives the language of the script or format of the data. If the attribute is present, its value must be a valid MIME type, optionally with parameters. The charset parameter must not be specified. (The default, which is used if the attribute is absent, is
"text/javascript".) [RFC2046]
The src attribute, if specified, gives the address of the external script resource to use. The value of the attribute must be a valid URL identifying a script resource of the type given by the type attribute, if the attribute is present, or of the type "text/javascript", if
the attribute is absent.
The charset attribute gives the character encoding of the external script resource. The attribute must not be specified if the src attribute is not present. If the attribute is set, its value must be a valid character encoding name, must be the preferred name for that
encoding, and must match the encoding given in the charset parameter of the Content-Type metadata of the external file, if any. [IANACHARSET]
The async and defer attributes are boolean attributes that indicate how the script should be executed.
There are three possible modes that can be selected using these attributes. If the async attribute is present, then the script will be executed asynchronously, as soon as it is available. If the async attribute is not present but the defer attribute is present, then the
script is executed when the page has finished parsing. If neither attribute is present, then the script is fetched and executed immediately, before the user agent continues parsing the page. The exact processing details for these attributes is described below.
The defer attribute may be specified even if the async attribute is specified, to cause legacy Web browsers that only support defer (and not async) to fall back to the defer behavior instead of the synchronous blocking behavior that is the default.
Changing the src, type, charset, async, and defer attributes dynamically has no direct effect; these attribute are only used at specific times described below (namely, when the element is inserted into the document).
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This is where the script is compiled and actually executed.
3. Fire a simple event called load at the script element.
The DOM attributes src, type, charset, async, and defer, each must reflect the respective content attributes of the same name.
script . text [ = value ]
Returns the contents of the element, ignoring child nodes that aren't text nodes.
Can be set, to replace the element's children with the given value.
The DOM attribute text must return a concatenation of the contents of all the text nodes that are direct children of the script element (ignoring any other nodes such as comments or elements), in tree order. On setting, it must act the same way as the textContent
DOM attribute.
In this example, two script elements are used. One embeds an external script, and the other includes some data.
<script src="game-engine.js"></script>
<script type="text/x-game-map">
........U.........e
o............A....e
.....A.....AAA....e
.A..AAA...AAAAA...e
</script>
The data in this case might be used by the script to generate the map of a video game. The data doesn't have to be used that way, though; maybe the map data is actually embedded in other parts of the page's markup, and the data block here is just used by
the site's search engine to help users who are looking for particular features in their game maps.
When inserted using the document.write() method, script elements execute (typically synchronously), but when inserted using innerHTML and outerHTML attributes, they do not execute at all.
4.3.1.1 Scripting languages
A user agent is said to support the scripting language if the script block's type matches the MIME type of a scripting language that the user agent implements.
The following lists some MIME types and the languages to which they refer:
application/ecmascript
application/javascript
application/x-ecmascript
application/x-javascript
text/ecmascript
text/javascript
text/javascript1.0
text/javascript1.1
text/javascript1.2
text/javascript1.3
text/javascript1.4
text/javascript1.5
text/jscript
text/livescript
text/x-ecmascript
text/x-javascript
JavaScript. [ECMA262]
text/javascript;e4x=1
JavaScript with ECMAScript for XML. [ECMA357]
User agents may support other MIME types and other languages.
When examining types to determine if they support the language, user agents must not ignore unknown MIME parameters — types with unknown parameters must be assumed to be unsupported.
4.3.1.2 Inline documentation for external scripts
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If a script element's src attribute is specified, then the contents of the script element, if any, must be such that the value of the DOM text attribute, which is derived from the element's contents, matches the documentation production in the following ABNF, the
character set for which is Unicode. [ABNF]
documentation = *( *( space / tab / comment ) [ line-comment ] newline )
comment = slash star *( not-star / star not-slash ) 1*star slash
line-comment = slash slash *not-newline
; characters
tab = %x0009 ; U+0009 TAB
newline = %x000A ; U+000A LINE FEED
space = %x0020 ; U+0020 SPACE
star = %x002A ; U+002A ASTERISK
slash = %x002F ; U+002F SOLIDUS
not-newline = %x0000-0009 / %x000B-10FFFF
; a Unicode character other than U+000A LINE FEED
not-star = %x0000-0029 / %x002B-10FFFF
; a Unicode character other than U+002A ASTERISK
not-slash = %x0000-002E / %x0030-10FFFF
; a Unicode character other than U+002F SOLIDUS
This allows authors to include documentation, such as license information or API information, inside their documents while still referring to external script files. The syntax is constrained so that authors don't accidentally include what looks like valid script while
also providing a src attribute.
<script src="cool-effects.js">
// create new instances using:
// var e = new Effect();
// start the effect using .play, stop using .stop:
// e.play();
// e.stop();
</script>
4.3.2 The noscript element
Categories
Metadata content.
Flow content.
Phrasing content.
Contexts in which this element may be used:
In a head element of an HTML document, if there are no ancestor noscript elements.
Where phrasing content is expected in HTML documents, if there are no ancestor noscript elements.
Content model:
When scripting is disabled, in a head element: in any order, zero or more link elements, zero or more style elements, and zero or more meta elements.
When scripting is disabled, not in a head element: transparent, but there must be no noscript element descendants.
Otherwise: text that conforms to the requirements given in the prose.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.
The noscript element represents nothing if scripting is enabled, and represents its children if scripting is disabled. It is used to present different markup to user agents that support scripting and those that don't support scripting, by affecting how the document is
parsed.
When used in HTML documents, the allowed content model is as follows:
In a head element, if scripting is disabled for the noscript element
The noscript element must contain only link, style, and meta elements.
In a head element, if scripting is enabled for the noscript element
The noscript element must contain only text, except that invoking the HTML fragment parsing algorithm with the noscript element as the context element and the text contents as the input must result in a list of nodes that consists only of link, style, and
meta elements, and no parse errors.
Outside of head elements, if scripting is disabled for the noscript element
The noscript element's content model is transparent, with the additional restriction that a noscript element must not have a noscript element as an ancestor (that is, noscript can't be nested).
Outside of head elements, if scripting is enabled for the noscript element
The noscript element must contain only text, except that the text must be such that running the following algorithm results in a conforming document with no noscript elements and no script elements, and such that no step in the algorithm causes an
HTML parser to flag a parse error:
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4. Let current section be the last child section of the current current section.
5. Go back to the substep labeled finding the deepest child.
When exiting a sectioning content element or a sectioning root element
The current outlinee is the element being exited.
Let current section be the first section in the outline of the current outlinee element.
Skip to the next step in the overall set of steps. (The walk is over.)
If the current outlinee is null.
Do nothing.
When entering a heading content element
If the current section has no heading, let the element being entered be the heading for the current section.
Otherwise, if the element being entered has a rank equal to or greater than the heading of the last section of the outline of the current outlinee, then create a new section and append it to the outline of the current outlinee element, so that this new
section is the new last section of that outline. Let current section be that new section. Let the element being entered be the new heading for the current section.
Otherwise, run these substeps:
1. Let candidate section be current section.
2. If the element being entered has a rank lower than the rank of the heading of the candidate section, then create a new section, and append it to candidate section. (This does not change which section is the last section in the outline.) Let
current section be this new section. Let the element being entered be the new heading for the current section. Abort these substeps.
3. Let new candidate section be the section that contains candidate section in the outline of current outlinee.
4. Let candidate section be new candidate section.
5. Return to step 2.
Push the element being entered onto the stack. (This causes the algorithm to skip any descendants of the element.)
Recall that h1 has the highest rank, and h6 has the lowest rank.
Otherwise
Do nothing.
In addition, whenever you exit a node, after doing the steps above, if current section is not null, associate the node with the section current section.
5. If the current outlinee is null, then there was no sectioning content element or sectioning root element in the DOM. There is no outline. Abort these steps.
6. Associate any nodes that were not associated with a section in the steps above with current outlinee as their section.
7. Associate all nodes with the heading of the section with which they are associated, if any.
8. If current outlinee is the body element, then the outline created for that element is the outline of the entire document.
The tree of sections created by the algorithm above, or a proper subset thereof, must be used when generating document outlines, for example when generating tables of contents.
When creating an interactive table of contents, entries should jump the user to the relevant sectioning content element, if the section was created for a real element in the original document, or to the relevant heading content element, if the section in the tree was
generated for a heading in the above process.
Selecting the first section of the document therefore always takes the user to the top of the document, regardless of where the first heading in the body is to be found.
The following JavaScript function shows how the tree walk could be implemented. The root argument is the root of the tree to walk, and the enter and exit arguments are callbacks that are called with the nodes as they are entered and exited. [ECMA262]
function (root, enter, exit) {
var node = root;
start: while (node) {
enter(node);
if (node.firstChild) {
node = node.firstChild;
continue start;
}
while (node) {
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target
ping
rel
media
hreflang
type
DOM interface:
[Stringifies=href] interface HTMLAnchorElement : HTMLElement {
attribute DOMString href;
attribute DOMString target;
attribute DOMString ping;
attribute DOMString rel;
readonly attribute DOMTokenList relList;
attribute DOMString media;
attribute DOMString hreflang;
attribute DOMString type;
// URL decomposition attributes
attribute DOMString protocol;
attribute DOMString host;
attribute DOMString hostname;
attribute DOMString port;
attribute DOMString pathname;
attribute DOMString search;
attribute DOMString hash;
};
If the a element has an href attribute, then it represents a hyperlink (a hypertext anchor).
If the a element has no href attribute, then the element represents a placeholder for where a link might otherwise have been placed, if it had been relevant.
The target, ping, rel, media, hreflang, and type attributes must be omitted if the href attribute is not present.
If a site uses a consistent navigation tool bar on every page, then the link that would normally link to the page itself could be marked up using an a element:
<nav>
<ul>
<li> <a href="/">Home</a> </li>
<li> <a href="/news">News</a> </li>
<li> <a>Examples</a> </li>
<li> <a href="/legal">Legal</a> </li>
</ul>
</nav>
Interactive user agents should allow users to follow hyperlinks created using the a element. The href, target and ping attributes decide how the link is followed. The rel, media, hreflang, and type attributes may be used to indicate to the user the likely nature
of the target resource before the user follows the link.
The activation behavior of a elements that represent hyperlinks is to run the following steps:
1. If the DOMActivate event in question is not trusted (i.e. a click() method call was the reason for the event being dispatched), and the a element's target attribute is such that applying the rules for choosing a browsing context given a browsing context
name, using the value of the target attribute as the browsing context name, would result in there not being a chosen browsing context, then raise an INVALID_ACCESS_ERR exception and abort these steps.
2. If the target of the click event is an img element with an ismap attribute specified, then server-side image map processing must be performed, as follows:
1. If the DOMActivate event was dispatched as the result of a real pointing-device-triggered click event on the img element, then let x be the distance in CSS pixels from the left edge of the image's left border, if it has one, or the left edge of the image
otherwise, to the location of the click, and let y be the distance in CSS pixels from the top edge of the image's top border, if it has one, or the top edge of the image otherwise, to the location of the click. Otherwise, let x and y be zero.
2. Let the hyperlink suffix be a U+003F QUESTION MARK character, the value of x expressed as a base-ten integer using ASCII digits (U+0030 DIGIT ZERO to U+0039 DIGIT NINE), a U+002C COMMA character, and the value of y expressed as a base-
ten integer using ASCII digits.
3. Finally, the user agent must follow the hyperlink defined by the a element. If the steps above defined a hyperlink suffix, then take that into account when following the hyperlink.
The DOM attributes href, ping, target, rel, media, hreflang, and type, must reflect the respective content attributes of the same name.
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Global attributes
datetime
DOM interface:
interface HTMLTimeElement : HTMLElement {
attribute DOMString dateTime;
readonly attribute Date date;
readonly attribute Date time;
readonly attribute Date timezone;
};
The time element represents a precise date and/or a time in the proleptic Gregorian calendar. [GREGORIAN]
This element is intended as a way to encode modern dates and times in a machine-readable way so that user agents can offer to add them to the user's calendar. For example, adding birthday reminders or scheduling events.
The time element is not intended for encoding times for which a precise date or time cannot be established. For example, it would be inappropriate for encoding times like "one millisecond after the big bang", "the early part of the Jurassic period", or "a
winter around 250 BCE".
For dates before the introduction of the Gregorian calendar, authors are encouraged to not use the time element, or else to be very careful about converting dates and times from the period to the Gregorian calendar. This is complicated by the manner in
which the Gregorian calendar was phased in, which occurred at different times in different countries, ranging from partway through the 16th century all the way to early in the 20th.
The datetime attribute, if present, must contain a valid date or time string that identifies the date or time being specified.
If the datetime attribute is not present, then the date or time must be specified in the content of the element, such that the element's textContent is a valid date or time string in content, and the date, if any, must be expressed using the Gregorian calendar.
If the datetime attribute is present, then the element may be empty, in which case the user agent should convey the attribute's value to the user when rendering the element.
The time element can be used to encode dates, for example in Microformats. The following shows a hypothetical way of encoding an event using a variant on hCalendar that uses the time element:
<div class="vevent">
<a class="url" href="http://www.web2con.com/">http://www.web2con.com/</a>
<span class="summary">Web 2.0 Conference</span>:
<time class="dtstart" datetime="2007-10-05">October 5</time> -
<time class="dtend" datetime="2007-10-20">19</time>,
at the <span class="location">Argent Hotel, San Francisco, CA</span>
</div>
The time element is not necessary for encoding dates or times. In the following snippet, the time is encoded using time, so that it can be restyled (e.g. using XBL2) to match local conventions, while the year is not marked up at all, since marking it up would
not be particularly useful.
<p>I usually have a snack at <time>16:00</time>.</p>
<p>I've liked model trains since at least 1983.</p>
Using a styling technology that supports restyling times, the first paragraph from the above snippet could be rendered as follows:
I usually have a snack at 4pm.
Or it could be rendered as follows:
I usually have a snack at 16h00.
The dateTime DOM attribute must reflect the datetime content attribute.
User agents, to obtain the date, time, and time zone represented by a time element, must follow these steps:
1. If the datetime attribute is present, then use the rules to parse a date or time string with the flag in attribute from the value of that attribute, and let the result be result.
2. Otherwise, use the rules to parse a date or time string with the flag in content from the element's textContent, and let the result be result.
3. If result is empty (because the parsing failed), then the date is unknown, the time is unknown, and the time zone is unknown.
4. Otherwise: if result contains a date, then that is the date; if result contains a time, then that is the time; and if result contains a time zone, then the time zone is the element's time zone. (A time zone can only be present if both a date and a time are also present.)
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Categories
Flow content.
Phrasing content.
Contexts in which these elements may be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.
The sup element represents a superscript and the sub element represents a subscript.
These elements must be used only to mark up typographical conventions with specific meanings, not for typographical presentation for presentation's sake. For example, it would be inappropriate for the sub and sup elements to be used in the name of the LaTeX
document preparation system. In general, authors should use these elements only if the absence of those elements would change the meaning of the content.
When the sub element is used inside a var element, it represents the subscript that identifies the variable in a family of variables.
<p>The coordinate of the <var>i</var>th point is
(<var>x<sub><var>i</var></sub></var>, <var>y<sub><var>i</var></sub></var>).
For example, the 10th point has coordinate
(<var>x<sub>10</sub></var>, <var>y<sub>10</sub></var>).</p>
In certain languages, superscripts are part of the typographical conventions for some abbreviations.
<p>The most beautiful women are
<span lang="fr"><abbr>M<sup>lle</sup></abbr> Gwendoline</span> and
<span lang="fr"><abbr>M<sup>me</sup></abbr> Denise</span>.</p>
Mathematical expressions often use subscripts and superscripts. Authors are encouraged to use MathML for marking up mathematics, but authors may opt to use sub and sup if detailed mathematical markup is not desired. [MathML]
<var>E</var>=<var>m</var><var>c</var><sup>2</sup>
f(<var>x</var>, <var>n</var>) = log<sub>4</sub><var>x</var><sup><var>n</var></sup>
4.6.18 The span element
Categories
Flow content.
Phrasing content.
Contexts in which this element may be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
interface HTMLSpanElement : HTMLElement {};
The span element doesn't mean anything on its own, but can be useful when used together with other attributes, e.g. class, lang, or dir. It represents its children.
4.6.19 The i element
Categories
Flow content.
Phrasing content.
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Another case where the b element is appropriate is in marking up the lede (or lead) sentence or paragraph. The following example shows how a BBC article about kittens adopting a rabbit as their own could be marked up:
<article>
<h2>Kittens 'adopted' by pet rabbit</h2>
<p><b>Six abandoned kittens have found an unexpected new
mother figure — a pet rabbit.</b></p>
<p>Veterinary nurse Melanie Humble took the three-week-old
kittens to her Aberdeen home.</p>
[...]
The b element should be used as a last resort when no other element is more appropriate. In particular, headings should use the h1 to h6 elements, stress emphasis should use the em element, importance should be denoted with the strong element, and text marked
or highlighted should use the mark element.
The following would be incorrect usage:
<p><b>WARNING!</b> Do not frob the barbinator!</p>
In the previous example, the correct element to use would have been strong, not b.
Style sheets can be used to format b elements, just like any other element can be restyled. Thus, it is not the case that content in b elements will necessarily be boldened.
4.6.21 The bdo element
Categories
Flow content.
Phrasing content.
Contexts in which this element may be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
Also, the dir global attribute has special semantics on this element.
DOM interface:
Uses HTMLElement.
The bdo element represents explicit text directionality formatting control for its children. It allows authors to override the Unicode bidi algorithm by explicitly specifying a direction override. [BIDI]
Authors must specify the dir attribute on this element, with the value ltr to specify a left-to-right override and with the value rtl to specify a right-to-left override.
If the element has the dir attribute set to the exact value ltr, then for the purposes of the bidi algorithm, the user agent must act as if there was a U+202D LEFT-TO-RIGHT OVERRIDE character at the start of the element, and a U+202C POP DIRECTIONAL
FORMATTING at the end of the element.
If the element has the dir attribute set to the exact value rtl, then for the purposes of the bidi algorithm, the user agent must act as if there was a U+202E RIGHT-TO-LEFT OVERRIDE character at the start of the element, and a U+202C POP DIRECTIONAL
FORMATTING at the end of the element.
The requirements on handling the bdo element for the bidi algorithm may be implemented indirectly through the style layer. For example, an HTML+CSS user agent should implement these requirements by implementing the CSS 'unicode-bidi' property. [CSS]
4.6.22 The ruby element
Categories
Flow content.
Phrasing content.
Contexts in which this element may be used:
Where phrasing content is expected.
Content model:
One or more groups of: phrasing content followed either by a single rt element, or an rp element, an rt element, and another rp element.
Content attributes:
Global attributes
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<dt>Shopkeeper
<dd>Sorry, <span title="This is, of course, a lie.">we're
closing for lunch</span>.
</dialog>
For longer annotations, the a element should be used, pointing to an element later in the document. The convention is that the contents of the link be a number in square brackets.
In this example, a footnote in the dialog links to a paragraph below the dialog. The paragraph then reciprocally links back to the dialog, allowing the user to return to the location of the footnote.
<dialog>
<dt>Announcer
<dd>Number 16: The <i>hand</i>.
<dt>Interviewer
<dd>Good evening. I have with me in the studio tonight Mr
Norman St John Polevaulter, who for the past few years has
been contradicting people. Mr Polevaulter, why <em>do</em>
you contradict people?
<dt>Norman
<dd>I don't. <a href="#fn1" id="r1">[1]</a>
<dt>Interviewer
<dd>You told me you did!
</dialog>
<section>
<p id="fn1"><a href="#r1">[1]</a> This is, naturally, a lie,
but paradoxically if it were true he could not say so without
contradicting the interviewer and thus making it false.</p>
</section>
For side notes, longer annotations that apply to entire sections of the text rather than just specific words or sentences, the aside element should be used.
In this example, a sidebar is given after a dialog, giving some context to the dialog.
<dialog>
<dt>Customer
<dd>I will not buy this record, it is scratched.
<dt>Shopkeeper
<dd>I'm sorry?
<dt>Customer
<dd>I will not buy this record, it is scratched.
<dt>Shopkeeper
<dd>No no no, this's'a tobacconist's.
</dialog>
<aside>
<p>In 1970, the British Empire lay in ruins, and foreign
nationalists frequented the streets — many of them Hungarians
(not the streets — the foreign nationals). Sadly, Alexander
Yalt has been publishing incompetently-written phrase books.
</aside>
For figures or tables, footnotes can be included in the relevant legend or caption element, or in surrounding prose.
In this example, a table has cells with footnotes that are given in prose. A figure element is used to give a single legend to the combination of the table and its footnotes.
<figure>
<legend>Table 1. Alternative activities for knights.</legend>
<table>
<tr>
<th> Activity
<th> Location
<th> Cost
<tr>
<td> Dance
<td> Wherever possible
<td> £0<sup><a href="#fn1">1</a></sup>
<tr>
<td> Routines, chorus scenes<sup><a href="#fn2">2</a></sup>
<td> Undisclosed
<td> Undisclosed
<tr>
<td> Dining<sup><a href="#fn3">3</a></sup>
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<img src="promblem-packed-action.png" alt="ROUGH COPY! Promblem-Packed Action!">
<p>...was aired. A lawyer, armed with a Bigger Notebook, launched a
preemptive strike using snowballs. A complete copy of the trailer is
included with Exhibit B.</p>
<figure>
<img src="ex-a.png" alt="Two squiggles on a dirty piece of paper.">
<legend>Exhibit A. The alleged <cite>rough copy</cite> comic.</legend>
</figure>
<figure>
<video src="ex-b.mov"></video>
<legend>Exhibit B. The <code>Rough Copy</cite> trailer.</legend>
</figure>
<p>The case was resolved out of court.</p>
Here, a part of a poem is marked up using figure.
<figure>
<p>'Twas brillig, and the slithy toves<br>
Did gyre and gimble in the wabe;<br>
All mimsy were the borogoves,<br>
And the mome raths outgrabe.</p>
<legend><cite>Jabberwocky</cite> (first verse). Lewis Carroll, 1832-98</legend>
</figure>
In this example, which could be part of a much larger work discussing a castle, the figure has three images in it.
<figure>
<img src="castle1423.jpeg" title="Etching. Anonymous, ca. 1423."
alt="The castle has one tower, and a tall wall around it.">
<img src="castle1858.jpeg" title="Oil-based paint on canvas. Maria Towle, 1858."
alt="The castle now has two towers and two walls.">
<img src="castle1999.jpeg" title="Film photograph. Peter Jankle, 1999."
alt="The castle lies in ruins, the original tower all that remains in one piece.">
<legend>The castle through the ages: 1423, 1858, and 1999 respectively.</legend>
</figure>
4.8.2 The img element
Categories
Flow content.
Phrasing content.
Embedded content.
If the element has a usemap attribute: Interactive content.
Contexts in which this element may be used:
Where embedded content is expected.
Content model:
Empty.
Content attributes:
Global attributes
alt
src
usemap
ismap
width
height
DOM interface:
[NamedConstructor=Image(),
NamedConstructor=Image(in unsigned long width),
NamedConstructor=Image(in unsigned long width, in unsigned long height)]
interface HTMLImageElement : HTMLElement {
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The task source for these tasks is the DOM manipulation task source.
What an img element represents depends on the src attribute and the alt attribute.
If the src attribute is set and the alt attribute is set to the empty string
The image is either decorative or supplemental to the rest of the content, redundant with some other information in the document.
If the image is available and the user agent is configured to display that image, then the element represents the image specified by the src attribute.
Otherwise, the element represents nothing, and may be omitted completely from the rendering. User agents may provide the user with a notification that an image is present but has been omitted from the rendering.
If the src attribute is set and the alt attribute is set to a value that isn't empty
The image is a key part of the content; the alt attribute gives a textual equivalent or replacement for the image.
If the image is available and the user agent is configured to display that image, then the element represents the image specified by the src attribute.
Otherwise, the element represents the text given by the alt attribute. User agents may provide the user with a notification that an image is present but has been omitted from the rendering.
If the src attribute is set and the alt attribute is not
The image might be a key part of the content, and there is no textual equivalent of the image available.
In a conforming document, the absence of the alt attribute indicates that the image is a key part of the content but that a textual replacement for the image was not available when the image was generated.
If the image is available, the element represents the image specified by the src attribute.
If the image is not available or if the user agent is not configured to display the image, then the user agent should display some sort of indicator that there is an image that is not being rendered, and may, if requested by the user, or if so configured, or when
required to provide contextual information in response to navigation, provide caption information for the image, derived as follows:
1. If the image has a title attribute whose value is not the empty string, then the value of that attribute is the caption information; abort these steps.
2. If the image is the child of a figure element that has a child legend element, then the contents of the first such legend element are the caption information; abort these steps.
3. Run the algorithm to create the outline for the document.
4. If the img element did not end up associated with a heading in the outline, or if there are any other images that are lacking an alt attribute and that are associated with the same heading in the outline as the img element in question, then there is no
caption information; abort these steps.
5. The caption information is the heading with which the image is associated according to the outline.
If the src attribute is not set and either the alt attribute is set to the empty string or the alt attribute is not set at all
The element represents nothing.
Otherwise
The element represents the text given by the alt attribute.
The alt attribute does not represent advisory information. User agents must not present the contents of the alt attribute in the same way as content of the title attribute.
User agents may always provide the user with the option to display any image, or to prevent any image from being displayed. User agents may also apply image analysis heuristics to help the user make sense of the image when the user is unable to make direct use of
the image, e.g. due to a visual disability or because they are using a text terminal with no graphics capabilities.
The contents of img elements, if any, are ignored for the purposes of rendering.
The usemap attribute, if present, can indicate that the image has an associated image map.
The ismap attribute, when used on an element that is a descendant of an a element with an href attribute, indicates by its presence that the element provides access to a server-side image map. This affects how events are handled on the corresponding a element.
The ismap attribute is a boolean attribute. The attribute must not be specified on an element that does not have an ancestor a element with an href attribute.
The img element supports dimension attributes.
The DOM attributes alt, src, useMap, and isMap each must reflect the respective content attributes of the same name.
image . width [ = value ]
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image . height [ = value ]
These attributes return the actual rendered dimensions of the image, or zero if the dimensions are not known.
They can be set, to change the corresponding content attributes.
image . complete
Returns true if the image has been downloaded, decoded, and found to be valid; otherwise, returns false.
image = new Image( [ width [, height ] ] )
Returns a new img element, with the width and height attributes set to the values passed in the relevant arguments, if applicable.
The DOM attributes width and height must return the rendered width and height of the image, in CSS pixels, if the image is being rendered, and is being rendered to a visual medium; or else the intrinsic width and height of the image, in CSS pixels, if the image is
available but not being rendered to a visual medium; or else 0, if the image is not available or its dimensions are not known. [CSS]
On setting, they must act as if they reflected the respective content attributes of the same name.
The DOM attribute complete must return true if the user agent has fetched the image specified in the src attribute, and it is in a supported image type (i.e. it was decoded without fatal errors), even if the final task queued by the networking task source for the fetching
of the image resource has not yet been processed. Otherwise, the attribute must return false.
The value of complete can thus change while a script is executing.
Three constructors are provided for creating HTMLImageElement objects (in addition to the factory methods from DOM Core such as createElement()): Image(), Image(width), and Image(width, height). When invoked as constructors, these must return
a new HTMLImageElement object (a new img element). If the width argument is present, the new object's width content attribute must be set to width. If the height argument is also present, the new object's height content attribute must be set to height.
A single image can have different appropriate alternative text depending on the context.
In each of the following cases, the same image is used, yet the alt text is different each time. The image is the coat of arms of the Canton Geneva in Switzerland.
Here it is used as a supplementary icon:
<p>I lived in <img src="carouge.svg" alt=""> Carouge.</p>
Here it is used as an icon representing the town:
<p>Home town: <img src="carouge.svg" alt="Carouge"></p>
Here it is used as part of a text on the town:
<p>Carouge has a coat of arms.</p>
<p><img src="carouge.svg" alt="The coat of arms depicts a lion, sitting in front of a tree."></p>
<p>It is used as decoration all over the town.</p>
Here it is used as a way to support a similar text where the description is given as well as, instead of as an alternative to, the image:
<p>Carouge has a coat of arms.</p>
<p><img src="carouge.svg" alt=""></p>
<p>The coat of arms depicts a lion, sitting in front of a tree.
It is used as decoration all over the town.</p>
Here it is used as part of a story:
<p>He picked up the folder and a piece of paper fell out.</p>
<p><img src="carouge.svg" alt="Shaped like a shield, the paper had a
red background, a green tree, and a yellow lion with its tongue
hanging out and whose tail was shaped like an S."></p>
<p>He stared at the folder. S! The answer he had been looking for all
this time was simply the letter S! How had he not seen that before? It all
came together now. The phone call where Hector had referred to a lion's tail,
the time Marco had stuck his tongue out...</p>
Here it is not known at the time of publication what the image will be, only that it will be a coat of arms of some kind, and thus no replacement text can be provided, and instead only a brief caption for the image is provided, in the title attribute:
<p>The last user to have uploaded a coat of arms uploaded this one:</p>
<p><img src="last-uploaded-coat-of-arms.cgi" title="User-uploaded coat of arms."></p>
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Any other attribute that has no namespace (see prose).
DOM interface:
interface HTMLEmbedElement : HTMLElement {
attribute DOMString src;
attribute DOMString type;
attribute DOMString width;
attribute DOMString height;
};
Depending on the type of content instantiated by the embed element, the node may also support other interfaces.
The embed element represents an integration point for an external (typically non-HTML) application or interactive content.
The src attribute gives the address of the resource being embedded. The attribute, if present, must contain a valid URL.
The type attribute, if present, gives the MIME type of the plugin to instantiate. The value must be a valid MIME type, optionally with parameters. If both the type attribute and the src attribute are present, then the type attribute must specify the same type as the
explicit Content-Type metadata of the resource given by the src attribute. [RFC2046]
When the element is created with neither a src attribute nor a type attribute, and when attributes are removed such that neither attribute is present on the element anymore, and when the element has a media element ancestor, and when the element has an ancestor
object element that is not showing its fallback content, any plugins instantiated for the element must be removed, and the embed element represents nothing.
When the sandboxed plugins browsing context flag is set on the browsing context for which the embed element's document is the active document, then the user agent must render the embed element in a manner that conveys that the plugin was disabled. The user
agent may offer the user the option to override the sandbox and instantiate the plugin anyway; if the user invokes such an option, the user agent must act as if the sandboxed plugins browsing context flag was not set for the purposes of this element.
Plugins are disabled in sandboxed browsing contexts because they might not honor the restrictions imposed by the sandbox (e.g. they might allow scripting even when scripting in the sandbox is disabled). User agents should convey the danger of overriding the
sandbox to the user if an option to do so is provided.
When the element is created with a src attribute, and whenever the src attribute is subsequently set, and whenever the type attribute is set or removed while the element has a src attribute, if the element is not in a sandboxed browsing context, not a descendant of
a media element, and not a descendant of an object element that is not showing its fallback content, the user agent must resolve the value of the attribute, relative to the element, and if that is successful, should fetch the resulting absolute URL. The task that is
queued by the networking task source once the resource has been fetched must find and instantiate an appropriate plugin based on the content's type, and hand that plugin the content of the resource, replacing any previously instantiated plugin for the element.
Fetching the resource must delay the load event of the element's document.
The type of the content being embedded is defined as follows:
1. If the element has a type attribute, and that attribute's value is a type that a plugin supports, then the value of the type attribute is the content's type.
2. Otherwise, if the <path> component of the URL of the specified resource (after any redirects) matches a pattern that a plugin supports, then the content's type is the type that that plugin can handle.
For example, a plugin might say that it can handle resources with <path> components that end with the four character string ".swf".
3. Otherwise, if the specified resource has explicit Content-Type metadata, then that is the content's type.
4. Otherwise, the content has no type and there can be no appropriate plugin for it.
Whether the resource is fetched successfully or not (e.g. whether the response code was a 2xx code or equivalent) must be ignored when determining the resource's type and when handing the resource to the plugin.
This allows servers to return data for plugins even with error responses (e.g. HTTP 500 Internal Server Error codes can still contain plugin data).
When the element is created with a type attribute and no src attribute, and whenever the type attribute is subsequently set, so long as no src attribute is set, and whenever the src attribute is removed when the element has a type attribute, if the element is not in
a sandboxed browsing context, user agents should find and instantiate an appropriate plugin based on the value of the type attribute.
Any (namespace-less) attribute may be specified on the embed element, so long as its name is XML-compatible and contains no characters in the range U+0041 .. U+005A (LATIN CAPITAL LETTER A LATIN CAPITAL LETTER Z).
All attributes in HTML documents get lowercased automatically, so the restriction on uppercase letters doesn't affect such documents.
The user agent should pass the names and values of all the attributes of the embed element that have no namespace to the plugin used, when it is instantiated.
If the plugin instantiated for the embed element supports a scriptable interface, the HTMLEmbedElement object representing the element should expose that interface while the element is instantiated.
The embed element has no fallback content. If the user agent can't find a suitable plugin, then the user agent must use a default plugin. (This default could be as simple as saying "Unsupported Format".)
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The embed element supports dimension attributes.
The DOM attributes src and type each must reflect the respective content attributes of the same name.
4.8.5 The object element
Categories
Flow content.
Phrasing content.
Embedded content.
If the element has a usemap attribute: Interactive content.
Listed, submittable, form-associated element.
Contexts in which this element may be used:
Where embedded content is expected.
Content model:
Zero or more param elements, then, transparent.
Content attributes:
Global attributes
data
type
name
usemap
form
width
height
DOM interface:
interface HTMLObjectElement : HTMLElement {
attribute DOMString data;
attribute DOMString type;
attribute DOMString name;
attribute DOMString useMap;
readonly attribute HTMLFormElement form;
attribute DOMString width;
attribute DOMString height;
readonly attribute Document contentDocument;
readonly attribute WindowProxy contentWindow;
};
Depending on the type of content instantiated by the object element, the node may also support other interfaces.
The object element can represent an external resource, which, depending on the type of the resource, will either be treated as an image, as a nested browsing context, or as an external resource to be processed by a plugin.
The data attribute, if present, specifies the address of the resource. If present, the attribute must be a valid URL.
The type attribute, if present, specifies the type of the resource. If present, the attribute must be a valid MIME type, optionally with parameters. [RFC2046]
One or both of the data and type attributes must be present.
The name attribute, if present, must be a valid browsing context name. The given value is used to name the nested browsing context, if applicable.
When the element is created, and subsequently whenever the classid attribute changes or is removed, or, if the classid attribute is not present, whenever the data attribute changes or is removed, or, if neither classid attribute nor the data attribute are present,
whenever the type attribute changes or is removed, the user agent must run the following steps to determine what the object element represents:
1. If the element has an ancestor media element, or has an ancestor object element that is not showing its fallback content, then jump to the last step in the overall set of steps (fallback).
2. If the classid attribute is present, and has a value that isn't the empty string, then: if the user agent can find a plugin suitable according to the value of the classid attribute, and plugins aren't being sandboxed, then that plugin should be used, and the value of
the data attribute, if any, should be passed to the plugin. If no suitable plugin can be found, or if the plugin reports an error, jump to the last step in the overall set of steps (fallback).
3. If the data attribute is present, then:
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If the element has a controls attribute: Interactive content.
Contexts in which this element may be used:
Where embedded content is expected.
Content model:
If the element has a src attribute: transparent, but with no media element descendants.
If the element does not have a src attribute: one or more source elements, then, transparent, but with no media element descendants.
Content attributes:
Global attributes
src
autobuffer
autoplay
loop
controls
DOM interface:
[NamedConstructor=Audio(),
NamedConstructor=Audio(in DOMString src)]
interface HTMLAudioElement : HTMLMediaElement {
// no members
};
An audio element represents a sound or audio stream.
Content may be provided inside the audio element. User agents should not show this content to the user; it is intended for older Web browsers which do not support audio, so that legacy audio plugins can be tried, or to show text to the users of these older browser
informing them of how to access the audio contents.
In particular, this content is not fallback content intended to address accessibility concerns. To make audio content accessible to the deaf or to those with other physical or cognitive disabilities, authors are expected to provide alternative media streams and/
or to embed accessibility aids (such as transcriptions) into their media streams.
The audio element is a media element whose media data is ostensibly audio data.
The src, autobuffer, autoplay, loop, and controls attributes are the attributes common to all media elements.
When an audio element is potentially playing, it must have its audio data played synchronized with the current playback position, at the specified volume with the specified mute state.
When an audio element is not potentially playing, audio must not play for the element.
audio = new Audio( [ url ] )
Returns a new audio element, with the src attribute set to the value passed in the argument, if applicable.
Two constructors are provided for creating HTMLAudioElement objects (in addition to the factory methods from DOM Core such as createElement()): Audio() and Audio(src). When invoked as constructors, these must return a new HTMLAudioElement
object (a new audio element). The element must have its autobuffer attribute set to the literal value "autobuffer". If the src argument is present, the object created must have its src content attribute set to the provided value, and the user agent must invoke the
object's resource selection algorithm before returning.
4.8.9 The source element
Categories
None.
Contexts in which this element may be used:
As a child of a media element, before any flow content.
Content model:
Empty.
Content attributes:
Global attributes
src
type
media
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DOM interface:
interface HTMLSourceElement : HTMLElement {
attribute DOMString src;
attribute DOMString type;
attribute DOMString media;
};
The source element allows authors to specify multiple media resources for media elements. It does not represent anything on its own.
The src attribute gives the address of the media resource. The value must be a valid URL. This attribute must be present.
The type attribute gives the type of the media resource, to help the user agent determine if it can play this media resource before fetching it. If specified, its value must be a MIME type. The codecs parameter may be specified and might be necessary to specify
exactly how the resource is encoded. [RFC2046] [RFC4281]
The following list shows some examples of how to use the codecs= MIME parameter in the type attribute.
H.264 Simple baseline profile video (main and extended video compatible) level 3 and Low-Complexity AAC audio in MP4 container
<source src='video.mp4' type='video/mp4; codecs="avc1.42E01E, mp4a.40.2"'>
H.264 Extended profile video (baseline-compatible) level 3 and Low-Complexity AAC audio in MP4 container
<source src='video.mp4' type='video/mp4; codecs="avc1.58A01E, mp4a.40.2"'>
H.264 Main profile video level 3 and Low-Complexity AAC audio in MP4 container
<source src='video.mp4' type='video/mp4; codecs="avc1.4D401E, mp4a.40.2"'>
H.264 'High' profile video (incompatible with main, baseline, or extended profiles) level 3 and Low-Complexity AAC audio in MP4 container
<source src='video.mp4' type='video/mp4; codecs="avc1.64001E, mp4a.40.2"'>
MPEG-4 Visual Simple Profile Level 0 video and Low-Complexity AAC audio in MP4 container
<source src='video.mp4' type='video/mp4; codecs="mp4v.20.8, mp4a.40.2"'>
MPEG-4 Advanced Simple Profile Level 0 video and Low-Complexity AAC audio in MP4 container
<source src='video.mp4' type='video/mp4; codecs="mp4v.20.240, mp4a.40.2"'>
MPEG-4 Visual Simple Profile Level 0 video and AMR audio in 3GPP container
<source src='video.3gp' type='video/3gpp; codecs="mp4v.20.8, samr"'>
Theora video and Vorbis audio in Ogg container
<source src='video.ogv' type='video/ogg; codecs="theora, vorbis"'>
Theora video and Speex audio in Ogg container
<source src='video.ogv' type='video/ogg; codecs="theora, speex"'>
Vorbis audio alone in Ogg container
<source src='audio.ogg' type='audio/ogg; codecs=vorbis'>
Speex audio alone in Ogg container
<source src='audio.spx' type='audio/ogg; codecs=speex'>
FLAC audio alone in Ogg container
<source src='audio.oga' type='audio/ogg; codecs=flac'>
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Dirac video and Vorbis audio in Ogg container
<source src='video.ogv' type='video/ogg; codecs="dirac, vorbis"'>
Theora video and Vorbis audio in Matroska container
<source src='video.mkv' type='video/x-matroska; codecs="theora, vorbis"'>
The media attribute gives the intended media type of the media resource, to help the user agent determine if this media resource is useful to the user before fetching it. Its value must be a valid media query. [MQ]
If a source element is inserted as a child of a media element that is in a Document and whose networkState has the value NETWORK_EMPTY, the user agent must invoke the media element's resource selection algorithm.
The DOM attributes src, type, and media must reflect the respective content attributes of the same name.
4.8.10 Media elements
Media elements implement the following interface:
interface HTMLMediaElement : HTMLElement {
// error state
readonly attribute MediaError error;
// network state
attribute DOMString src;
readonly attribute DOMString currentSrc;
const unsigned short NETWORK_EMPTY = 0;
const unsigned short NETWORK_IDLE = 1;
const unsigned short NETWORK_LOADING = 2;
const unsigned short NETWORK_LOADED = 3;
const unsigned short NETWORK_NO_SOURCE = 4;
readonly attribute unsigned short networkState;
attribute boolean autobuffer;
readonly attribute TimeRanges buffered;
void load();
DOMString canPlayType(in DOMString type);
// ready state
const unsigned short HAVE_NOTHING = 0;
const unsigned short HAVE_METADATA = 1;
const unsigned short HAVE_CURRENT_DATA = 2;
const unsigned short HAVE_FUTURE_DATA = 3;
const unsigned short HAVE_ENOUGH_DATA = 4;
readonly attribute unsigned short readyState;
readonly attribute boolean seeking;
// playback state
attribute float currentTime;
readonly attribute float startTime;
readonly attribute float duration;
readonly attribute boolean paused;
attribute float defaultPlaybackRate;
attribute float playbackRate;
readonly attribute TimeRanges played;
readonly attribute TimeRanges seekable;
readonly attribute boolean ended;
attribute boolean autoplay;
attribute boolean loop;
void play();
void pause();
// cue ranges
void addCueRange(in DOMString className, in DOMString id, in float start, in float end, in boolean pauseOnExit, in CueRangeCallback enterCallback, in CueRangeCallback exitCallback);
void removeCueRanges(in DOMString className);
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// controls
attribute boolean controls;
attribute float volume;
attribute boolean muted;
};
[Callback=FunctionOnly, NoInterfaceObject]
interface CueRangeCallback {
void handleEvent(in DOMString id);
};
The media element attributes, src, autobuffer, autoplay, loop, and controls, apply to all media elements. They are defined in this section.
Media elements are used to present audio data, or video and audio data, to the user. This is referred to as media data in this section, since this section applies equally to media elements for audio or for video. The term media resource is used to refer to the complete
set of media data, e.g. the complete video file, or complete audio file.
Unless otherwise specified, the task source for all the tasks queued in this section and its subsections is the media element event task source.
4.8.10.1 Error codes
media . error
Returns a MediaError object representing the current error state of the element.
Returns null if there is no error.
All media elements have an associated error status, which records the last error the element encountered since its resource selection algorithm was last invoked. The error attribute, on getting, must return the MediaError object created for this last error, or null if
there has not been an error.
interface MediaError {
const unsigned short MEDIA_ERR_ABORTED = 1;
const unsigned short MEDIA_ERR_NETWORK = 2;
const unsigned short MEDIA_ERR_DECODE = 3;
const unsigned short MEDIA_ERR_SRC_NOT_SUPPORTED = 4;
readonly attribute unsigned short code;
};
media . error . code
Returns the current error's error code, from the list below.
The code attribute of a MediaError object must return the code for the error, which must be one of the following:
MEDIA_ERR_ABORTED (numeric value 1)
The fetching process for the media resource was aborted by the user agent at the user's request.
MEDIA_ERR_NETWORK (numeric value 2)
A network error of some description caused the user agent to stop fetching the media resource, after the resource was established to be usable.
MEDIA_ERR_DECODE (numeric value 3)
An error of some description occurred while decoding the media resource, after the resource was established to be usable.
MEDIA_ERR_SRC_NOT_SUPPORTED (numeric value 4)
The media resource indicated by the src attribute was not suitable.
4.8.10.2 Location of the media resource
The src content attribute on media elements gives the address of the media resource (video, audio) to show. The attribute, if present, must contain a valid URL.
If a src attribute of a media element that is in a Document and whose networkState has the value NETWORK_EMPTY is set or changed, the user agent must invoke the media element's resource selection algorithm.
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The src DOM attribute on media elements must reflect the respective content attribute of the same name.
media . currentSrc
Returns the address of the current media resource.
Returns the empty string when there is no media resource.
The currentSrc DOM attribute is initially the empty string. Its value is changed by the resource selection algorithm defined below.
There are two ways to specify a media resource, the src attribute, or source elements. The attribute overrides the elements.
4.8.10.3 MIME types
A media resource can be described in terms of its type, specifically a MIME type, optionally with a codecs parameter. [RFC2046] [RFC4281].
Types are usually somewhat incomplete descriptions; for example "video/mpeg" doesn't say anything except what the container type is, and even a type like "video/mp4; codecs="avc1.42E01E, mp4a.40.2"" doesn't include information like the actual bitrate
(only the maximum bitrate). Thus, given a type, a user agent can often only know whether it might be able to play media of that type (with varying levels of confidence), or whether it definitely cannot play media of that type.
A type that the user agent knows it cannot render is one that describes a resource that the user agent definitely does not support, for example because it doesn't recognize the container type, or it doesn't support the listed codecs.
The MIME type "application/octet-stream" is never a type that the user agent knows it cannot render. User agents must treat that type as equivalent to the lack of any explicit Content-Type metadata when it is used to label a potential media resource.
media . canPlayType(type)
Returns the empty string (a negative response), "maybe", or "probably" based on how confident the user agent is that it can play media resources of the given type.
The canPlayType(type) method must return the empty string if type is a type that the user agent knows it cannot render; it must return "probably" if the user agent is confident that the type represents a media resource that it can render if used in with this audio or
video element; and it must return "maybe" otherwise. Implementors are encouraged to return "maybe" unless the type can be confidently established as being supported or not. Generally, a user agent should never return "probably" if the type doesn't have a
codecs parameter.
This script tests to see if the user agent supports a (fictional) new format to dynamically decide whether to use a video element or a plugin:
<section id="video">
<p><a href="playing-cats.nfv">Download video</a></p>
</section>
<script>
var videoSection = document.getElementById('video');
var videoElement = document.createElement('video');
var support = videoElement.canPlayType('video/x-new-fictional-format;codecs="kittens,bunnies"');
if (support != "probably" && "New Fictional Video Plug-in" in navigator.plugins) {
// not confident of browser support
// but we have a plugin
// so use plugin instead
videoElement = document.createElement("embed");
} else if (support == "") {
// no support from browser and no plugin
// do nothing
videoElement = null;
}
if (videoElement) {
while (videoSection.hasChildNodes())
videoSection.removeChild(videoSection.firstChild);
videoElement.setAttribute("src", "playing-cats.nfv");
videoSection.appendChild(videoElement);
}
</script>
The type attribute of the source element allows the user agent to avoid downloading resources that use formats it cannot render.
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4. • If absolute URL was not obtained successfully, then end the synchronous section, and jump down to the failed step below.
5. • If candidate has a type attribute whose value, when parsed as a MIME type (including any codecs described by the codec parameter), represents a type that the user agent knows it cannot render, then end the synchronous section, and jump down to
the failed step below.
6. • If candidate has a media attribute whose value, when processed according to the rules for media queries, does not match the current environment, then end the synchronous section, and jump down to the failed step below. [MQ]
7. End the synchronous section, continuing the remaining steps asynchronously.
8. Run the resource fetch algorithm with absolute URL. If that algorithm returns without aborting this one, then the load failed.
9. Failed: Queue a task to fire a simple event called error at the candidate element.
10. Asynchronously await a stable state. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with •.)
11. • Find next candidate: Let candidate be null.
12. • Search loop: If the node after pointer is the end of the list, then jump o the waiting step below.
13. • If the node after pointer is a source element, let candidate be that element.
14. • Advance pointer so that the node before pointer is now the node that was after pointer, and the node after pointer is the node after the node that used to be after pointer, if any.
15. • If candidate is null, jump back to the search loop step. Otherwise, jump back to the process candidate step.
16. • Waiting: Set the element's networkState attribute to the NETWORK_NO_SOURCE value.
17. • Set the element's delaying-the-load-event flag to false. This stops delaying the load event.
18. End the synchronous section, continuing the remaining steps asynchronously.
19. Wait until the node after pointer is a node other than the end of the list. (This step might wait forever.)
20. Asynchronously await a stable state. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with •.)
21. • Set the element's delaying-the-load-event flag back to true (this delays the load event again, in case it hasn't been fired yet).
22. • Set the networkState back to NETWORK_LOADING.
23. • Jump back to the find next candidate step above.
The resource fetch algorithm for a media element and a given absolute URL is as follows:
1. Let the current media resource be the resource given by the absolute URL passed to this algorithm. This is now the element's media resource.
2. Set the currentSrc attribute to the absolute URL of the current media resource.
3. Begin to fetch the current media resource.
Every 350ms (±200ms) or for every byte received, whichever is least frequent, queue a task to fire a progress event called progress at the element.
If at any point the user agent has received no data for more than about three seconds, then queue a task to fire a progress event called stalled at the element.
User agents may allow users to selectively block or slow media data downloads. When a media element's download has been blocked altogether, the user agent must act as if it was stalled (as opposed to acting as if the connection was closed). The rate of the
download may also be throttled automatically by the user agent, e.g. to balance the download with other connections sharing the same bandwidth.
User agents may decide to not download more content at any time, e.g. after buffering five minutes of a one hour media resource, while waiting for the user to decide whether to play the resource or not, or while waiting for user input in an interactive resource.
When a media element's download has been suspended, the user agent must set the networkState to NETWORK_IDLE and queue a task to fire a progress event called suspend at the element. If and when downloading of the resource resumes, the user
agent must set the networkState to NETWORK_LOADING.
The autobuffer attribute provides a hint that the author expects that downloading the entire resource optimistically will be worth it, even in the absence of the autoplay attribute. In the absence of either attribute, the user agent is likely to find that waiting until
the user starts playback before downloading any further content leads to a more efficient use of the network resources.
When a user agent decides to completely stall a download, e.g. if it is waiting until the user starts playback before downloading any further content, the element's delaying-the-load-event flag must be set to false. This stops delaying the load event.
The user agent may use whatever means necessary to fetch the resource (within the constraints put forward by this and other specifications); for example, reconnecting to the server in the face of network errors, using HTTP partial range requests, or switching to
a streaming protocol. The user agent must consider a resource erroneous only if it has given up trying to fetch it.
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media . currentTime [ = value ]
Returns the current playback position, in seconds.
Can be set, to seek to the given time.
Will throw an INVALID_STATE_ERR exception if there is no selected media resource. Will throw an INDEX_SIZE_ERR exception if the given time is not within the ranges to which the user agent can seek.
media . startTime
Returns the earliest possible position, in seconds. This is the time for the start of the current clip. It might not be zero if the clip's timeline is not zero-based, or if the resource is a streaming resource (in which case it gives the earliest time that the user
agent is able to seek back to).
The duration attribute must return the length of the media resource, in seconds. If no media data is available, then the attributes must return the Not-a-Number (NaN) value. If the media resource is known to be unbounded (e.g. a streaming radio), then the attribute
must return the positive Infinity value.
The user agent must determine the duration of the media resource before playing any part of the media data and before setting readyState to a value equal to or greater than HAVE_METADATA, even if doing so requires seeking to multiple parts of the resource.
When the length of the media resource changes (e.g. from being unknown to known, or from a previously established length to a new length) the user agent must queue a task to fire a simple event called durationchange at the media element.
If an "infinite" stream ends for some reason, then the duration would change from positive Infinity to the time of the last frame or sample in the stream, and the durationchange event would be fired. Similarly, if the user agent initially estimated the media
resource's duration instead of determining it precisely, and later revises the estimate based on new information, then the duration would change and the durationchange event would be fired.
Media elements have a current playback position, which must initially be zero. The current position is a time.
The currentTime attribute must, on getting, return the current playback position, expressed in seconds. On setting, the user agent must seek to the new value (which might raise an exception).
If the media resource is a streaming resource, then the user agent might be unable to obtain certain parts of the resource after it has expired from its buffer. Similarly, some media resources might have a timeline that doesn't start at zero. The earliest possible
position is the earliest position in the stream or resource that the user agent can ever obtain again.
The startTime attribute must, on getting, return the earliest possible position, expressed in seconds.
When the earliest possible position changes, then: if the current playback position is before the earliest possible position, the user agent must seek to the earliest possible position; otherwise, if the user agent has not fired a timeupdate event at the element in the past
15 to 250ms, then the user agent must queue a task to fire a simple event called timeupdate at the element.
User agents must act as if the timeline of the media resource increases linearly starting from the earliest possible position, even if the underling media data has out-of-order or even overlapping time codes.
For example, if two clips have been concatenated into one video file, but the video format exposes the original times for the two clips, the video data might expose a timeline that goes, say, 00:15..00:29 and then 00:05..00:38. However, the user agent would
not expose those times; it would instead expose the times as 00:15..00:29 and 00:29..01:02, as a single video.
The loop attribute is a boolean attribute that, if specified, indicates that the media element is to seek back to the start of the media resource upon reaching the end.
The loop DOM attribute must reflect the content attribute of the same name.
4.8.10.7 The ready states
media . readyState
Returns a value that expresses the current state of the element with respect to rendering the current playback position, from the codes in the list below.
Media elements have a ready state, which describes to what degree they are ready to be rendered at the current playback position. The possible values are as follows; the ready state of a media element at any particular time is the greatest value describing the state of
the element:
HAVE_NOTHING (numeric value 0)
No information regarding the media resource is available. No data for the current playback position is available. Media elements whose networkState attribute is NETWORK_EMPTY are always in the HAVE_NOTHING state.
HAVE_METADATA (numeric value 1)
Enough of the resource has been obtained that the duration of the resource is available. In the case of a video element, the dimensions of the video are also available. The API will no longer raise an exception when seeking. No media data is available for the
immediate current playback position.
HAVE_CURRENT_DATA (numeric value 2)
Data for the immediate current playback position is available, but either not enough data is available that the user agent could successfully advance the current playback position in the direction of playback at all without immediately reverting to the
HAVE_METADATA state, or there is no more data to obtain in the direction of playback. For example, in video this corresponds to the user agent having data from the current frame, but not the next frame; and to when playback has ended.
HAVE_FUTURE_DATA (numeric value 3)
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A class name
A group of related ranges can be given the same class name so that they can all be removed at the same time.
An identifier
A string can be assigned to each cue range for identification by script. The string need not be unique and can contain any value.
A start time
An end time
The actual time range, using the same timeline as the media resource itself.
A "pause" boolean
A flag indicating whether to pause playback on exit.
An "enter" callback
A callback that is called when the current playback position enters the range.
An "exit" callback
A callback that is called when the current playback position exits the range.
An "active" boolean
A flag indicating whether the range is active or not.
The addCueRange(className, id, start, end, pauseOnExit, enterCallback, exitCallback) method must, when called, add a cue range to the media element, that cue range having the class name className, the identifier id, the start time start
(in seconds), the end time end (in seconds), the "pause" boolean with the same value as pauseOnExit, the "enter" callback enterCallback, the "exit" callback exitCallback, and an "active" boolean that is true if the current playback position is equal to or greater than the
start time and less than the end time, and false otherwise.
The removeCueRanges(className) method must, when called, remove all the cue ranges of the media element which have the class name className.
4.8.10.9 Playing the media resource
media . paused
Returns true if playback is paused; false otherwise.
media . ended
Returns true if playback has reached the end of the media resource.
media . defaultPlaybackRate [ = value ]
Returns the default rate of playback, for when the user is not fast-forwarding or reversing through the media resource.
Can be set, to change the default rate of playback.
The default rate has no direct effect on playback, but if the user switches to a fast-forward mode, when they return to the normal playback mode, it is expected that the rate of playback will be returned to the default rate of playback.
media . playbackRate [ = value ]
Returns the current rate playback, where 1.0 is normal speed.
Can be set, to change the rate of playback.
media . played
Returns a TimeRanges object that represents the ranges of the media resource that the user agent has played.
media . play()
Sets the paused attribute to false, loading the media resource and beginning playback if necessary. If the playback had ended, will restart it from the start.
media . pause()
Sets the paused attribute to true, loading the media resource if necessary.
The paused attribute represents whether the media element is paused or not. The attribute must initially be true.
A media element is said to be potentially playing when its paused attribute is false, the readyState attribute is either HAVE_FUTURE_DATA or HAVE_ENOUGH_DATA, the element has not ended playback, playback has not stopped due to errors, and the element has
not paused for user interaction.
A media element is said to have ended playback when the element's readyState attribute is HAVE_METADATA or greater, and either the current playback position is the end of the media resource and the direction of playback is forwards and the media element does
not have a loop attribute specified, or the current playback position is the earliest possible position and the direction of playback is backwards.
The ended attribute must return true if the media element has ended playback and the direction of playback is forwards, and false otherwise.
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If the attribute is absent, then the user agent should avoid making a user interface available that could conflict with an author-provided user interface. User agents may make the following features available, however, even when the attribute is absent:
User agents may provide controls to affect playback of the media resource (e.g. play, pause, seeking, and volume controls), but such features should not interfere with the page's normal rendering. For example, such features could be exposed in the media element's
context menu.
Where possible (specifically, for starting, stopping, pausing, and unpausing playback, for muting or changing the volume of the audio, and for seeking), user interface features exposed by the user agent must be implemented in terms of the DOM API described above,
so that, e.g., all the same events fire.
The controls DOM attribute must reflect the content attribute of the same name.
media . volume [ = value ]
Returns the current playback volume, as a number in the range 0.0 to 1.0, where 0.0 is the quietest and 1.0 the loudest.
Can be set, to change the volume.
Throws an INDEX_SIZE_ERR if the new value is not in the range 0.0 .. 1.0.
media . muted [ = value ]
Returns true if audio is muted, overriding the volume attribute, and false if the volume attribute is being honored.
Can be set, to change whether the audio is muted or not.
The volume attribute must return the playback volume of any audio portions of the media element, in the range 0.0 (silent) to 1.0 (loudest). Initially, the volume must be 1.0, but user agents may remember the last set value across sessions, on a per-site basis or
otherwise, so the volume may start at other values. On setting, if the new value is in the range 0.0 to 1.0 inclusive, the attribute must be set to the new value and the playback volume must be correspondingly adjusted as soon as possible after setting the attribute, with
0.0 being silent, and 1.0 being the loudest setting, values in between increasing in loudness. The range need not be linear. The loudest setting may be lower than the system's loudest possible setting; for example the user could have set a maximum volume. If the new
value is outside the range 0.0 to 1.0 inclusive, then, on setting, an INDEX_SIZE_ERR exception must be raised instead.
The muted attribute must return true if the audio channels are muted and false otherwise. Initially, the audio channels should not be muted (false), but user agents may remember the last set value across sessions, on a per-site basis or otherwise, so the muted state
may start as muted (true). On setting, the attribute must be set to the new value; if the new value is true, audio playback for this media resource must then be muted, and if false, audio playback must then be enabled.
Whenever either the muted or volume attributes are changed, the user agent must queue a task to fire a simple event called volumechange at the media element.
4.8.10.12 Time ranges
Objects implementing the TimeRanges interface represent a list of ranges (periods) of time.
interface TimeRanges {
readonly attribute unsigned long length;
float start(in unsigned long index);
float end(in unsigned long index);
};
media . length
Returns the number of ranges in the object.
time = media . start(index)
Returns the time for the start of the range with the given index.
Throws an INDEX_SIZE_ERR if the index is out of range.
time = media . end(index)
Returns the time for the end of the range with the given index.
Throws an INDEX_SIZE_ERR if the index is out of range.
The length DOM attribute must return the number of ranges represented by the object.
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The start(index) method must return the position of the start of the indexth range represented by the object, in seconds measured from the start of the timeline that the object covers.
The end(index) method must return the position of the end of the indexth range represented by the object, in seconds measured from the start of the timeline that the object covers.
These methods must raise INDEX_SIZE_ERR exceptions if called with an index argument greater than or equal to the number of ranges represented by the object.
When a TimeRanges object is said to be a normalized TimeRanges object, the ranges it represents must obey the following criteria:
q The start of a range must be greater than the end of all earlier ranges.
q The start of a range must be less than the end of that same range.
In other words, the ranges in such an object are ordered, don't overlap, aren't empty, and don't touch (adjacent ranges are folded into one bigger range).
The timelines used by the objects returned by the buffered, seekable and played DOM attributes of media elements must be the same as that element's media resource's timeline.
4.8.10.13 Event summary
The following events fire on media elements as part of the processing model described above:
Event name Interface Dispatched when... Preconditions
loadstart ProgressEvent [PROGRESS] The user agent begins looking for media data, as part of the resource selection algorithm. networkState equals NETWORK_LOADING
progress ProgressEvent [PROGRESS] The user agent is fetching media data. networkState equals NETWORK_LOADING
suspend ProgressEvent [PROGRESS] The user agent is intentionally not currently fetching media data, but does not have the entire media networkState equals NETWORK_IDLE
resource downloaded.
load ProgressEvent [PROGRESS] The user agent finishes fetching the entire media resource. networkState equals NETWORK_LOADED
abort ProgressEvent [PROGRESS] The user agent stops fetching the media data before it is completely downloaded. error is an object with the code MEDIA_ERR_ABORTED. networkState equals either
NETWORK_EMPTY or NETWORK_LOADED, depending on when the download was aborted.
error ProgressEvent [PROGRESS] An error occurs while fetching the media data. error is an object with the code MEDIA_ERR_NETWORK or higher. networkState equals either
NETWORK_EMPTY or NETWORK_LOADED, depending on when the download was aborted.
emptied Event A media element whose networkState was previously not in the NETWORK_EMPTY state has just networkState is NETWORK_EMPTY; all the DOM attributes are in their initial states.
switched to that state (either because of a fatal error during load that's about to be reported, or because the
load() method was invoked while the resource selection algorithm was already running, in which case it is
fired synchronously during the load() method call).
stalled ProgressEvent The user agent is trying to fetch media data, but data is unexpectedly not forthcoming. networkState is NETWORK_LOADING.
play Event Playback has begun. Fired after the play() method has returned. paused is newly false.
pause Event Playback has been paused. Fired after the pause method has returned. paused is newly true.
loadedmetadata Event The user agent has just determined the duration and dimensions of the media resource. readyState is newly equal to HAVE_METADATA or greater for the first time.
loadeddata Event The user agent can render the media data at the current playback position for the first time. readyState newly increased to HAVE_CURRENT_DATA or greater for the first time.
waiting Event Playback has stopped because the next frame is not available, but the user agent expects that frame to readyState is newly equal to or less than HAVE_CURRENT_DATA, and paused is false. Either
become available in due course. seeking is true, or the current playback position is not contained in any of the ranges in
buffered. It is possible for playback to stop for two other reasons without paused being false, but
those two reasons do not fire this event: maybe playback ended, or playback stopped due to errors.
playing Event Playback has started. readyState is newly equal to or greater than HAVE_FUTURE_DATA, paused is false, seeking is
false, or the current playback position is contained in one of the ranges in buffered.
canplay Event The user agent can resume playback of the media data, but estimates that if playback were to be started readyState newly increased to HAVE_FUTURE_DATA or greater.
now, the media resource could not be rendered at the current playback rate up to its end without having to
stop for further buffering of content.
canplaythrough Event The user agent estimates that if playback were to be started now, the media resource could be rendered at readyState is newly equal to HAVE_ENOUGH_DATA.
the current playback rate all the way to its end without having to stop for further buffering.
seeking Event The seeking DOM attribute changed to true and the seek operation is taking long enough that the user
agent has time to fire the event.
seeked Event The seeking DOM attribute changed to false.
timeupdate Event The current playback position changed as part of normal playback or in an especially interesting way, for
example discontinuously.
ended Event Playback has stopped because the end of the media resource was reached. currentTime equals the end of the media resource; ended is true.
ratechange Event Either the defaultPlaybackRate or the playbackRate attribute has just been updated.
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durationchange Event The duration attribute has just been updated.
volumechange Event Either the volume attribute or the muted attribute has changed. Fired after the relevant attribute's setter
has returned.
4.8.10.14 Security and privacy considerations
The main security and privacy implications of the video and audio elements come from the ability to embed media cross-origin. There are two directions that threats can flow: from hostile content to a victim page, and from a hostile page to victim content.
If a victim page embeds hostile content, the threat is that the content might contain scripted code that attempts to interact with the Document that embeds the content. To avoid this, user agents must ensure that there is no access from the content to the embedding
page. In the case of media content that uses DOM concepts, the embedded content must be treated as if it was in its own unrelated top-level browsing context.
For instance, if an SVG animation was embedded in a video element, the user agent would not give it access to the DOM of the outer page. From the perspective of scripts in the SVG resource, the SVG file would appear to be in a lone top-level browsing
context with no parent.
If a hostile page embeds victim content, the threat is that the embedding page could obtain information from the content that it would not otherwise have access to. The API does expose some information: the existence of the media, its type, its duration, its size, and the
performance characteristics of its host. Such information is already potentially problematic, but in practice the same information can more or less be obtained using the img element, and so it has been deemed acceptable.
However, significantly more sensitive information could be obtained if the user agent further exposes metadata within the content such as subtitles or chapter titles. This version of the API does not expose such information. Future extensions to this API will likely reuse
a mechanism such as CORS to check that the embedded content's site has opted in to exposing such information. [CORS]
An attacker could trick a user running within a corporate network into visiting a site that attempts to load a video from a previously leaked location on the corporation's intranet. If such a video included confidential plans for a new product, then being able to read
the subtitles would present a confidentiality breach.
4.8.11 The canvas element
Categories
Flow content.
Phrasing content.
Embedded content.
Contexts in which this element may be used:
Where embedded content is expected.
Content model:
Transparent.
Content attributes:
Global attributes
width
height
DOM interface:
interface HTMLCanvasElement : HTMLElement {
attribute unsigned long width;
attribute unsigned long height;
DOMString toDataURL([Optional] in DOMString type, [Variadic] in any args);
Object getContext(in DOMString contextId);
};
The canvas element represents a resolution-dependent bitmap canvas, which can be used for rendering graphs, game graphics, or other visual images on the fly.
Authors should not use the canvas element in a document when a more suitable element is available. For example, it is inappropriate to use a canvas element to render a page heading: if the desired presentation of the heading is graphically intense, it should be
marked up using appropriate elements (typically h1) and then styled using CSS and supporting technologies such as XBL.
When authors use the canvas element, they must also provide content that, when presented to the user, conveys essentially the same function or purpose as the bitmap canvas. This content may be placed as content of the canvas element. The contents of the
canvas element, if any, are the element's fallback content.
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In interactive visual media, if scripting is enabled for the canvas element, the canvas element represents an embedded element with a dynamically created image.
In non-interactive, static, visual media, if the canvas element has been previously painted on (e.g. if the page was viewed in an interactive visual medium and is now being printed, or if some script that ran during the page layout process painted on the element), then
the canvas element represents embedded content with the current image and size. Otherwise, the element represents its fallback content instead.
In non-visual media, and in visual media if scripting is disabled for the canvas element, the canvas element represents its fallback content instead.
The canvas element has two attributes to control the size of the coordinate space: width and height. These attributes, when specified, must have values that are valid non-negative integers. The rules for parsing non-negative integers must be used to obtain their
numeric values. If an attribute is missing, or if parsing its value returns an error, then the default value must be used instead. The width attribute defaults to 300, and the height attribute defaults to 150.
The intrinsic dimensions of the canvas element equal the size of the coordinate space, with the numbers interpreted in CSS pixels. However, the element can be sized arbitrarily by a style sheet. During rendering, the image is scaled to fit this layout size.
The size of the coordinate space does not necessarily represent the size of the actual bitmap that the user agent will use internally or during rendering. On high-definition displays, for instance, the user agent may internally use a bitmap with two device pixels per unit in
the coordinate space, so that the rendering remains at high quality throughout.
Whenever the width and height attributes are set (whether to a new value or to the previous value), the bitmap and any associated contexts must be cleared back to their initial state and reinitialized with the newly specified coordinate space dimensions.
The width and height DOM attributes must reflect the respective content attributes of the same name.
Only one square appears to be drawn in the following example:
// canvas is a reference to a <canvas> element
var context = canvas.getContext('2d');
context.fillRect(0,0,50,50);
canvas.setAttribute('width', '300'); // clears the canvas
context.fillRect(0,100,50,50);
canvas.width = canvas.width; // clears the canvas
context.fillRect(100,0,50,50); // only this square remains
When the canvas is initialized it must be set to fully transparent black.
To draw on the canvas, authors must first obtain a reference to a context using the getContext(contextId) method of the canvas element.
context = canvas . getContext(contextId)
Returns an object that exposes an API for drawing on the canvas.
Returns null if the given context ID is not supported.
This specification only defines one context, with the name "2d". If getContext() is called with that exact string for its contextId argument, then the UA must return a reference to an object implementing CanvasRenderingContext2D. Other specifications may define
their own contexts, which would return different objects.
Vendors may also define experimental contexts using the syntax vendorname-context, for example, moz-3d.
When the UA is passed an empty string or a string specifying a context that it does not support, then it must return null. String comparisons must be case-sensitive.
A future version of this specification will probably define a 3d context (probably based on the OpenGL ES API).
url = canvas . toDataURL( [ type, ... ])
Returns a data: URL for the image in the canvas.
The first argument, if provided, controls the type of the image to be returned (e.g. PNG or JPEG). The default is image/png; that type is also used if the given type isn't supported. The other arguments are specific to the type, and control the way that
the image is generated, as given in the table below.
The toDataURL() method must, when called with no arguments, return a data: URL containing a representation of the image as a PNG file. [PNG].
If the canvas has no pixels (i.e. either its horizontal dimension or its vertical dimension is zero) then the method must return the string "data:,". (This is the shortest data: URL; it represents the empty string in a text/plain resource.)
When the toDataURL(type) method, when called with one or more arguments, must return a data: URL containing a representation of the image in the format given by type. The possible values are MIME types with no parameters, for example image/png,
image/jpeg, or even maybe image/svg+xml if the implementation actually keeps enough information to reliably render an SVG image from the canvas.
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attribute float shadowOffsetY; // (default 0)
attribute float shadowBlur; // (default 0)
attribute DOMString shadowColor; // (default transparent black)
// rects
void clearRect(in float x, in float y, in float w, in float h);
void fillRect(in float x, in float y, in float w, in float h);
void strokeRect(in float x, in float y, in float w, in float h);
// path API
void beginPath();
void closePath();
void moveTo(in float x, in float y);
void lineTo(in float x, in float y);
void quadraticCurveTo(in float cpx, in float cpy, in float x, in float y);
void bezierCurveTo(in float cp1x, in float cp1y, in float cp2x, in float cp2y, in float x, in float y);
void arcTo(in float x1, in float y1, in float x2, in float y2, in float radius);
void rect(in float x, in float y, in float w, in float h);
void arc(in float x, in float y, in float radius, in float startAngle, in float endAngle, in boolean anticlockwise);
void fill();
void stroke();
void clip();
boolean isPointInPath(in float x, in float y);
// text
attribute DOMString font; // (default 10px sans-serif)
attribute DOMString textAlign; // "start", "end", "left", "right", "center" (default: "start")
attribute DOMString textBaseline; // "top", "hanging", "middle", "alphabetic", "ideographic", "bottom" (default: "alphabetic")
void fillText(in DOMString text, in float x, in float y, [Optional] in float maxWidth);
void strokeText(in DOMString text, in float x, in float y, [Optional] in float maxWidth);
TextMetrics measureText(in DOMString text);
// drawing images
void drawImage(in HTMLImageElement image, in float dx, in float dy, [Optional] in float dw, in float dh);
void drawImage(in HTMLImageElement image, in float sx, in float sy, in float sw, in float sh, in float dx, in float dy, in float dw, in float dh);
void drawImage(in HTMLCanvasElement image, in float dx, in float dy, [Optional] in float dw, in float dh);
void drawImage(in HTMLCanvasElement image, in float sx, in float sy, in float sw, in float sh, in float dx, in float dy, in float dw, in float dh);
void drawImage(in HTMLVideoElement image, in float dx, in float dy, [Optional] in float dw, in float dh);
void drawImage(in HTMLVideoElement image, in float sx, in float sy, in float sw, in float sh, in float dx, in float dy, in float dw, in float dh);
// pixel manipulation
ImageData createImageData(in float sw, in float sh);
ImageData createImageData(in ImageData imagedata);
ImageData getImageData(in float sx, in float sy, in float sw, in float sh);
void putImageData(in ImageData imagedata, in float dx, in float dy, [Optional] in float dirtyX, in float dirtyY, in float dirtyWidth, in float dirtyHeight);
};
interface CanvasGradient {
// opaque object
void addColorStop(in float offset, in DOMString color);
};
interface CanvasPattern {
// opaque object
};
interface TextMetrics {
readonly attribute float width;
};
interface ImageData {
readonly attribute unsigned long width;
readonly attribute unsigned long height;
readonly attribute CanvasPixelArray data;
};
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[IndexGetter, IndexSetter]
interface CanvasPixelArray {
readonly attribute unsigned long length;
};
context . canvas
Returns the canvas element.
The canvas attribute must return the canvas element that the context paints on.
Unless otherwise stated, for the 2D context interface, any method call with a numeric argument whose value is infinite or a NaN value must be ignored.
Whenever the CSS value currentColor is used as a color in this API, the "computed value of the 'color' property" for the purposes of determining the computed value of the currentColor keyword is the computed value of the 'color' property on the element in
question at the time that the color is specified (e.g. when the appropriate attribute is set, or when the method is called; not when the color is rendered or otherwise used). If the computed value of the 'color' property is undefined for a particular case (e.g. because the
element is not in a Document), then the "computed value of the 'color' property" for the purposes of determining the computed value of the currentColor keyword is fully opaque black. [CSSCOLOR]
4.8.11.1.1 The canvas state
Each context maintains a stack of drawing states. Drawing states consist of:
q The current transformation matrix.
q The current clipping region.
q The current values of the following attributes: strokeStyle, fillStyle, globalAlpha, lineWidth, lineCap, lineJoin, miterLimit, shadowOffsetX, shadowOffsetY, shadowBlur, shadowColor, globalCompositeOperation, font,
textAlign, textBaseline.
The current path and the current bitmap are not part of the drawing state. The current path is persistent, and can only be reset using the beginPath() method. The current bitmap is a property of the canvas, not the context.
context . save()
Pushes the current state onto the stack.
context . restore()
Pops the top state on the stack, restoring the context to that state.
The save() method must push a copy of the current drawing state onto the drawing state stack.
The restore() method must pop the top entry in the drawing state stack, and reset the drawing state it describes. If there is no saved state, the method must do nothing.
4.8.11.1.2 Transformations
The transformation matrix is applied to coordinates when creating shapes and paths.
When the context is created, the transformation matrix must initially be the identity transform. It may then be adjusted using the transformation methods.
The transformations must be performed in reverse order. For instance, if a scale transformation that doubles the width is applied, followed by a rotation transformation that rotates drawing operations by a quarter turn, and a rectangle twice as wide as it is tall is then
drawn on the canvas, the actual result will be a square.
context . scale(x, y)
Changes the transformation matrix to apply a scaling transformation with the given characteristics.
context . rotate(angle)
Changes the transformation matrix to apply a rotation transformation with the given characteristics.
context . translate(x, y)
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Changes the transformation matrix to apply a translation transformation with the given characteristics.
context . transform(m11, m12, m21, m22, dx, dy)
Changes the transformation matrix to apply the matrix given by the arguments as described below.
context . setTransform(m11, m12, m21, m22, dx, dy)
Changes the transformation matrix to the matrix given by the arguments as described below.
The scale(x, y) method must add the scaling transformation described by the arguments to the transformation matrix. The x argument represents the scale factor in the horizontal direction and the y argument represents the scale factor in the vertical direction. The
factors are multiples.
The rotate(angle) method must add the rotation transformation described by the argument to the transformation matrix. The angle argument represents a clockwise rotation angle expressed in radians.
The translate(x, y) method must add the translation transformation described by the arguments to the transformation matrix. The x argument represents the translation distance in the horizontal direction and the y argument represents the translation distance in
the vertical direction. The arguments are in coordinate space units.
The transform(m11, m12, m21, m22, dx, dy) method must multiply the current transformation matrix with the matrix described by:
m11 m21 dx
m12 m22 dy
0 0 1
The setTransform(m11, m12, m21, m22, dx, dy) method must reset the current transform to the identity matrix, and then invoke the transform(m11, m12, m21, m22, dx, dy) method with the same arguments.
4.8.11.1.3 Compositing
context . globalAlpha [ = value ]
Returns the current alpha value applied to rendering operations.
Can be set, to change the alpha value. Values outside of the range 0.0 .. 1.0 are ignored.
context . globalCompositeOperation [ = value ]
Returns the current composition operation, from the list below.
Can be set, to change the composition operation. Unknown values are ignored.
All drawing operations are affected by the global compositing attributes, globalAlpha and globalCompositeOperation.
The globalAlpha attribute gives an alpha value that is applied to shapes and images before they are composited onto the canvas. The value must be in the range from 0.0 (fully transparent) to 1.0 (no additional transparency). If an attempt is made to set the attribute
to a value outside this range (including Infinity and NaN values), the attribute must retain its previous value. When the context is created, the globalAlpha attribute must initially have the value 1.0.
The globalCompositeOperation attribute sets how shapes and images are drawn onto the existing bitmap, once they have had globalAlpha and the current transformation matrix applied. It must be set to a value from the following list. In the descriptions below,
the source image, A, is the shape or image being rendered, and the destination image, B, is the current state of the bitmap.
source-atop
A atop B. Display the source image wherever both images are opaque. Display the destination image wherever the destination image is opaque but the source image is transparent. Display transparency elsewhere.
source-in
A in B. Display the source image wherever both the source image and destination image are opaque. Display transparency elsewhere.
source-out
A out B. Display the source image wherever the source image is opaque and the destination image is transparent. Display transparency elsewhere.
source-over (default)
A over B. Display the source image wherever the source image is opaque. Display the destination image elsewhere.
destination-atop
B atop A. Same as source-atop but using the destination image instead of the source image and vice versa.
destination-in
B in A. Same as source-in but using the destination image instead of the source image and vice versa.
destination-out
B out A. Same as source-out but using the destination image instead of the source image and vice versa.
destination-over
B over A. Same as source-over but using the destination image instead of the source image and vice versa.
lighter
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A plus B. Display the sum of the source image and destination image, with color values approaching 1 as a limit.
copy
A (B is ignored). Display the source image instead of the destination image.
xor
A xor B. Exclusive OR of the source image and destination image.
vendorName-operationName
Vendor-specific extensions to the list of composition operators should use this syntax.
These values are all case-sensitive — they must be used exactly as shown. User agents must not recognize values that are not a case-sensitive match for one of the values given above.
The operators in the above list must be treated as described by the Porter-Duff operator given at the start of their description (e.g. A over B). [PORTERDUFF]
On setting, if the user agent does not recognize the specified value, it must be ignored, leaving the value of globalCompositeOperation unaffected.
When the context is created, the globalCompositeOperation attribute must initially have the value source-over.
4.8.11.1.4 Colors and styles
context . strokeStyle [ = value ]
Returns the current style used for stroking shapes.
Can be set, to change the stroke style.
The style can be either a string containing a CSS color, or a CanvasGradient or CanvasPattern object. Invalid values are ignored.
context . fillStyle [ = value ]
Returns the current style used for filling shapes.
Can be set, to change the fill style.
The style can be either a string containing a CSS color, or a CanvasGradient or CanvasPattern object. Invalid values are ignored.
The strokeStyle attribute represents the color or style to use for the lines around shapes, and the fillStyle attribute represents the color or style to use inside the shapes.
Both attributes can be either strings, CanvasGradients, or CanvasPatterns. On setting, strings must be parsed as CSS <color> values and the color assigned, and CanvasGradient and CanvasPattern objects must be assigned themselves. [CSSCOLOR] If
the value is a string but is not a valid color, or is neither a string, a CanvasGradient, nor a CanvasPattern, then it must be ignored, and the attribute must retain its previous value.
On getting, if the value is a color, then the serialization of the color must be returned. Otherwise, if it is not a color but a CanvasGradient or CanvasPattern, then the respective object must be returned. (Such objects are opaque and therefore only useful for
assigning to other attributes or for comparison to other gradients or patterns.)
The serialization of a color for a color value is a string, computed as follows: if it has alpha equal to 1.0, then the string is a lowercase six-digit hex value, prefixed with a "#" character (U+0023 NUMBER SIGN), with the first two digits representing the red component,
the next two digits representing the green component, and the last two digits representing the blue component, the digits being in the range 0-9 a-f (U+0030 to U+0039 and U+0061 to U+0066). Otherwise, the color value has alpha less than 1.0, and the string is the
color value in the CSS rgba() functional-notation format: the literal string rgba (U+0072 U+0067 U+0062 U+0061) followed by a U+0028 LEFT PARENTHESIS, a base-ten integer in the range 0-255 representing the red component (using digits 0-9, U+0030 to U
+0039, in the shortest form possible), a literal U+002C COMMA and U+0020 SPACE, an integer for the green component, a comma and a space, an integer for the blue component, another comma and space, a U+0030 DIGIT ZERO, a U+002E FULL STOP
(representing the decimal point), one or more digits in the range 0-9 (U+0030 to U+0039) representing the fractional part of the alpha value, and finally a U+0029 RIGHT PARENTHESIS.
When the context is created, the strokeStyle and fillStyle attributes must initially have the string value #000000.
There are two types of gradients, linear gradients and radial gradients, both represented by objects implementing the opaque CanvasGradient interface.
Once a gradient has been created (see below), stops are placed along it to define how the colors are distributed along the gradient. The color of the gradient at each stop is the color specified for that stop. Between each such stop, the colors and the alpha component
must be linearly interpolated over the RGBA space without premultiplying the alpha value to find the color to use at that offset. Before the first stop, the color must be the color of the first stop. After the last stop, the color must be the color of the last stop. When there
are no stops, the gradient is transparent black.
gradient . addColorStop(offset, color)
Adds a color stop with the given color to the gradient at the given offset. 0.0 is the offset at one end of the gradient, 1.0 is the offset at the other end.
Throws an INDEX_SIZE_ERR exception if the offset it out of range. Throws a SYNTAX_ERR exception if the color cannot be parsed.
gradient = context . createLinearGradient(x0, y0, x1, y1)
Returns a CanvasGradient object that represents a linear gradient that paints along the line given by the coordinates represented by the arguments.
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The image argument is an instance of either HTMLImageElement, HTMLCanvasElement, or HTMLVideoElement. If the image is of the wrong type or null, the implementation must raise a TYPE_MISMATCH_ERR exception.
If the image argument is an HTMLImageElement object whose complete attribute is false, then the implementation must raise an INVALID_STATE_ERR exception.
If the image argument is an HTMLVideoElement object whose readyState attribute is either HAVE_NOTHING or HAVE_METADATA, then the implementation must raise an INVALID_STATE_ERR exception.
If the image argument is an HTMLCanvasElement object with either a horizontal dimension or a vertical dimension equal to zero, then the implementation must raise an INVALID_STATE_ERR exception.
Patterns must be painted so that the top left of the first image is anchored at the origin of the coordinate space, and images are then repeated horizontally to the left and right (if the repeat-x string was specified) or vertically up and down (if the repeat-y string was
specified) or in all four directions all over the canvas (if the repeat string was specified). The images are not scaled by this process; one CSS pixel of the image must be painted on one coordinate space unit. Of course, patterns must actually be painted only where the
stroking or filling effect requires that they be drawn, and are affected by the current transformation matrix.
When the createPattern() method is passed an animated image as its image argument, the user agent must use the poster frame of the animation, or, if there is no poster frame, the first frame of the animation.
When the image argument is an HTMLVideoElement, then the frame at the current playback position must be used as the source image.
4.8.11.1.5 Line styles
context . lineWidth [ = value ]
Returns the current line width.
Can be set, to change the line width. Values that are not finite values greater than zero are ignored.
context . lineCap [ = value ]
Returns the current line cap style.
Can be set, to change the line cap style.
The possible line cap styles are butt, round, and square. Other values are ignored.
context . lineJoin [ = value ]
Returns the current line join style.
Can be set, to change the line join style.
The possible line join styles are bevel, round, and miter. Other values are ignored.
context . miterLimit [ = value ]
Returns the current miter limit ratio.
Can be set, to change the miter limit ratio. Values that are not finite values greater than zero are ignored.
The lineWidth attribute gives the width of lines, in coordinate space units. On setting, zero, negative, infinite, and NaN values must be ignored, leaving the value unchanged.
When the context is created, the lineWidth attribute must initially have the value 1.0.
The lineCap attribute defines the type of endings that UAs will place on the end of lines. The three valid values are butt, round, and square. The butt value means that the end of each line has a flat edge perpendicular to the direction of the line (and that no
additional line cap is added). The round value means that a semi-circle with the diameter equal to the width of the line must then be added on to the end of the line. The square value means that a rectangle with the length of the line width and the width of half the line
width, placed flat against the edge perpendicular to the direction of the line, must be added at the end of each line. On setting, any other value than the literal strings butt, round, and square must be ignored, leaving the value unchanged.
When the context is created, the lineCap attribute must initially have the value butt.
The lineJoin attribute defines the type of corners that UAs will place where two lines meet. The three valid values are bevel, round, and miter.
On setting, any other value than the literal strings bevel, round, and miter must be ignored, leaving the value unchanged.
When the context is created, the lineJoin attribute must initially have the value miter.
A join exists at any point in a subpath shared by two consecutive lines. When a subpath is closed, then a join also exists at its first point (equivalent to its last point) connecting the first and last lines in the subpath.
In addition to the point where the join occurs, two additional points are relevant to each join, one for each line: the two corners found half the line width away from the join point, one perpendicular to each line, each on the side furthest from the other line.
A filled triangle connecting these two opposite corners with a straight line, with the third point of the triangle being the join point, must be rendered at all joins. The lineJoin attribute controls whether anything else is rendered. The three aforementioned values have
the following meanings:
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The bevel value means that this is all that is rendered at joins.
The round value means that a filled arc connecting the two aforementioned corners of the join, abutting (and not overlapping) the aforementioned triangle, with the diameter equal to the line width and the origin at the point of the join, must be rendered at joins.
The miter value means that a second filled triangle must (if it can given the miter length) be rendered at the join, with one line being the line between the two aforementioned corners, abutting the first triangle, and the other two being continuations of the outside edges
of the two joining lines, as long as required to intersect without going over the miter length.
The miter length is the distance from the point where the join occurs to the intersection of the line edges on the outside of the join. The miter limit ratio is the maximum allowed ratio of the miter length to half the line width. If the miter length would cause the miter limit
ratio to be exceeded, this second triangle must not be rendered.
The miter limit ratio can be explicitly set using the miterLimit attribute. On setting, zero, negative, infinite, and NaN values must be ignored, leaving the value unchanged.
When the context is created, the miterLimit attribute must initially have the value 10.0.
4.8.11.1.6 Shadows
All drawing operations are affected by the four global shadow attributes.
context . shadowColor [ = value ]
Returns the current shadow color.
Can be set, to change the shadow color. Values that cannot be parsed as CSS colors are ignored.
context . shadowOffsetX [ = value ]
context . shadowOffsetY [ = value ]
Returns the current shadow offset.
Can be set, to change the shadow offset. Values that are not finite numbers are ignored.
context . shadowBlur [ = value ]
Returns the current level of blur applied to shadows.
Can be set, to change the blur level. Values that are not finite numbers greater than or equal to zero are ignored.
The shadowColor attribute sets the color of the shadow.
When the context is created, the shadowColor attribute initially must be fully-transparent black.
On getting, the serialization of the color must be returned.
On setting, the new value must be parsed as a CSS <color> value and the color assigned. If the value is not a valid color, then it must be ignored, and the attribute must retain its previous value. [CSSCOLOR]
The shadowOffsetX and shadowOffsetY attributes specify the distance that the shadow will be offset in the positive horizontal and positive vertical distance respectively. Their values are in coordinate space units. They are not affected by the current transformation
matrix.
When the context is created, the shadow offset attributes must initially have the value 0.
On getting, they must return their current value. On setting, the attribute being set must be set to the new value, except if the value is infinite or NaN, in which case the new value must be ignored.
The shadowBlur attribute specifies the size of the blurring effect. (The units do not map to coordinate space units, and are not affected by the current transformation matrix.)
When the context is created, the shadowBlur attribute must initially have the value 0.
On getting, the attribute must return its current value. On setting the attribute must be set to the new value, except if the value is negative, infinite or NaN, in which case the new value must be ignored.
Shadows are only drawn if the opacity component of the alpha component of the color of shadowColor is non-zero and either the shadowBlur is non-zero, or the shadowOffsetX is non-zero, or the shadowOffsetY is non-zero.
When shadows are drawn, they must be rendered as follows:
1. Let A be the source image for which a shadow is being created.
2. Let B be an infinite transparent black bitmap, with a coordinate space and an origin identical to A.
3. Copy the alpha channel of A to B, offset by shadowOffsetX in the positive x direction, and shadowOffsetY in the positive y direction.
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context . quadraticCurveTo(cpx, cpy, x, y)
Adds the given point to the current path, connected to the previous one by a quadratic Bézier curve with the given control point.
context . bezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y)
Adds the given point to the current path, connected to the previous one by a cubic Bézier curve with the given control points.
context . arcTo(x1, y1, x2, y2, radius)
Adds a point to the current path, connected to the previous one by a straight line, then adds a second point to the current path, connected to the previous one by an arc whose properties are described by the arguments.
Throws an INDEX_SIZE_ERR exception if the given radius is negative.
context . arc(x, y, radius, startAngle, endAngle, anticlockwise)
Adds points to the subpath such that the arc described by the circumference of the circle described by the arguments, starting at the given start angle and ending at the given end angle, going in the given direction, is added to the path, connected to the
previous point by a straight line.
Throws an INDEX_SIZE_ERR exception if the given radius is negative.
context . rect(x, y, w, h)
Adds a new closed subpath to the path, representing the given rectangle.
context . fill()
Fills the subpaths with the current fill style.
context . stroke()
Strokes the subpaths with the current stroke style.
context . clip()
Further constrains the clipping region to the given path.
context . isPointInPath(x, y)
Returns true if the given point is in the current path.
Initially, the context's path must have zero subpaths.
The points and lines added to the path by these methods must be transformed according to the current transformation matrix as they are added.
The beginPath() method must empty the list of subpaths so that the context once again has zero subpaths.
The moveTo(x, y) method must create a new subpath with the specified point as its first (and only) point.
When the user agent is to ensure there is a subpath for a coordinate (x, y), the user agent must check to see if the context has any subpaths, and if it does not, then the user agent must create a new subpath with the point (x, y) as its first (and only) point, as if the
moveTo() method had been called.
The closePath() method must do nothing if the context has no subpaths. Otherwise, it must mark the last subpath as closed, create a new subpath whose first point is the same as the previous subpath's first point, and finally add this new subpath to the path.
If the last subpath had more than one point in its list of points, then this is equivalent to adding a straight line connecting the last point back to the first point, thus "closing" the shape, and then repeating the last (possibly implied) moveTo() call.
New points and the lines connecting them are added to subpaths using the methods described below. In all cases, the methods only modify the last subpath in the context's paths.
The lineTo(x, y) method must ensure there is a subpath for (x, y) if the context has no subpaths. Otherwise, it must connect the last point in the subpath to the given point (x, y) using a straight line, and must then add the given point (x, y) to the subpath.
The quadraticCurveTo(cpx, cpy, x, y) method must ensure there is a subpath for (cpx, cpy), and then must connect the last point in the subpath to the given point (x, y) using a quadratic Bézier curve with control point (cpx, cpy), and must then add the given
point (x, y) to the subpath. [BEZIER]
The bezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y) method must ensure there is a subpath for (cp1x, cp1y), and then must connect the last point in the subpath to the given point (x, y) using a cubic Bézier curve with control points (cp1x, cp1y) and (cp2x,
cp2y). Then, it must add the point (x, y) to the subpath. [BEZIER]
The arcTo(x1, y1, x2, y2, radius) method must first ensure there is a subpath for (x1, y1). Then, the behavior depends on the arguments and the last point in the subpath, as described below.
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Negative values for radius must cause the implementation to raise an INDEX_SIZE_ERR exception.
Let the point (x0, y0) be the last point in the subpath.
If the point (x0, y0) is equal to the point (x1, y1), or if the point (x1, y1) is equal to the point (x2, y2), or if the radius radius is zero, then the method must add the point (x1, y1) to the subpath, and connect that point to the previous point (x0, y0) by a straight line.
Otherwise, if the points (x0, y0), (x1, y1), and (x2, y2) all lie on a single straight line, then the method must add the point (x1, y1) to the subpath, and connect that point to the previous point (x0, y0) by a straight line.
Otherwise, let The Arc be the shortest arc given by circumference of the circle that has radius radius, and that has one point tangent to the half-infinite line that crosses the point (x0, y0) and ends at the point (x1, y1), and that has a different point tangent to the half-
infinite line that ends at the point (x1, y1) and crosses the point (x2, y2). The points at which this circle touches these two lines are called the start and end tangent points respectively. The method must connect the point (x0, y0) to the start tangent point by a straight
line, adding the start tangent point to the subpath, and then must connect the start tangent point to the end tangent point by The Arc, adding the end tangent point to the subpath.
The arc(x, y, radius, startAngle, endAngle, anticlockwise) method draws an arc. If the context has any subpaths, then the method must add a straight line from the last point in the subpath to the start point of the arc. In any case, it must draw the arc
between the start point of the arc and the end point of the arc, and add the start and end points of the arc to the subpath. The arc and its start and end points are defined as follows:
Consider a circle that has its origin at (x, y) and that has radius radius. The points at startAngle and endAngle along this circle's circumference, measured in radians clockwise from the positive x-axis, are the start and end points respectively.
If the anticlockwise argument is false and endAngle-startAngle is equal to or greater than 2π, or, if the anticlockwise argument is true and startAngle-endAngle is equal to or greater than 2π, then the arc is the whole circumference of this circle.
Otherwise, the arc is the path along the circumference of this circle from the start point to the end point, going anti-clockwise if the anticlockwise argument is true, and clockwise otherwise. Since the points are on the circle, as opposed to being simply angles from zero,
the arc can never cover an angle greater than 2π radians. If the two points are the same, or if the radius is zero, then the arc is defined as being of zero length in both directions.
Negative values for radius must cause the implementation to raise an INDEX_SIZE_ERR exception.
The rect(x, y, w, h) method must create a new subpath containing just the four points (x, y), (x+w, y), (x+w, y+h), (x, y+h), with those four points connected by straight lines, and must then mark the subpath as closed. It must then create a new subpath with the
point (x, y) as the only point in the subpath.
The fill() method must fill all the subpaths of the current path, using fillStyle, and using the non-zero winding number rule. Open subpaths must be implicitly closed when being filled (without affecting the actual subpaths).
Thus, if two overlapping but otherwise independent subpaths have opposite windings, they cancel out and result in no fill. If they have the same winding, that area just gets painted once.
The stroke() method must calculate the strokes of all the subpaths of the current path, using the lineWidth, lineCap, lineJoin, and (if appropriate) miterLimit attributes, and then fill the combined stroke area using the strokeStyle attribute.
Since the subpaths are all stroked as one, overlapping parts of the paths in one stroke operation are treated as if their union was what was painted.
Paths, when filled or stroked, must be painted without affecting the current path, and must be subject to shadow effects, global alpha, the clipping region, and global composition operators. (Transformations affect the path when the path is created, not when it is
painted, though the stroke style is still affected by the transformation during painting.)
Zero-length line segments must be pruned before stroking a path. Empty subpaths must be ignored.
The clip() method must create a new clipping region by calculating the intersection of the current clipping region and the area described by the current path, using the non-zero winding number rule. Open subpaths must be implicitly closed when computing the
clipping region, without affecting the actual subpaths. The new clipping region replaces the current clipping region.
When the context is initialized, the clipping region must be set to the rectangle with the top left corner at (0,0) and the width and height of the coordinate space.
The isPointInPath(x, y) method must return true if the point given by the x and y coordinates passed to the method, when treated as coordinates in the canvas coordinate space unaffected by the current transformation, is inside the current path as determined by
the non-zero winding number rule; and must return false otherwise. Points on the path itself are considered to be inside the path. If either of the arguments is infinite or NaN, then the method must return false.
4.8.11.1.9 Text
context . font [ = value ]
Returns the current font settings.
Can be set, to change the font. The syntax is the same as for the CSS 'font' property; values that cannot be parsed as CSS font values are ignored.
Relative keywords and lengths are computed relative to the default font, 10px sans-serif.
context . textAlign [ = value ]
Returns the current text alignment settings.
Can be set, to change the alignment. The possible values are start, end, left, right, and center. The default is start. Other values are ignored.
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context . textBaseline [ = value ]
Returns the current baseline alignment settings.
Can be set, to change the baseline alignment. The possible values and their meanings are given below. The default is alphabetic. Other values are ignored.
context . fillText(text, x, y [, maxWidth ] )
context . strokeText(text, x, y [, maxWidth ] )
Fills or strokes (respectively) the given text at the given position. If a maximum width is provided, the text will be scaled to fit that width if necessary.
metrics = context . measureText(text)
Returns a TextMetrics object with the metrics of the given text in the current font.
metrics . width
Returns the advance width of the text that was passed to the measureText() method.
The font DOM attribute, on setting, must be parsed the same way as the 'font' property of CSS (but without supporting property-independent stylesheet syntax like 'inherit'), and the resulting font must be assigned to the context, with the 'line-height' component forced
to 'normal'. If the new value is syntactically incorrect (including using property-independent stylesheet syntax like 'inherit' or 'initial'), then it must be ignored, without assigning a new font value. [CSS]
Font names must be interpreted in the context of the canvas element's stylesheets; any fonts embedded using @font-face must therefore be available once they are loaded. (If a font is referenced before it is fully loaded, then it must be treated as if it was an
unknown font, falling back to another as described by the relevant CSS specifications.) [CSSWEBFONTS]
Only vector fonts should be used by the user agent; if a user agent were to use bitmap fonts then transformations would likely make the font look very ugly.
On getting, the font attribute must return the serialized form of the current font of the context (with no 'line-height' component). [CSSOM]
For example, after the following statement:
context.font = 'italic 400 12px/2 Unknown Font, sans-serif';
...the expression context.font would evaluate to the string "italic 12px Unknown Font, sans-serif". The "400" font-weight doesn't appear because that is the default value. The line-height doesn't appear because it is forced to "normal", the
default value.
When the context is created, the font of the context must be set to 10px sans-serif. When the 'font-size' component is set to lengths using percentages, 'em' or 'ex' units, or the 'larger' or 'smaller' keywords, these must be interpreted relative to the computed value of the
'font-size' property of the corresponding canvas element at the time that the attribute is set. When the 'font-weight' component is set to the relative values 'bolder' and 'lighter', these must be interpreted relative to the computed value of the 'font-weight' property of the
corresponding canvas element at the time that the attribute is set. If the computed values are undefined for a particular case (e.g. because the canvas element is not in a Document), then the relative keywords must be interpreted relative to the normal-weight 10px
sans-serif default.
The textAlign DOM attribute, on getting, must return the current value. On setting, if the value is one of start, end, left, right, or center, then the value must be changed to the new value. Otherwise, the new value must be ignored. When the context is
created, the textAlign attribute must initially have the value start.
The textBaseline DOM attribute, on getting, must return the current value. On setting, if the value is one of top, hanging, middle, alphabetic, ideographic, or bottom, then the value must be changed to the new value. Otherwise, the new value must be
ignored. When the context is created, the textBaseline attribute must initially have the value alphabetic.
The textBaseline attribute's allowed keywords correspond to alignment points in the font:
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The keywords map to these alignment points as follows:
top
The top of the em square
hanging
The hanging baseline
middle
The middle of the em square
alphabetic
The alphabetic baseline
ideographic
The ideographic baseline
bottom
The bottom of the em square
The fillText() and strokeText() methods take three or four arguments, text, x, y, and optionally maxWidth, and render the given text at the given (x, y) coordinates ensuring that the text isn't wider than maxWidth if specified, using the current font, textAlign,
and textBaseline values. Specifically, when the methods are called, the user agent must run the following steps:
1. Let font be the current font of the context, as given by the font attribute.
2. Replace all the space characters in text with U+0020 SPACE characters.
3. Form a hypothetical infinitely wide CSS line box containing a single inline box containing the text text, with all the properties at their initial values except the 'font' property of the inline box set to font and the 'direction' property of the inline box set to the
directionality of the canvas element. [CSS]
4. If the maxWidth argument was specified and the hypothetical width of the inline box in the hypothetical line box is greater than maxWidth CSS pixels, then change font to have a more condensed font (if one is available or if a reasonably readable one can be
synthesized by applying a horizontal scale factor to the font) or a smaller font, and return to the previous step.
5. Let the anchor point be a point on the inline box, determined by the textAlign and textBaseline values, as follows:
Horizontal position:
If textAlign is left
If textAlign is start and the directionality of the canvas element is 'ltr'
If textAlign is end and the directionality of the canvas element is 'rtl'
Let the anchor point's horizontal position be the left edge of the inline box.
If textAlign is right
If textAlign is end and the directionality of the canvas element is 'ltr'
If textAlign is start and the directionality of the canvas element is 'rtl'
Let the anchor point's horizontal position be the right edge of the inline box.
If textAlign is center
Let the anchor point's horizontal position be half way between the left and right edges of the inline box.
Vertical position:
If textBaseline is top
Let the anchor point's vertical position be the top of the em box of the first available font of the inline box.
If textBaseline is hanging
Let the anchor point's vertical position be the hanging baseline of the first available font of the inline box.
If textBaseline is middle
Let the anchor point's vertical position be half way between the bottom and the top of the em box of the first available font of the inline box.
If textBaseline is alphabetic
Let the anchor point's vertical position be the alphabetic baseline of the first available font of the inline box.
If textBaseline is ideographic
Let the anchor point's vertical position be the ideographic baseline of the first available font of the inline box.
If textBaseline is bottom
Let the anchor point's vertical position be the bottom of the em box of the first available font of the inline box.
6. Paint the hypothetical inline box as the shape given by the text's glyphs, as transformed by the current transformation matrix, and anchored and sized so that before applying the current transformation matrix, the anchor point is at (x, y) and each CSS pixel is
mapped to one coordinate space unit.
For fillText() fillStyle must be applied to the glyphs and strokeStyle must be ignored. For strokeText() the reverse holds and strokeStyle must be applied to the glyph outlines and fillStyle must be ignored.
Text is painted without affecting the current path, and is subject to shadow effects, global alpha, the clipping region, and global composition operators.
The measureText() method takes one argument, text. When the method is invoked, the user agent must replace all the space characters in text with U+0020 SPACE characters, and then must form a hypothetical infinitely wide CSS line box containing a single inline
box containing the text text, with all the properties at their initial values except the 'font' property of the inline element set to the current font of the context, as given by the font attribute, and must then return a new TextMetrics object with its width attribute set to
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the width of that inline box, in CSS pixels. [CSS]
The TextMetrics interface is used for the objects returned from measureText(). It has one attribute, width, which is set by the measureText() method.
Glyphs rendered using fillText() and strokeText() can spill out of the box given by the font size (the em square size) and the width returned by measureText() (the text width). This version of the specification does not provide a way to obtain the
bounding box dimensions of the text. If the text is to be rendered and removed, care needs to be taken to replace the entire area of the canvas that the clipping region covers, not just the box given by the em square height and measured text width.
A future version of the 2D context API may provide a way to render fragments of documents, rendered using CSS, straight to the canvas. This would be provided in preference to a dedicated way of doing multiline layout.
4.8.11.1.10 Images
To draw images onto the canvas, the drawImage method can be used.
This method can be invoked with three different sets of arguments:
q drawImage(image, dx, dy)
q drawImage(image, dx, dy, dw, dh)
q drawImage(image, sx, sy, sw, sh, dx, dy, dw, dh)
Each of those three can take either an HTMLImageElement, an HTMLCanvasElement, or an HTMLVideoElement for the image argument.
context . drawImage(image, dx, dy)
context . drawImage(image, dx, dy, dw, dh)
context . drawImage(image, sx, sy, sw, sh, dx, dy, dw, dh)
Draws the given image onto the canvas. The arguments are interpreted as follows:
If the first argument isn't an img, canvas, or video element, throws a TYPE_MISMATCH_ERR exception. If the image is not fully decoded yet, or has no image data, throws an INVALID_STATE_ERR exception. If the second argument isn't one of the
allowed values, throws a SYNTAX_ERR exception.
If not specified, the dw and dh arguments must default to the values of sw and sh, interpreted such that one CSS pixel in the image is treated as one unit in the canvas coordinate space. If the sx, sy, sw, and sh arguments are omitted, they must default to 0, 0, the
image's intrinsic width in image pixels, and the image's intrinsic height in image pixels, respectively.
The image argument is an instance of either HTMLImageElement, HTMLCanvasElement, or HTMLVideoElement. If the image is of the wrong type or null, the implementation must raise a TYPE_MISMATCH_ERR exception.
If the image argument is an HTMLImageElement object whose complete attribute is false, then the implementation must raise an INVALID_STATE_ERR exception.
If the image argument is an HTMLVideoElement object whose readyState attribute is either HAVE_NOTHING or HAVE_METADATA, then the implementation must raise an INVALID_STATE_ERR exception.
If the image argument is an HTMLCanvasElement object with either a horizontal dimension or a vertical dimension equal to zero, then the implementation must raise an INVALID_STATE_ERR exception.
The source rectangle is the rectangle whose corners are the four points (sx, sy), (sx+sw, sy), (sx+sw, sy+sh), (sx, sy+sh).
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If the source rectangle is not entirely within the source image, or if one of the sw or sh arguments is zero, the implementation must raise an INDEX_SIZE_ERR exception.
The destination rectangle is the rectangle whose corners are the four points (dx, dy), (dx+dw, dy), (dx+dw, dy+dh), (dx, dy+dh).
When drawImage() is invoked, the region of the image specified by the source rectangle must be painted on the region of the canvas specified by the destination rectangle, after applying the current transformation matrix to the points of the destination rectangle.
The original image data of the source image must be used, not the image as it is rendered (e.g. width and height attributes on the source element have no effect).
This specification does not define the algorithm to use when scaling the image, if necessary.
When a canvas is drawn onto itself, the drawing model requires the source to be copied before the image is drawn back onto the canvas, so it is possible to copy parts of a canvas onto overlapping parts of itself.
When the drawImage() method is passed an animated image as its image argument, the user agent must use the poster frame of the animation, or, if there is no poster frame, the first frame of the animation.
When the image argument is an HTMLVideoElement, then the frame at the current playback position must be used as the source image.
Images are painted without affecting the current path, and are subject to shadow effects, global alpha, the clipping region, and global composition operators.
4.8.11.1.11 Pixel manipulation
imagedata = context . createImageData(sw, sh)
Returns an ImageData object with the given dimensions in CSS pixels (which might map to a different number of actual device pixels exposed by the object itself). All the pixels in the returned object are transparent black.
imagedata = context . createImageData(imagedata)
Returns an ImageData object with the same dimensions as the argument. All the pixels in the returned object are transparent black.
Throws a NOT_SUPPORTED_ERR exception if the argument is null.
imagedata = context . getImageData(sx, sy, sw, sh)
Returns an ImageData object containing the image data for the given rectangle of the canvas.
Throws a NOT_SUPPORTED_ERR exception if any of the arguments are not finite. Throws an INDEX_SIZE_ERR exception if the either of the width or height arguments are zero.
imagedata . width
imagedata . height
Returns the actual dimensions of the data in the ImageData object, in device pixels.
imagedata . data
Returns the one-dimensional array containing the data.
context . putImageData(imagedata, dx, dy [, dirtyX, dirtyY, dirtyWidth, dirtyHeight ])
Paints the data from the given ImageData object onto the canvas. If a dirty rectangle is provided, only the pixels from that rectangle are painted.
The globalAlpha and globalCompositeOperation attributes, as well as the shadow attributes, are ignored for the purposes of this method call; pixels in the canvas are replaced wholesale, with no composition, alpha blending, no shadows, etc.
If the first argument isn't an ImageData object, throws a TYPE_MISMATCH_ERR exception. Throws a NOT_SUPPORTED_ERR exception if any of the other arguments are not finite.
The createImageData() method is used to instantiate new blank ImageData objects. When the method is invoked with two arguments sw and sh, it must return an ImageData object representing a rectangle with a width in CSS pixels equal to the absolute
magnitude of sw and a height in CSS pixels equal to the absolute magnitude of sh. When invoked with a single imagedata argument, it must return an ImageData object representing a rectangle with the same dimensions as the ImageData object passed as the
argument. The ImageData object return must be filled with transparent black.
The getImageData(sx, sy, sw, sh) method must return an ImageData object representing the underlying pixel data for the area of the canvas denoted by the rectangle whose corners are the four points (sx, sy), (sx+sw, sy), (sx+sw, sy+sh), (sx, sy+sh), in
canvas coordinate space units. Pixels outside the canvas must be returned as transparent black. Pixels must be returned as non-premultiplied alpha values.
If any of the arguments to createImageData() or getImageData() are infinite or NaN, or if the createImageData() method is invoked with only one argument but that argument is null, the method must instead raise a NOT_SUPPORTED_ERR exception. If either
the sw or sh arguments are zero, the method must instead raise an INDEX_SIZE_ERR exception.
ImageData objects must be initialized so that their width attribute is set to w, the number of physical device pixels per row in the image data, their height attribute is set to h, the number of rows in the image data, and their data attribute is initialized to a
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CanvasPixelArray object holding the image data. At least one pixel's worth of image data must be returned.
The CanvasPixelArray object provides ordered, indexed access to the color components of each pixel of the image data. The data must be represented in left-to-right order, row by row top to bottom, starting with the top left, with each pixel's red, green, blue, and
alpha components being given in that order for each pixel. Each component of each device pixel represented in this array must be in the range 0..255, representing the 8 bit value for that component. The components must be assigned consecutive indices starting with
0 for the top left pixel's red component.
The CanvasPixelArray object thus represents h×w×4 integers. The length attribute of a CanvasPixelArray object must return this number.
The object's indices of the supported indexed properties are the numbers in the range 0 .. h×w×4-1.
When a CanvasPixelArray object is indexed to retrieve an indexed property index, the value returned must be the value of the indexth component in the array.
When a CanvasPixelArray object is indexed to modify an indexed property index with value value, the value of the indexth component in the array must be set to value. JS undefined values must be converted to zero. Other values must first be converted to
numbers using JavaScript's ToNumber algorithm, and if the result is a NaN value, then the value must be converted to zero. If the result is less than 0, it must be clamped to zero. If the result is more than 255, it must be clamped to 255. If the number is not an integer, it
should be rounded to the nearest integer using the IEEE 754r convertToIntegerTiesToEven rounding mode. [ECMA262] [IEEE754R]
The width and height (w and h) might be different from the sw and sh arguments to the above methods, e.g. if the canvas is backed by a high-resolution bitmap, or if the sw and sh arguments are negative.
The putImageData(imagedata, dx, dy, dirtyX, dirtyY, dirtyWidth, dirtyHeight) method writes data from ImageData structures back to the canvas.
If any of the arguments to the method are infinite or NaN, the method must raise a NOT_SUPPORTED_ERR exception.
If the first argument to the method is null or not an ImageData object then the putImageData() method must raise a TYPE_MISMATCH_ERR exception.
When the last four arguments are omitted, they must be assumed to have the values 0, 0, the width member of the imagedata structure, and the height member of the imagedata structure, respectively.
When invoked with arguments that do not, per the last few paragraphs, cause an exception to be raised, the putImageData() method must act as follows:
1. Let dxdevice be the x-coordinate of the device pixel in the underlying pixel data of the canvas corresponding to the dx coordinate in the canvas coordinate space.
Let dydevice be the y-coordinate of the device pixel in the underlying pixel data of the canvas corresponding to the dy coordinate in the canvas coordinate space.
2. If dirtyWidth is negative, let dirtyX be dirtyX+dirtyWidth, and let dirtyWidth be equal to the absolute magnitude of dirtyWidth.
If dirtyHeight is negative, let dirtyY be dirtyY+dirtyHeight, and let dirtyHeight be equal to the absolute magnitude of dirtyHeight.
3. If dirtyX is negative, let dirtyWidth be dirtyWidth+dirtyX, and let dirtyX be zero.
If dirtyY is negative, let dirtyHeight be dirtyHeight+dirtyY, and let dirtyY be zero.
4. If dirtyX+dirtyWidth is greater than the width attribute of the imagedata argument, let dirtyWidth be the value of that width attribute, minus the value of dirtyX.
If dirtyY+dirtyHeight is greater than the height attribute of the imagedata argument, let dirtyHeight be the value of that height attribute, minus the value of dirtyY.
5. If, after those changes, either dirtyWidth or dirtyHeight is negative or zero, stop these steps without affecting the canvas.
6. Otherwise, for all integer values of x and y where dirtyX ≤ x < dirtyX+dirtyWidth and dirtyY ≤ y < dirtyY+dirtyHeight, copy the four channels of the pixel with coordinate (x, y) in the imagedata data structure to the pixel with coordinate (dxdevice+x, dydevice+y) in the
underlying pixel data of the canvas.
The handling of pixel rounding when the specified coordinates do not exactly map to the device coordinate space is not defined by this specification, except that the following must result in no visible changes to the rendering:
context.putImageData(context.getImageData(x, y, w, h), p, q);
...for any value of x, y, w, and h and where p is the smaller of x and the sum of x and w, and q is the smaller of y and the sum of y and h; and except that the following two calls:
context.createImageData(w, h);
context.getImageData(0, 0, w, h);
...must return ImageData objects with the same dimensions, for any value of w and h. In other words, while user agents may round the arguments of these methods so that they map to device pixel boundaries, any rounding performed must be performed consistently
for all of the createImageData(), getImageData() and putImageData() operations.
Due to the lossy nature of converting to and from premultiplied alpha color values, pixels that have just been set using putImageData() might be returned to an equivalent getImageData() as different values.
The current path, transformation matrix, shadow attributes, global alpha, the clipping region, and global composition operator must not affect the getImageData() and putImageData() methods.
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The data returned by getImageData() is at the resolution of the canvas backing store, which is likely to not be one device pixel to each CSS pixel if the display used is a high resolution display.
In the following example, the script generates an ImageData object so that it can draw onto it.
// canvas is a reference to a <canvas> element
var context = canvas.getContext('2d');
// create a blank slate
var data = context.createImageData(canvas.width, canvas.height);
// create some plasma
FillPlasma(data, 'green'); // green plasma
// add a cloud to the plasma
AddCloud(data, data.width/2, data.height/2); // put a cloud in the middle
// paint the plasma+cloud on the canvas
context.putImageData(data, 0, 0);
// support methods
function FillPlasma(data, color) { ... }
function AddCloud(data, x, y) { ... }
Here is an example of using getImageData() and putImageData() to implement an edge detection filter.
<!DOCTYPE HTML>
<html>
<head>
<title>Edge detection demo</title>
<script>
var image = new Image();
function init() {
image.onload = demo;
image.src = "image.jpeg";
}
function demo() {
var canvas = document.getElementsByTagName('canvas')[0];
var context = canvas.getContext('2d');
// draw the image onto the canvas
context.drawImage(image, 0, 0);
// get the image data to manipulate
var input = context.getImageData(0, 0, canvas.width, canvas.height);
// get an empty slate to put the data into
var output = context.createImageData(canvas.width, canvas.height);
// alias some variables for convenience
// notice that we are using input.width and input.height here
// as they might not be the same as canvas.width and canvas.height
// (in particular, they might be different on high-res displays)
var w = input.width, h = input.height;
var inputData = input.data;
var outputData = output.data;
// edge detection
for (var y = 1; y < h-1; y += 1) {
for (var x = 1; x < w-1; x += 1) {
for (var c = 0; c < 3; c += 1) {
var i = (y*w + x)*4 + c;
outputData[i] = 127 + -inputData[i - w*4 - 4] - inputData[i - w*4] - inputData[i - w*4 + 4] +
-inputData[i - 4] + 8*inputData[i] - inputData[i + 4] +
-inputData[i + w*4 - 4] - inputData[i + w*4] - inputData[i + w*4 + 4];
}
outputData[(y*w + x)*4 + 3] = 255; // alpha
}
}
// put the image data back after manipulation
context.putImageData(output, 0, 0);
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coords
shape
href
target
ping
rel
media
hreflang
type
DOM interface:
[Stringifies=href] interface HTMLAreaElement : HTMLElement {
attribute DOMString alt;
attribute DOMString coords;
attribute DOMString shape;
attribute DOMString href;
attribute DOMString target;
attribute DOMString ping;
attribute DOMString rel;
readonly attribute DOMTokenList relList;
attribute DOMString media;
attribute DOMString hreflang;
attribute DOMString type;
// URL decomposition attributes
attribute DOMString protocol;
attribute DOMString host;
attribute DOMString hostname;
attribute DOMString port;
attribute DOMString pathname;
attribute DOMString search;
attribute DOMString hash;
};
The area element represents either a hyperlink with some text and a corresponding area on an image map, or a dead area on an image map.
If the area element has an href attribute, then the area element represents a hyperlink. In this case, the alt attribute must be present. It specifies the text of the hyperlink. Its value must be text that, when presented with the texts specified for the other hyperlinks of
the image map, and with the alternative text of the image, but without the image itself, provides the user with the same kind of choice as the hyperlink would when used without its text but with its shape applied to the image. The alt attribute may be left blank if there is
another area element in the same image map that points to the same resource and has a non-blank alt attribute.
If the area element has no href attribute, then the area represented by the element cannot be selected, and the alt attribute must be omitted.
In both cases, the shape and coords attributes specify the area.
The shape attribute is an enumerated attribute. The following table lists the keywords defined for this attribute. The states given in the first cell of the rows with keywords give the states to which those keywords map. Some of the keywords are non-conforming, as noted
in the last column.
State Keywords Notes
Circle state circle
circ Non-conforming
Default state default
Polygon state poly
polygon Non-conforming
Rectangle state rect
rectangle Non-conforming
The attribute may be omitted. The missing value default is the rectangle state.
The coords attribute must, if specified, contain a valid list of integers. This attribute gives the coordinates for the shape described by the shape attribute. The processing for this attribute is described as part of the image map processing model.
In the circle state, area elements must have a coords attribute present, with three integers, the last of which must be non-negative. The first integer must be the distance in CSS pixels from the left edge of the image to the center of the circle, the second integer must
be the distance in CSS pixels from the top edge of the image to the center of the circle, and the third integer must be the radius of the circle, again in CSS pixels.
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Circle state
Let x be the first number in coords, y be the second number, and r be the third number.
The shape is a circle whose center is x CSS pixels from the left edge of the image and x CSS pixels from the top edge of the image, and whose radius is r pixels.
Default state
The shape is a rectangle that exactly covers the entire image.
Polygon state
Let xi be the (2i)th entry in coords, and yi be the (2i+1)th entry in coords (the first entry in coords being the one with index 0).
Let the coordinates be (xi, yi), interpreted in CSS pixels measured from the top left of the image, for all integer values of i from 0 to (N/2)-1, where N is the number of items in coords.
The shape is a polygon whose vertices are given by the coordinates, and whose interior is established using the even-odd rule. [GRAPHICS]
Rectangle state
Let x1 be the first number in coords, y1 be the second number, x2 be the third number, and y2 be the fourth number.
The shape is a rectangle whose top-left corner is given by the coordinate (x1, y1) and whose bottom right corner is given by the coordinate (x2, y2), those coordinates being interpreted as CSS pixels from the top left corner of the image.
For historical reasons, the coordinates must be interpreted relative to the displayed image, even if it stretched using CSS or the image element's width and height attributes.
Mouse clicks on an image associated with a set of layered shapes per the above algorithm must be dispatched to the top-most shape covering the point that the pointing device indicated (if any), and then, must be dispatched again (with a new Event object) to the
image element itself. User agents may also allow individual area elements representing hyperlinks to be selected and activated (e.g. using a keyboard); events from this are not also propagated to the image.
Because a map element (and its area elements) can be associated with multiple img and object elements, it is possible for an area element to correspond to multiple focusable areas of the document.
Image maps are live; if the DOM is mutated, then the user agent must act as if it had rerun the algorithms for image maps.
4.8.15 MathML
The math element from the MathML namespace falls into the embedded content category for the purposes of the content models in this specification.
User agents must handle text other than inter-element whitespace found in MathML elements whose content models do not allow raw text by pretending for the purposes of MathML content models, layout, and rendering that that text is actually wrapped in an mtext
element in the MathML namespace. (Such text is not, however, conforming.)
User agents must act as if any MathML element whose contents does not match the element's content model was replaced, for the purposes of MathML layout and rendering, by an merror element in the MathML namespace containing some appropriate error
message.
To enable authors to use MathML tools that only accept MathML in its XML form, interactive HTML user agents are encouraged to provide a way to export any MathML fragment as a namespace-well-formed XML fragment.
4.8.16 SVG
The svg element from the SVG namespace falls into the embedded content, phrasing content, and flow content categories for the purposes of the content models in this specification.
To enable authors to use SVG tools that only accept SVG in its XML form, interactive HTML user agents are encouraged to provide a way to export any SVG fragment as a namespace-well-formed XML fragment.
When the SVG foreignObject element contains elements from the HTML namespace, such elements must all be flow content. [SVG]
The content model for title elements in the SVG namespace inside HTML documents is phrasing content. (This further constrains the requirements given in the SVG specification.)
4.8.17 Dimension attributes
Author requirements: The width and height attributes on img, iframe, embed, object, video, and, when their type attribute is in the Image Button state, input elements may be specified to give the dimensions of the visual content of the element (the width
and height respectively, relative to the nominal direction of the output medium), in CSS pixels. The attributes, if specified, must have values that are valid non-negative integers.
The specified dimensions given may differ from the dimensions specified in the resource itself, since the resource may have a resolution that differs from the CSS pixel resolution. (On screens, CSS pixels have a resolution of 96ppi, but in general the CSS pixel
resolution depends on the reading distance.) If both attributes are specified, then one of the following statements must be true:
q specified width - 0.5 ≤ specified height * target ratio ≤ specified width + 0.5
q specified height - 0.5 ≤ specified width / target ratio ≤ specified height + 0.5
q specified height = specified width = 0
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The target ratio is the ratio of the intrinsic width to the intrinsic height in the resource. The specified width and specified height are the values of the width and height attributes respectively.
The two attributes must be omitted if the resource in question does not have both an intrinsic width and an intrinsic height.
If the two attributes are both zero, it indicates that the element is not intended for the user (e.g. it might be a part of a service to count page views).
The dimension attributes are not intended to be used to stretch the image.
User agent requirements: User agents are expected to use these attributes as hints for the rendering.
The width and height DOM attributes on the iframe, embed, object, and video elements must reflect the respective content attributes of the same name.
4.9 Tabular data
4.9.1 Introduction
This section is non-normative.
...examples, how to write tables accessibly, a brief mention of the table model, etc...
4.9.2 The table element
Categories
Flow content.
Contexts in which this element may be used:
Where flow content is expected.
Content model:
In this order: optionally a caption element, followed by either zero or more colgroup elements, followed optionally by a thead element, followed optionally by a tfoot element, followed by either zero or more tbody elements or one or more tr
elements, followed optionally by a tfoot element (but there can only be one tfoot element child in total).
Content attributes:
Global attributes
DOM interface:
interface HTMLTableElement : HTMLElement {
attribute HTMLTableCaptionElement caption;
HTMLElement createCaption();
void deleteCaption();
attribute HTMLTableSectionElement tHead;
HTMLElement createTHead();
void deleteTHead();
attribute HTMLTableSectionElement tFoot;
HTMLElement createTFoot();
void deleteTFoot();
readonly attribute HTMLCollection tBodies;
HTMLElement createTBody();
readonly attribute HTMLCollection rows;
HTMLElement insertRow([Optional] in long index);
void deleteRow(in long index);
};
The table element represents data with more than one dimension, in the form of a table.
The table element takes part in the table model.
Tables must not be used as layout aids. Historically, some Web authors have misused tables in HTML as a way to control their page layout. This usage is non-conforming, because tools attempting to extract tabular data from such documents would obtain very
confusing results. In particular, users of accessibility tools like screen readers are likely to find it very difficult to navigate pages with tables used for la](https://image.slidesharecdn.com/manual-html-5-byreparaciondepc-cl-130309121920-phpapp02/85/Manual-html-5-by-reparaciondepc-cl-217-320.jpg)
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- 1. HTML 5 HTML 5 A vocabulary and associated APIs for HTML and XHTML http://dev.w3.org/html5/spec/Overview.html (1 de 570)01-08-2009 6:55:53
- 2. HTML 5 Editor's Draft 1 August 2009 Latest Published Version: http://www.w3.org/TR/html5/ Latest Editor's Draft: http://www.w3.org/html/wg/html5/ Previous Versions: http://www.w3.org/TR/2009/WD-html5-20090423/ http://www.w3.org/TR/2009/WD-html5-20090212/ http://www.w3.org/TR/2008/WD-html5-20080610/ http://www.w3.org/TR/2008/WD-html5-20080122/ Editors: Ian Hickson, Google, Inc. David Hyatt, Apple, Inc. This specification is available in the following formats: single page HTML, multipage HTML. This is $Revision: 1.2719 $. Copyright © 2009 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply. Abstract This specification defines the 5th major revision of the core language of the World Wide Web: the Hypertext Markup Language (HTML). In this version, new features are introduced to help Web application authors, new elements are introduced based on research into prevailing authoring practices, and special attention has been given to defining clear conformance criteria for user agents in an effort to improve interoperability. http://dev.w3.org/html5/spec/Overview.html (2 de 570)01-08-2009 6:55:53
- 3. HTML 5 Status of this document This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the most recently formally published revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/. The WHATWG version of this specification is available under a license that permits reuse of the specification text. If you wish to make comments regarding this document, please send them to public-html-comments@w3.org (subscribe, archives) or whatwg@whatwg.org (subscribe, archives), or submit them using our public bug database. All feedback is welcome. We maintain a list of all e-mails that have not yet been considered and a list of all bug reports that have not yet been resolved. Implementors should be aware that this specification is not stable. Implementors who are not taking part in the discussions are likely to find the specification changing out from under them in incompatible ways. Vendors interested in implementing this specification before it eventually reaches the Candidate Recommendation stage should join the aforementioned mailing lists and take part in the discussions. The publication of this document by the W3C as a W3C Working Draft does not imply that all of the participants in the W3C HTML working group endorse the contents of the specification. Indeed, for any section of the specification, one can usually find many members of the working group or of the W3C as a whole who object strongly to the current text, the existence of the section at all, or the idea that the working group should even spend time discussing the concept of that section. The latest stable version of the editor's draft of this specification is always available on the W3C CVS server and in the WHATWG Subversion repository. The latest editor's working copy (which may contain unfinished text in the process of being prepared) is also available. There are various ways to follow the change history for the specification: E-mail notifications of changes HTML-Diffs mailing list (diff-marked HTML versions for each change): http://lists.w3.org/Archives/Public/public-html-diffs/latest Commit-Watchers mailing list (complete source diffs): http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org Real-time notifications of changes: Generated diff-marked HTML versions for each change: http://twitter.com/HTML5 All (non-editorial) changes to the spec source: http://twitter.com/WHATWG Browsable version-control record of all changes: CVSWeb interface with side-by-side diffs: http://dev.w3.org/cvsweb/html5/spec/Overview.html Annotated summary with unified diffs: http://html5.org/tools/web-apps-tracker Raw Subversion interface: svn checkout http://svn.whatwg.org/webapps/ The W3C HTML Working Group is the W3C working group responsible for this specification's progress along the W3C Recommendation track. This specification is the 1 August 2009 Editor's Draft. This specification is also being produced by the WHATWG. The two specifications are identical from the table of contents onwards. This specification is intended to replace (be a new version of) what was previously the HTML4, XHTML 1.0, and DOM2 HTML specifications. This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy. Stability Different parts of this specification are at different levels of maturity. http://dev.w3.org/html5/spec/Overview.html (3 de 570)01-08-2009 6:55:53
- 4. HTML 5 Table of contents 1. 1 Introduction 1. 1.1 Background 2. 1.2 Audience 3. 1.3 Scope 4. 1.4 History 5. 1.5 Design notes 1. 1.5.1 Serializability of script execution 2. 1.5.2 Compliance with other specifications 6. 1.6 Relationships to other specifications 1. 1.6.1 Relationship to HTML 4.01 and DOM2 HTML 2. 1.6.2 Relationship to XHTML 1.x 7. 1.7 HTML vs XHTML 8. 1.8 Structure of this specification 1. 1.8.1 How to read this specification 2. 1.8.2 Typographic conventions 9. 1.9 A quick introduction to HTML 2. 2 Common infrastructure 1. 2.1 Terminology 1. 2.1.1 XML 2. 2.1.2 DOM trees 3. 2.1.3 Scripting 4. 2.1.4 Plugins 5. 2.1.5 Character encodings 6. 2.1.6 Resources 2. 2.2 Conformance requirements 1. 2.2.1 Dependencies 2. 2.2.2 Extensibility 3. 2.3 Case-sensitivity and string comparison 4. 2.4 Common microsyntaxes 1. 2.4.1 Common parser idioms 2. 2.4.2 Boolean attributes 3. 2.4.3 Keywords and enumerated attributes 4. 2.4.4 Numbers 1. 2.4.4.1 Non-negative integers 2. 2.4.4.2 Signed integers 3. 2.4.4.3 Real numbers 4. 2.4.4.4 Ratios 5. 2.4.4.5 Percentages and lengths 6. 2.4.4.6 Lists of integers 7. 2.4.4.7 Lists of dimensions 5. 2.4.5 Dates and times 1. 2.4.5.1 Months 2. 2.4.5.2 Dates 3. 2.4.5.3 Times 4. 2.4.5.4 Local dates and times 5. 2.4.5.5 Global dates and times 6. 2.4.5.6 Weeks 7. 2.4.5.7 Vaguer moments in time 6. 2.4.6 Colors 7. 2.4.7 Space-separated tokens 8. 2.4.8 Comma-separated tokens 9. 2.4.9 Reversed DNS identifiers 10. 2.4.10 References http://dev.w3.org/html5/spec/Overview.html (4 de 570)01-08-2009 6:55:53
- 5. HTML 5 5. 2.5 URLs 1. 2.5.1 Terminology 2. 2.5.2 Dynamic changes to base URLs 3. 2.5.3 Interfaces for URL manipulation 6. 2.6 Fetching resources 1. 2.6.1 Protocol concepts 2. 2.6.2 Encrypted HTTP and related security concerns 3. 2.6.3 Determining the type of a resource 7. 2.7 Character encodings 8. 2.8 Common DOM interfaces 1. 2.8.1 Reflecting content attributes in DOM attributes 2. 2.8.2 Collections 1. 2.8.2.1 HTMLCollection 2. 2.8.2.2 HTMLAllCollection 3. 2.8.2.3 HTMLFormControlsCollection 4. 2.8.2.4 HTMLOptionsCollection 5. 2.8.2.5 HTMLPropertyCollection 3. 2.8.3 DOMTokenList 4. 2.8.4 DOMSettableTokenList 5. 2.8.5 Safe passing of structured data 6. 2.8.6 DOMStringMap 7. 2.8.7 DOM feature strings 8. 2.8.8 Exceptions 9. 2.8.9 Garbage collection 3. 3 Semantics, structure, and APIs of HTML documents 1. 3.1 Introduction 2. 3.2 Documents 1. 3.2.1 Documents in the DOM 2. 3.2.2 Security 3. 3.2.3 Resource metadata management 4. 3.2.4 DOM tree accessors 3. 3.3 Elements 1. 3.3.1 Semantics 2. 3.3.2 Elements in the DOM 3. 3.3.3 Global attributes 1. 3.3.3.1 The id attribute 2. 3.3.3.2 The title attribute 3. 3.3.3.3 The lang and xml:lang attributes 4. 3.3.3.4 The xml:base attribute (XML only) 5. 3.3.3.5 The dir attribute 6. 3.3.3.6 The class attribute 7. 3.3.3.7 The style attribute 8. 3.3.3.8 Embedding custom non-visible data 4. 3.4 Content models 1. 3.4.1 Kinds of content 1. 3.4.1.1 Metadata content 2. 3.4.1.2 Flow content 3. 3.4.1.3 Sectioning content 4. 3.4.1.4 Heading content 5. 3.4.1.5 Phrasing content 6. 3.4.1.6 Embedded content 7. 3.4.1.7 Interactive content 2. 3.4.2 Transparent content models 5. 3.5 Paragraphs 6. 3.6 APIs in HTML documents 7. 3.7 Interactions with XPath and XSLT 8. 3.8 Dynamic markup insertion 1. 3.8.1 Controlling the input stream http://dev.w3.org/html5/spec/Overview.html (5 de 570)01-08-2009 6:55:53
- 6. HTML 5 2. 3.8.2 document.write() 3. 3.8.3 document.writeln() 4. 3.8.4 innerHTML 5. 3.8.5 outerHTML 6. 3.8.6 insertAdjacentHTML() 4. 4 The elements of HTML 1. 4.1 The root element 1. 4.1.1 The html element 2. 4.2 Document metadata 1. 4.2.1 The head element 2. 4.2.2 The title element 3. 4.2.3 The base element 4. 4.2.4 The link element 5. 4.2.5 The meta element 1. 4.2.5.1 Standard metadata names 2. 4.2.5.2 Other metadata names 3. 4.2.5.3 Pragma directives 4. 4.2.5.4 Other pragma directives 5. 4.2.5.5 Specifying the document's character encoding 6. 4.2.6 The style element 7. 4.2.7 Styling 3. 4.3 Scripting 1. 4.3.1 The script element 1. 4.3.1.1 Scripting languages 2. 4.3.1.2 Inline documentation for external scripts 2. 4.3.2 The noscript element 4. 4.4 Sections 1. 4.4.1 The body element 2. 4.4.2 The section element 3. 4.4.3 The nav element 4. 4.4.4 The article element 5. 4.4.5 The aside element 6. 4.4.6 The h1, h2, h3, h4, h5, and h6 elements 7. 4.4.7 The hgroup element 8. 4.4.8 The header element 9. 4.4.9 The footer element 10. 4.4.10 The address element 11. 4.4.11 Headings and sections 1. 4.4.11.1 Creating an outline 2. 4.4.11.2 Distinguishing site-wide headings from page headings 5. 4.5 Grouping content 1. 4.5.1 The p element 2. 4.5.2 The hr element 3. 4.5.3 The br element 4. 4.5.4 The pre element 5. 4.5.5 The dialog element 6. 4.5.6 The blockquote element 7. 4.5.7 The ol element 8. 4.5.8 The ul element 9. 4.5.9 The li element 10. 4.5.10 The dl element 11. 4.5.11 The dt element 12. 4.5.12 The dd element 13. 4.5.13 Common grouping idioms 1. 4.5.13.1 Tag clouds 6. 4.6 Text-level semantics 1. 4.6.1 The a element 2. 4.6.2 The q element 3. 4.6.3 The cite element http://dev.w3.org/html5/spec/Overview.html (6 de 570)01-08-2009 6:55:53
- 7. HTML 5 4. 4.6.4 The em element 5. 4.6.5 The strong element 6. 4.6.6 The small element 7. 4.6.7 The mark element 8. 4.6.8 The dfn element 9. 4.6.9 The abbr element 10. 4.6.10 The time element 11. 4.6.11 The progress element 12. 4.6.12 The meter element 13. 4.6.13 The code element 14. 4.6.14 The var element 15. 4.6.15 The samp element 16. 4.6.16 The kbd element 17. 4.6.17 The sub and sup elements 18. 4.6.18 The span element 19. 4.6.19 The i element 20. 4.6.20 The b element 21. 4.6.21 The bdo element 22. 4.6.22 The ruby element 23. 4.6.23 The rt element 24. 4.6.24 The rp element 25. 4.6.25 Usage summary 26. 4.6.26 Footnotes 7. 4.7 Edits 1. 4.7.1 The ins element 2. 4.7.2 The del element 3. 4.7.3 Attributes common to ins and del elements 4. 4.7.4 Edits and paragraphs 5. 4.7.5 Edits and lists 8. 4.8 Embedded content 1. 4.8.1 The figure element 2. 4.8.2 The img element 1. 4.8.2.1 Requirements for providing text to act as an alternative for images 1. 4.8.2.1.1 A link or button containing nothing but the image 2. 4.8.2.1.2 A phrase or paragraph with an alternative graphical representation: charts, diagrams, graphs, maps, illustrations 3. 4.8.2.1.3 A short phrase or label with an alternative graphical representation: icons, logos 4. 4.8.2.1.4 Text that has been rendered to a graphic for typographical effect 5. 4.8.2.1.5 A graphical representation of some of the surrounding text 6. 4.8.2.1.6 A purely decorative image that doesn't add any information 7. 4.8.2.1.7 A group of images that form a single larger picture with no links 8. 4.8.2.1.8 A group of images that form a single larger picture with links 9. 4.8.2.1.9 A key part of the content 10. 4.8.2.1.10 An image not intended for the user 11. 4.8.2.1.11 An image in an e-mail or private document intended for a specific person who is known to be able to view images 12. 4.8.2.1.12 General guidelines 13. 4.8.2.1.13 Guidance for markup generators 14. 4.8.2.1.14 Guidance for conformance checkers 3. 4.8.3 The iframe element 4. 4.8.4 The embed element 5. 4.8.5 The object element 6. 4.8.6 The param element 7. 4.8.7 The video element 8. 4.8.8 The audio element 9. 4.8.9 The source element 10. 4.8.10 Media elements 1. 4.8.10.1 Error codes 2. 4.8.10.2 Location of the media resource 3. 4.8.10.3 MIME types 4. 4.8.10.4 Network states 5. 4.8.10.5 Loading the media resource 6. 4.8.10.6 Offsets into the media resource 7. 4.8.10.7 The ready states http://dev.w3.org/html5/spec/Overview.html (7 de 570)01-08-2009 6:55:53
- 8. HTML 5 8. 4.8.10.8 Cue ranges 9. 4.8.10.9 Playing the media resource 10. 4.8.10.10 Seeking 11. 4.8.10.11 User interface 12. 4.8.10.12 Time ranges 13. 4.8.10.13 Event summary 14. 4.8.10.14 Security and privacy considerations 11. 4.8.11 The canvas element 1. 4.8.11.1 The 2D context 1. 4.8.11.1.1 The canvas state 2. 4.8.11.1.2 Transformations 3. 4.8.11.1.3 Compositing 4. 4.8.11.1.4 Colors and styles 5. 4.8.11.1.5 Line styles 6. 4.8.11.1.6 Shadows 7. 4.8.11.1.7 Simple shapes (rectangles) 8. 4.8.11.1.8 Complex shapes (paths) 9. 4.8.11.1.9 Text 10. 4.8.11.1.10 Images 11. 4.8.11.1.11 Pixel manipulation 12. 4.8.11.1.12 Drawing model 2. 4.8.11.2 Color spaces and color correction 3. 4.8.11.3 Security with canvas elements 12. 4.8.12 The map element 13. 4.8.13 The area element 14. 4.8.14 Image maps 1. 4.8.14.1 Authoring 2. 4.8.14.2 Processing model 15. 4.8.15 MathML 16. 4.8.16 SVG 17. 4.8.17 Dimension attributes 9. 4.9 Tabular data 1. 4.9.1 Introduction 2. 4.9.2 The table element 3. 4.9.3 The caption element 4. 4.9.4 The colgroup element 5. 4.9.5 The col element 6. 4.9.6 The tbody element 7. 4.9.7 The thead element 8. 4.9.8 The tfoot element 9. 4.9.9 The tr element 10. 4.9.10 The td element 11. 4.9.11 The th element 12. 4.9.12 Attributes common to td and th elements 13. 4.9.13 Processing model 1. 4.9.13.1 Forming a table 2. 4.9.13.2 Forming relationships between data cells and header cells 10. 4.10 Forms 1. 4.10.1 The form element 2. 4.10.2 The fieldset element 3. 4.10.3 The label element 4. 4.10.4 The input element 1. 4.10.4.1 States of the type attribute 1. 4.10.4.1.1 Hidden state 2. 4.10.4.1.2 Text state and Search state 3. 4.10.4.1.3 Telephone state 4. 4.10.4.1.4 URL state 5. 4.10.4.1.5 E-mail state 6. 4.10.4.1.6 Password state 7. 4.10.4.1.7 Date and Time state 8. 4.10.4.1.8 Date state 9. 4.10.4.1.9 Month state 10. 4.10.4.1.10 Week state http://dev.w3.org/html5/spec/Overview.html (8 de 570)01-08-2009 6:55:53
- 9. HTML 5 11. 4.10.4.1.11 Time state 12. 4.10.4.1.12 Local Date and Time state 13. 4.10.4.1.13 Number state 14. 4.10.4.1.14 Range state 15. 4.10.4.1.15 Color state 16. 4.10.4.1.16 Checkbox state 17. 4.10.4.1.17 Radio Button state 18. 4.10.4.1.18 File Upload state 19. 4.10.4.1.19 Submit Button state 20. 4.10.4.1.20 Image Button state 21. 4.10.4.1.21 Reset Button state 22. 4.10.4.1.22 Button state 2. 4.10.4.2 Common input element attributes 1. 4.10.4.2.1 The autocomplete attribute 2. 4.10.4.2.2 The list attribute 3. 4.10.4.2.3 The readonly attribute 4. 4.10.4.2.4 The size attribute 5. 4.10.4.2.5 The required attribute 6. 4.10.4.2.6 The multiple attribute 7. 4.10.4.2.7 The maxlength attribute 8. 4.10.4.2.8 The pattern attribute 9. 4.10.4.2.9 The min and max attributes 10. 4.10.4.2.10 The step attribute 11. 4.10.4.2.11 The placeholder attribute 3. 4.10.4.3 Common input element APIs 4. 4.10.4.4 Common event behaviors 5. 4.10.5 The button element 6. 4.10.6 The select element 7. 4.10.7 The datalist element 8. 4.10.8 The optgroup element 9. 4.10.9 The option element 10. 4.10.10 The textarea element 11. 4.10.11 The keygen element 12. 4.10.12 The output element 13. 4.10.13 Association of controls and forms 14. 4.10.14 Attributes common to form controls 1. 4.10.14.1 Naming form controls 2. 4.10.14.2 Enabling and disabling form controls 3. 4.10.14.3 A form control's value 4. 4.10.14.4 Autofocusing a form control 5. 4.10.14.5 Limiting user input length 6. 4.10.14.6 Form submission 15. 4.10.15 Constraints 1. 4.10.15.1 Definitions 2. 4.10.15.2 Constraint validation 3. 4.10.15.3 The constraint validation API 4. 4.10.15.4 Security 16. 4.10.16 Form submission 1. 4.10.16.1 Introduction 2. 4.10.16.2 Implicit submission 3. 4.10.16.3 Form submission algorithm 4. 4.10.16.4 URL-encoded form data 5. 4.10.16.5 Multipart form data 6. 4.10.16.6 Plain text form data 17. 4.10.17 Resetting a form 18. 4.10.18 Event dispatch 11. 4.11 Interactive elements 1. 4.11.1 The details element 2. 4.11.2 The datagrid element 1. 4.11.2.1 Introduction 1. 4.11.2.1.1 Example: a datagrid backed by a static table element 2. 4.11.2.1.2 Example: a datagrid backed by nested ol elements 3. 4.11.2.1.3 Example: a datagrid backed by a server http://dev.w3.org/html5/spec/Overview.html (9 de 570)01-08-2009 6:55:53
- 10. HTML 5 2. 4.11.2.2 Populating the datagrid 1. 4.11.2.2.1 The listener 2. 4.11.2.2.2 The columns 3. 4.11.2.2.3 The rows 4. 4.11.2.2.4 The cells 3. 4.11.2.3 Listening to notifications from the datagrid 3. 4.11.3 The command element 4. 4.11.4 The bb element 1. 4.11.4.1 Browser button types 1. 4.11.4.1.1 The make application state 5. 4.11.5 The menu element 1. 4.11.5.1 Introduction 2. 4.11.5.2 Building menus and tool bars 3. 4.11.5.3 Context menus 4. 4.11.5.4 Tool bars 6. 4.11.6 Commands 1. 4.11.6.1 Using the a element to define a command 2. 4.11.6.2 Using the button element to define a command 3. 4.11.6.3 Using the input element to define a command 4. 4.11.6.4 Using the option element to define a command 5. 4.11.6.5 Using the command element to define a command 6. 4.11.6.6 Using the bb element to define a command 7. 4.11.6.7 Using the accesskey attribute on a label element to define a command 8. 4.11.6.8 Using the accesskey attribute on a legend element to define a command 9. 4.11.6.9 Using the accesskey attribute to define a command on other elements 12. 4.12 Miscellaneous elements 1. 4.12.1 The legend element 2. 4.12.2 The div element 13. 4.13 Matching HTML elements using selectors 5. 5 Microdata 1. 5.1 Introduction 1. 5.1.1 The basic syntax 2. 5.1.2 Typed items 3. 5.1.3 Selecting names when defining vocabularies 4. 5.1.4 Using the microdata DOM API 2. 5.2 Encoding microdata 1. 5.2.1 The microdata model 2. 5.2.2 Items: the item attribute 3. 5.2.3 Associating names with items 4. 5.2.4 Names: the itemprop attribute 5. 5.2.5 Values 3. 5.3 Microdata DOM API 4. 5.4 Predefined vocabularies 1. 5.4.1 General 2. 5.4.2 vCard 1. 5.4.2.1 Examples 3. 5.4.3 vEvent 1. 5.4.3.1 Examples 4. 5.4.4 Licensing works 1. 5.4.4.1 Examples 5. 5.5 Converting HTML to other formats 1. 5.5.1 JSON 2. 5.5.2 RDF 3. 5.5.3 vCard 4. 5.5.4 iCalendar 5. 5.5.5 Atom 6. 6 Web browsers 1. 6.1 Browsing contexts http://dev.w3.org/html5/spec/Overview.html (10 de 570)01-08-2009 6:55:53
- 11. HTML 5 1. 6.1.1 Nested browsing contexts 1. 6.1.1.1 Navigating nested browsing contexts in the DOM 2. 6.1.2 Auxiliary browsing contexts 1. 6.1.2.1 Navigating auxiliary browsing contexts in the DOM 3. 6.1.3 Secondary browsing contexts 4. 6.1.4 Security 5. 6.1.5 Groupings of browsing contexts 6. 6.1.6 Browsing context names 2. 6.2 The WindowProxy object 3. 6.3 The Window object 1. 6.3.1 Security 2. 6.3.2 APIs for creating and navigating browsing contexts by name 3. 6.3.3 Accessing other browsing contexts 4. 6.3.4 Named access on the Window object 5. 6.3.5 Garbage collection and browsing contexts 6. 6.3.6 Browser interface elements 4. 6.4 Origin 1. 6.4.1 Relaxing the same-origin restriction 5. 6.5 Scripting 1. 6.5.1 Introduction 2. 6.5.2 Enabling and disabling scripting 3. 6.5.3 Processing model 1. 6.5.3.1 Definitions 2. 6.5.3.2 Calling scripts 3. 6.5.3.3 Creating scripts 4. 6.5.3.4 Killing scripts 4. 6.5.4 Event loops 1. 6.5.4.1 Definitions 2. 6.5.4.2 Processing model 3. 6.5.4.3 Generic task sources 5. 6.5.5 The javascript: protocol 6. 6.5.6 Events 1. 6.5.6.1 Event handler attributes 2. 6.5.6.2 Event handler attributes on elements, Document objects, and Window objects 3. 6.5.6.3 Event firing 4. 6.5.6.4 Events and the Window object 5. 6.5.6.5 Runtime script errors 6. 6.6 Timers 7. 6.7 User prompts 1. 6.7.1 Simple dialogs 2. 6.7.2 Printing 3. 6.7.3 Dialogs implemented using separate documents 8. 6.8 System state and capabilities 1. 6.8.1 Client identification 2. 6.8.2 Custom scheme and content handlers 1. 6.8.2.1 Security and privacy 2. 6.8.2.2 Sample user interface 3. 6.8.3 Manually releasing the storage mutex 9. 6.9 Offline Web applications 1. 6.9.1 Introduction 1. 6.9.1.1 Event summary 2. 6.9.2 Application caches 3. 6.9.3 The cache manifest syntax 1. 6.9.3.1 A sample manifest 2. 6.9.3.2 Writing cache manifests 3. 6.9.3.3 Parsing cache manifests 4. 6.9.4 Updating an application cache 5. 6.9.5 Matching a fallback namespace 6. 6.9.6 The application cache selection algorithm 7. 6.9.7 Changes to the networking model http://dev.w3.org/html5/spec/Overview.html (11 de 570)01-08-2009 6:55:53
- 12. HTML 5 8. 6.9.8 Expiring application caches 9. 6.9.9 Application cache API 10. 6.9.10 Browser state 10. 6.10 Session history and navigation 1. 6.10.1 The session history of browsing contexts 2. 6.10.2 The History interface 3. 6.10.3 Activating state object entries 4. 6.10.4 The Location interface 1. 6.10.4.1 Security 5. 6.10.5 Implementation notes for session history 11. 6.11 Browsing the Web 1. 6.11.1 Navigating across documents 2. 6.11.2 Page load processing model for HTML files 3. 6.11.3 Page load processing model for XML files 4. 6.11.4 Page load processing model for text files 5. 6.11.5 Page load processing model for images 6. 6.11.6 Page load processing model for content that uses plugins 7. 6.11.7 Page load processing model for inline content that doesn't have a DOM 8. 6.11.8 Navigating to a fragment identifier 9. 6.11.9 History traversal 10. 6.11.10 Unloading documents 1. 6.11.10.1 Event definition 12. 6.12 Links 1. 6.12.1 Hyperlink elements 2. 6.12.2 Following hyperlinks 1. 6.12.2.1 Hyperlink auditing 3. 6.12.3 Link types 1. 6.12.3.1 Link type "alternate" 2. 6.12.3.2 Link type "archives" 3. 6.12.3.3 Link type "author" 4. 6.12.3.4 Link type "bookmark" 5. 6.12.3.5 Link type "external" 6. 6.12.3.6 Link type "feed" 7. 6.12.3.7 Link type "help" 8. 6.12.3.8 Link type "icon" 9. 6.12.3.9 Link type "license" 10. 6.12.3.10 Link type "nofollow" 11. 6.12.3.11 Link type "noreferrer" 12. 6.12.3.12 Link type "pingback" 13. 6.12.3.13 Link type "prefetch" 14. 6.12.3.14 Link type "search" 15. 6.12.3.15 Link type "stylesheet" 16. 6.12.3.16 Link type "sidebar" 17. 6.12.3.17 Link type "tag" 18. 6.12.3.18 Hierarchical link types 1. 6.12.3.18.1 Link type "index" 2. 6.12.3.18.2 Link type "up" 19. 6.12.3.19 Sequential link types 1. 6.12.3.19.1 Link type "first" 2. 6.12.3.19.2 Link type "last" 3. 6.12.3.19.3 Link type "next" 4. 6.12.3.19.4 Link type "prev" 20. 6.12.3.20 Other link types 7. 7 User Interaction 1. 7.1 Introduction 2. 7.2 The hidden attribute 3. 7.3 Activation 4. 7.4 Scrolling elements into view 5. 7.5 Focus 1. 7.5.1 Sequential focus navigation http://dev.w3.org/html5/spec/Overview.html (12 de 570)01-08-2009 6:55:53
- 13. HTML 5 2. 7.5.2 Focus management 3. 7.5.3 Document-level focus APIs 4. 7.5.4 Element-level focus APIs 6. 7.6 The accesskey attribute 7. 7.7 The text selection APIs 1. 7.7.1 APIs for the browsing context selection 2. 7.7.2 APIs for the text field selections 8. 7.8 The contenteditable attribute 1. 7.8.1 User editing actions 2. 7.8.2 Making entire documents editable 9. 7.9 Spelling and grammar checking 10. 7.10 Drag and drop 1. 7.10.1 Introduction 2. 7.10.2 The DragEvent and DataTransfer interfaces 3. 7.10.3 Events fired during a drag-and-drop action 4. 7.10.4 Drag-and-drop processing model 1. 7.10.4.1 When the drag-and-drop operation starts or ends in another document 2. 7.10.4.2 When the drag-and-drop operation starts or ends in another application 5. 7.10.5 The draggable attribute 6. 7.10.6 Copy and paste 1. 7.10.6.1 Copy to clipboard 2. 7.10.6.2 Cut to clipboard 3. 7.10.6.3 Paste from clipboard 4. 7.10.6.4 Paste from selection 7. 7.10.7 Security risks in the drag-and-drop model 11. 7.11 Undo history 1. 7.11.1 Introduction 2. 7.11.2 Definitions 3. 7.11.3 The UndoManager interface 4. 7.11.4 Undo: moving back in the undo transaction history 5. 7.11.5 Redo: moving forward in the undo transaction history 6. 7.11.6 The UndoManagerEvent interface and the undo and redo events 7. 7.11.7 Implementation notes 12. 7.12 Editing APIs 8. 8 Communication 1. 8.1 Event definitions 2. 8.2 Cross-document messaging 1. 8.2.1 Introduction 2. 8.2.2 Security 1. 8.2.2.1 Authors 2. 8.2.2.2 User agents 3. 8.2.3 Posting messages 4. 8.2.4 Posting messages with message ports 3. 8.3 Channel messaging 1. 8.3.1 Introduction 2. 8.3.2 Message channels 3. 8.3.3 Message ports 1. 8.3.3.1 Ports and garbage collection 9. 9 The HTML syntax 1. 9.1 Writing HTML documents 1. 9.1.1 The DOCTYPE 2. 9.1.2 Elements 1. 9.1.2.1 Start tags 2. 9.1.2.2 End tags 3. 9.1.2.3 Attributes 4. 9.1.2.4 Optional tags 5. 9.1.2.5 Restrictions on content models http://dev.w3.org/html5/spec/Overview.html (13 de 570)01-08-2009 6:55:53
- 14. HTML 5 6. 9.1.2.6 Restrictions on the contents of CDATA and RCDATA elements 3. 9.1.3 Text 1. 9.1.3.1 Newlines 4. 9.1.4 Character references 5. 9.1.5 CDATA sections 6. 9.1.6 Comments 2. 9.2 Parsing HTML documents 1. 9.2.1 Overview of the parsing model 2. 9.2.2 The input stream 1. 9.2.2.1 Determining the character encoding 2. 9.2.2.2 Preprocessing the input stream 3. 9.2.2.3 Changing the encoding while parsing 3. 9.2.3 Parse state 1. 9.2.3.1 The insertion mode 2. 9.2.3.2 The stack of open elements 3. 9.2.3.3 The list of active formatting elements 4. 9.2.3.4 The element pointers 5. 9.2.3.5 Other parsing state flags 4. 9.2.4 Tokenization 1. 9.2.4.1 Data state 2. 9.2.4.2 Character reference data state 3. 9.2.4.3 Tag open state 4. 9.2.4.4 Close tag open state 5. 9.2.4.5 Tag name state 6. 9.2.4.6 Before attribute name state 7. 9.2.4.7 Attribute name state 8. 9.2.4.8 After attribute name state 9. 9.2.4.9 Before attribute value state 10. 9.2.4.10 Attribute value (double-quoted) state 11. 9.2.4.11 Attribute value (single-quoted) state 12. 9.2.4.12 Attribute value (unquoted) state 13. 9.2.4.13 Character reference in attribute value state 14. 9.2.4.14 After attribute value (quoted) state 15. 9.2.4.15 Self-closing start tag state 16. 9.2.4.16 Bogus comment state 17. 9.2.4.17 Markup declaration open state 18. 9.2.4.18 Comment start state 19. 9.2.4.19 Comment start dash state 20. 9.2.4.20 Comment state 21. 9.2.4.21 Comment end dash state 22. 9.2.4.22 Comment end state 23. 9.2.4.23 Comment end bang state 24. 9.2.4.24 Comment end space state 25. 9.2.4.25 DOCTYPE state 26. 9.2.4.26 Before DOCTYPE name state 27. 9.2.4.27 DOCTYPE name state 28. 9.2.4.28 After DOCTYPE name state 29. 9.2.4.29 Before DOCTYPE public identifier state 30. 9.2.4.30 DOCTYPE public identifier (double-quoted) state 31. 9.2.4.31 DOCTYPE public identifier (single-quoted) state 32. 9.2.4.32 After DOCTYPE public identifier state 33. 9.2.4.33 Before DOCTYPE system identifier state 34. 9.2.4.34 DOCTYPE system identifier (double-quoted) state 35. 9.2.4.35 DOCTYPE system identifier (single-quoted) state 36. 9.2.4.36 After DOCTYPE system identifier state 37. 9.2.4.37 Bogus DOCTYPE state 38. 9.2.4.38 CDATA section state 39. 9.2.4.39 Tokenizing character references 5. 9.2.5 Tree construction 1. 9.2.5.1 Creating and inserting elements 2. 9.2.5.2 Closing elements that have implied end tags 3. 9.2.5.3 Foster parenting 4. 9.2.5.4 The "initial" insertion mode http://dev.w3.org/html5/spec/Overview.html (14 de 570)01-08-2009 6:55:53
- 15. HTML 5 5. 9.2.5.5 The "before html" insertion mode 6. 9.2.5.6 The "before head" insertion mode 7. 9.2.5.7 The "in head" insertion mode 8. 9.2.5.8 The "in head noscript" insertion mode 9. 9.2.5.9 The "after head" insertion mode 10. 9.2.5.10 The "in body" insertion mode 11. 9.2.5.11 The "in CDATA/RCDATA" insertion mode 12. 9.2.5.12 The "in table" insertion mode 13. 9.2.5.13 The "in table text" insertion mode 14. 9.2.5.14 The "in caption" insertion mode 15. 9.2.5.15 The "in column group" insertion mode 16. 9.2.5.16 The "in table body" insertion mode 17. 9.2.5.17 The "in row" insertion mode 18. 9.2.5.18 The "in cell" insertion mode 19. 9.2.5.19 The "in select" insertion mode 20. 9.2.5.20 The "in select in table" insertion mode 21. 9.2.5.21 The "in foreign content" insertion mode 22. 9.2.5.22 The "after body" insertion mode 23. 9.2.5.23 The "in frameset" insertion mode 24. 9.2.5.24 The "after frameset" insertion mode 25. 9.2.5.25 The "after after body" insertion mode 26. 9.2.5.26 The "after after frameset" insertion mode 6. 9.2.6 The end 7. 9.2.7 Coercing an HTML DOM into an infoset 8. 9.2.8 An introduction to error handling and strange cases in the parser 1. 9.2.8.1 Misnested tags: <b><i></b></i> 2. 9.2.8.2 Misnested tags: <b><p></b></p> 3. 9.2.8.3 Unexpected markup in tables 4. 9.2.8.4 Scripts that modify the page as it is being parsed 3. 9.3 Namespaces 4. 9.4 Serializing HTML fragments 5. 9.5 Parsing HTML fragments 6. 9.6 Named character references 10. 10 The XHTML syntax 1. 10.1 Writing XHTML documents 2. 10.2 Parsing XHTML documents 3. 10.3 Serializing XHTML fragments 4. 10.4 Parsing XHTML fragments 11. 11 Rendering 1. 11.1 Introduction 2. 11.2 The CSS user agent style sheet and presentational hints 1. 11.2.1 Introduction 2. 11.2.2 Display types 3. 11.2.3 Margins and padding 4. 11.2.4 Alignment 5. 11.2.5 Fonts and colors 6. 11.2.6 Punctuation and decorations 7. 11.2.7 Resetting rules for inherited properties 8. 11.2.8 The hr element 9. 11.2.9 The fieldset element 3. 11.3 Replaced elements 1. 11.3.1 Embedded content 2. 11.3.2 Images 3. 11.3.3 Attributes for embedded content and images 4. 11.3.4 Image maps 5. 11.3.5 Tool bars 4. 11.4 Bindings 1. 11.4.1 Introduction http://dev.w3.org/html5/spec/Overview.html (15 de 570)01-08-2009 6:55:53
- 16. HTML 5 2. 11.4.2 The bb element 3. 11.4.3 The button element 4. 11.4.4 The datagrid element 5. 11.4.5 The details element 6. 11.4.6 The input element as a text entry widget 7. 11.4.7 The input element as domain-specific widgets 8. 11.4.8 The input element as a range control 9. 11.4.9 The input element as a color well 10. 11.4.10 The input element as a check box and radio button widgets 11. 11.4.11 The input element as a file upload control 12. 11.4.12 The input element as a button 13. 11.4.13 The marquee element 14. 11.4.14 The meter element 15. 11.4.15 The progress element 16. 11.4.16 The select element 17. 11.4.17 The textarea element 18. 11.4.18 The keygen element 19. 11.4.19 The time element 5. 11.5 Frames and framesets 6. 11.6 Interactive media 1. 11.6.1 Links, forms, and navigation 2. 11.6.2 The mark element 3. 11.6.3 The title attribute 4. 11.6.4 Editing hosts 7. 11.7 Print media 8. 11.8 Interaction with CSS 1. 11.8.1 Selectors 12. 12 Obsolete features 1. 12.1 Conforming but obsolete features 1. 12.1.1 Warnings for obsolete but conforming features 2. 12.2 Non-conforming features 3. 12.3 Requirements for implementations 1. 12.3.1 The applet element 2. 12.3.2 The marquee element 3. 12.3.3 Frames 4. 12.3.4 Other elements, attributes and APIs 13. 13 Things that you can't do with this specification because they are better handled using other technologies that are further described herein 1. 13.1 Localization 2. 13.2 Declarative 3D scenes 3. 13.3 Rendering and the DOM 14. Index 15. References 16. Acknowledgements http://dev.w3.org/html5/spec/Overview.html (16 de 570)01-08-2009 6:55:53
- 17. HTML 5 1 Introduction 1.1 Background This section is non-normative. The World Wide Web's markup language has always been HTML. HTML was primarily designed as a language for semantically describing scientific documents, although its general design and adaptations over the years has enabled it to be used to describe a number of other types of documents. The main area that has not been adequately addressed by HTML is a vague subject referred to as Web Applications. This specification attempts to rectify this, while at the same time updating the HTML specifications to address issues raised in the past few years. 1.2 Audience This section is non-normative. This specification is intended for authors of documents and scripts that use the features defined in this specification, implementors of tools that operate on pages that use the features defined in this specification, and individuals wishing to establish the correctness of documents or implementations with respect to the requirements of this specification. This document is probably not suited to readers who do not already have at least a passing familiarity with Web technologies, as in places it sacrifices clarity for precision, and brevity for completeness. More approachable tutorials and authoring guides can provide a gentler introduction to the topic. In particular, familiarity with the basics of DOM Core and DOM Events is necessary for a complete understanding of some of the more technical parts of this specification. An understanding of Web IDL, HTTP, XML, Unicode, character encodings, JavaScript, and CSS will also be helpful in places but is not essential. 1.3 Scope This section is non-normative. This specification is limited to providing a semantic-level markup language and associated semantic-level scripting APIs for authoring accessible pages on the Web ranging from static documents to dynamic applications. The scope of this specification does not include providing mechanisms for media-specific customization of presentation (although default rendering rules for Web browsers are included at the end of this specification, and several mechanisms for hooking into CSS are provided as part of the language). The scope of this specification does not include documenting every HTML or DOM feature supported by Web browsers. Browsers support many features that are considered to be very bad for accessibility or that are otherwise inappropriate. For example, the blink element is clearly presentational and authors wishing to cause text to blink should instead use CSS. The scope of this specification is not to describe an entire operating system. In particular, hardware configuration software, image manipulation tools, and applications that users would be expected to use with high-end workstations on a daily basis are out of scope. In terms of applications, this specification is targeted specifically at applications that would be expected to be used by users on an occasional basis, or regularly but from disparate locations, with low CPU requirements. For instance online purchasing systems, searching systems, games (especially multiplayer online games), public telephone books or address books, communications software (e-mail clients, instant messaging clients, discussion software), document editing software, etc. 1.4 History This section is non-normative. Work on HTML 5 originally started in late 2003, as a proof of concept to show that it was possible to extend HTML 4's forms to provide many of the features that XForms 1.0 introduced, without requiring browsers to implement rendering engines that were incompatible with existing HTML Web pages. At this early stage, while the draft was already publicly available, and input was already being solicited from all sources, the specification was only under Opera Software's copyright. In early 2004, some of the principles that underlie this effort, as well as an early draft proposal covering just forms-related features, were presented to the W3C jointly by Mozilla and Opera at a workshop discussing the future of Web Applications on the Web. The proposal was rejected on the grounds that the proposal conflicted with the previously chosen direction for the Web's evolution. Shortly thereafter, Apple, Mozilla, and Opera jointly announced their intent to continue working on the effort. A public mailing list was created, and the drafts were moved to the WHATWG site. The copyright was subsequently amended to be jointly owned by all three vendors, and to allow reuse of the specifications. In 2006, the W3C expressed interest in the specification, and created a working group chartered to work with the WHATWG on the development of the HTML 5 specifications. The working group opened in 2007. Apple, Mozilla, and Opera allowed the W3C to publish the specifications under the W3C copyright, while keeping versions with the less restrictive license on the WHATWG site. Since then, both groups have been working together. 1.5 Design notes http://dev.w3.org/html5/spec/Overview.html (17 de 570)01-08-2009 6:55:53
- 18. HTML 5 This section is non-normative. It must be admitted that many aspects of HTML appear at first glance to be nonsensical and inconsistent. HTML, its supporting DOM APIs, as well as many of its supporting technologies, have been developed over a period of several decades by a wide array of people with different priorities who, in many cases, did not know of each other's existence. Features have thus arisen from many sources, and have not always been designed in especially consistent ways. Furthermore, because of the unique characteristics of the Web, implementation bugs have often become de-facto, and now de-jure, standards, as content is often unintentionally written in ways that rely on them before they can be fixed. Despite all this, efforts have been made to adhere to certain design goals. These are described in the next few subsections. 1.5.1 Serializability of script execution This section is non-normative. To avoid exposing Web authors to the complexities of multithreading, the HTML and DOM APIs are designed such that no script can ever detect the simultaneous execution of other scripts. Even with workers, the intent is that the behavior of implementations can be thought of as completely serialising the execution of all scripts in all browsing contexts. The navigator.getStorageUpdates() method, in this model, is equivalent to allowing other scripts to run while the calling script is blocked. 1.5.2 Compliance with other specifications This section is non-normative. This specification interacts with and relies on a wide variety of other specifications. In certain circumstances, unfortunately, the desire to be compatible with legacy content has led to this specification violating the requirements of these other specifications. Whenever this has occurred, the transgressions have been noted as "willful violations". 1.6 Relationships to other specifications 1.6.1 Relationship to HTML 4.01 and DOM2 HTML This section is non-normative. This specification describes a new revision of the HTML language and its associated DOM API. The requirements in this specification for features that were already in HTML 4 and DOM2 HTML are based primarily on the implementation and deployment experience collected over the past ten years. Some features have been removed from the language, based on best current practices; implementation requirements for some of these, as well as for non-standard features that have nonetheless garnered wide use, are still included in this specification to allow implementations to continue supporting legacy content. [HTML4] [DOM2HTML] A separate document has been published by the W3C HTML working group to provide a more detailed reference of the differences between this specification and the language described in the HTML 4 specification. [HTMLDIFF] 1.6.2 Relationship to XHTML 1.x This section is non-normative. This specification is intended to replace XHTML 1.0 as the normative definition of the XML serialization of the HTML vocabulary. [XHTML10] While this specification updates the semantics and requirements of the vocabulary defined by XHTML Modularization 1.1 and used by XHTML 1.1, it does not attempt to provide a replacement for the modularization scheme defined and used by those (and other) specifications, and therefore cannot be considered a complete replacement for them. [XHTMLMOD] [XHTML11] Thus, authors and implementors who do not need such a modularization scheme can consider this specification a replacement for XHTML 1.x, but those who do need such a mechanism are encouraged to continue using the XHTML 1.1 line of specifications. 1.7 HTML vs XHTML This section is non-normative. This specification defines an abstract language for describing documents and applications, and some APIs for interacting with in-memory representations of resources that use this language. The in-memory representation is known as "DOM5 HTML", or "the DOM" for short. http://dev.w3.org/html5/spec/Overview.html (18 de 570)01-08-2009 6:55:53
- 19. HTML 5 There are various concrete syntaxes that can be used to transmit resources that use this abstract language, two of which are defined in this specification. The first such concrete syntax is "HTML5". This is the format recommended for most authors. It is compatible with all legacy Web browsers. If a document is transmitted with the MIME type text/html, then it will be processed as an "HTML5" document by Web browsers. The second concrete syntax uses XML, and is known as "XHTML5". When a document is transmitted with an XML MIME type, such as application/xhtml+xml, then it is processed by an XML processor by Web browsers, and treated as an "XHTML5" document. Authors are reminded that the processing for XML and HTML differs; in particular, even minor syntax errors will prevent an XML document from being rendered fully, whereas they would be ignored in the "HTML5" syntax. The "DOM5 HTML", "HTML5", and "XHTML5" representations cannot all represent the same content. For example, namespaces cannot be represented using "HTML5", but they are supported in "DOM5 HTML" and "XHTML5". Similarly, documents that use the noscript feature can be represented using "HTML5", but cannot be represented with "XHTML5" and "DOM5 HTML". Comments that contain the string "-->" can be represented in "DOM5 HTML" but not in "HTML5" and "XHTML5". And so forth. 1.8 Structure of this specification This section is non-normative. This specification is divided into the following major sections: Common Infrastructure The conformance classes, algorithms, definitions, and the common underpinnings of the rest of the specification. Semantics, structure, and APIs of HTML documents Documents are built from elements. These elements form a tree using the DOM. This section defines the features of this DOM, as well as introducing the features common to all elements, and the concepts used in defining elements. Elements Each element has a predefined meaning, which is explained in this section. Rules for authors on how to use the element, along with user agent requirements for how to handle each element, are also given. Microdata This specification introduces a mechanism for adding machine-readable annotations to documents, so that tools can extract trees of name/value pairs from the document. This section describes this mechanism and some algorithms that can be used to convert HTML documents into other formats. Web Browsers HTML documents do not exist in a vacuum — this section defines many of the features that affect environments that deal with multiple pages, links between pages, and running scripts. User Interaction HTML documents can provide a number of mechanisms for users to interact with and modify content, which are described in this section. The Communication APIs This section describes some mechanisms that applications written in HTML can use to communicate with other applications from different domains running on the same client. The HTML Syntax The XHTML Syntax All of these features would be for naught if they couldn't be represented in a serialized form and sent to other people, and so these sections define the syntaxes of HTML, along with rules for how to parse content using those syntaxes. There are also a couple of appendices, defining rendering rules for Web browsers and listing obsolete features and areas that are out of scope for this specification. 1.8.1 How to read this specification This specification should be read like all other specifications. First, it should be read cover-to-cover, multiple times. Then, it should be read backwards at least once. Then it should be read by picking random sections from the contents list and following all the cross- references. 1.8.2 Typographic conventions This is a definition, requirement, or explanation. This is a note. This is an example. This is an open issue. This is a warning. interface Example { // this is an IDL definition }; http://dev.w3.org/html5/spec/Overview.html (19 de 570)01-08-2009 6:55:53
- 20. HTML 5 variable = object . method( [ optionalArgument ] ) This is a note to authors describing the usage of an interface. /* this is a CSS fragment */ The defining instance of a term is marked up like this. Uses of that term are marked up like this or like this. The defining instance of an element, attribute, or API is marked up like this. References to that element, attribute, or API are marked up like this. Other code fragments are marked up like this. Variables are marked up like this. This is an implementation requirement. 1.9 A quick introduction to HTML This section is non-normative. A basic HTML document looks like this: <!DOCTYPE HTML> <html> <head> <title>Sample page</title> </head> <body> <h1>Sample page</h1> <p>This is a <a href="demo.html">simple</a> sample.</p> <!-- this is a comment --> </body> </html> HTML documents consist of a tree of elements and text. Each element is denoted in the source by a start tag, such as "<body>", and an end tag, such as "</body>". (Certain start tags and end tags can in certain cases be omitted and are implied by other tags.) Tags have to be nested such that elements are all completely within each other, without overlapping: <p>This is <em>very <strong>wrong</em>!</strong></p> <p>This <em>is <strong>correct</strong>.</em></p> This specification defines a set of elements that can be used in HTML, along with rules about the ways in which the elements can be nested. Elements can have attributes, which control how the elements work. In the example above, there is a hyperlink, formed using the a element and its href attribute: <a href="demo.html">simple</a> Attributes are placed inside the start tag, and consist of a name and a value, separated by an "=" character. The attribute value can be left unquoted if it doesn't contain any special characters. Otherwise, it has to be quoted using either single or double quotes. The value, along with the "=" character, can be omitted altogether if the value is the empty string. <!-- empty attributes --> <input name=address disabled> <input name=address disabled=""> <!-- attributes with a value --> <input name=address maxlength=200> <input name=address maxlength='200'> <input name=address maxlength="200"> HTML user agents (e.g. Web browsers) then parse this markup, turning it into a DOM (Document Object Model) tree. A DOM tree is an in-memory representation of a document. DOM trees contain several kinds of nodes, in particular a DOCTYPE node, elements, text nodes, and comment nodes. The markup snippet at the top of this section would be turned into the following DOM tree: http://dev.w3.org/html5/spec/Overview.html (20 de 570)01-08-2009 6:55:53
- 21. HTML 5 q DOCTYPE: html q html r head s #text: ••• s title s #text: Sample page s #text: •• r #text: •• r body s #text: ••• s h1 s #text: Sample page s #text: ••• s p s #text: This is a s a href="demo.html" s #text: simple s #text: sample. s #text: ••• s #comment: this is a comment s #text: ••• The root element of this tree is the html element, which is the element always found at the root of HTML documents. It contains two elements, head and body, as well as a text node between them. There are many more text nodes in the DOM tree than one would initially expect, because the source contains a number of spaces (presented by "•") and line breaks ("•") that all end up as text nodes in the DOM. The head element contains a title element, which itself contains a text node with the text "Sample page". Similarly, the body element contains an h1 element, a p element, and a comment. This DOM tree can be manipulated from scripts in the page. Scripts (typically in JavaScript) are small programs that can be embedded using the script element or using event handler content attributes. For example, here is a form with a script that sets the value of the form's output element to say "Hello World": <form name="main"> Result: <output name="result"></output> <script> document.forms.main.elements.result.value = 'Hello World'; </script> </form> Each element in the DOM tree is represented by an object, and these objects have APIs so that they can be manipulated. For instance, a link (e.g. the a element in the tree above) can have its "href" attributed changed in several ways: var a = document.links[0]; // obtain the first link in the document a.href = 'sample.html'; // change the destination URL of the link a.protocol = 'https'; // change just the scheme part of the URL a.setAttribute('href', 'http://example.com/'); // change the content attribute directly Since DOM trees are used as the way to represent HTML documents when they are processed and presented by implementations (especially interactive implementations like Web browsers), this specification is mostly phrased in terms of DOM trees, instead of the markup described above. HTML documents represent a media-independent description of interactive content. HTML documents might be rendered to a screen, or through a speech synthesizer, or on a braille display. To influence exactly how such rendering takes place, authors can use a styling language such as CSS. In the following example, the page has been made yellow-on-blue using CSS. <!DOCTYPE HTML> <html> <head> <title>Sample styled page</title> <style> body { background: navy; color: yellow; } </style> </head> <body> <h1>Sample styled page</h1> http://dev.w3.org/html5/spec/Overview.html (21 de 570)01-08-2009 6:55:53
- 22. HTML 5 <p>This page is just a demo.</p> </body> </html> For more details on how to use HTML, authors are encouraged to consult tutorials and guides. Some of the examples included in this specification might also be of use, but the novice author is cautioned that this specification, by necessity, defines the language with a level of detail that may be difficult to understand at first. http://dev.w3.org/html5/spec/Overview.html (22 de 570)01-08-2009 6:55:53
- 23. HTML 5 2 Common infrastructure 2.1 Terminology This specification refers to both HTML and XML attributes and DOM attributes, often in the same context. When it is not clear which is being referred to, they are referred to as content attributes for HTML and XML attributes, and DOM attributes for those from the DOM. Similarly, the term "properties" is used for both JavaScript object properties and CSS properties. When these are ambiguous they are qualified as object properties and CSS properties respectively. Generally, when the specification states that a feature applies to the HTML syntax or the XHTML syntax, it also includes the other. When a feature specifically only applies to one of the two languages, it is called out by explicitly stating that it does not apply to the other format, as in "for HTML, ... (this does not apply to XHTML)". This specification uses the term document to refer to any use of HTML, ranging from short static documents to long essays or reports with rich multimedia, as well as to fully-fledged interactive applications. For simplicity, terms such as shown, displayed, and visible might sometimes be used when referring to the way a document is rendered to the user. These terms are not meant to imply a visual medium; they must be considered to apply to other media in equivalent ways. When an algorithm B says to return to another algorithm A, it implies that A called B. Upon returning to A, the implementation must continue from where it left off in calling B. 2.1.1 XML To ease migration from HTML to XHTML, UAs conforming to this specification will place elements in HTML in the http://www.w3.org/1999/xhtml namespace, at least for the purposes of the DOM and CSS. The term "elements in the HTML namespace", or "HTML elements" for short, when used in this specification, thus refers to both HTML and XHTML elements. Unless otherwise stated, all elements defined or mentioned in this specification are in the http://www.w3.org/1999/xhtml namespace, and all attributes defined or mentioned in this specification have no namespace (they are in the per-element partition). When an XML name, such as an attribute or element name, is referred to in the form prefix:localName, as in xml:id or svg:rect, it refers to a name with the local name localName and the namespace given by the prefix, as defined by the following table: xml http://www.w3.org/XML/1998/namespace html http://www.w3.org/1999/xhtml svg http://www.w3.org/2000/svg Attribute names are said to be XML-compatible if they match the Name production defined in XML, they contain no U+003A COLON (:) characters, and their first three characters are not an ASCII case-insensitive match for the string "xml". [XML] The term XML MIME type is used to refer to the MIME types text/xml, application/xml, and any MIME type ending with the four characters "+xml". [RFC3023] 2.1.2 DOM trees The term root element, when not explicitly qualified as referring to the document's root element, means the furthest ancestor element node of whatever node is being discussed, or the node itself if it has no ancestors. When the node is a part of the document, then that is indeed the document's root element; however, if the node is not currently part of the document tree, the root element will be an orphaned node. A node's home subtree is the subtree rooted at that node's root element. The Document of a Node (such as an element) is the Document that the Node's ownerDocument DOM attribute returns. When an element's root element is the root element of a Document, it is said to be in a Document. An element is said to have been inserted into a document when its root element changes and is now the document's root element. Analogously, an element is said to have been removed from a document when its root element changes from being the document's root element to being another element. If a Node is in a Document then that Document is always the Node's Document, and the Node's ownerDocument DOM attribute thus always returns that Document. The term tree order means a pre-order, depth-first traversal of DOM nodes involved (through the parentNode/childNodes relationship). When it is stated that some element or attribute is ignored, or treated as some other value, or handled as if it was something else, this refers only to the processing of the node after it is in the DOM. A user agent must not mutate the DOM in such situations. The term text node refers to any Text node, including CDATASection nodes; specifically, any Node with node type TEXT_NODE (3) or CDATA_SECTION_NODE (4). [DOM3CORE] A content attribute is said to change value only if its new value is different than its previous value; setting an attribute to a value it already has does not change it. 2.1.3 Scripting http://dev.w3.org/html5/spec/Overview.html (23 de 570)01-08-2009 6:55:53
- 24. HTML 5 The construction "a Foo object", where Foo is actually an interface, is sometimes used instead of the more accurate "an object implementing the interface Foo". A DOM attribute is said to be getting when its value is being retrieved (e.g. by author script), and is said to be setting when a new value is assigned to it. If a DOM object is said to be live, then that means that any attributes returning that object must always return the same object (not a new object each time), and the attributes and methods on that object must operate on the actual underlying data, not a snapshot of the data. The terms fire and dispatch are used interchangeably in the context of events, as in the DOM Events specifications. [DOM3EVENTS] 2.1.4 Plugins The term plugin is used to mean any content handler for Web content types that are either not supported by the user agent natively or that do not expose a DOM, which supports rendering the content as part of the user agent's interface. Typically such content handlers are provided by third parties. One example of a plugin would be a PDF viewer that is instantiated in a browsing context when the user navigates to a PDF file. This would count as a plugin regardless of whether the party that implemented the PDF viewer component was the same as that which implemented the user agent itself. However, a PDF viewer application that launches separate from the user agent (as opposed to using the same interface) is not a plugin by this definition. This specification does not define a mechanism for interacting with plugins, as it is expected to be user-agent- and platform-specific. Some UAs might opt to support a plugin mechanism such as the Netscape Plugin API; others might use remote content converters or have built-in support for certain types. [NPAPI] Browsers should take extreme care when interacting with external content intended for plugins. When third-party software is run with the same privileges as the user agent itself, vulnerabilities in the third-party software become as dangerous as those in the user agent. 2.1.5 Character encodings An ASCII-compatible character encoding is a single-byte or variable-length encoding in which the bytes 0x09, 0x0A, 0x0C, 0x0D, 0x20 - 0x22, 0x26, 0x27, 0x2C - 0x3F, 0x41 - 0x5A, and 0x61 - 0x7A, ignoring bytes that are the second and later bytes of multibyte sequences, all correspond to single-byte sequences that map to the same Unicode characters as those bytes in ANSI_X3.4-1968 (US-ASCII). [RFC1345] This includes such encodings as Shift_JIS and variants of ISO-2022, even though it is possible in these encodings for bytes like 0x70 to be part of longer sequences that are unrelated to their interpretation as ASCII. It excludes such encodings as UTF-7, UTF-16, HZ-GB-2312, GSM03.38, and EBCDIC variants. 2.1.6 Resources The specification uses the term supported when referring to whether a user agent has an implementation capable of decoding the semantics of an external resource. A format or type is said to be supported if the implementation can process an external resource of that format or type without critical aspects of the resource being ignored. Whether a specific resource is supported can depend on what features of the resource's format are in use. For example, a PNG image would be considered to be in a supported format if its pixel data could be decoded and rendered, even if, unbeknownst to the implementation, the image actually also contained animation data. A MPEG4 video file would not be considered to be in a supported format if the compression format used was not supported, even if the implementation could determine the dimensions of the movie from the file's metadata. The term MIME type is used to refer to what is sometimes called an Internet media type in protocol literature. The term media type in this specification is used to refer to the type of media intended for presentation, as used by the CSS specifications. [RFC2046] [MQ] 2.2 Conformance requirements All diagrams, examples, and notes in this specification are non-normative, as are all sections explicitly marked non-normative. Everything else in this specification is normative. The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this document are to be interpreted as described in RFC2119. For readability, these words do not appear in all uppercase letters in this specification. [RFC2119] Requirements phrased in the imperative as part of algorithms (such as "strip any leading space characters" or "return false and abort these steps") are to be interpreted with the meaning of the key word ("must", "should", "may", etc) used in introducing the algorithm. This specification describes the conformance criteria for user agents (relevant to implementors) and documents (relevant to authors and authoring tool implementors). There is no implied relationship between document conformance requirements and implementation conformance requirements. User agents are not free to handle non-conformant documents as they please; the processing model described in this specification applies to implementations regardless of the conformity of the input documents. User agents fall into several (overlapping) categories with different conformance requirements. Web browsers and other interactive user agents Web browsers that support the XHTML syntax must process elements and attributes from the HTML namespace found in XML documents as described in this specification, so that users can interact with them, unless the semantics of those elements have been http://dev.w3.org/html5/spec/Overview.html (24 de 570)01-08-2009 6:55:53
- 25. HTML 5 overridden by other specifications. A conforming XHTML processor would, upon finding an XHTML script element in an XML document, execute the script contained in that element. However, if the element is found within a transformation expressed in XSLT (assuming the user agent also supports XSLT), then the processor would instead treat the script element as an opaque element that forms part of the transform. Web browsers that support the HTML syntax must process documents labeled as text/html as described in this specification, so that users can interact with them. User agents that support scripting must also be conforming implementations of the IDL fragments in this specification, as described in the Web IDL specification. [WEBIDL] Non-interactive presentation user agents User agents that process HTML and XHTML documents purely to render non-interactive versions of them must comply to the same conformance criteria as Web browsers, except that they are exempt from requirements regarding user interaction. Typical examples of non-interactive presentation user agents are printers (static UAs) and overhead displays (dynamic UAs). It is expected that most static non-interactive presentation user agents will also opt to lack scripting support. A non-interactive but dynamic presentation UA would still execute scripts, allowing forms to be dynamically submitted, and so forth. However, since the concept of "focus" is irrelevant when the user cannot interact with the document, the UA would not need to support any of the focus-related DOM APIs. User agents with no scripting support Implementations that do not support scripting (or which have their scripting features disabled entirely) are exempt from supporting the events and DOM interfaces mentioned in this specification. For the parts of this specification that are defined in terms of an events model or in terms of the DOM, such user agents must still act as if events and the DOM were supported. Scripting can form an integral part of an application. Web browsers that do not support scripting, or that have scripting disabled, might be unable to fully convey the author's intent. Conformance checkers Conformance checkers must verify that a document conforms to the applicable conformance criteria described in this specification. Automated conformance checkers are exempt from detecting errors that require interpretation of the author's intent (for example, while a document is non-conforming if the content of a blockquote element is not a quote, conformance checkers running without the input of human judgement do not have to check that blockquote elements only contain quoted material). Conformance checkers must check that the input document conforms when parsed without a browsing context (meaning that no scripts are run, and that the parser's scripting flag is disabled), and should also check that the input document conforms when parsed with a browsing context in which scripts execute, and that the scripts never cause non-conforming states to occur other than transiently during script execution itself. (This is only a "SHOULD" and not a "MUST" requirement because it has been proven to be impossible. [COMPUTABLE]) The term "HTML5 validator" can be used to refer to a conformance checker that itself conforms to the applicable requirements of this specification. XML DTDs cannot express all the conformance requirements of this specification. Therefore, a validating XML processor and a DTD cannot constitute a conformance checker. Also, since neither of the two authoring formats defined in this specification are applications of SGML, a validating SGML system cannot constitute a conformance checker either. To put it another way, there are three types of conformance criteria: 1. Criteria that can be expressed in a DTD. 2. Criteria that cannot be expressed by a DTD, but can still be checked by a machine. 3. Criteria that can only be checked by a human. A conformance checker must check for the first two. A simple DTD-based validator only checks for the first class of errors and is therefore not a conforming conformance checker according to this specification. Data mining tools Applications and tools that process HTML and XHTML documents for reasons other than to either render the documents or check them for conformance should act in accordance to the semantics of the documents that they process. A tool that generates document outlines but increases the nesting level for each paragraph and does not increase the nesting level for each section would not be conforming. Authoring tools and markup generators Authoring tools and markup generators must generate conforming documents. Conformance criteria that apply to authors also apply to authoring tools, where appropriate. Authoring tools are exempt from the strict requirements of using elements only for their specified purpose, but only to the extent that authoring tools are not yet able to determine author intent. For example, it is not conforming to use an address element for arbitrary contact information; that element can only be used for marking up contact information for the author of the document or section. However, since an authoring tool is likely unable to determine the difference, an authoring tool is exempt from that requirement. In terms of conformance checking, an editor is therefore required to output documents that conform to the same extent that a conformance checker will verify. When an authoring tool is used to edit a non-conforming document, it may preserve the conformance errors in sections of the document that were not edited during the editing session (i.e. an editing tool is allowed to round-trip erroneous content). However, an authoring tool must not claim that the output is conformant if errors have been so preserved. Authoring tools are expected to come in two broad varieties: tools that work from structure or semantic data, and tools that work on a What-You-See-Is-What-You-Get media-specific editing basis (WYSIWYG). The former is the preferred mechanism for tools that author HTML, since the structure in the source information can be used to make informed choices regarding which HTML elements and attributes are most appropriate. However, WYSIWYG tools are legitimate. WYSIWYG tools should use elements they know are appropriate, and should not use elements that they do not know to be appropriate. This might in certain extreme cases mean limiting the use of flow elements to just a http://dev.w3.org/html5/spec/Overview.html (25 de 570)01-08-2009 6:55:53
- 26. HTML 5 few elements, like div, b, i, and span and making liberal use of the style attribute. All authoring tools, whether WYSIWYG or not, should make a best effort attempt at enabling users to create well-structured, semantically rich, media-independent content. Some conformance requirements are phrased as requirements on elements, attributes, methods or objects. Such requirements fall into two categories: those describing content model restrictions, and those describing implementation behavior. Those in the former category are requirements on documents and authoring tools. Those in the second category are requirements on user agents. Conformance requirements phrased as algorithms or specific steps may be implemented in any manner, so long as the end result is equivalent. (In particular, the algorithms defined in this specification are intended to be easy to follow, and not intended to be performant.) User agents may impose implementation-specific limits on otherwise unconstrained inputs, e.g. to prevent denial of service attacks, to guard against running out of memory, or to work around platform-specific limitations. For compatibility with existing content and prior specifications, this specification describes two authoring formats: one based on XML (referred to as the XHTML syntax), and one using a custom format inspired by SGML (referred to as the HTML syntax). Implementations may support only one of these two formats, although supporting both is encouraged. XML documents that use elements or attributes from the HTML namespace and that are served over the wire (e.g. by HTTP) must be sent using an XML MIME type such as application/xml or application/xhtml+xml and must not be served as text/html. [RFC3023] Documents that use the HTML syntax, if they are served over the wire (e.g. by HTTP) must be labeled with the text/html MIME type. The language in this specification assumes that the user agent expands all entity references, and therefore does not include entity reference nodes in the DOM. If user agents do include entity reference nodes in the DOM, then user agents must handle them as if they were fully expanded when implementing this specification. For example, if a requirement talks about an element's child text nodes, then any text nodes that are children of an entity reference that is a child of that element would be used as well. Entity references to unknown entities must be treated as if they contained just an empty text node for the purposes of the algorithms defined in this specification. 2.2.1 Dependencies This specification relies on several other underlying specifications. XML Implementations that support the XHTML syntax must support some version of XML, as well as its corresponding namespaces specification, because that syntax uses an XML serialization with namespaces. [XML] [XMLNAMES] DOM The Document Object Model (DOM) is a representation — a model — of a document and its content. The DOM is not just an API; the conformance criteria of HTML implementations are defined, in this specification, in terms of operations on the DOM. [DOM3CORE] Implementations must support some version of DOM Core and DOM Events, because this specification is defined in terms of the DOM, and some of the features are defined as extensions to the DOM Core interfaces. [DOM3CORE] [DOM3EVENTS] Web IDL The IDL fragments in this specification must be interpreted as required for conforming IDL fragments, as described in the Web IDL specification. [WEBIDL] Unless otherwise specified, if a DOM attribute that is a floating point number type (float) is assigned an Infinity or Not-a-Number value, a NOT_SUPPORTED_ERR exception must be raised. Unless otherwise specified, if a method with an argument that is a floating point number type (float) is passed an Infinity or Not-a-Number value, a NOT_SUPPORTED_ERR exception must be raised. JavaScript Some parts of the language described by this specification only support JavaScript as the underlying scripting language. [ECMA262] The term "JavaScript" is used to refer to ECMA262, rather than the official term ECMAScript, since the term JavaScript is more widely known. Similarly, the MIME type used to refer to JavaScript in this specification is text/javascript, since that is the most commonly used type, despite it being an officially obsoleted type according to RFC 4329. [RFC4329] Media Queries Implementations must support some version of the Media Queries language. [MQ] This specification does not require support of any particular network transport protocols, style sheet language, scripting language, or any of the DOM and WebAPI specifications beyond those described above. However, the language described by this specification is biased towards CSS as the styling language, JavaScript as the scripting language, and HTTP as the network protocol, and several features assume that those languages and protocols are in use. This specification might have certain additional requirements on character encodings, image formats, audio formats, and video formats in the respective sections. 2.2.2 Extensibility Vendor-specific proprietary extensions to this specification are strongly discouraged. Documents must not use such extensions, as doing so reduces interoperability and fragments the user base, allowing only users of specific user agents to access the content in question. If markup extensions are needed, they should be done using XML, with elements or attributes from custom namespaces. If DOM extensions are needed, the members should be prefixed by vendor-specific strings to prevent clashes with future versions of this specification. Extensions must be defined so that the use of extensions does not contradict nor cause the non-conformance of functionality defined in the specification. For example, while strongly discouraged to do so, an implementation "Foo Browser" could add a new DOM attribute "fooTypeTime" to a control's DOM interface that returned the time it took the user to select the current value of a control (say). On the other http://dev.w3.org/html5/spec/Overview.html (26 de 570)01-08-2009 6:55:53
- 27. HTML 5 hand, defining a new control that appears in a form's elements array would be in violation of the above requirement, as it would violate the definition of elements given in this specification. User agents must treat elements and attributes that they do not understand as semantically neutral; leaving them in the DOM (for DOM processors), and styling them according to CSS (for CSS processors), but not inferring any meaning from them. 2.3 Case-sensitivity and string comparison This specification defines several comparison operators for strings. Comparing two strings in a case-sensitive manner means comparing them exactly, code point for code point. Comparing two strings in an ASCII case-insensitive manner means comparing them exactly, code point for code point, except that the characters in the range U+0041 .. U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) and the corresponding characters in the range U+0061 .. U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z) are considered to also match. Comparing two strings in a compatibility caseless manner means using the Unicode compatibility caseless match operation to compare the two strings. [UNICODECASE] Converting a string to ASCII uppercase means replacing all characters in the range U+0061 .. U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z) with the corresponding characters in the range U+0041 .. U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z). Converting a string to ASCII lowercase means replacing all characters in the range U+0041 .. U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) with the corresponding characters in the range U+0061 .. U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z). A string pattern is a prefix match for a string s when pattern is not longer than s and truncating s to pattern's length leaves the two strings as matches of each other. 2.4 Common microsyntaxes There are various places in HTML that accept particular data types, such as dates or numbers. This section describes what the conformance criteria for content in those formats is, and how to parse them. Implementors are strongly urged to carefully examine any third-party libraries they might consider using to implement the parsing of syntaxes described below. For example, date libraries are likely to implement error handling behavior that differs from what is required in this specification, since error-handling behavior is often not defined in specifications that describe date syntaxes similar to those used in this specification, and thus implementations tend to vary greatly in how they handle errors. 2.4.1 Common parser idioms The space characters, for the purposes of this specification, are U+0020 SPACE, U+0009 CHARACTER TABULATION (tab), U+000A LINE FEED (LF), U+000C FORM FEED (FF), and U+000D CARRIAGE RETURN (CR). The White_Space characters are those that have the Unicode property "White_Space". [UNICODE] The alphanumeric ASCII characters are those in the ranges U+0030 DIGIT ZERO .. U+0039 DIGIT NINE, U+0041 LATIN CAPITAL LETTER A .. U+005A LATIN CAPITAL LETTER Z, U+0061 LATIN SMALL LETTER A .. U+007A LATIN SMALL LETTER Z. Some of the micro-parsers described below follow the pattern of having an input variable that holds the string being parsed, and having a position variable pointing at the next character to parse in input. For parsers based on this pattern, a step that requires the user agent to collect a sequence of characters means that the following algorithm must be run, with characters being the set of characters that can be collected: 1. Let input and position be the same variables as those of the same name in the algorithm that invoked these steps. 2. Let result be the empty string. 3. While position doesn't point past the end of input and the character at position is one of the characters, append that character to the end of result and advance position to the next character in input. 4. Return result. The step skip whitespace means that the user agent must collect a sequence of characters that are space characters. The step skip White_Space characters means that the user agent must collect a sequence of characters that are White_Space characters. In both cases, the collected characters are not used. [UNICODE] When a user agent is to strip line breaks from a string, the user agent must remove any U+000A LINE FEED (LF) and U+000D CARRIAGE RETURN (CR) characters from that string. The code-point length of a string is the number of Unicode code points in that string. 2.4.2 Boolean attributes A number of attributes are boolean attributes. The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value. If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace. http://dev.w3.org/html5/spec/Overview.html (27 de 570)01-08-2009 6:55:53
- 28. HTML 5 The values "true" and "false" are not allowed on boolean attributes. To represent a false value, the attribute has to be omitted altogether. 2.4.3 Keywords and enumerated attributes Some attributes are defined as taking one of a finite set of keywords. Such attributes are called enumerated attributes. The keywords are each defined to map to a particular state (several keywords might map to the same state, in which case some of the keywords are synonyms of each other; additionally, some of the keywords can be said to be non-conforming, and are only in the specification for historical reasons). In addition, two default states can be given. The first is the invalid value default, the second is the missing value default. If an enumerated attribute is specified, the attribute's value must be an ASCII case-insensitive match for one of the given keywords that are not said to be non-conforming, with no leading or trailing whitespace. When the attribute is specified, if its value is an ASCII case-insensitive match for one of the given keywords then that keyword's state is the state that the attribute represents. If the attribute value matches none of the given keywords, but the attribute has an invalid value default, then the attribute represents that state. Otherwise, if the attribute value matches none of the keywords but there is a missing value default state defined, then that is the state represented by the attribute. Otherwise, there is no default, and invalid values must be ignored. When the attribute is not specified, if there is a missing value default state defined, then that is the state represented by the (missing) attribute. Otherwise, the absence of the attribute means that there is no state represented. The empty string can be a valid keyword. 2.4.4 Numbers 2.4.4.1 Non-negative integers A string is a valid non-negative integer if it consists of one or more characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). A valid non-negative integer represents the number that is represented in base ten by that string of digits. The rules for parsing non-negative integers are as given in the following algorithm. When invoked, the steps must be followed in the order given, aborting at the first step that returns a value. This algorithm will either return zero, a positive integer, or an error. Leading spaces are ignored. Trailing spaces and any trailing garbage characters are ignored. 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Let value have the value 0. 4. Skip whitespace. 5. If position is past the end of input, return an error. 6. If the next character is a U+002B PLUS SIGN character (+), advance position to the next character. 7. If position is past the end of input, return an error. 8. If the next character is not one of U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), then return an error. 9. Loop: If the next character is one of U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9): 1. Multiply value by ten. 2. Add the value of the current character (0..9) to value. 3. Advance position to the next character. 4. If position is not past the end of input, return to the top of the step labeled loop in the overall algorithm (that's the step within which these substeps find themselves). 10. Return value. 2.4.4.2 Signed integers A string is a valid integer if it consists of one or more characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), optionally prefixed with a U+002D HYPHEN-MINUS ("-") character. A valid integer without a U+002D HYPHEN-MINUS ("-") prefix represents the number that is represented in base ten by that string of digits. A valid integer with a U+002D HYPHEN-MINUS ("-") prefix represents the number represented in base ten by the string of digits http://dev.w3.org/html5/spec/Overview.html (28 de 570)01-08-2009 6:55:53
- 29. HTML 5 that follows the U+002D HYPHEN-MINUS, subtracted from zero. The rules for parsing integers are similar to the rules for non-negative integers, and are as given in the following algorithm. When invoked, the steps must be followed in the order given, aborting at the first step that returns a value. This algorithm will either return an integer or an error. Leading spaces are ignored. Trailing spaces and trailing garbage characters are ignored. 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Let value have the value 0. 4. Let sign have the value "positive". 5. Skip whitespace. 6. If position is past the end of input, return an error. 7. If the character indicated by position (the first character) is a U+002D HYPHEN-MINUS ("-") character: 1. Let sign be "negative". 2. Advance position to the next character. 3. If position is past the end of input, return an error. Otherwise, if the character indicated by position (the first character) is a U+002B PLUS SIGN character (+), then advance position to the next character. (The "+" is ignored, but it is not conforming.) 8. If the next character is not one of U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), then return an error. 9. If the next character is one of U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9): 1. Multiply value by ten. 2. Add the value of the current character (0..9) to value. 3. Advance position to the next character. 4. If position is not past the end of input, return to the top of step 9 in the overall algorithm (that's the step within which these substeps find themselves). 10. If sign is "positive", return value, otherwise return the result of subtracting value from zero. 2.4.4.3 Real numbers A string is a valid floating point number if it consists of: 1. Optionally, a U+002D HYPHEN-MINUS ("-") character. 2. A series of one or more characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). 3. Optionally: 1. A single U+002E FULL STOP (".") character. 2. A series of one or more characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). 4. Optionally: 1. Either a U+0065 LATIN SMALL LETTER E character or a U+0045 LATIN CAPITAL LETTER E character. 2. Optionally, a U+002D HYPHEN-MINUS ("-") character or U+002B PLUS SIGN ("+") character. 3. A series of one or more characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). A valid floating point number represents the number obtained by multiplying the significand by ten raised to the power of the exponent, where the significand is the first number, interpreted as base ten (including the decimal point and the number after the decimal point, if any, and interpreting the significand as a negative number if the whole string starts with a U+002D HYPHEN-MINUS ("-") character and the number is not zero), and where the exponent is the number after the E, if any (interpreted as a negative number if there is a U +002D HYPHEN-MINUS ("-") character between the E and the number and the number is not zero, or else ignoring a U+002B PLUS SIGN ("+") character between the E and the number if there is one). If there is no E, then the exponent is treated as zero. The values ±Infinity and NaN are not valid floating point numbers. The best representation of the floating point number n is the string obtained from applying the JavaScript operator ToString to n. The rules for parsing floating point number values are as given in the following algorithm. As with the previous algorithms, when this one is invoked, the steps must be followed in the order given, aborting at the first step that returns something. This algorithm will either return a number or an error. Leading spaces are ignored. Trailing spaces and garbage characters are ignored. 1. Let input be the string being parsed. http://dev.w3.org/html5/spec/Overview.html (29 de 570)01-08-2009 6:55:53
- 30. HTML 5 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Let value have the value 1. 4. Let divisor have the value 1. 5. Let exponent have the value 1. 6. Skip whitespace. 7. If position is past the end of input, return an error. 8. If the character indicated by position is a U+002D HYPHEN-MINUS ("-") character: 1. Change value and divisor to −1. 2. Advance position to the next character. 3. If position is past the end of input, return an error. 9. If the character indicated by position is not one of U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), then return an error. 10. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), and interpret the resulting sequence as a base-ten integer. Multiply value by that integer. 11. If position is past the end of input, return value. 12. If the character indicated by position is a U+002E FULL STOP ("."), run these substeps: 1. Advance position to the next character. 2. If position is past the end of input, or if the character indicated by position is not one of U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), then return value. 3. Fraction loop: Multiply divisor by ten. 4. Add the value of the current character interpreted as a base-ten digit (0..9) divided by divisor, to value. 5. Advance position to the next character. 6. If position is past the end of input, then return value. 7. If the character indicated by position is one of U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), return to the step labeled fraction loop in these substeps. 13. If the character indicated by position is a U+0065 LATIN SMALL LETTER E character or a U+0045 LATIN CAPITAL LETTER E character, run these substeps: 1. Advance position to the next character. 2. If position is past the end of input, then return value. 3. If the character indicated by position is a U+002D HYPHEN-MINUS ("-") character: 1. Change exponent to −1. 2. Advance position to the next character. 3. If position is past the end of input, then return value. Otherwise, if the character indicated by position is a U+002B PLUS SIGN ("+") character: 1. Advance position to the next character. 2. If position is past the end of input, then return value. 4. If the character indicated by position is not one of U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), then return value. 5. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), and interpret the resulting sequence as a base-ten integer. Multiply exponent by that integer. 6. Multiply value by ten raised to the exponentth power. 14. Return value. http://dev.w3.org/html5/spec/Overview.html (30 de 570)01-08-2009 6:55:53
- 31. HTML 5 2.4.4.4 Ratios The algorithms described in this section are used by the progress and meter elements. A valid denominator punctuation character is one of the characters from the table below. There is a value associated with each denominator punctuation character, as shown in the table below. Denominator Punctuation Character Value U+0025 PERCENT SIGN % 100 U+066A ARABIC PERCENT SIGN • 100 U+FE6A SMALL PERCENT SIGN • 100 U+FF05 FULLWIDTH PERCENT SIGN • 100 U+2030 PER MILLE SIGN ‰ 1000 U+2031 PER TEN THOUSAND SIGN • 10000 The steps for finding one or two numbers of a ratio in a string are as follows: 1. If the string is empty, then return nothing and abort these steps. 2. Find a number in the string according to the algorithm below, starting at the start of the string. 3. If the sub-algorithm in step 2 returned nothing or returned an error condition, return nothing and abort these steps. 4. Set number1 to the number returned by the sub-algorithm in step 2. 5. Starting with the character immediately after the last one examined by the sub-algorithm in step 2, skip all White_Space characters in the string (this might match zero characters). 6. If there are still further characters in the string, and the next character in the string is a valid denominator punctuation character, set denominator to that character. 7. If the string contains any other characters in the range U+0030 DIGIT ZERO to U+0039 DIGIT NINE, but denominator was given a value in the step 6, return nothing and abort these steps. 8. Otherwise, if denominator was given a value in step 6, return number1 and denominator and abort these steps. 9. Find a number in the string again, starting immediately after the last character that was examined by the sub-algorithm in step 2. 10. If the sub-algorithm in step 9 returned nothing or an error condition, return number1 and abort these steps. 11. Set number2 to the number returned by the sub-algorithm in step 9. 12. Starting with the character immediately after the last one examined by the sub-algorithm in step 9, skip all White_Space characters in the string (this might match zero characters). 13. If there are still further characters in the string, and the next character in the string is a valid denominator punctuation character, return nothing and abort these steps. 14. If the string contains any other characters in the range U+0030 DIGIT ZERO to U+0039 DIGIT NINE, return nothing and abort these steps. 15. Otherwise, return number1 and number2. The algorithm to find a number is as follows. It is given a string and a starting position, and returns either nothing, a number, or an error condition. 1. Starting at the given starting position, ignore all characters in the given string until the first character that is either a U+002E FULL STOP or one of the ten characters in the range U+0030 DIGIT ZERO to U+0039 DIGIT NINE. 2. If there are no such characters, return nothing and abort these steps. 3. Starting with the character matched in step 1, collect all the consecutive characters that are either a U+002E FULL STOP or one of the ten characters in the range U+0030 DIGIT ZERO to U+0039 DIGIT NINE, and assign this string of one or more characters to string. 4. If string consists of just a single U+002E FULL STOP character or if it contains more than one U+002E FULL STOP character then return an error condition and abort these steps. 5. Parse string according to the rules for parsing floating point number values, to obtain number. This step cannot fail (string is guaranteed to be a valid floating point number). 6. Return number. 2.4.4.5 Percentages and lengths http://dev.w3.org/html5/spec/Overview.html (31 de 570)01-08-2009 6:55:53
- 32. HTML 5 The rules for parsing dimension values are as given in the following algorithm. When invoked, the steps must be followed in the order given, aborting at the first step that returns a value. This algorithm will either return a number greater than or equal to 1.0, or an error; if a number is returned, then it is further categorized as either a percentage or a length. 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Skip whitespace. 4. If position is past the end of input, return an error. 5. If the next character is a U+002B PLUS SIGN character (+), advance position to the next character. 6. Collect a sequence of characters that are U+0030 DIGIT ZERO (0) characters, and discard them. 7. If position is past the end of input, return an error. 8. If the next character is not one of U+0031 DIGIT ONE (1) .. U+0039 DIGIT NINE (9), then return an error. 9. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), and interpret the resulting sequence as a base-ten integer. Let value be that number. 10. If position is past the end of input, return value as an integer. 11. If the next character is a U+002E FULL STOP character (.): 1. Advance position to the next character. 2. If the next character is not one of U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), then return value as an integer. 3. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). Let length be the number of characters collected. Let fraction be the result of interpreting the collected characters as a base-ten integer, and then dividing length that number by 10 . 4. Increment value by fraction. 12. If position is past the end of input, return value as a length. 13. If the next character is a U+0025 PERCENT SIGN character (%), return value as a percentage. 14. Return value as a length. 2.4.4.6 Lists of integers A valid list of integers is a number of valid integers separated by U+002C COMMA characters, with no other characters (e.g. no space characters). In addition, there might be restrictions on the number of integers that can be given, or on the range of values allowed. The rules for parsing a list of integers are as follows: 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Let numbers be an initially empty list of integers. This list will be the result of this algorithm. 4. If there is a character in the string input at position position, and it is either a U+0020 SPACE, U+002C COMMA, or U+003B SEMICOLON character, then advance position to the next character in input, or to beyond the end of the string if there are no more characters. 5. If position points to beyond the end of input, return numbers and abort. 6. If the character in the string input at position position is a U+0020 SPACE, U+002C COMMA, or U+003B SEMICOLON character, then return to step 4. 7. Let negated be false. 8. Let value be 0. 9. Let started be false. This variable is set to true when the parser sees a number or a U+002D HYPHEN-MINUS ("-") character. 10. Let got number be false. This variable is set to true when the parser sees a number. http://dev.w3.org/html5/spec/Overview.html (32 de 570)01-08-2009 6:55:53
- 33. HTML 5 11. Let finished be false. This variable is set to true to switch parser into a mode where it ignores characters until the next separator. 12. Let bogus be false. 13. Parser: If the character in the string input at position position is: A U+002D HYPHEN-MINUS character Follow these substeps: 1. If got number is true, let finished be true. 2. If finished is true, skip to the next step in the overall set of steps. 3. If started is true, let negated be false. 4. Otherwise, if started is false and if bogus is false, let negated be true. 5. Let started be true. A character in the range U+0030 DIGIT ZERO .. U+0039 DIGIT NINE Follow these substeps: 1. If finished is true, skip to the next step in the overall set of steps. 2. Multiply value by ten. 3. Add the value of the digit, interpreted in base ten, to value. 4. Let started be true. 5. Let got number be true. A U+0020 SPACE character A U+002C COMMA character A U+003B SEMICOLON character Follow these substeps: 1. If got number is false, return the numbers list and abort. This happens if an entry in the list has no digits, as in "1,2,x,4". 2. If negated is true, then negate value. 3. Append value to the numbers list. 4. Jump to step 4 in the overall set of steps. A character in the range U+0001 .. U+001F, U+0021 .. U+002B, U+002D .. U+002F, U+003A, U+003C .. U+0040, U+005B .. U+0060, U+007b .. U+007F (i.e. any other non-alphabetic ASCII character) Follow these substeps: 1. If got number is true, let finished be true. 2. If finished is true, skip to the next step in the overall set of steps. 3. Let negated be false. Any other character Follow these substeps: 1. If finished is true, skip to the next step in the overall set of steps. 2. Let negated be false. 3. Let bogus be true. 4. If started is true, then return the numbers list, and abort. (The value in value is not appended to the list first; it is dropped.) 14. Advance position to the next character in input, or to beyond the end of the string if there are no more characters. 15. If position points to a character (and not to beyond the end of input), jump to the big Parser step above. 16. If negated is true, then negate value. http://dev.w3.org/html5/spec/Overview.html (33 de 570)01-08-2009 6:55:54
- 34. HTML 5 17. If got number is true, then append value to the numbers list. 18. Return the numbers list and abort. 2.4.4.7 Lists of dimensions The rules for parsing a list of dimensions are as follows. These rules return a list of zero or more pairs consisting of a number and a unit, the unit being one of percentage, relative, and absolute. 1. Let raw input be the string being parsed. 2. If the last character in raw input is a U+002C COMMA character (","), then remove that character from raw input. 3. Split the string raw input on commas. Let raw tokens be the resulting list of tokens. 4. Let result be an empty list of number/unit pairs. 5. For each token in raw tokens, run the following substeps: 1. Let input be the token. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Let value be the number 0. 4. Let unit be absolute. 5. If position is past the end of input, set unit to relative and jump to the last substep. 6. If the character at position is a character in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), interpret the resulting sequence as an integer in base ten, and increment value by that integer. 7. If the character at position is a U+002E FULL STOP character (.), run these substeps: 1. Collect a sequence of characters consisting of space characters and characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). Let s be the resulting sequence. 2. Remove all space characters in s. 3. If s is not the empty string, run these subsubsteps: 1. Let length be the number of characters in s (after the spaces were removed). length 2. Let fraction be the result of interpreting s as a base-ten integer, and then dividing that number by 10 . 3. Increment value by fraction. 8. Skip whitespace. 9. If the character at position is a U+0025 PERCENT SIGN (%) character, then set unit to percentage. Otherwise, if the character at position is a U+002A ASTERISK character (*), then set unit to relative. 10. Add an entry to result consisting of the number given by value and the unit given by unit. 6. Return the list result. 2.4.5 Dates and times In the algorithms below, the number of days in month month of year year is: 31 if month is 1, 3, 5, 7, 8, 10, or 12; 30 if month is 4, 6, 9, or 11; 29 if month is 2 and year is a number divisible by 400, or if year is a number divisible by 4 but not by 100; and 28 otherwise. This takes into account leap years in the Gregorian calendar. [GREGORIAN] The digits in the date and time syntaxes defined in this section must be characters in the range U+0030 DIGIT ZERO to U+0039 DIGIT NINE, used to express numbers in base ten. While the formats described here are intended to be subsets of the corresponding ISO8601 formats, this specification defines parsing rules in much more detail than ISO8601. Implementators are therefore encouraged to carefully examine any date parsing libraries before using them to implement the parsing rules described below; ISO8601 libraries might not parse dates and times exactly the same manner. [ISO8601] http://dev.w3.org/html5/spec/Overview.html (34 de 570)01-08-2009 6:55:54
- 35. HTML 5 2.4.5.1 Months A month consists of a specific proleptic Gregorian date with no time-zone information and no date information beyond a year and a month. [GREGORIAN] A string is a valid month string representing a year year and month month if it consists of the following components in the given order: 1. Four or more digits, representing year, where year > 0 2. A U+002D HYPHEN-MINUS character (-) 3. Two digits, representing the month month, in the range 1 ≤ month ≤ 12 The rules to parse a month string are as follows. This will either return a year and month, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing. 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Parse a month component to obtain year and month. If this returns nothing, then fail. 4. If position is not beyond the end of input, then fail. 5. Return year and month. The rules to parse a month component, given an input string and a position, are as follows. This will either return a year and a month, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing. 1. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not at least four characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the year. 2. If year is not a number greater than zero, then fail. 3. If position is beyond the end of input or if the character at position is not a U+002D HYPHEN-MINUS character, then fail. Otherwise, move position forwards one character. 4. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the month. 5. If month is not a number in the range 1 ≤ month ≤ 12, then fail. 6. Return year and month. 2.4.5.2 Dates A date consists of a specific proleptic Gregorian date with no time-zone information, consisting of a year, a month, and a day. [GREGORIAN] A string is a valid date string representing a year year, month month, and day day if it consists of the following components in the given order: 1. A valid month string, representing year and month 2. A U+002D HYPHEN-MINUS character (-) 3. Two digits, representing day, in the range 1 ≤ day ≤ maxday where maxday is the number of days in the month month and year year The rules to parse a date string are as follows. This will either return a date, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing. 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Parse a date component to obtain year, month, and day. If this returns nothing, then fail. 4. If position is not beyond the end of input, then fail. 5. Let date be the date with year year, month month, and day day. http://dev.w3.org/html5/spec/Overview.html (35 de 570)01-08-2009 6:55:54
- 36. HTML 5 6. Return date. The rules to parse a date component, given an input string and a position, are as follows. This will either return a year, a month, and a day, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing. 1. Parse a month component to obtain year and month. If this returns nothing, then fail. 2. Let maxday be the number of days in month month of year year. 3. If position is beyond the end of input or if the character at position is not a U+002D HYPHEN-MINUS character, then fail. Otherwise, move position forwards one character. 4. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the day. 5. If day is not a number in the range 1 ≤ month ≤ maxday, then fail. 6. Return year, month, and day. 2.4.5.3 Times A time consists of a specific time with no time-zone information, consisting of an hour, a minute, a second, and a fraction of a second. A string is a valid time string representing an hour hour, a minute minute, and a second second if it consists of the following components in the given order: 1. Two digits, representing hour, in the range 0 ≤ hour ≤ 23 2. A U+003A COLON character (:) 3. Two digits, representing minute, in the range 0 ≤ minute ≤ 59 4. Optionally (required if second is non-zero): 1. A U+003A COLON character (:) 2. Two digits, representing the integer part of second, in the range 0 ≤ s ≤ 59 3. Optionally (required if second is not an integer): 1. A 002E FULL STOP character (.) 2. One or more digits, representing the fractional part of second The second component cannot be 60 or 61; leap seconds cannot be represented. The rules to parse a time string are as follows. This will either return a time, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing. 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Parse a time component to obtain hour, minute, and second. If this returns nothing, then fail. 4. If position is not beyond the end of input, then fail. 5. Let time be the time with hour hour, minute minute, and second second. 6. Return time. The rules to parse a time component, given an input string and a position, are as follows. This will either return an hour, a minute, and a second, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing. 1. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the hour. 2. If hour is not a number in the range 0 ≤ hour ≤ 23, then fail. 3. If position is beyond the end of input or if the character at position is not a U+003A COLON character, then fail. Otherwise, move position forwards one character. 4. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the minute. 5. If minute is not a number in the range 0 ≤ minute ≤ 59, then fail. http://dev.w3.org/html5/spec/Overview.html (36 de 570)01-08-2009 6:55:54
- 37. HTML 5 6. Let second be a string with the value "0". 7. If position is not beyond the end of input and the character at position is a U+003A COLON, then run these substeps: 1. Advance position to the next character in input. 2. If position is beyond the end of input, or at the last character in input, or if the next two characters in input starting at position are not two characters both in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), then fail. 3. Collect a sequence of characters that are either characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9) or U+002E FULL STOP characters. If the collected sequence has more than one U+002E FULL STOP characters, or if the last character in the sequence is a U+002E FULL STOP character, then fail. Otherwise, let the collected string be second instead of its previous value. 8. Interpret second as a base-ten number (possibly with a fractional part). Let second be that number instead of the string version. 9. If second is not a number in the range 0 ≤ second < 60, then fail. 10. Return hour, minute, and second. 2.4.5.4 Local dates and times A local date and time consists of a specific proleptic Gregorian date, consisting of a year, a month, and a day, and a time, consisting of an hour, a minute, a second, and a fraction of a second, but expressed without a time zone. [GREGORIAN] A string is a valid local date and time string representing a date and time if it consists of the following components in the given order: 1. A valid date string representing the date. 2. A U+0054 LATIN CAPITAL LETTER T character. 3. A valid time string representing the time. The rules to parse a local date and time string are as follows. This will either return a date and time, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing. 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Parse a date component to obtain year, month, and day. If this returns nothing, then fail. 4. If position is beyond the end of input or if the character at position is not a U+0054 LATIN CAPITAL LETTER T character then fail. Otherwise, move position forwards one character. 5. Parse a time component to obtain hour, minute, and second. If this returns nothing, then fail. 6. If position is not beyond the end of input, then fail. 7. Let date be the date with year year, month month, and day day. 8. Let time be the time with hour hour, minute minute, and second second. 9. Return date and time. 2.4.5.5 Global dates and times A global date and time consists of a specific proleptic Gregorian date, consisting of a year, a month, and a day, and a time, consisting of an hour, a minute, a second, and a fraction of a second, expressed with a time zone, consisting of a number of hours and minutes. [GREGORIAN] A string is a valid global date and time string representing a date, time, and a time-zone offset if it consists of the following components in the given order: 1. A valid date string representing the date 2. A U+0054 LATIN CAPITAL LETTER T character 3. A valid time string representing the time 4. Either: r A U+005A LATIN CAPITAL LETTER Z character, allowed only if the time zone is UTC r Or: http://dev.w3.org/html5/spec/Overview.html (37 de 570)01-08-2009 6:55:54
- 38. HTML 5 1. Either a U+002B PLUS SIGN character (+) or a U+002D HYPHEN-MINUS (-) character, representing the sign of the time-zone offset 2. Two digits, representing the hours component hour of the time-zone offset, in the range 0 ≤ hour ≤ 23 3. A U+003A COLON character (:) 4. Two digits, representing the minutes component minute of the time-zone offset, in the range 0 ≤ minute ≤ 59 This format allows for time zone offsets from -23:59 to +23:59. In practice, however, the range of actual time zones is -12:00 to +14:00, and the minutes component of actual time zones is always either 00, 30, or 45. The following are some examples of dates written as valid global date and time strings. "0037-12-13T00:00Z" Midnight UTC on the birthday of Nero (the Roman Emperor). "1979-10-14T12:00:00.001-04:00" One millisecond after noon on October 14th 1979, in the time zone in use on the east coast of North America during daylight saving time. "8592-01-01T02:09+02:09" Midnight UTC on the 1st of January, 8592. The time zone associated with that time is two hours and nine minutes ahead of UTC, which is not a real time zone currently, but is nonetheless allowed. Several things are notable about these dates: q Years with fewer than four digits have to be zero-padded. The date "37-12-13" would not be a valid date. q To unambiguously identify a moment in time prior to the introduction of the Gregorian calendar, the date has to be first converted to the Gregorian calendar from the calendar in use at the time (e.g. from the Julian calendar). The date of Nero's birth is the 15th of December 37, in the Julian Calendar, which is the 13th of December 37 in the proleptic Gregorian Calendar. q The time and time-zone components are not optional. q Dates before the year zero can't be represented as a datetime in this version of HTML. q Time zones differ based on daylight savings time. The rules to parse a global date and time string are as follows. This will either return a time in UTC, with associated time-zone information for round tripping or display purposes, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing. 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Parse a date component to obtain year, month, and day. If this returns nothing, then fail. 4. If position is beyond the end of input or if the character at position is not a U+0054 LATIN CAPITAL LETTER T character then fail. Otherwise, move position forwards one character. 5. Parse a time component to obtain hour, minute, and second. If this returns nothing, then fail. 6. If position is beyond the end of input, then fail. 7. Parse a time-zone component to obtain timezonehours and timezoneminutes. If this returns nothing, then fail. 8. If position is not beyond the end of input, then fail. 9. Let time be the moment in time at year year, month month, day day, hours hour, minute minute, second second, subtracting timezonehours hours and timezoneminutes minutes. That moment in time is a moment in the UTC time zone. 10. Let timezone be timezonehours hours and timezoneminutes minutes from UTC. 11. Return time and timezone. The rules to parse a time-zone component, given an input string and a position, are as follows. This will either return time-zone hours and time-zone minutes, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing. 1. If the character at position is a U+005A LATIN CAPITAL LETTER Z, then: 1. Let timezonehours be 0. 2. Let timezoneminutes be 0. 3. Advance position to the next character in input. Otherwise, if the character at position is either a U+002B PLUS SIGN ("+") or a U+002D HYPHEN-MINUS ("-"), then: 1. If the character at position is a U+002B PLUS SIGN ("+"), let sign be "positive". Otherwise, it's a U+002D HYPHEN-MINUS ("-"); let sign be "negative". http://dev.w3.org/html5/spec/Overview.html (38 de 570)01-08-2009 6:55:54
- 39. HTML 5 2. Advance position to the next character in input. 3. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the timezonehours. 4. If timezonehours is not a number in the range 0 ≤ timezonehours ≤ 23, then fail. 5. If sign is "negative", then negate timezonehours. 6. If position is beyond the end of input or if the character at position is not a U+003A COLON character, then fail. Otherwise, move position forwards one character. 7. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the timezoneminutes. 8. If timezoneminutes is not a number in the range 0 ≤ timezoneminutes ≤ 59, then fail. 9. If sign is "negative", then negate timezoneminutes. 2. Return timezonehours and timezoneminutes. 2.4.5.6 Weeks A week consists of a week-year number and a week number representing a seven day period. Each week-year in this calendaring system has either 52 weeks or 53 weeks, as defined below. A week is a seven-day period. The week starting on the Gregorian date Monday December 29th 1969 (1969-12-29) is defined as week number 1 in week-year 1970. Consecutive weeks are numbered sequentially. The week before the number 1 week in a week-year is the last week in the previous week-year, and vice versa. [GREGORIAN] A week-year with a number year has 53 weeks if it corresponds to either a year year in the proleptic Gregorian calendar that has a Thursday as its first day (January 1st), or a year year in the proleptic Gregorian calendar that has a Wednesday as its first day (January 1st) and where year is a number divisible by 400, or a number divisible by 4 but not by 100. All other week-years have 52 weeks. The week number of the last day of a week-year with 53 weeks is 53; the week number of the last day of a week-year with 52 weeks is 52. The week-year number of a particular day can be different than the number of the year that contains that day in the proleptic Gregorian calendar. The first week in a week-year y is the week that contains the first Thursday of the Gregorian year y. A string is a valid week string representing a week-year year and week week if it consists of the following components in the given order: 1. Four or more digits, representing year, where year > 0 2. A U+002D HYPHEN-MINUS character (-) 3. A U+0057 LATIN CAPITAL LETTER W character 4. Two digits, representing the week week, in the range 1 ≤ week ≤ maxweek, where maxweek is the week number of the last day of week-year year The rules to parse a week string are as follows. This will either return a week-year number and week number, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing. 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not at least four characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the year. 4. If year is not a number greater than zero, then fail. 5. If position is beyond the end of input or if the character at position is not a U+002D HYPHEN-MINUS character, then fail. Otherwise, move position forwards one character. 6. If position is beyond the end of input or if the character at position is not a U+0057 LATIN CAPITAL LETTER W character, then fail. Otherwise, move position forwards one character. 7. Collect a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9). If the collected sequence is not exactly two characters long, then fail. Otherwise, interpret the resulting sequence as a base-ten integer. Let that number be the week. 8. Let maxweek be the week number of the last day of year year. 9. If week is not a number in the range 1 ≤ week ≤ maxweek, then fail. 10. If position is not beyond the end of input, then fail. http://dev.w3.org/html5/spec/Overview.html (39 de 570)01-08-2009 6:55:54
- 40. HTML 5 11. Return the week-year number year and the week number week. 2.4.5.7 Vaguer moments in time A date or time string consists of either a date, a time, or a global date and time. A string is a valid date or time string if it is also one of the following: q A valid date string. q A valid time string. q A valid global date and time string. A string is a valid date or time string in content if it consists of zero or more White_Space characters, followed by a valid date or time string, followed by zero or more further White_Space characters. The rules to parse a date or time string are as follows. The algorithm is invoked with a flag indicating if the in attribute variant or the in content variant is to be used. The algorithm will either return a date, a time, a global date and time, or nothing. If at any point the algorithm says that it "fails", this means that it is aborted at that point and returns nothing. 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. For the in content variant: skip White_Space characters. 4. Set start position to the same position as position. 5. Set the date present and time present flags to true. 6. Parse a date component to obtain year, month, and day. If this fails, then set the date present flag to false. 7. If date present is true, and position is not beyond the end of input, and the character at position is a U+0054 LATIN CAPITAL LETTER T character, then advance position to the next character in input. Otherwise, if date present is true, and either position is beyond the end of input or the character at position is not a U+0054 LATIN CAPITAL LETTER T character, then set time present to false. Otherwise, if date present is false, set position back to the same position as start position. 8. If the time present flag is true, then parse a time component to obtain hour, minute, and second. If this returns nothing, then set the time present flag to false. 9. If both the date present and time present flags are false, then fail. 10. If the date present and time present flags are both true, but position is beyond the end of input, then fail. 11. If the date present and time present flags are both true, parse a time-zone component to obtain timezonehours and timezoneminutes. If this returns nothing, then fail. 12. For the in content variant: skip White_Space characters. 13. If position is not beyond the end of input, then fail. 14. If the date present flag is true and the time present flag is false, then let date be the date with year year, month month, and day day, and return date. Otherwise, if the time present flag is true and the date present flag is false, then let time be the time with hour hour, minute minute, and second second, and return time. Otherwise, let time be the moment in time at year year, month month, day day, hours hour, minute minute, second second, subtracting timezonehours hours and timezoneminutes minutes, that moment in time being a moment in the UTC time zone; let timezone be timezonehours hours and timezoneminutes minutes from UTC; and return time and timezone. 2.4.6 Colors A simple color consists of three 8-bit numbers in the range 0..255, representing the red, green, and blue components of the color respectively, in the sRGB color space. [SRGB] A string is a valid simple color if it is exactly seven characters long, and the first character is a U+0023 NUMBER SIGN (#) character, and the remaining six characters are all in the range U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), U+0041 LATIN CAPITAL LETTER A .. U+0046 LATIN CAPITAL LETTER F, U+0061 LATIN SMALL LETTER A .. U+0066 LATIN SMALL LETTER F, with the first two digits representing the red component, the middle two digits representing the green component, and the last two digits representing the blue component, in hexadecimal. A string is a valid lowercase simple color if it is a valid simple color and doesn't use any characters in the range U+0041 LATIN CAPITAL LETTER A .. U+0046 LATIN CAPITAL LETTER F. http://dev.w3.org/html5/spec/Overview.html (40 de 570)01-08-2009 6:55:54
- 41. HTML 5 The rules for parsing simple color values are as given in the following algorithm. When invoked, the steps must be followed in the order given, aborting at the first step that returns a value. This algorithm will either return a simple color or an error. 1. Let input be the string being parsed. 2. If input is not exactly seven characters long, then return an error. 3. If the first character in input is not a U+0023 NUMBER SIGN (#) character, then return an error. 4. If the last six characters of input are not all in the range U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), U+0041 LATIN CAPITAL LETTER A .. U+0046 LATIN CAPITAL LETTER F, U+0061 LATIN SMALL LETTER A .. U+0066 LATIN SMALL LETTER F, then return an error. 5. Let result be a simple color. 6. Interpret the second and third characters as a hexadecimal number and let the result be the red component of result. 7. Interpret the fourth and fifth characters as a hexadecimal number and let the result be the green component of result. 8. Interpret the sixth and seventh characters as a hexadecimal number and let the result be the blue component of result. 9. Return result. The rules for serializing simple color values given a simple color are as given in the following algorithm: 1. Let result be a string consisting of a single U+0023 NUMBER SIGN (#) character. 2. Convert the red, green, and blue components in turn to two-digit hexadecimal numbers using the digits U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9) and U+0061 LATIN SMALL LETTER A .. U+0066 LATIN SMALL LETTER F, zero-padding if necessary, and append these numbers to result, in the order red, green, blue. 3. Return result, which will be a valid lowercase simple color. Some obsolete legacy attributes parse colors in a more complicated manner, using the rules for parsing a legacy color value, which are given in the following algorithm. When invoked, the steps must be followed in the order given, aborting at the first step that returns a value. This algorithm will either return a simple color or an error. 1. Let input be the string being parsed. 2. If input is the empty string, then return an error. 3. If input is an ASCII case-insensitive match for the string "transparent", then return an error. 4. If input is an ASCII case-insensitive match for one of the keywords listed in the SVG color keywords or CSS2 System Colors sections of the CSS3 Color specification, then return the simple color corresponding to that keyword. [CSSCOLOR] 5. If input is four characters long, and the first character in input is a U+0023 NUMBER SIGN (#) character, and the last three characters of input are all in the range U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), U+0041 LATIN CAPITAL LETTER A .. U+0046 LATIN CAPITAL LETTER F, and U+0061 LATIN SMALL LETTER A .. U+0066 LATIN SMALL LETTER F, then run these substeps: 1. Let result be a simple color. 2. Interpret the second character of input as a hexadecimal digit; let the red component of result be the resulting number multiplied by 17. 3. Interpret the third character of input as a hexadecimal digit; let the green component of result be the resulting number multiplied by 17. 4. Interpret the fourth character of input as a hexadecimal digit; let the blue component of result be the resulting number multiplied by 17. 5. Return result. 6. Replace any characters in input that have a Unicode code point greater than U+FFFF (i.e. any characters that are not in the basic multilingual plane) with the two-character string "00". 7. If input is longer than 128 characters, truncate input, leaving only the first 128 characters. 8. If the first character in input is a U+0023 NUMBER SIGN character (#), remove it. 9. Replace any character in input that is not in the range U+0030 DIGIT ZERO (0) .. U+0039 DIGIT NINE (9), U+0041 LATIN CAPITAL LETTER A .. U+0046 LATIN CAPITAL LETTER F, and U+0061 LATIN SMALL LETTER A .. U+0066 LATIN SMALL LETTER F with the character U+0030 DIGIT ZERO (0). 10. While input's length is zero or not a multiple of three, append a U+0030 DIGIT ZERO (0) character to input. 11. Split input into three strings of equal length, to obtain three components. Let length be the length of those components (one third the length of input). http://dev.w3.org/html5/spec/Overview.html (41 de 570)01-08-2009 6:55:54
- 42. HTML 5 12. If length is greater than 8, then remove the leading length-8 characters in each component, and let length be 8. 13. While length is greater than two and the first character in each component is a U+0030 DIGIT ZERO (0) character, remove that character and reduce length by one. 14. If length is still greater than two, truncate each component, leaving only the first two characters in each. 15. Let result be a simple color. 16. Interpret the first component as a hexadecimal number; let the red component of result be the resulting number. 17. Interpret the second component as a hexadecimal number; let the green component of result be the resulting number. 18. Interpret the third component as a hexadecimal number; let the blue component of result be the resulting number. 19. Return result. The 2D graphics context has a separate color syntax that also handles opacity. 2.4.7 Space-separated tokens A set of space-separated tokens is a set of zero or more words separated by one or more space characters, where words consist of any string of one or more characters, none of which are space characters. A string containing a set of space-separated tokens may have leading or trailing space characters. An unordered set of unique space-separated tokens is a set of space-separated tokens where none of the words are duplicated. An ordered set of unique space-separated tokens is a set of space-separated tokens where none of the words are duplicated but where the order of the tokens is meaningful. Sets of space-separated tokens sometimes have a defined set of allowed values. When a set of allowed values is defined, the tokens must all be from that list of allowed values; other values are non-conforming. If no such set of allowed values is provided, then all values are conforming. When a user agent has to split a string on spaces, it must use the following algorithm: 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Let tokens be a list of tokens, initially empty. 4. Skip whitespace 5. While position is not past the end of input: 1. Collect a sequence of characters that are not space characters. 2. Add the string collected in the previous step to tokens. 3. Skip whitespace 6. Return tokens. When a user agent has to remove a token from a string, it must use the following algorithm: 1. Let input be the string being modified. 2. Let token be the token being removed. It will not contain any space characters. 3. Let output be the output string, initially empty. 4. Let position be a pointer into input, initially pointing at the start of the string. 5. If position is beyond the end of input, set the string being modified to output, and abort these steps. http://dev.w3.org/html5/spec/Overview.html (42 de 570)01-08-2009 6:55:54
- 43. HTML 5 6. If the character at position is a space character: 1. Append the character at position to the end of output. 2. Increment position so it points at the next character in input. 3. Return to step 5 in the overall set of steps. 7. Otherwise, the character at position is the first character of a token. Collect a sequence of characters that are not space characters, and let that be s. 8. If s is exactly equal to token, then: 1. Skip whitespace (in input). 2. Remove any space characters currently at the end of output. 3. If position is not past the end of input, and output is not the empty string, append a single U+0020 SPACE character at the end of output. 9. Otherwise, append s to the end of output. 10. Return to step 6 in the overall set of steps. This causes any occurrences of the token to be removed from the string, and any spaces that were surrounding the token to be collapsed to a single space, except at the start and end of the string, where such spaces are removed. 2.4.8 Comma-separated tokens A set of comma-separated tokens is a set of zero or more tokens each separated from the next by a single U+002C COMMA character (,), where tokens consist of any string of zero or more characters, neither beginning nor ending with space characters, nor containing any U+002C COMMA characters (,), and optionally surrounded by space characters. For instance, the string " a ,b,,d d " consists of four tokens: "a", "b", the empty string, and "d d". Leading and trailing whitespace around each token doesn't count as part of the token, and the empty string can be a token. Sets of comma-separated tokens sometimes have further restrictions on what consists a valid token. When such restrictions are defined, the tokens must all fit within those restrictions; other values are non-conforming. If no such restrictions are specified, then all values are conforming. When a user agent has to split a string on commas, it must use the following algorithm: 1. Let input be the string being parsed. 2. Let position be a pointer into input, initially pointing at the start of the string. 3. Let tokens be a list of tokens, initially empty. 4. Token: If position is past the end of input, jump to the last step. 5. Collect a sequence of characters that are not U+002C COMMA characters (,). Let s be the resulting sequence (which might be the empty string). 6. Remove any leading or trailing sequence of space characters from s. 7. Add s to tokens. 8. If position is not past the end of input, then the character at position is a U+002C COMMA character (,); advance position past that character. 9. Jump back to the step labeled token. 10. Return tokens. 2.4.9 Reversed DNS identifiers A valid reversed DNS identifier is a string that consists of a series of IDNA labels in reverse order (i.e. starting with the top-level domain), the prefix of which, when reversed and converted to ASCII, corresponds to a registered domain. For instance, the string "com.example.xn--74h" is a valid reversed DNS identifier because the string "example.com" is a registered domain. To check if a string is a valid reversed DNS identifier, conformance checkers must run the following algorithm: http://dev.w3.org/html5/spec/Overview.html (43 de 570)01-08-2009 6:55:54
- 44. HTML 5 1. Apply the IDNA ToASCII algorithm to the string, with both the AllowUnassigned and UseSTD3ASCIIRules flags set, but between steps 2 and 3 of the general ToASCII/ToUnicode algorithm (i.e. after splitting the domain name into individual labels), reverse the order of the labels. If ToASCII fails to convert one of the components of the string, e.g. because it is too long or because it contains invalid characters, then the string is not valid; abort these steps. [RFC3490] 2. Check that the end of the resulting string matches a suffix in the Public Suffix List, and that there is at least one domain label before the matching substring. If it does not, or if there is not, then the string is not valid; abort these steps. [PSL] 3. Check that the domain name up to the label before the prefix that was matched in the previous string is a registered domain name. 2.4.10 References A valid hash-name reference to an element of type type is a string consisting of a U+0023 NUMBER SIGN (#) character followed by a string which exactly matches the value of the name attribute of an element in the document with type type. The rules for parsing a hash-name reference to an element of type type are as follows: 1. If the string being parsed does not contain a U+0023 NUMBER SIGN character, or if the first such character in the string is the last character in the string, then return null and abort these steps. 2. Let s be the string from the character immediately after the first U+0023 NUMBER SIGN character in the string being parsed up to the end of that string. 3. Return the first element of type type that has an id attribute whose value is a case-sensitive match for s or a name attribute whose value is a compatibility caseless match for s. 2.5 URLs 2.5.1 Terminology A URL is a string used to identify a resource. A URL is a valid URL if it is a valid Web address as defined by the Web addresses specification. [WEBADDRESSES] A URL is an absolute URL if it is an absolute Web address as defined by the Web addresses specification. [WEBADDRESSES] To parse a URL url into its component parts, the user agent must use the parse a Web address algorithm defined by the Web addresses specification. [WEBADDRESSES] Parsing a URL results in the following components, again as defined by the Web addresses specification: q <scheme> q <host> q <port> q <hostport> q <path> q <query> q <fragment> q <host-specific> To resolve a URL to an absolute URL relative to either another absolute URL or an element, the user agent must use the resolve a Web address algorithm defined by the Web addresses specification. [WEBADDRESSES] The document base URL of a Document object is the document base Web address as defined by the Web addresses specification. [WEBADDRESSES] The term "URL" in this specification is used in a manner distinct from the precise technical meaning it is given in RFC 3986. Readers familiar with that RFC will find it easier to read this specification if they pretend the term "URL" as used herein is really called something else altogether. This is a willful violation of RFC 3986. [RFC3986] 2.5.2 Dynamic changes to base URLs When an xml:base attribute changes, the attribute's element, and all descendant elements, are affected by a base URL change. When a document's document base URL changes, all elements in that document are affected by a base URL change. When an element is moved from one document to another, if the two documents have different base URLs, then that element and all its descendants are affected by a base URL change. When an element is affected by a base URL change, it must act as described in the following list: If the element is a hyperlink element If the absolute URL identified by the hyperlink is being shown to the user, or if any data derived from that URL is affecting the display, then the href attribute should be re-resolved relative to the element and the UI updated appropriately. http://dev.w3.org/html5/spec/Overview.html (44 de 570)01-08-2009 6:55:54
- 45. HTML 5 For example, the CSS :link/:visited pseudo-classes might have been affected. If the hyperlink has a ping attribute and its absolute URL(s) are being shown to the user, then the ping attribute's tokens should be re-resolved relative to the element and the UI updated appropriately. If the element is a q, blockquote, section, article, ins, or del element with a cite attribute If the absolute URL identified by the cite attribute is being shown to the user, or if any data derived from that URL is affecting the display, then the URL should be re-resolved relative to the element and the UI updated appropriately. Otherwise The element is not directly affected. Changing the base URL doesn't affect the image displayed by img elements, although subsequent accesses of the src DOM attribute from script will return a new absolute URL that might no longer correspond to the image being shown. 2.5.3 Interfaces for URL manipulation An interface that has a complement of URL decomposition attributes will have seven attributes with the following definitions: attribute DOMString protocol; attribute DOMString host; attribute DOMString hostname; attribute DOMString port; attribute DOMString pathname; attribute DOMString search; attribute DOMString hash; o . protocol [ = value ] Returns the current scheme of the underlying URL. Can be set, to change the underlying URL's scheme. o . host [ = value ] Returns the current host and port (if it's not the default port) in the underlying URL. Can be set, to change the underlying URL's host and port. The host and the port are separated by a colon. The port part, if omitted, will be assumed to be the current scheme's default port. o . hostname [ = value ] Returns the current host in the underlying URL. Can be set, to change the underlying URL's host. o . port [ = value ] Returns the current port in the underlying URL. Can be set, to change the underlying URL's port. o . pathname [ = value ] Returns the current path in the underlying URL. Can be set, to change the underlying URL's path. o . search [ = value ] Returns the current query component in the underlying URL. Can be set, to change the underlying URL's query component. o . hash [ = value ] Returns the current fragment identifier in the underlying URL. Can be set, to change the underlying URL's fragment identifier. The attributes defined to be URL decomposition attributes must act as described for the attributes with the same corresponding names in this section. http://dev.w3.org/html5/spec/Overview.html (45 de 570)01-08-2009 6:55:54
- 46. HTML 5 In addition, an interface with a complement of URL decomposition attributes will define an input, which is a URL that the attributes act on, and a common setter action, which is a set of steps invoked when any of the attributes' setters are invoked. The seven URL decomposition attributes have similar requirements. On getting, if the input is an absolute URL that fulfills the condition given in the "getter condition" column corresponding to the attribute in the table below, the user agent must return the part of the input URL given in the "component" column, with any prefixes specified in the "prefix" column appropriately added to the start of the string and any suffixes specified in the "suffix" column appropriately added to the end of the string. Otherwise, the attribute must return the empty string. On setting, the new value must first be mutated as described by the "setter preprocessor" column, then mutated by %-escaping any characters in the new value that are not valid in the relevant component as given by the "component" column. Then, if the input is an absolute URL and the resulting new value fulfills the condition given in the "setter condition" column, the user agent must make a new string output by replacing the component of the URL given by the "component" column in the input URL with the new value; otherwise, the user agent must let output be equal to the input. Finally, the user agent must invoke the common setter action with the value of output. When replacing a component in the URL, if the component is part of an optional group in the URL syntax consisting of a character followed by the component, the component (including its prefix character) must be included even if the new value is the empty string. The previous paragraph applies in particular to the ":" before a <port> component, the "?" before a <query> component, and the "#" before a <fragment> component. For the purposes of the above definitions, URLs must be parsed using the URL parsing rules defined in this specification. Attribute Component Getter Condition Prefix Suffix Setter Preprocessor Setter Condition protocol <scheme> — — U+003A COLON (":") Remove all trailing U+003A COLON (":") characters The new value is not the empty string host <hostport> input is hierarchical and uses a server-based naming — — — The new value is not the empty string and input is authority hierarchical and uses a server-based naming authority hostname <host> input is hierarchical and uses a server-based naming — — Remove all leading U+002F SOLIDUS ("/") characters The new value is not the empty string and input is authority hierarchical and uses a server-based naming authority port <port> input is hierarchical, uses a server-based naming — — Remove any characters in the new value that are not in the input is hierarchical and uses a server-based naming authority, and contained a <port> component (possibly range U+0030 DIGIT ZERO .. U+0039 DIGIT NINE. If the authority an empty one) resulting string is empty, set it to a single U+0030 DIGIT ZERO character ('0'). pathname <path> input is hierarchical — — If it has no leading U+002F SOLIDUS ("/") character, prepend a — U+002F SOLIDUS ("/") character to the new value search <query> input is hierarchical, and contained a <query> U+003F QUESTION MARK ("?") — Remove one leading U+003F QUESTION MARK ("?") — component (possibly an empty one) character, if any hash <fragment> input contained a <fragment> component (possibly an U+0023 NUMBER SIGN ("#") — Remove one leading U+0023 NUMBER SIGN ("#") character, if — empty one) any The table below demonstrates how the getter condition for search results in different results depending on the exact original syntax of the URL: Input URL search value Explanation http://example.com/ empty string No <query> component in input URL. http://example.com/? ? There is a <query> component, but it is empty. The question mark in the resulting value is the prefix. http://example.com/?test ?test The <query> component has the value "test". http://example.com/?test# ?test The (empty) <fragment> component is not part of the <query> component. 2.6 Fetching resources When a user agent is to fetch a resource, the following steps must be run: 1. If the resource is identified by the URL about:blank, then return the empty string and abort these steps. 2. Perform the remaining steps asynchronously. 3. If the resource is identified by an absolute URL, and the resource is to be obtained using a idempotent action (such as an HTTP GET or equivalent), and it is already being downloaded for other reasons (e.g. another invocation of this algorithm), and the user agent is configured such that it is to reuse the data from the existing download instead of initiating a new one, then use the results of the existing download instead of starting a new one. Otherwise, at a time convenient to the user and the user agent, download (or otherwise obtain) the resource, applying the semantics of the relevant specifications (e.g. performing an HTTP GET or POST operation, or reading the file from disk, following redirects, dereferencing javascript: URLs, etc). For purposes of generating the address of the resource from which Request-URIs are obtained as required by HTTP for the Referer (sic) header, the user agent must use the document's current address of the appropriate Document as given by this list. [HTTP] When navigating http://dev.w3.org/html5/spec/Overview.html (46 de 570)01-08-2009 6:55:54
- 47. HTML 5 The active document of the source browsing context. When fetching resources for an element The element's Document. When fetching resources in response to a call to an API The active document of the browsing context of the first script. 4. If there are cookies to be set, then the user agent must run the following substeps: 1. Wait until ownership of the storage mutex can be taken by this instance of the fetching algorithm. 2. Take ownership of the storage mutex. 3. Update the cookies. [COOKIES] 4. Release the storage mutex so that it is once again free. 5. When the resource is available, or if there is an error of some description, queue a task that uses the resource as appropriate. If the resource can be processed incrementally, as, for instance, with a progressively interlaced JPEG or an HTML file, additional tasks may be queued to process the data as it is downloaded. The task source for these tasks is the networking task source. The application cache processing model introduces some changes to the networking model to handle the returning of cached resources. The navigation processing model handles redirects itself, overriding the redirection handling that would be done by the fetching algorithm. Whether the type sniffing rules apply to the fetched resource depends on the algorithm that invokes the rules — they are not always applicable. 2.6.1 Protocol concepts User agents can implement a variety of transfer protocols, but this specification mostly defines behavior in terms of HTTP. [HTTP] The HTTP GET method is equivalent to the default retrieval action of the protocol. For example, RETR in FTP. Such actions are idempotent and safe, in HTTP terms. The HTTP response codes are equivalent to statuses in other protocols that have the same basic meanings. For example, a "file not found" error is equivalent to a 404 code, a server error is equivalent to a 5xx code, and so on. The HTTP headers are equivalent to fields in other protocols that have the same basic meaning. For example, the HTTP authentication headers are equivalent to the authentication aspects of the FTP protocol. 2.6.2 Encrypted HTTP and related security concerns Anything in this specification that refers to HTTP also applies to HTTP-over-TLS, as represented by URLs representing the https scheme. User agents should report certificate errors to the user and must either refuse to download resources sent with erroneous certificates or must act as if such resources were in fact served with no encryption. User agents should warn the user that there is a potential problem whenever the user visits a page that the user has previously visited, if the page uses less secure encryption on the second visit. Not doing so can result in users not noticing man-in-the-middle attacks. If a user connects to a server with a self-signed certificate, the user agent could allow the connection but just act as if there had been no encryption. If the user agent instead allowed the user to override the problem and then displayed the page as if it was fully and safely encrypted, the user could be easily tricked into accepting man-in-the-middle connections. If a user connects to a server with full encryption, but the page then refers to an external resource that has an expired certificate, then the user agent will act as if the resource was unavailable, possibly also reporting the problem to the user. If the user agent instead allowed the resource to be used, then an attacker could just look for "secure" sites that used resources from a different host and only apply man-in-the-middle attacks to that host, for example taking over scripts in the page. If a user bookmarks a site that uses a CA-signed certificate, and then later revisits that site directly but the site has started using a self-signed certificate, the user agent could warn the user that a man-in-the-middle attack is likely underway, instead of simply acting as if the page was not encrypted. 2.6.3 Determining the type of a resource The Content-Type metadata of a resource must be obtained and interpreted in a manner consistent with the requirements of the Content-Type Processing Model specification. [MIMESNIFF] The algorithm for extracting an encoding from a Content-Type, given a string s, is given in the Content-Type Processing Model specification. It either returns an encoding or nothing. [MIMESNIFF] http://dev.w3.org/html5/spec/Overview.html (47 de 570)01-08-2009 6:55:54
- 48. HTML 5 The sniffed type of a resource must be found in a manner consistent with the requirements given in the Content-Type Processing Model specification for finding that sniffed type. [MIMESNIFF] The rules for sniffing images specifically are also defined in the Content-Type Processing Model specification. [MIMESNIFF] It is imperative that the rules in the Content-Type Processing Model specification be followed exactly. When a user agent uses different heuristics for content type detection than the server expects, security problems can occur. For more details, see the Content-Type Processing Model specification. [MIMESNIFF] 2.7 Character encodings User agents must at a minimum support the UTF-8 and Windows-1252 encodings, but may support more. It is not unusual for Web browsers to support dozens if not upwards of a hundred distinct character encodings. User agents must support the preferred MIME name of every character encoding they support that has a preferred MIME name, and should support all the IANA-registered aliases. [IANACHARSET] When comparing a string specifying a character encoding with the name or alias of a character encoding to determine if they are equal, user agents must use the Charset Alias Matching rules defined in Unicode Technical Standard #22. [UTS22] For instance, "GB_2312-80" and "g.b.2312(80)" are considered equivalent names. In addition, user agents must support the aliases given in the following table, so that labels from the first column are treated as equivalent to the labels given in the corresponding cell from the second column on the same row. Additional character encoding aliases Alias Corresponding encoding References x-sjis windows-31J [SHIFTJIS] [WIN31J] windows-932 windows-31J [WIN31J] x-x-big5 Big5 [BIG5] When a user agent would otherwise use an encoding given in the first column of the following table to either convert content to Unicode characters or convert Unicode characters to bytes, it must instead use the encoding given in the cell in the second column of the same row. When a byte or sequence of bytes is treated differently due to this encoding aliasing, it is said to have been misinterpreted for compatibility. Character encoding overrides Input encoding Replacement encoding References EUC-KR windows-949 [EUCKR] [WIN949] GB2312 GBK [RFC1345] [GBK] GB_2312-80 GBK [RFC1345] [GBK] ISO-8859-1 windows-1252 [RFC1345] [WIN1252] ISO-8859-9 windows-1254 [RFC1345] [WIN1254] ISO-8859-11 windows-874 [ISO885911] [WIN874] KS_C_5601-1987 windows-949 [RFC1345] [WIN949] Shift_JIS windows-31J [SHIFTJIS] [WIN31J] TIS-620 windows-874 [TIS620] [WIN874] US-ASCII windows-1252 [RFC1345] [WIN1252] The requirement to treat certain encodings as other encodings according to the table above is a willful violation of the W3C Character Model specification, motivated by a desire for compatibility with legacy content. [CHARMOD] When a user agent is to use the UTF-16 encoding but no BOM has been found, user agents must default to UTF-16LE. The requirement to default UTF-16 to LE rather than BE is a willful violation of RFC 2781, motivated by a desire for compatibility with legacy content. [CHARMOD] User agents must not support the CESU-8, UTF-7, BOCU-1 and SCSU encodings. [CESU8] [UTF7] [BOCU1] [SCSU] Support for encodings based on EBCDIC is not recommended. This encoding is rarely used for publicly-facing Web content. Support for UTF-32 is not recommended. This encoding is rarely used, and frequently implemented incorrectly. http://dev.w3.org/html5/spec/Overview.html (48 de 570)01-08-2009 6:55:54
- 49. HTML 5 This specification does not make any attempt to support EBCDIC-based encodings and UTF-32 in its algorithms; support and use of these encodings can thus lead to unexpected behavior in implementations of this specification. 2.8 Common DOM interfaces 2.8.1 Reflecting content attributes in DOM attributes Some DOM attributes are defined to reflect a particular content attribute. This means that on getting, the DOM attribute returns the current value of the content attribute, and on setting, the DOM attribute changes the value of the content attribute to the given value. A list of reflecting DOM attributes and their corresponding content attributes is given in the index. In general, on getting, if the content attribute is not present, the DOM attribute must act as if the content attribute's value is the empty string; and on setting, if the content attribute is not present, it must first be added. If a reflecting DOM attribute is a DOMString attribute whose content attribute is defined to contain a URL, then on getting, the DOM attribute must resolve the value of the content attribute relative to the element and return the resulting absolute URL if that was successful, or the empty string otherwise; and on setting, must set the content attribute to the specified literal value. If the content attribute is absent, the DOM attribute must return the default value, if the content attribute has one, or else the empty string. If a reflecting DOM attribute is a DOMString attribute whose content attribute is defined to contain one or more URLs, then on getting, the DOM attribute must split the content attribute on spaces and return the concatenation of resolving each token URL to an absolute URL relative to the element, with a single U+0020 SPACE character between each URL, ignoring any tokens that did not resolve successfully. If the content attribute is absent, the DOM attribute must return the default value, if the content attribute has one, or else the empty string. On setting, the DOM attribute must set the content attribute to the specified literal value. If a reflecting DOM attribute is a DOMString whose content attribute is an enumerated attribute, and the DOM attribute is limited to only known values, then, on getting, the DOM attribute must return the conforming value associated with the state the attribute is in (in its canonical case), or the empty string if the attribute is in a state that has no associated keyword value; and on setting, if the new value is an ASCII case-insensitive match for one of the keywords given for that attribute, then the content attribute must be set to the conforming value associated with the state that the attribute would be in if set to the given new value, otherwise, if the new value is the empty string, then the content attribute must be removed, otherwise, the setter must raise a SYNTAX_ERR exception. If a reflecting DOM attribute is a DOMString but doesn't fall into any of the above categories, then the getting and setting must be done in a transparent, case-preserving manner. If a reflecting DOM attribute is a boolean attribute, then on getting the DOM attribute must return true if the attribute is set, and false if it is absent. On setting, the content attribute must be removed if the DOM attribute is set to false, and must be set to have the same value as its name if the DOM attribute is set to true. (This corresponds to the rules for boolean content attributes.) If a reflecting DOM attribute is a signed integer type (long) then, on getting, the content attribute must be parsed according to the rules for parsing signed integers, and if that is successful, and the value is in the range of the DOM attribute's type, the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, then the default value must be returned instead, or 0 if there is no default value. On setting, the given value must be converted to the shortest possible string representing the number as a valid integer and then that string must be used as the new content attribute value. If a reflecting DOM attribute is an unsigned integer type (unsigned long) then, on getting, the content attribute must be parsed according to the rules for parsing non-negative integers, and if that is successful, and the value is in the range of the DOM attribute's type, the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, the default value must be returned instead, or 0 if there is no default value. On setting, the given value must be converted to the shortest possible string representing the number as a valid non-negative integer and then that string must be used as the new content attribute value. If a reflecting DOM attribute is an unsigned integer type (unsigned long) that is limited to only positive non-zero numbers, then the behavior is similar to the previous case, but zero is not allowed. On getting, the content attribute must first be parsed according to the rules for parsing non-negative integers, and if that is successful, and the value is in the range of the DOM attribute's type, the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, the default value must be returned instead, or 1 if there is no default value. On setting, if the value is zero, the user agent must fire an INDEX_SIZE_ERR exception. Otherwise, the given value must be converted to the shortest possible string representing the number as a valid non- negative integer and then that string must be used as the new content attribute value. If a reflecting DOM attribute is a floating point number type (float) and it doesn't fall into one of the earlier categories, then, on getting, the content attribute must be parsed according to the rules for parsing floating point number values, and if that is successful, and the value is in the range of the DOM attribute's type, the resulting value must be returned. If, on the other hand, it fails or returns an out of range value, or if the attribute is absent, the default value must be returned instead, or 0.0 if there is no default value. On setting, the given value must be converted to the best representation of the floating point number and then that string must be used as the new content attribute value. The values ±Infinity and NaN throw an exception on setting, as defined by Web IDL. [WEBIDL] If a reflecting DOM attribute is of the type DOMTokenList or DOMSettableTokenList, then on getting it must return a DOMTokenList or DOMSettableTokenList object (as appropriate) whose underlying string is the element's corresponding content attribute. When the object mutates its underlying string, the content attribute must itself be immediately mutated. When the attribute is absent, then the string represented by the object is the empty string; when the object mutates this empty string, the user agent must first add the corresponding content attribute, and then mutate that attribute instead. The same DOMTokenList object must be returned every time for each attribute. If a reflecting DOM attribute has the type HTMLElement, or an interface that descends from HTMLElement, then, on getting, it must run the following algorithm (stopping at the first point where a value is returned): 1. If the corresponding content attribute is absent, then the DOM attribute must return null. 2. Let candidate be the element that the document.getElementById() method would find if it was passed as its argument the current value of the corresponding content attribute. 3. If candidate is null, or if it is not type-compatible with the DOM attribute, then the DOM attribute must return null. 4. Otherwise, it must return candidate. On setting, if the given element has an id attribute, then the content attribute must be set to the value of that id attribute. Otherwise, the DOM attribute must be set to the empty string. http://dev.w3.org/html5/spec/Overview.html (49 de 570)01-08-2009 6:55:54
- 50. HTML 5 2.8.2 Collections The HTMLCollection, HTMLAllCollection, HTMLFormControlsCollection, HTMLOptionsCollection, and HTMLPropertyCollection interfaces represent various lists of DOM nodes. Collectively, objects implementing these interfaces are called collections. When a collection is created, a filter and a root are associated with the collection. For example, when the HTMLCollection object for the document.images attribute is created, it is associated with a filter that selects only img elements, and rooted at the root of the document. The collection then represents a live view of the subtree rooted at the collection's root, containing only nodes that match the given filter. The view is linear. In the absence of specific requirements to the contrary, the nodes within the collection must be sorted in tree order. The rows list is not in tree order. An attribute that returns a collection must return the same object every time it is retrieved. 2.8.2.1 HTMLCollection The HTMLCollection interface represents a generic collection of elements. [Callable=namedItem] interface HTMLCollection { readonly attribute unsigned long length; [IndexGetter] Element item(in unsigned long index); [NameGetter] Element namedItem(in DOMString name); HTMLAllCollection tags(in DOMString tagName); }; collection . length Returns the number of elements in the collection. element = collection . item(index) collection[index] Returns the item with index index from the collection. The items are sorted in tree order. Returns null if index is out of range. element = collection . namedItem(name) collection[name] collection(name) Returns the first item with ID or name name from the collection. Returns null if no element with that ID or name could be found. Only a, applet, area, embed, form, frame, frameset, iframe, img, and object elements can have a name for the purpose of this method; their name is given by the value of their name attribute. collection = collection . tags(tagName) Returns a collection that is a filtered view of the current collection, containing only elements with the given tag name. The object's indices of the supported indexed properties are the numbers in the range zero to one less than the number of nodes represented by the collection. If there are no such elements, then there are no supported indexed properties. The length attribute must return the number of nodes represented by the collection. The item(index) method must return the indexth node in the collection. If there is no indexth node in the collection, then the method must return null. The names of the supported named properties consist of the values of the name attributes of each a, applet, area, embed, form, frame, frameset, iframe, img, and object element represented by the collection with a name attribute, plus the list of IDs that the elements represented by the collection have. http://dev.w3.org/html5/spec/Overview.html (50 de 570)01-08-2009 6:55:54
- 51. HTML 5 The namedItem(key) method must return the first node in the collection that matches the following requirements: q It is an a, applet, area, embed, form, frame, frameset, iframe, img, or object element with a name attribute equal to key, or, q It is an element with an ID key. If no such elements are found, then the method must return null. The tags(tagName) method must return an HTMLAllCollection rooted at the same node as the HTMLCollection object on which the method was invoked, whose filter matches only HTML elements whose local name is the tagName argument and that already match the filter of the HTMLCollection object on which the method was invoked. In HTML documents, the argument must first be converted to ASCII lowercase. 2.8.2.2 HTMLAllCollection The HTMLAllCollection interface represents a generic collection of elements just like HTMLCollection, with the exception that its namedItem() method returns an HTMLCollection object when there are multiple matching elements. [Callable=namedItem] interface HTMLAllCollection { readonly attribute unsigned long length; [IndexGetter] Element item(in unsigned long index); [NameGetter] Object namedItem(in DOMString name); HTMLAllCollection tags(in DOMString tagName); }; collection . length Returns the number of elements in the collection. element = collection . item(index) collection[index] Returns the item with index index from the collection. The items are sorted in tree order. Returns null if index is out of range. element = collection . namedItem(name) collection = collection . namedItem(name) collection[name] collection(name) Returns the item with ID or name name from the collection. If there are multiple matching items, then an HTMLAllCollection object containing all those elements is returned. Returns null if no element with that ID or name could be found. Only a, applet, area, embed, form, frame, frameset, iframe, img, and object elements can have a name for the purpose of this method; their name is given by the value of their name attribute. collection = collection . tags(tagName) Returns a collection that is a filtered view of the current collection, containing only elements with the given tag name. The object's indices of the supported indexed properties are the numbers in the range zero to one less than the number of nodes represented by the collection. If there are no such elements, then there are no supported indexed properties. The length attribute must return the number of nodes represented by the collection. The item(index) method must return the indexth node in the collection. If there is no indexth node in the collection, then the method must return null. The names of the supported named properties consist of the values of the name attributes of each a, applet, area, embed, form, frame, frameset, iframe, img, and object element represented by the collection with a name attribute, plus the list of IDs that the elements represented by the collection have. The namedItem(key) method must act according to the following algorithm: 1. Let collection be an HTMLAllCollection object rooted at the same node as the HTMLAllCollection object on which the method was invoked, whose filter matches only only elements that already match the filter of the HTMLAllCollection object on http://dev.w3.org/html5/spec/Overview.html (51 de 570)01-08-2009 6:55:54
- 52. HTML 5 which the method was invoked and that are either: r a, applet, area, embed, form, frame, frameset, iframe, img, or object elements with a name attribute equal to key, or, r elements with an ID key. 2. If, at the time the method is called, there is exactly one node in collection, then return that node and stop the algorithm. 3. Otherwise, if, at the time the method is called, collection is empty, return null and stop the algorithm. 4. Otherwise, return collection. The tags(tagName) method must return an HTMLAllCollection rooted at the same node as the HTMLAllCollection object on which the method was invoked, whose filter matches only HTML elements whose local name is the tagName argument and that already match the filter of the HTMLAllCollection object on which the method was invoked. In HTML documents, the argument must first be converted to ASCII lowercase. 2.8.2.3 HTMLFormControlsCollection The HTMLFormControlsCollection interface represents a collection of listed elements in form and fieldset elements. [Callable=namedItem] interface HTMLFormControlsCollection { readonly attribute unsigned long length; [IndexGetter] HTMLElement item(in unsigned long index); [NameGetter] Object namedItem(in DOMString name); }; interface RadioNodeList : NodeList { attribute DOMString value; }; collection . length Returns the number of elements in the collection. element = collection . item(index) collection[index] Returns the item with index index from the collection. The items are sorted in tree order. Returns null if index is out of range. element = collection . namedItem(name) radioNodeList = collection . namedItem(name) collection[name] collection(name) Returns the item with ID or name name from the collection. If there are multiple matching items, then a RadioNodeList object containing all those elements is returned. Returns null if no element with that ID or name could be found. radioNodeList . value [ = value ] Returns the value of the first checked radio button represented by the object. Can be set, to check the first radio button with the given value represented by the object. The object's indices of the supported indexed properties are the numbers in the range zero to one less than the number of nodes represented by the collection. If there are no such elements, then there are no supported indexed properties. The length attribute must return the number of nodes represented by the collection. The item(index) method must return the indexth node in the collection. If there is no indexth node in the collection, then the method must return null. http://dev.w3.org/html5/spec/Overview.html (52 de 570)01-08-2009 6:55:54
- 53. HTML 5 The names of the supported named properties consist of the values of all the id and name attributes of all the elements represented by the collection. The namedItem(name) method must act according to the following algorithm: 1. If, at the time the method is called, there is exactly one node in the collection that has either an id attribute or a name attribute equal to name, then return that node and stop the algorithm. 2. Otherwise, if there are no nodes in the collection that have either an id attribute or a name attribute equal to name, then return null and stop the algorithm. 3. Otherwise, create a RadioNodeList object representing a live view of the HTMLFormControlsCollection object, further filtered so that the only nodes in the RadioNodeList object are those that have either an id attribute or a name attribute equal to name. The nodes in the RadioNodeList object must be sorted in tree order. 4. Return that RadioNodeList object. A members of the RadioNodeList interface inherited from the NodeList interface must behave as they would on a NodeList object. The value DOM attribute on the RadioNodeList object, on getting, must return the value returned by running the following steps: 1. Let element be the first element in tree order represented by the RadioNodeList object that is an input element whose type attribute is in the Radio Button state and whose checkedness is true. Otherwise, let it be null. 2. If element is null, or if it is an element with no value attribute, return the empty string. 3. Otherwise, return the value of element's value attribute. On setting, the value DOM attribute must run the following steps: 1. Let element be the first element in tree order represented by the RadioNodeList object that is an input element whose type attribute is in the Radio Button state and whose value content attribute is present and equal to the new value, if any. Otherwise, let it be null. 2. If element is not null, then set its checkedness to true. 2.8.2.4 HTMLOptionsCollection The HTMLOptionsCollection interface represents a list of option elements. It is always rooted on a select element and has attributes and methods that manipulate that element's descendants. [Callable=namedItem] interface HTMLOptionsCollection { attribute unsigned long length; [IndexGetter] HTMLOptionElement item(in unsigned long index); [NameGetter] Object namedItem(in DOMString name); void add(in HTMLElement element, [Optional] in HTMLElement before); void add(in HTMLElement element, in long before); void remove(in long index); }; collection . length [ = value ] Returns the number of elements in the collection. When set to a smaller number, truncates the number of option elements in the corresponding container. When set to a greater number, adds new blank option elements to that container. element = collection . item(index) collection[index] Returns the item with index index from the collection. The items are sorted in tree order. Returns null if index is out of range. element = collection . namedItem(name) nodeList = collection . namedItem(name) collection[name] http://dev.w3.org/html5/spec/Overview.html (53 de 570)01-08-2009 6:55:54
- 54. HTML 5 collection(name) Returns the item with ID or name name from the collection. If there are multiple matching items, then a NodeList object containing all those elements is returned. Returns null if no element with that ID could be found. collection . add(element [, before ] ) Inserts element before the node given by before. The before argument can be a number, in which case element is inserted before the item with that number, or an element from the collection, in which case element is inserted before that element. If before is omitted, null, or a number out of range, then element will be added at the end of the list. This method will throw a HIERARCHY_REQUEST_ERR exception if element is an ancestor of the element into which it is to be inserted. If element is not an option or optgroup element, then the method does nothing. The object's indices of the supported indexed properties are the numbers in the range zero to one less than the number of nodes represented by the collection. If there are no such elements, then there are no supported indexed properties. On getting, the length attribute must return the number of nodes represented by the collection. On setting, the behavior depends on whether the new value is equal to, greater than, or less than the number of nodes represented by the collection at that time. If the number is the same, then setting the attribute must do nothing. If the new value is greater, then n new option elements with no attributes and no child nodes must be appended to the select element on which the HTMLOptionsCollection is rooted, where n is the difference between the two numbers (new value minus old value). If the new value is lower, then the last n nodes in the collection must be removed from their parent nodes, where n is the difference between the two numbers (old value minus new value). Setting length never removes or adds any optgroup elements, and never adds new children to existing optgroup elements (though it can remove children from them). The item(index) method must return the indexth node in the collection. If there is no indexth node in the collection, then the method must return null. The names of the supported named properties consist of the values of all the id and name attributes of all the elements represented by the collection. The namedItem(name) method must act according to the following algorithm: 1. If, at the time the method is called, there is exactly one node in the collection that has either an id attribute or a name attribute equal to name, then return that node and stop the algorithm. 2. Otherwise, if there are no nodes in the collection that have either an id attribute or a name attribute equal to name, then return null and stop the algorithm. 3. Otherwise, create a NodeList object representing a live view of the HTMLOptionsCollection object, further filtered so that the only nodes in the NodeList object are those that have either an id attribute or a name attribute equal to name. The nodes in the NodeList object must be sorted in tree order. 4. Return that NodeList object. The add(element, before) method must act according to the following algorithm: 1. If element is not an option or optgroup element, then return and abort these steps. 2. If element is an ancestor of the select element on which the HTMLOptionsCollection is rooted, then throw a HIERARCHY_REQUEST_ERR exception. 3. If before is an element, but that element isn't a descendant of the select element on which the HTMLOptionsCollection is rooted, then throw a NOT_FOUND_ERR exception. 4. If element and before are the same element, then return and abort these steps. 5. If before is a node, then let reference be that node. Otherwise, if before is an integer, and there is a beforeth node in the collection, let reference be that node. Otherwise, let reference be null. 6. If reference is not null, let parent be the parent node of reference. Otherwise, let parent be the select element on which the HTMLOptionsCollection is rooted. 7. Act as if the DOM Core insertBefore() method was invoked on the parent node, with element as the first argument and reference as the second argument. The remove(index) method must act according to the following algorithm: 1. If the number of nodes represented by the collection is zero, abort these steps. 2. If index is not a number greater than or equal to 0 and less than the number of nodes represented by the collection, let element be the first element in the collection. Otherwise, let element be the indexth element in the collection. 3. Remove element from its parent node. http://dev.w3.org/html5/spec/Overview.html (54 de 570)01-08-2009 6:55:54
- 55. HTML 5 2.8.2.5 HTMLPropertyCollection The HTMLPropertyCollection interface represents a collection of elements that add name-value pairs to a particular item in the microdata model. [Callable=namedItem] interface HTMLPropertyCollection { readonly attribute unsigned long length; [IndexGetter] HTMLElement item(in unsigned long index); readonly attribute DOMStringList names; [NameGetter] PropertyNodeList namedItem(in DOMString name); }; typedef sequence<any> PropertyValueArray; interface PropertyNodeList : NodeList { attribute PropertyValueArray contents; }; collection . length Returns the number of elements in the collection. collection . names Returns a DOMStringList with the property names of the elements in the collection. element = collection . item(index) collection[index] Returns the element with index index from the collection. The items are sorted in tree order. Returns null if index is out of range. propertyNodeList = collection . namedItem(name) collection[name] collection(name) Returns a PropertyNodeList object containing any elements that add a property named name. propertyNodeList . contents Returns an array of the various values that the relevant elements have. The object's indices of the supported indexed properties are the numbers in the range zero to one less than the number of nodes represented by the collection. If there are no such elements, then there are no supported indexed properties. The length attribute must return the number of nodes represented by the collection. The item(index) method must return the indexth node in the collection. If there is no indexth node in the collection, then the method must return null. The names of the supported named properties consist of the property names of all the elements represented by the collection. The names attribute must return a live DOMStringList object giving the property names of all the elements represented by the collection, listed in tree order, but with duplicates removed, leaving only the first occurrence of each name. The same object must be returned each time. The namedItem(name) method must return a PropertyNodeList object representing a live view of the HTMLPropertyCollection object, further filtered so that the only nodes in the RadioNodeList object are those that have a property name equal to name. The nodes in the PropertyNodeList object must be sorted in tree order, and the same object must be returned each time a particular name is queried. A members of the PropertyNodeList interface inherited from the NodeList interface must behave as they would on a NodeList object. The contents DOM attribute on the PropertyNodeList object, on getting, must return a newly constructed DOMStringArray whose values are the values obtained from the content DOM property of each of the elements represented by the object, in tree order. http://dev.w3.org/html5/spec/Overview.html (55 de 570)01-08-2009 6:55:54
- 56. HTML 5 2.8.3 DOMTokenList The DOMTokenList interface represents an interface to an underlying string that consists of a set of space-separated tokens. DOMTokenList objects are always case-sensitive, even when the underlying string might ordinarily be treated in a case-insensitive manner. [Stringifies] interface DOMTokenList { readonly attribute unsigned long length; [IndexGetter] DOMString item(in unsigned long index); boolean contains(in DOMString token); void add(in DOMString token); void remove(in DOMString token); boolean toggle(in DOMString token); }; tokenlist . length Returns the number of tokens in the string. element = tokenlist . item(index) tokenlist[index] Returns the token with index index. The tokens are returned in the order they are found in the underlying string. Returns null if index is out of range. hastoken = tokenlist . contains(token) Returns true if the token is present; false otherwise. Throws a SYNTAX_ERR exception if token is empty. Throws an INVALID_CHARACTER_ERR exception if token contains any spaces. tokenlist . add(token) Adds token, unless it is already present. Throws a SYNTAX_ERR exception if token is empty. Throws an INVALID_CHARACTER_ERR exception if token contains any spaces. tokenlist . remove(token) Removes token if it is present. Throws a SYNTAX_ERR exception if token is empty. Throws an INVALID_CHARACTER_ERR exception if token contains any spaces. hastoken = tokenlist . toggle(token) Adds token if it is not present, or removes it if it is. Throws a SYNTAX_ERR exception if token is empty. Throws an INVALID_CHARACTER_ERR exception if token contains any spaces. The length attribute must return the number of tokens that result from splitting the underlying string on spaces. This is the length. The object's indices of the supported indexed properties are the numbers in the range zero to length-1, unless the length is zero, in which case there are no supported indexed properties. The item(index) method must split the underlying string on spaces, preserving the order of the tokens as found in the underlying string, and then return the indexth item in this list. If index is equal to or greater than the number of tokens, then the method must return null. For example, if the string is "a b a c" then there are four tokens: the token with index 0 is "a", the token with index 1 is "b", the token with index 2 is "a", and the token with index 3 is "c". The contains(token) method must run the following algorithm: http://dev.w3.org/html5/spec/Overview.html (56 de 570)01-08-2009 6:55:54
- 57. HTML 5 1. If the token argument is the empty string, then raise a SYNTAX_ERR exception and stop the algorithm. 2. If the token argument contains any space characters, then raise an INVALID_CHARACTER_ERR exception and stop the algorithm. 3. Otherwise, split the underlying string on spaces to get the list of tokens in the object's underlying string. 4. If the token indicated by token is a case-sensitive match for one of the tokens in the object's underlying string then return true and stop this algorithm. 5. Otherwise, return false. The add(token) method must run the following algorithm: 1. If the token argument is the empty string, then raise a SYNTAX_ERR exception and stop the algorithm. 2. If the token argument contains any space characters, then raise an INVALID_CHARACTER_ERR exception and stop the algorithm. 3. Otherwise, split the underlying string on spaces to get the list of tokens in the object's underlying string. 4. If the given token is a case-sensitive match for one of the tokens in the DOMTokenList object's underlying string then stop the algorithm. 5. Otherwise, if the DOMTokenList object's underlying string is not the empty string and the last character of that string is not a space character, then append a U+0020 SPACE character to the end of that string. 6. Append the value of token to the end of the DOMTokenList object's underlying string. The remove(token) method must run the following algorithm: 1. If the token argument is the empty string, then raise a SYNTAX_ERR exception and stop the algorithm. 2. If the token argument contains any space characters, then raise an INVALID_CHARACTER_ERR exception and stop the algorithm. 3. Otherwise, remove the given token from the underlying string. The toggle(token) method must run the following algorithm: 1. If the token argument is the empty string, then raise a SYNTAX_ERR exception and stop the algorithm. 2. If the token argument contains any space characters, then raise an INVALID_CHARACTER_ERR exception and stop the algorithm. 3. Otherwise, split the underlying string on spaces to get the list of tokens in the object's underlying string. 4. If the given token is a case-sensitive match for one of the tokens in the DOMTokenList object's underlying string then remove the given token from the underlying string and stop the algorithm, returning false. 5. Otherwise, if the DOMTokenList object's underlying string is not the empty string and the last character of that string is not a space character, then append a U+0020 SPACE character to the end of that string. 6. Append the value of token to the end of the DOMTokenList object's underlying string. 7. Return true. Objects implementing the DOMTokenList interface must stringify to the object's underlying string representation. 2.8.4 DOMSettableTokenList The DOMSettableTokenList interface is the same as the DOMTokenList interface, except that it allows the underlying string to be directly changed. [Stringifies] interface DOMSettableTokenList : DOMTokenList { attribute DOMString value; }; tokenlist . value Returns the underlying string. Can be set, to change the underlying string. http://dev.w3.org/html5/spec/Overview.html (57 de 570)01-08-2009 6:55:54
- 58. HTML 5 An object implementing the DOMSettableTokenList interface must act as defined for the DOMTokenList interface, except for the value attribute defined here. The value attribute must return the underlying string on getting, and must replace the underlying string with the new value on setting. 2.8.5 Safe passing of structured data When a user agent is required to obtain a structured clone of an object, it must run the following algorithm, which either returns a separate object, or throws an exception. 1. Let input be the object being cloned. 2. Let memory be a list of objects, initially empty. (This is used to catch cycles.) 3. Let output be the object resulting from calling the internal structured cloning algorithm with input and memory. 4. Return output. The internal structured cloning algorithm is always called with two arguments, input and memory, and its behavior depends on the type of input, as follows: If input is the undefined value Return the undefined value. If input is the null value Return the null value. If input is the false value Return the false value. If input is the true value Return the true value. If input is a Number object Return a newly constructed Number object with the same value as input. If input is a String object Return a newly constructed String object with the same value as input. If input is a Date object Return a newly constructed Date object with the same value as input. If input is a RegExp object Return a newly constructed RegExp object with the same pattern and flags as input. The value of the lastIndex property is not copied. If input is a ImageData object Return a newly constructed ImageData object with the same width and height as input, and with a newly constructed CanvasPixelArray for its data attribute, with the same length and pixel values as the input's. If input is a host object (e.g. a DOM node) Return the null value. If input is an Array object If input is an Object object 1. If input is in memory, then throw a NOT_SUPPORTED_ERR exception and abort the overall structured clone algorithm. 2. Otherwise, let new memory be a list consisting of the items in memory with the addition of input. 3. Create a new object, output, of the same type as input: either an Array or an Object. 4. For each enumerable property in input, add a corresponding property to output having the same name, and having a value created from invoking the internal structured cloning algorithm recursively with the value of the property as the "input" argument and new memory as the "memory" argument. The order of the properties in the input and output objects must be the same. This does not walk the prototype chain. 5. Return output. If input is another native object type (e.g. Error) Return the null value. 2.8.6 DOMStringMap The DOMStringMap interface represents a set of name-value pairs. It exposes these using the scripting language's native mechanisms for property access. http://dev.w3.org/html5/spec/Overview.html (58 de 570)01-08-2009 6:55:54
- 59. HTML 5 When a DOMStringMap object is instantiated, it is associated with three algorithms, one for getting the list of name-value pairs, one for setting names to certain values, and one for deleting names. [NameCreator, NameDeleter, NameGetter, NameSetter] interface DOMStringMap {}; The names of the supported named properties on a DOMStringMap object at any instant are the names of each pair returned from the algorithm for getting the list of name-value pairs at that instant. When a DOMStringMap object is indexed to retrieve a named property name, the value returned must be the value component of the name-value pair whose name component is name in the list returned by the algorithm for getting the list of name-value pairs. When a DOMStringMap object is indexed to create or modify a named property name with value value, the algorithm for setting names to certain values must be run, passing name as the name and the result of converting value to a DOMString as the value. When a DOMStringMap object is indexed to delete a named property named name, the algorithm for deleting names must be run, passing name as the name. The DOMStringMap interface definition here is only intended for JavaScript environments. Other language bindings will need to define how DOMStringMap is to be implemented for those languages. The dataset attribute on elements exposes the data-* attributes on the element. Given the following fragment and elements with similar constructions: <img class="tower" id="tower5" data-x="12" data-y="5" data-ai="robotarget" data-hp="46" data-ability="flames" src="towers/rocket.png alt="Rocket Tower"> ...one could imagine a function splashDamage() that takes some arguments, the first of which is the element to process: function splashDamage(node, x, y, damage) { if (node.classList.contains('tower') && // checking the 'class' attribute node.dataset.x == x && // reading the 'data-x' attribute node.dataset.y == y) { // reading the 'data-y' attribute var hp = parseInt(node.dataset.hp); // reading the 'data-hp' attribute hp = hp - damage; if (hp < 0) { hp = 0; node.dataset.ai = 'dead'; // setting the 'data-ai' attribute delete node.dataset.ability; // removing the 'data-ability' attribute } node.dataset.hp = hp; // setting the 'data-hp' attribute } } 2.8.7 DOM feature strings DOM3 Core defines mechanisms for checking for interface support, and for obtaining implementations of interfaces, using feature strings. [DOM3CORE] Authors are strongly discouraged from using these, as they are notoriously unreliable and imprecise. Authors are encouraged to rely on explicit feature testing or the graceful degradation behavior intrinsic to some of the features in this specification. For historical reasons, user agents should return the true value when the hasFeature(feature, version) method of the DOMImplementation interface is invoked with feature set to either "HTML" or "XHTML" and version set to either "1.0" or "2.0". 2.8.8 Exceptions The following DOMException codes are defined in DOM Core. [DOMCORE] 1. INDEX_SIZE_ERR 2. DOMSTRING_SIZE_ERR 3. HIERARCHY_REQUEST_ERR 4. WRONG_DOCUMENT_ERR 5. INVALID_CHARACTER_ERR 6. NO_DATA_ALLOWED_ERR 7. NO_MODIFICATION_ALLOWED_ERR 8. NOT_FOUND_ERR 9. NOT_SUPPORTED_ERR 10. INUSE_ATTRIBUTE_ERR 11. INVALID_STATE_ERR 12. SYNTAX_ERR 13. INVALID_MODIFICATION_ERR http://dev.w3.org/html5/spec/Overview.html (59 de 570)01-08-2009 6:55:54
- 60. HTML 5 14. NAMESPACE_ERR 15. INVALID_ACCESS_ERR 16. VALIDATION_ERR 17. TYPE_MISMATCH_ERR 18. SECURITY_ERR 19. NETWORK_ERR 20. ABORT_ERR 21. URL_MISMATCH_ERR 22. QUOTA_EXCEEDED_ERR 23. DATAGRID_MODEL_ERR 81. PARSE_ERR 82. SERIALISE_ERR 2.8.9 Garbage collection There is an implied strong reference from any DOM attribute that returns a pre-existing object to that object. For example, the document.location attribute means that there is a strong reference from a Document object to its Location object. Similarly, there is always a strong reference from a Document to any descendant nodes, and from any node to its owner Document. http://dev.w3.org/html5/spec/Overview.html (60 de 570)01-08-2009 6:55:54
- 61. HTML 5 3 Semantics, structure, and APIs of HTML documents 3.1 Introduction This section is non-normative. An introduction to marking up a document. 3.2 Documents Every XML and HTML document in an HTML UA is represented by a Document object. [DOM3CORE] The document's address is an absolute URL that is set when the Document is created. The document's current address is an absolute URL that can change during the lifetime of the Document, for example when the user navigates to a fragment identifier on the page. The document's current address must be set to the document's address when the Document is created. When a Document is created by a script using the createDocument() API, the document's address is the same as the document's address of the active document of the script's browsing context. Document objects are assumed to be XML documents unless they are flagged as being HTML documents when they are created. Whether a document is an HTML document or an XML document affects the behavior of certain APIs, as well as a few CSS rendering rules. [CSS] A Document object created by the createDocument() API on the DOMImplementation object is initially an XML document, but can be made into an HTML document by calling document.open() on it. 3.2.1 Documents in the DOM All Document objects (in user agents implementing this specification) must also implement the HTMLDocument interface, available using binding-specific methods. (This is the case whether or not the document in question is an HTML document or indeed whether it contains any HTML elements at all.) Document objects must also implement the document-level interface of any other namespaces found in the document that the UA supports. For example, if an HTML implementation also supports SVG, then the Document object implements both HTMLDocument and SVGDocument. Because the HTMLDocument interface is now obtained using binding-specific casting methods instead of simply being the primary interface of the document object, it is no longer defined as inheriting from Document. [NameGetter=OverrideBuiltins, ImplementedOn=Document] interface HTMLDocument { // resource metadata management [PutForwards=href] readonly attribute Location location; readonly attribute DOMString URL; attribute DOMString domain; readonly attribute DOMString referrer; attribute DOMString cookie; readonly attribute DOMString lastModified; readonly attribute DOMString compatMode; attribute DOMString charset; readonly attribute DOMString characterSet; readonly attribute DOMString defaultCharset; readonly attribute DOMString readyState; // DOM tree accessors attribute DOMString title; attribute DOMString dir; attribute HTMLElement body; readonly attribute HTMLCollection images; readonly attribute HTMLCollection embeds; readonly attribute HTMLCollection plugins; readonly attribute HTMLCollection links; readonly attribute HTMLCollection forms; readonly attribute HTMLCollection scripts; http://dev.w3.org/html5/spec/Overview.html (61 de 570)01-08-2009 6:55:54
- 62. HTML 5 NodeList getElementsByName(in DOMString elementName); NodeList getElementsByClassName(in DOMString classNames); NodeList getItems([Optional] in DOMString typeNames); // dynamic markup insertion attribute DOMString innerHTML; HTMLDocument open([Optional] in DOMString type, [Optional] in DOMString replace); WindowProxy open(in DOMString url, in DOMString name, in DOMString features, [Optional] in boolean replace); void close(); void write([Variadic] in DOMString text); void writeln([Variadic] in DOMString text); // user interaction Selection getSelection(); readonly attribute Element activeElement; boolean hasFocus(); attribute DOMString designMode; boolean execCommand(in DOMString commandId); boolean execCommand(in DOMString commandId, in boolean showUI); boolean execCommand(in DOMString commandId, in boolean showUI, in DOMString value); boolean queryCommandEnabled(in DOMString commandId); boolean queryCommandIndeterm(in DOMString commandId); boolean queryCommandState(in DOMString commandId); boolean queryCommandSupported(in DOMString commandId); DOMString queryCommandValue(in DOMString commandId); readonly attribute HTMLCollection commands; // event handler DOM attributes attribute Function onabort; attribute Function onblur; attribute Function oncanplay; attribute Function oncanplaythrough; attribute Function onchange; attribute Function onclick; attribute Function oncontextmenu; attribute Function ondblclick; attribute Function ondrag; attribute Function ondragend; attribute Function ondragenter; attribute Function ondragleave; attribute Function ondragover; attribute Function ondragstart; attribute Function ondrop; attribute Function ondurationchange; attribute Function onemptied; attribute Function onended; attribute Function onerror; attribute Function onfocus; attribute Function onformchange; attribute Function onforminput; attribute Function oninput; attribute Function oninvalid; attribute Function onkeydown; attribute Function onkeypress; attribute Function onkeyup; attribute Function onload; attribute Function onloadeddata; attribute Function onloadedmetadata; attribute Function onloadstart; attribute Function onmousedown; attribute Function onmousemove; attribute Function onmouseout; attribute Function onmouseover; attribute Function onmouseup; http://dev.w3.org/html5/spec/Overview.html (62 de 570)01-08-2009 6:55:54
- 63. HTML 5 attribute Function onmousewheel; attribute Function onpause; attribute Function onplay; attribute Function onplaying; attribute Function onprogress; attribute Function onratechange; attribute Function onreadystatechange; attribute Function onscroll; attribute Function onseeked; attribute Function onseeking; attribute Function onselect; attribute Function onshow; attribute Function onstalled; attribute Function onsubmit; attribute Function onsuspend; attribute Function ontimeupdate; attribute Function onvolumechange; attribute Function onwaiting; }; Since the HTMLDocument interface holds methods and attributes related to a number of disparate features, the members of this interface are described in various different sections. 3.2.2 Security User agents must raise a SECURITY_ERR exception whenever any of the members of an HTMLDocument object are accessed by scripts whose effective script origin is not the same as the Document's effective script origin. 3.2.3 Resource metadata management document . URL Returns the document's address. document . referrer Returns the address of the Document from which the user navigated to this one, unless it was blocked or there was no such document, in which case it returns the empty string. The noreferrer link type can be used to block the referrer. The URL attribute must return the document's address. The referrer attribute must return either the current address of the active document of the source browsing context at the time the navigation was started (that is, the page which navigated the browsing context to the current document), or the empty string if there is no such originating page, or if the UA has been configured not to report referrers in this case, or if the navigation was initiated for a hyperlink with a noreferrer keyword. In the case of HTTP, the referrer DOM attribute will match the Referer (sic) header that was sent when fetching the current page. Typically user agents are configured to not report referrers in the case where the referrer uses an encrypted protocol and the current page does not (e.g. when navigating from an https: page to an http: page). document . cookie [ = value ] Returns the HTTP cookies that apply to the Document. If there are no cookies or cookies can't be applied to this resource, the empty string will be returned. Can be set, to add a new cookie to the element's set of HTTP cookies. If the Document has no browsing context an INVALID_STATE_ERR exception will be thrown. If the contents are sandboxed into a unique origin, a SECURITY_ERR exception will be thrown. The cookie attribute represents the cookies of the resource. http://dev.w3.org/html5/spec/Overview.html (63 de 570)01-08-2009 6:55:54
- 64. HTML 5 On getting, if the document is not associated with a browsing context then the user agent must raise an INVALID_STATE_ERR exception. Otherwise, if the sandboxed origin browsing context flag was set on the browsing context of the Document when the Document was created, the user agent must raise a SECURITY_ERR exception. Otherwise, if the document's address does not use a server-based naming authority, it must return the empty string. Otherwise, it must first obtain the storage mutex and then return the same string as the value of the Cookie HTTP header it would include if fetching the resource indicated by the document's address over HTTP, as per RFC 2109 section 4.3.4 or later specifications, excluding HTTP-only cookies. [RFC2109] [RFC2965] On setting, if the document is not associated with a browsing context then the user agent must raise an INVALID_STATE_ERR exception. Otherwise, if the sandboxed origin browsing context flag was set on the browsing context of the Document when the Document was created, the user agent must raise a SECURITY_ERR exception. Otherwise, if the document's address does not use a server-based naming authority, it must do nothing. Otherwise, the user agent must obtain the storage mutex and then act as it would when processing cookies if it had just attempted to fetch the document's address over HTTP, and had received a response with a Set-Cookie header whose value was the specified value, as per RFC 2109 sections 4.3.1, 4.3.2, and 4.3.3 or later specifications, but without overwriting the values of HTTP-only cookies. [RFC2109] [RFC2965] This specification does not define what makes an HTTP-only cookie, and at the time of publication the editor is not aware of any reference for HTTP-only cookies. They are a feature supported by some Web browsers wherein an "httponly" parameter added to the cookie string causes the cookie to be hidden from script. Since the cookie attribute is accessible across frames, the path restrictions on cookies are only a tool to help manage which cookies are sent to which parts of the site, and are not in any way a security feature. document . lastModified Returns the date of the last modification to the document, as reported by the server, in the form "MM/DD/YYYY hh:mm:ss". If the last modification date is not known, the current time is returned instead. The lastModified attribute, on getting, must return the date and time of the Document's source file's last modification, in the user's local time zone, in the following format: 1. The month component of the date. 2. A U+002F SOLIDUS character ('/'). 3. The day component of the date. 4. A U+002F SOLIDUS character ('/'). 5. The year component of the date. 6. A U+0020 SPACE character. 7. The hours component of the time. 8. A U+003A COLON character (':'). 9. The minutes component of the time. 10. A U+003A COLON character (':'). 11. The seconds component of the time. All the numeric components above, other than the year, must be given as two digits in the range U+0030 DIGIT ZERO to U+0039 DIGIT NINE representing the number in base ten, zero-padded if necessary. The year must be given as four or more digits in the range U +0030 DIGIT ZERO to U+0039 DIGIT NINE representing the number in base ten, zero-padded if necessary. The Document's source file's last modification date and time must be derived from relevant features of the networking protocols used, e.g. from the value of the HTTP Last-Modified header of the document, or from metadata in the file system for local files. If the last modification date and time are not known, the attribute must return the current date and time in the above format. document . compatMode In a conforming document, returns the string "CSS1Compat". (In quirks mode documents, returns the string "BackCompat", but a conforming document can never trigger quirks mode.) A Document is always set to one of three modes: no quirks mode, the default; quirks mode, used typically for legacy documents; and limited quirks mode, also known as "almost standards" mode. The mode is only ever changed from the default by the HTML parser, based on the presence, absence, or value of the DOCTYPE string. http://dev.w3.org/html5/spec/Overview.html (64 de 570)01-08-2009 6:55:54
- 65. HTML 5 The compatMode DOM attribute must return the literal string "CSS1Compat" unless the document has been set to quirks mode by the HTML parser, in which case it must instead return the literal string "BackCompat". document . charset [ = value ] Returns the document's character encoding. Can be set, to dynamically change the document's character encoding. New values that are not IANA-registered aliases supported by the user agent are ignored. document . characterSet Returns the document's character encoding. document . defaultCharset Returns what might be the user agent's default character encoding. Documents have an associated character encoding. When a Document object is created, the document's character encoding must be initialized to UTF-16. Various algorithms during page loading affect this value, as does the charset setter. [IANACHARSET] The charset DOM attribute must, on getting, return the preferred MIME name of the document's character encoding. On setting, if the new value is an IANA-registered alias for a character encoding supported by the user agent, the document's character encoding must be set to that character encoding. (Otherwise, nothing happens.) The characterSet DOM attribute must, on getting, return the preferred MIME name of the document's character encoding. The defaultCharset DOM attribute must, on getting, return the preferred MIME name of a character encoding, possibly the user's default encoding, or an encoding associated with the user's current geographical location, or any arbitrary encoding name. document . readyState Returns "loading" while the Document is loading, and "complete" once it has loaded. The readystatechange event fires on the Document object when this value changes. Each document has a current document readiness. When a Document object is created, it must have its current document readiness set to the string "loading" if the document is associated with an HTML parser or an XML parser, or to the string "complete" otherwise. Various algorithms during page loading affect this value. When the value is set, the user agent must fire a simple event called readystatechange at the Document object. A Document is said to have an active parser if it is associated with an HTML parser or an XML parser that has not yet been stopped or aborted. The readyState DOM attribute must, on getting, return the current document readiness. 3.2.4 DOM tree accessors The html element of a document is the document's root element, if there is one and it's an html element, or null otherwise. The head element of a document is the first head element that is a child of the html element, if there is one, or null otherwise. document . title [ = value ] Returns the document's title, as given by the title element. Can be set, to update the document's title. If there is no head element, the new value is ignored. In SVG documents, the SVGDocument interface's title attribute takes precedence. The title element of a document is the first title element in the document (in tree order), if there is one, or null otherwise. http://dev.w3.org/html5/spec/Overview.html (65 de 570)01-08-2009 6:55:54
- 66. HTML 5 The title attribute must, on getting, run the following algorithm: 1. If the root element is an svg element in the "http://www.w3.org/2000/svg" namespace, and the user agent supports SVG, then return the value that would have been returned by the DOM attribute of the same name on the SVGDocument interface. [SVG] 2. Otherwise, let value be a concatenation of the data of all the child text nodes of the title element, in tree order, or the empty string if the title element is null. 3. Replace any sequence of two or more consecutive space characters in value with a single U+0020 SPACE character. 4. Remove any leading or trailing space characters in value. 5. Return value. On setting, the following algorithm must be run. Mutation events must be fired as appropriate. 1. If the root element is an svg element in the "http://www.w3.org/2000/svg" namespace, and the user agent supports SVG, then the setter must defer to the setter for the DOM attribute of the same name on the SVGDocument interface (if it is readonly, then this will raise an exception). Stop the algorithm here. [SVG] 2. If the title element is null and the head element is null, then the attribute must do nothing. Stop the algorithm here. 3. If the title element is null, then a new title element must be created and appended to the head element. 4. The children of the title element (if any) must all be removed. 5. A single Text node whose data is the new value being assigned must be appended to the title element. The title attribute on the HTMLDocument interface should shadow the attribute of the same name on the SVGDocument interface when the user agent supports both HTML and SVG. [SVG] document . body [ = value ] Returns the body element. Can be set, to replace the body element. If the new value is not a body or frameset element, this will throw a HIERARCHY_REQUEST_ERR exception. The body element of a document is the first child of the html element that is either a body element or a frameset element. If there is no such element, it is null. If the body element is null, then when the specification requires that events be fired at "the body element", they must instead be fired at the Document object. The body attribute, on getting, must return the body element of the document (either a body element, a frameset element, or null). On setting, the following algorithm must be run: 1. If the new value is not a body or frameset element, then raise a HIERARCHY_REQUEST_ERR exception and abort these steps. 2. Otherwise, if the new value is the same as the body element, do nothing. Abort these steps. 3. Otherwise, if the body element is not null, then replace that element with the new value in the DOM, as if the root element's replaceChild() method had been called with the new value and the incumbent body element as its two arguments respectively, then abort these steps. 4. Otherwise, the the body element is null. Append the new value to the root element. document . images Returns an HTMLCollection of the img elements in the Document. document . embeds document . plugins Return an HTMLCollection of the embed elements in the Document. document . links http://dev.w3.org/html5/spec/Overview.html (66 de 570)01-08-2009 6:55:54
- 67. HTML 5 Returns an HTMLCollection of the a and area elements in the Document that have href attributes. document . forms Return an HTMLCollection of the form elements in the Document. document . scripts Return an HTMLCollection of the script elements in the Document. The images attribute must return an HTMLCollection rooted at the Document node, whose filter matches only img elements. The embeds attribute must return an HTMLCollection rooted at the Document node, whose filter matches only embed elements. The plugins attribute must return the same object as that returned by the embeds attribute. The links attribute must return an HTMLCollection rooted at the Document node, whose filter matches only a elements with href attributes and area elements with href attributes. The forms attribute must return an HTMLCollection rooted at the Document node, whose filter matches only form elements. The scripts attribute must return an HTMLCollection rooted at the Document node, whose filter matches only script elements. collection = document . getElementsByName(name) Returns a NodeList of elements in the Document that have a name attribute with the value name. collection = document . getElementsByClassName(classes) collection = element . getElementsByClassName(classes) Returns a NodeList of the elements in the object on which the method was invoked (a Document or an Element) that have all the classes given by classes. The classes argument is interpreted as a space-separated list of classes. The getElementsByName(name) method takes a string name, and must return a live NodeList containing all the HTML elements in that document that have a name attribute whose value is equal to the name argument (in a case-sensitive manner), in tree order. The getElementsByClassName(classNames) method takes a string that contains an unordered set of unique space-separated tokens representing classes. When called, the method must return a live NodeList object containing all the elements in the document, in tree order, that have all the classes specified in that argument, having obtained the classes by splitting a string on spaces. If there are no tokens specified in the argument, then the method must return an empty NodeList. If the document is in quirks mode, then the comparisons for the classes must be done in an ASCII case-insensitive manner, otherwise, the comparisons must be done in a case-sensitive manner. The getElementsByClassName(classNames) method on the HTMLElement interface must return a live NodeList with the nodes that the HTMLDocument getElementsByClassName() method would return when passed the same argument(s), excluding any elements that are not descendants of the HTMLElement object on which the method was invoked. HTML, SVG, and MathML elements define which classes they are in by having an attribute in the per-element partition with the name class containing a space-separated list of classes to which the element belongs. Other specifications may also allow elements in their namespaces to be labeled as being in specific classes. Given the following XHTML fragment: <div id="example"> <p id="p1" class="aaa bbb"/> <p id="p2" class="aaa ccc"/> <p id="p3" class="bbb ccc"/> </div> A call to document.getElementById('example').getElementsByClassName('aaa') would return a NodeList with the two paragraphs p1 and p2 in it. A call to getElementsByClassName('ccc bbb') would only return one node, however, namely p3. A call to document.getElementById('example').getElementsByClassName('bbb ccc ') would return the same thing. A call to getElementsByClassName('aaa,bbb') would return no nodes; none of the elements above are in the "aaa,bbb" class. The HTMLDocument interface supports named properties. The names of the supported named properties at any moment consist of the values of the name content attributes of all the applet, embed, form, iframe, img, and fallback-free object elements in the Document that have name content attributes, and the values of the id content attributes of all the applet and fallback-free object elements in the Document that have id content attributes, and the values of the id content attributes of all the img elements in the Document that have both name content attributes and id content attributes. http://dev.w3.org/html5/spec/Overview.html (67 de 570)01-08-2009 6:55:54
- 68. HTML 5 When the HTMLDocument object is indexed for property retrieval using a name name, then the user agent must return the value obtained using the following steps: 1. Let elements be the list of named elements with the name name in the Document. There will be at least one such element, by definition. 2. If elements has only one element, and that element is an iframe element, then return the WindowProxy object of the nested browsing context represented by that iframe element, and abort these steps. 3. Otherwise, if elements has only one element, return that element and abort these steps. 4. Otherwise return an HTMLCollection rooted at the Document node, whose filter matches only named elements with the name name. Named elements with the name name, for the purposes of the above algorithm, are those that are either: q applet, embed, form, iframe, img, or fallback-free object elements that have a name content attribute whose value is name, or q applet or fallback-free object elements that have an id content attribute whose value is name, or q img elements that have an id content attribute whose value is name, and that have a name content attribute present also. An object element is said to be fallback-free if it has no object or embed descendants. The dir attribute on the HTMLDocument interface is defined along with the dir content attribute. 3.3 Elements 3.3.1 Semantics Elements, attributes, and attribute values in HTML are defined (by this specification) to have certain meanings (semantics). For example, the ol element represents an ordered list, and the lang attribute represents the language of the content. Authors must not use elements, attributes, and attribute values for purposes other than their appropriate intended semantic purpose. Authors must not use elements, attributes, and attribute values that are not permitted by this specification or other applicable specifications. For example, the following document is non-conforming, despite being syntactically correct: <!DOCTYPE html> <html lang="en-GB"> <head> <title> Demonstration </title> </head> <body> <table> <tr> <td> My favourite animal is the cat. </td> </tr> <tr> <td> —<a href="http://example.org/~ernest/"><cite>Ernest</cite></a>, in an essay from 1992 </td> </tr> </table> </body> </html> ...because the data placed in the cells is clearly not tabular data (and the cite element mis-used). A corrected version of this document might be: <!DOCTYPE html> <html lang="en-GB"> <head> <title> Demonstration </title> </head> <body> <blockquote> <p> My favourite animal is the cat. </p> </blockquote> <p> —<a href="http://example.org/~ernest/">Ernest</a>, http://dev.w3.org/html5/spec/Overview.html (68 de 570)01-08-2009 6:55:54
- 69. HTML 5 in an essay from 1992 </p> </body> </html> This next document fragment, intended to represent the heading of a corporate site, is similarly non-conforming because the second line is not intended to be a heading of a subsection, but merely a subheading or subtitle (a subordinate heading for the same section). <body> <h1>ABC Company</h1> <h2>Leading the way in widget design since 1432</h2> ... The hgroup element should be used in these kinds of situations: <body> <hgroup> <h1>ABC Company</h1> <h2>Leading the way in widget design since 1432</h2> </hgroup> ... In the next example, there is a non-conforming attribute value ("carpet") and a non-conforming attribute ("texture"), which is not permitted by this specification: <label>Carpet: <input type="carpet" name="c" texture="deep pile"></label> Here would be an alternative and correct way to mark this up: <label>Carpet: <input type="text" class="carpet" name="c" data-texture="deep pile"></label> Through scripting and using other mechanisms, the values of attributes, text, and indeed the entire structure of the document may change dynamically while a user agent is processing it. The semantics of a document at an instant in time are those represented by the state of the document at that instant in time, and the semantics of a document can therefore change over time. User agents must update their presentation of the document as this occurs. HTML has a progress element that describes a progress bar. If its "value" attribute is dynamically updated by a script, the UA would update the rendering to show the progress changing. 3.3.2 Elements in the DOM The nodes representing HTML elements in the DOM must implement, and expose to scripts, the interfaces listed for them in the relevant sections of this specification. This includes HTML elements in XML documents, even when those documents are in another context (e.g. inside an XSLT transform). Elements in the DOM represent things; that is, they have intrinsic meaning, also known as semantics. For example, an ol element represents an ordered list. The basic interface, from which all the HTML elements' interfaces inherit, and which must be used by elements that have no additional requirements, is the HTMLElement interface. interface HTMLElement : Element { // DOM tree accessors NodeList getElementsByClassName(in DOMString classNames); // dynamic markup insertion attribute DOMString innerHTML; attribute DOMString outerHTML; void insertAdjacentHTML(in DOMString position, in DOMString text); // metadata attributes attribute DOMString id; attribute DOMString title; attribute DOMString lang; attribute DOMString dir; attribute DOMString className; readonly attribute DOMTokenList classList; readonly attribute DOMStringMap dataset; // microdata http://dev.w3.org/html5/spec/Overview.html (69 de 570)01-08-2009 6:55:54
- 70. HTML 5 [PutForwards=value] readonly attribute DOMSettableTokenList item; [PutForwards=value] readonly attribute DOMSettableTokenList itemprop; readonly attribute HTMLPropertyCollection properties; attribute DOMString content; attribute HTMLElement subject; // user interaction attribute boolean hidden; void click(); void scrollIntoView(); void scrollIntoView(in boolean top); attribute long tabIndex; void focus(); void blur(); attribute DOMString accessKey; readonly attribute DOMString accessKeyLabel; attribute boolean draggable; attribute DOMString contentEditable; readonly attribute boolean isContentEditable; attribute HTMLMenuElement contextMenu; attribute DOMString spellcheck; // command API readonly attribute DOMString commandType; readonly attribute DOMString label; readonly attribute DOMString icon; readonly attribute boolean disabled; readonly attribute boolean checked; // styling readonly attribute CSSStyleDeclaration style; // event handler DOM attributes attribute Function onabort; attribute Function onblur; attribute Function oncanplay; attribute Function oncanplaythrough; attribute Function onchange; attribute Function onclick; attribute Function oncontextmenu; attribute Function ondblclick; attribute Function ondrag; attribute Function ondragend; attribute Function ondragenter; attribute Function ondragleave; attribute Function ondragover; attribute Function ondragstart; attribute Function ondrop; attribute Function ondurationchange; attribute Function onemptied; attribute Function onended; attribute Function onerror; attribute Function onfocus; attribute Function onformchange; attribute Function onforminput; attribute Function oninput; attribute Function oninvalid; attribute Function onkeydown; attribute Function onkeypress; attribute Function onkeyup; attribute Function onload; attribute Function onloadeddata; attribute Function onloadedmetadata; attribute Function onloadstart; http://dev.w3.org/html5/spec/Overview.html (70 de 570)01-08-2009 6:55:54
- 71. HTML 5 attribute Function onmousedown; attribute Function onmousemove; attribute Function onmouseout; attribute Function onmouseover; attribute Function onmouseup; attribute Function onmousewheel; attribute Function onpause; attribute Function onplay; attribute Function onplaying; attribute Function onprogress; attribute Function onratechange; attribute Function onreadystatechange; attribute Function onscroll; attribute Function onseeked; attribute Function onseeking; attribute Function onselect; attribute Function onshow; attribute Function onstalled; attribute Function onsubmit; attribute Function onsuspend; attribute Function ontimeupdate; attribute Function onvolumechange; attribute Function onwaiting; }; interface HTMLUnknownElement : HTMLElement { }; The HTMLElement interface holds methods and attributes related to a number of disparate features, and the members of this interface are therefore described in various different sections of this specification. The HTMLUnknownElement interface must be used for HTML elements that are not defined by this specification. 3.3.3 Global attributes The following attributes are common to and may be specified on all HTML elements (even those not defined in this specification): q accesskey q class q contenteditable q contextmenu q dir q draggable q id q item q hidden q lang q itemprop q spellcheck q style q subject q tabindex q title In addition, unless otherwise specified, the following event handler content attributes may be specified on any HTML element: q onabort q onblur* q oncanplay q oncanplaythrough q onchange q onclick q oncontextmenu q ondblclick q ondrag q ondragend q ondragenter q ondragleave q ondragover http://dev.w3.org/html5/spec/Overview.html (71 de 570)01-08-2009 6:55:54
- 72. HTML 5 q ondragstart q ondrop q ondurationchange q onemptied q onended q onerror* q onfocus* q onformchange q onforminput q oninput q oninvalid q onkeydown q onkeypress q onkeyup q onload* q onloadeddata q onloadedmetadata q onloadstart q onmousedown q onmousemove q onmouseout q onmouseover q onmouseup q onmousewheel q onpause q onplay q onplaying q onprogress q onratechange q onreadystatechange q onscroll q onseeked q onseeking q onselect q onshow q onstalled q onsubmit q onsuspend q ontimeupdate q onvolumechange q onwaiting The attributes marked with an asterisk cannot be specified on body elements as those elements expose event handler attributes of the Window object with the same names. Also, custom data attributes (e.g. data-foldername or data-msgid) can be specified on any HTML element, to store custom data specific to the page. In HTML documents, elements in the HTML namespace may have an xmlns attribute specified, if, and only if, it has the exact value "http://www.w3.org/1999/xhtml". This does not apply to XML documents. In HTML, the xmlns attribute has absolutely no effect. It is basically a talisman. It is allowed merely to make migration to and from XHTML mildly easier. When parsed by an HTML parser, the attribute ends up in no namespace, not the "http://www.w3. org/2000/xmlns/" namespace like namespace declaration attributes in XML do. In XML, an xmlns attribute is part of the namespace declaration mechanism, and an element cannot actually have an xmlns attribute in no namespace specified. 3.3.3.1 The id attribute The id attribute represents its element's unique identifier. The value must be unique in the element's home subtree and must contain at least one character. The value must not contain any space characters. An element's unique identifier can be used for a variety of purposes, most notably as a way to link to specific parts of a document using fragment identifiers, as a way to target an element when scripting, and as a way to style a specific element from CSS. If the value is not the empty string, user agents must associate the element with the given value (exactly, including any space characters) for the purposes of ID matching within the element's home subtree (e.g. for selectors in CSS or for the getElementById() method in the DOM). Identifiers are opaque strings. Particular meanings should not be derived from the value of the id attribute. http://dev.w3.org/html5/spec/Overview.html (72 de 570)01-08-2009 6:55:54
- 73. HTML 5 This specification doesn't preclude an element having multiple IDs, if other mechanisms (e.g. DOM Core methods) can set an element's ID in a way that doesn't conflict with the id attribute. The id DOM attribute must reflect the id content attribute. 3.3.3.2 The title attribute The title attribute represents advisory information for the element, such as would be appropriate for a tooltip. On a link, this could be the title or a description of the target resource; on an image, it could be the image credit or a description of the image; on a paragraph, it could be a footnote or commentary on the text; on a citation, it could be further information about the source; and so forth. The value is text. If this attribute is omitted from an element, then it implies that the title attribute of the nearest ancestor HTML element with a title attribute set is also relevant to this element. Setting the attribute overrides this, explicitly stating that the advisory information of any ancestors is not relevant to this element. Setting the attribute to the empty string indicates that the element has no advisory information. If the title attribute's value contains U+000A LINE FEED (LF) characters, the content is split into multiple lines. Each U+000A LINE FEED (LF) character represents a line break. Caution is advised with respect to the use of newlines in title attributes. For instance, the following snippet actually defines an abbreviation's expansion with a line break in it: <p>My logs show that there was some interest in <abbr title="Hypertext Transport Protocol">HTTP</abbr> today.</p> Some elements, such as link, abbr, and input, define additional semantics for the title attribute beyond the semantics described above. The title DOM attribute must reflect the title content attribute. 3.3.3.3 The lang and xml:lang attributes The lang attribute (in no namespace) specifies the primary language for the element's contents and for any of the element's attributes that contain text. Its value must be a valid RFC 3066 language code, or the empty string. [RFC3066] The lang attribute in the XML namespace is defined in XML. [XML] If these attributes are omitted from an element, then the language of this element is the same as the language of its parent element, if any. Setting the attribute to the empty string indicates that the primary language is unknown. The lang attribute in no namespace may be used on any HTML element. The lang attribute in the XML namespace may be used on HTML elements in XML documents, as well as elements in other namespaces if the relevant specifications allow it (in particular, MathML and SVG allow lang attributes in the XML namespace to be specified on their elements). If both the lang attribute in no namespace and the lang attribute in the XML namespace are specified on the same element, they must have exactly the same value when compared in an ASCII case-insensitive manner. Authors must not use the lang attribute in the XML namespace in HTML documents. To ease migration to and from XHTML, authors may specify an attribute in no namespace with no prefix and with the literal localname "xml:lang" on HTML elements in HTML documents, but such attributes must only be specified if a lang attribute in no namespace is also specified, and both attributes must have the same value when compared in an ASCII case-insensitive manner. To determine the language of a node, user agents must look at the nearest ancestor element (including the element itself if the node is an element) that has a lang attribute in the XML namespace set or is an HTML element and has a lang in no namespace attribute set. That attribute specifies the language of the node. If both the lang attribute in no namespace and the lang attribute in the XML namespace are set on an element, user agents must use the lang attribute in the XML namespace, and the lang attribute in no namespace must be ignored for the purposes of determining the element's language. If no explicit language is given for the root element, but there is a document-wide default language set, then that is the language of the node. If there is no document-wide default language, then language information from a higher-level protocol (such as HTTP), if any, must be used as the final fallback language. In the absence of any language information, the default value is unknown (the empty string). If the resulting value is not a recognized language code, then it must be treated as an unknown language (as if the value was the empty string). User agents may use the element's language to determine proper processing or rendering (e.g. in the selection of appropriate fonts or pronunciations, or for dictionary selection). The lang DOM attribute must reflect the lang content attribute in no namespace. http://dev.w3.org/html5/spec/Overview.html (73 de 570)01-08-2009 6:55:54
- 74. HTML 5 3.3.3.4 The xml:base attribute (XML only) The xml:base attribute is defined in XML Base. [XMLBASE] The xml:base attribute may be used on elements of XML documents. Authors must not use the xml:base attribute in HTML documents. 3.3.3.5 The dir attribute The dir attribute specifies the element's text directionality. The attribute is an enumerated attribute with the keyword ltr mapping to the state ltr, and the keyword rtl mapping to the state rtl. The attribute has no defaults. The processing of this attribute is primarily performed by the presentation layer. For example, the rendering section in this specification defines a mapping from this attribute to the CSS 'direction' and 'unicode-bidi' properties, and CSS defines rendering in terms of those properties. The directionality of an element, which is used in particular by the canvas element's text rendering API, is either 'ltr' or 'rtl'. If the user agent supports CSS and the 'direction' property on this element has a computed value of either 'ltr' or 'rtl', then that is the directionality of the element. Otherwise, if the element is being rendered, then the directionality of the element is the directionality used by the presentation layer, potentially determined from the value of the dir attribute on the element. Otherwise, if the element's dir attribute has the state ltr, the element's directionality is 'ltr' (left-to-right); if the attribute has the state rtl, the element's directionality is 'rtl' (right-to-left); and otherwise, the element's directionality is the same as its parent element, or 'ltr' if there is no parent element. document . dir [ = value ] Returns the html element's dir attribute's value, if any. Can be set, to either "ltr" or "rtl", to replace the html element's dir attribute's value. If there is no html element, returns the empty string and ignores new values. The dir DOM attribute on an element must reflect the dir content attribute of that element, limited to only known values. The dir DOM attribute on HTMLDocument objects must reflect the dir content attribute of the html element, if any, limited to only known values. If there is no such element, then the attribute must return the empty string and do nothing on setting. Authors are strongly encouraged to use the dir attribute to indicate text direction rather than using CSS, since that way their documents will continue to render correctly even in the absence of CSS (e.g. as interpreted by search engines). 3.3.3.6 The class attribute Every HTML element may have a class attribute specified. The attribute, if specified, must have a value that is an unordered set of unique space-separated tokens representing the various classes that the element belongs to. The classes that an HTML element has assigned to it consists of all the classes returned when the value of the class attribute is split on spaces. Assigning classes to an element affects class matching in selectors in CSS, the getElementsByClassName() method in the DOM, and other such features. Authors may use any value in the class attribute, but are encouraged to use the values that describe the nature of the content, rather than values that describe the desired presentation of the content. The className and classList DOM attributes must both reflect the class content attribute. 3.3.3.7 The style attribute All HTML elements may have the style content attribute set. If specified, the attribute must contain only a list of zero or more semicolon-separated (;) CSS declarations. [CSS] In user agents that support CSS, the attribute's value must be parsed when the attribute is added or has its value changed, with its value treated as the body (the part inside the curly brackets) of a declaration block in a rule whose selector matches just the element on which the attribute is set. All URLs in the value must be resolved relative to the element when the attribute is parsed. For the purposes of the CSS cascade, the attribute must be considered to be a 'style' attribute at the author level. Documents that use style attributes on any of their elements must still be comprehensible and usable if those attributes were removed. http://dev.w3.org/html5/spec/Overview.html (74 de 570)01-08-2009 6:55:55
- 75. HTML 5 In particular, using the style attribute to hide and show content, or to convey meaning that is otherwise not included in the document, is non-conforming. (To hide and show content, use the hidden attribute.) element . style Returns a CSSStyleDeclaration object for the element's style attribute. The style DOM attribute must return a CSSStyleDeclaration whose value represents the declarations specified in the attribute, if present. Mutating the CSSStyleDeclaration object must create a style attribute on the element (if there isn't one already) and then change its value to be a value representing the serialized form of the CSSStyleDeclaration object. [CSSOM] In the following example, the words that refer to colors are marked up using the span element and the style attribute to make those words show up in the relevant colors in visual media. <p>My sweat suit is <span style="color: green; background: transparent">green</span> and my eyes are <span style="color: blue; background: transparent">blue</span>.</p> 3.3.3.8 Embedding custom non-visible data A custom data attribute is an attribute in no namespace whose name starts with the string "data-", has at least one character after the hyphen, is XML-compatible, and contains no characters in the range U+0041 .. U+005A (LATIN CAPITAL LETTER A .. LATIN CAPITAL LETTER Z). All attributes in HTML documents get lowercased automatically, so the restriction on uppercase letters doesn't affect such documents. Custom data attributes are intended to store custom data private to the page or application, for which there are no more appropriate attributes or elements. These attributes are not intended for use by software that is independent of the site that uses the attributes. For instance, a site about music could annotate list items representing tracks in an album with custom data attributes containing the length of each track. This information could then be used by the site itself to allow the user to sort the list by track length, or to filter the list for tracks of certain lengths. <ol> <li data-length="2m11s">Beyond The Sea</li> ... </ol> It would be inappropriate, however, for the user to use generic software not associated with that music site to search for tracks of a certain length by looking at this data. This is because these attributes are intended for use by the site's own scripts, and are not a generic extension mechanism for publicly-usable metadata. Every HTML element may have any number of custom data attributes specified, with any value. element . dataset Returns a DOMStringMap object for the element's data-* attributes. The dataset DOM attribute provides convenient accessors for all the data-* attributes on an element. On getting, the dataset DOM attribute must return a DOMStringMap object, associated with the following algorithms, which expose these attributes on their element: The algorithm for getting the list of name-value pairs 1. Let list be an empty list of name-value pairs. 2. For each content attribute on the element whose first five characters are the string "data-", add a name-value pair to list whose name is the attribute's name with the first five character removed and whose value is the attribute's value. 3. Return list. http://dev.w3.org/html5/spec/Overview.html (75 de 570)01-08-2009 6:55:55
- 76. HTML 5 The algorithm for setting names to certain values 1. Let name be the concatenation of the string data- and the name passed to the algorithm. 2. Let value be the value passed to the algorithm. 3. Set the value of the attribute with the name name, to the value value, replacing any previous value if the attribute already existed. If setAttribute() would have raised an exception when setting an attribute with the name name, then this must raise the same exception. The algorithm for deleting names 1. Let name be the concatenation of the string data- and the name passed to the algorithm. 2. Remove the attribute with the name name, if such an attribute exists. Do nothing otherwise. If a Web page wanted an element to represent a space ship, e.g. as part of a game, it would have to use the class attribute along with data-* attributes: <div class="spaceship" data-id="92432" data-weapons="laser 2" data-shields="50%" data-x="30" data-y="10" data-z="90"> <button class="fire" onclick="spaceships[this.parentNode.dataset.id].fire()"> Fire </button> </div> Authors should carefully design such extensions so that when the attributes are ignored and any associated CSS dropped, the page is still usable. User agents must not derive any implementation behavior from these attributes or values. Specifications intended for user agents must not define these attributes to have any meaningful values. 3.4 Content models All the elements in this specification have a defined content model, which describes what nodes are allowed inside the elements, and thus what the structure of an HTML document or fragment must look like. As noted in the conformance and terminology sections, for the purposes of determining if an element matches its content model or not, CDATASection nodes in the DOM are treated as equivalent to Text nodes, and entity reference nodes are treated as if they were expanded in place. The space characters are always allowed between elements. User agents represent these characters between elements in the source markup as text nodes in the DOM. Empty text nodes and text nodes consisting of just sequences of those characters are considered inter-element whitespace. Inter-element whitespace, comment nodes, and processing instruction nodes must be ignored when establishing whether an element matches its content model or not, and must be ignored when following algorithms that define document and element semantics. An element A is said to be preceded or followed by a second element B if A and B have the same parent node and there are no other element nodes or text nodes (other than inter-element whitespace) between them. Authors must not use elements in the HTML namespace anywhere except where they are explicitly allowed, as defined for each element, or as explicitly required by other specifications. For XML compound documents, these contexts could be inside elements from other namespaces, if those elements are defined as providing the relevant contexts. The Atom specification defines the Atom content element, when its type attribute has the value xhtml, as requiring that it contains a single HTML div element. Thus, a div element is allowed in that context, even though this is not explicitly normatively stated by this specification. [ATOM] In addition, elements in the HTML namespace may be orphan nodes (i.e. without a parent node). For example, creating a td element and storing it in a global variable in a script is conforming, even though td elements are otherwise only supposed to be used inside tr elements. var data = { name: "Banana", cell: document.createElement('td'), }; 3.4.1 Kinds of content Each element in HTML falls into zero or more categories that group elements with similar characteristics together. The following broad categories are used in this specification: q Metadata content http://dev.w3.org/html5/spec/Overview.html (76 de 570)01-08-2009 6:55:55
- 77. HTML 5 q Flow content q Sectioning content q Heading content q Phrasing content q Embedded content q Interactive content These categories are related as follows: In addition, certain elements are categorized as form-associated elements and further subcategorized to define their role in various form-related processing models. Some elements have unique requirements and do not fit into any particular category. 3.4.1.1 Metadata content Metadata content is content that sets up the presentation or behavior of the rest of the content, or that sets up the relationship of the document with other documents, or that conveys other "out of band" information. basecommandlinkmetanoscriptscriptstyletitle Elements from other namespaces whose semantics are primarily metadata-related (e.g. RDF) are also metadata content. Thus, in the XML serialization, one can use RDF, like this: <html xmlns="http://www.w3.org/1999/xhtml" xmlns:r="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <head> <title>Hedral's Home Page</title> <r:RDF> <Person xmlns="http://www.w3.org/2000/10/swap/pim/contact#" r:about="http://hedral.example.com/#"> <fullName>Cat Hedral</fullName> <mailbox r:resource="mailto:hedral@damowmow.com"/> <personalTitle>Sir</personalTitle> </Person> </r:RDF> </head> <body> <h1>My home page</h1> <p>I like playing with string, I guess. Sister says squirrels are fun too so sometimes I follow her to play with them.</p> </body> </html> This isn't possible in the HTML serialization, however. 3.4.1.2 Flow content Most elements that are used in the body of documents and applications are categorized as flow content. http://dev.w3.org/html5/spec/Overview.html (77 de 570)01-08-2009 6:55:55
- 78. HTML 5 aabbraddressarea (if it is a descendant of a map element) articleasideaudiobbbbdoblockquotebrbuttoncanvascitecodecommanddatagriddatalistdeldetailsdfndialogdivdlemembedfieldsetfigurefooterformh1h2h3h4h5h6headerhgrouphriiframeimginputinskbdkeygenlabellink (if the itemprop attribute is present)mapmarkmathmenumeta (if the itemprop attribute is present)meternavnoscriptobjectoloutputppreprogressqrubysampscriptsectionselectsmallspanstrongstyle (if the scoped attribute is present) subsupsvgtabletextareatimeulvarvideoText As a general rule, elements whose content model allows any flow content should have either at least one descendant text node that is not inter-element whitespace, or at least one descendant element node that is embedded content. For the purposes of this requirement, del elements and their descendants must not be counted as contributing to the ancestors of the del element. This requirement is not a hard requirement, however, as there are many cases where an element can be empty legitimately, for example when it is used as a placeholder which will later be filled in by a script, or when the element is part of a template and would on most pages be filled in but on some pages is not relevant. 3.4.1.3 Sectioning content Sectioning content is content that defines the scope of headings and footers. articleasidenavsection Each sectioning content element potentially has a heading and an outline. See the section on headings and sections for further details. There are also certain elements that are sectioning roots. These are distinct from sectioning content, but they can also have an outline. 3.4.1.4 Heading content Heading content defines the header of a section (whether explicitly marked up using sectioning content elements, or implied by the heading content itself). h1h2h3h4h5h6hgroup 3.4.1.5 Phrasing content Phrasing content is the text of the document, as well as elements that mark up that text at the intra-paragraph level. Runs of phrasing content form paragraphs. a (if it contains only phrasing content)abbrarea (if it is a descendant of a map element)audiobbbbdobrbuttoncanvascitecodecommanddatalistdel (if it contains only phrasing content)dfnemembediiframeimginputins (if it contains only phrasing content)kbdkeygenlabellink (if the itemprop attribute is present)map (if it contains only phrasing content)markmathmeta (if the itemprop attribute is present) meternoscriptobjectoutputprogressqrubysampscriptselectsmallspanstrongsubsupsvgtextareatimevarvideoText As a general rule, elements whose content model allows any phrasing content should have either at least one descendant text node that is not inter-element whitespace, or at least one descendant element node that is embedded content. For the purposes of this requirement, nodes that are descendants of del elements must not be counted as contributing to the ancestors of the del element. Most elements that are categorized as phrasing content can only contain elements that are themselves categorized as phrasing content, not any flow content. Text, in the context of content models, means text nodes. Text is sometimes used as a content model on its own, but is also phrasing content, and can be inter-element whitespace (if the text nodes are empty or contain just space characters). 3.4.1.6 Embedded content Embedded content is content that imports another resource into the document, or content from another vocabulary that is inserted into the document. audiocanvasembediframeimgmathobjectsvgvideo Elements that are from namespaces other than the HTML namespace and that convey content but not metadata, are embedded content for the purposes of the content models defined in this specification. (For example, MathML, or SVG.) Some embedded content elements can have fallback content: content that is to be used when the external resource cannot be used (e.g. because it is of an unsupported format). The element definitions state what the fallback is, if any. 3.4.1.7 Interactive content Interactive content is content that is specifically intended for user interaction. aaudio (if the controls attribute is present)bbbuttondatagriddetailsembediframeimg (if the usemap attribute is present)input (if the type attribute is not in the Hidden state)keygenlabelmenu (if the type attribute is in the tool bar state)object (if the usemap attribute is present)selecttextareavideo (if the controls attribute is present) http://dev.w3.org/html5/spec/Overview.html (78 de 570)01-08-2009 6:55:55
- 79. HTML 5 Certain elements in HTML have an activation behavior, which means that the user can activate them. This triggers a sequence of events dependent on the activation mechanism, and normally culminating in a click event followed by a DOMActivate event, as described below. The user agent should allow the user to manually trigger elements that have an activation behavior, for instance using keyboard or voice input, or through mouse clicks. When the user triggers an element with a defined activation behavior in a manner other than clicking it, the default action of the interaction event must be to run synthetic click activation steps on the element. When a user agent is to run synthetic click activation steps on an element, the user agent must run pre-click activation steps on the element, then fire a click event at the element. The default action of this click event must be to run post-click activation steps on the element. If the event is canceled, the user agent must run canceled activation steps on the element instead. Given an element target, the nearest activatable element is the element returned by the following algorithm: 1. If target has a defined activation behavior, then return target and abort these steps. 2. If target has a parent element, then set target to that parent element and return to the first step. 3. Otherwise, there is no nearest activatable element. When a pointing device is clicked, the user agent must run these steps: 1. Let e be the nearest activatable element of the element designated by the user, if any. 2. If there is an element e, run pre-click activation steps on it. 3. Dispatching the required click event. If there is an element e, then the default action of the click event must be to run post-click activation steps on element e. If there is an element e but the event is canceled, the user agent must run canceled activation steps on element e. The above doesn't happen for arbitrary synthetic events dispatched by author script. However, the click() method can be used to make it happen programmatically. When a user agent is to run pre-click activation steps on an element, it must run the pre-click activation steps defined for that element, if any. When a user agent is to run post-click activation steps on an element, the user agent must fire a simple event called DOMActivate that is cancelable at that element. The default action of this event must be to run final activation steps on that element. If the event is canceled, the user agent must run canceled activation steps on the element instead. When a user agent is to run canceled activation steps on an element, it must run the canceled activation steps defined for that element, if any. When a user agent is to run final activation steps on an element, it must run the activation behavior defined for that element. Activation behaviors can refer to the click and DOMActivate events that were fired by the steps above leading up to this point. 3.4.2 Transparent content models Some elements are described as transparent; they have "transparent" in the description of their content model. When a content model includes a part that is "transparent", those parts must not contain content that would not be conformant if all transparent elements in the tree were replaced, in their parent element, by the children in the "transparent" part of their content model, retaining order. When a transparent element has no parent, then the part of its content model that is "transparent" must instead be treated as accepting any flow content. 3.5 Paragraphs The term paragraph as defined in this section is distinct from (though related to) the p element defined later. The paragraph concept defined here is used to describe how to interpret documents. A paragraph is typically a run of phrasing content that forms a block of text with one or more sentences that discuss a particular topic, as in typography, but can also be used for more general thematic grouping. For instance, an address is also a paragraph, as is a part of a form, a byline, or a stanza in a poem. In the following example, there are two paragraphs in a section. There is also a heading, which contains phrasing content that is not a paragraph. Note how the comments and inter-element whitespace do not form paragraphs. <section> <h1>Example of paragraphs</h1> This is the <em>first</em> paragraph in this example. <p>This is the second.</p> http://dev.w3.org/html5/spec/Overview.html (79 de 570)01-08-2009 6:55:55
- 80. HTML 5 <!-- This is not a paragraph. --> </section> Paragraphs in flow content are defined relative to what the document looks like without the a, ins, del, and map elements complicating matters, since those elements, with their hybrid content models, can straddle paragraph boundaries, as shown in the first two examples below. Generally, having elements straddle paragraph boundaries is best avoided. Maintaining such markup can be difficult. The following example takes the markup from the earlier example and puts ins and del elements around some of the markup to show that the text was changed (though in this case, the changes admittedly don't make much sense). Notice how this example has exactly the same paragraphs as the previous one, despite the ins and del elements — the ins element straddles the heading and the first paragraph, and the del element straddles the boundary between the two paragraphs. <section> <ins><h1>Example of paragraphs</h1> This is the <em>first</em> paragraph in</ins> this example<del>. <p>This is the second.</p></del> <!-- This is not a paragraph. --> </section> Let view be a view of the DOM that replaces all a, ins, del, and map elements in the document with their contents. Then, in view, for each run of sibling phrasing content nodes uninterrupted by other types of content, in an element that accepts content other than phrasing content, let first be the first node of the run, and let last be the last node of the run. For each such run that consists of at least one node that is neither embedded content nor inter-element whitespace, a paragraph exists in the original DOM from immediately before first to immediately after last. (Paragraphs can thus span across a, ins, del, and map elements.) Conformance checkers may warn authors of cases where they have paragraphs that overlap each other (this can happen with object, video, audio, and canvas elements). A paragraph is also formed explicitly by p elements. The p element can be used to wrap individual paragraphs when there would otherwise not be any content other than phrasing content to separate the paragraphs from each other. In the following example, the link spans half of the first paragraph, all of the heading separating the two paragraphs, and half of the second paragraph. It straddles the paragraphs and the heading. <aside> Welcome! <a href="about.html"> This is home of... <h1>The Falcons!</h1> The Lockheed Martin multirole jet fighter aircraft! </a> This page discusses the F-16 Fighting Falcon's innermost secrets. </aside> Here is another way of marking this up, this time showing the paragraphs explicitly, and splitting the one link element into three: <aside> <p>Welcome! <a href="about.html">This is home of...</a></p> <h1><a href="about.html">The Falcons!</a></h1> <p><a href="about.html">The Lockheed Martin multirole jet fighter aircraft!</a> This page discusses the F-16 Fighting Falcon's innermost secrets.</p> </aside> It is possible for paragraphs to overlap when using certain elements that define fallback content. For example, in the following section: <section> <h1>My Cats</h1> You can play with my cat simulator. <object data="cats.sim"> To see the cat simulator, use one of the following links: <ul> <li><a href="cats.sim">Download simulator file</a> <li><a href="http://sims.example.com/watch?v=LYds5xY4INU">Use online simulator</a> </ul> Alternatively, upgrade to the Mellblom Browser. </object> I'm quite proud of it. </section> There are five paragraphs: http://dev.w3.org/html5/spec/Overview.html (80 de 570)01-08-2009 6:55:55
- 81. HTML 5 1. The paragraph that says "You can play with my cat simulator. object I'm quite proud of it.", where object is the object element. 2. The paragraph that says "To see the cat simulator, use one of the following links:". 3. The paragraph that says "Download simulator file". 4. The paragraph that says "Use online simulator". 5. The paragraph that says "Alternatively, upgrade to the Mellblom Browser.". The first paragraph is overlapped by the other four. A user agent that supports the "cats.sim" resource will only show the first one, but a user agent that shows the fallback will confusingly show the first sentence of the first paragraph as if it was in the same paragraph as the second one, and will show the last paragraph as if it was at the start of the second sentence of the first paragraph. To avoid this confusion, explicit p elements can be used. 3.6 APIs in HTML documents For HTML documents, and for HTML elements in HTML documents, certain APIs defined in DOM3 Core become case-insensitive or case-changing, as sometimes defined in DOM3 Core, and as summarized or required below. [DOM3CORE]. This does not apply to XML documents or to elements that are not in the HTML namespace despite being in HTML documents. Element.tagName and Node.nodeName These attributes must return element names converted to ASCII uppercase, regardless of the case with which they were created. Document.createElement() The canonical form of HTML markup is all-lowercase; thus, this method will lowercase the argument before creating the requisite element. Also, the element created must be in the HTML namespace. This doesn't apply to Document.createElementNS(). Thus, it is possible, by passing this last method a tag name in the wrong case, to create an element that claims to have the tag name of an element defined in this specification, but doesn't support its interfaces, because it really has another tag name not accessible from the DOM APIs. Element.setAttribute() Element.setAttributeNode() Attribute names are converted to ASCII lowercase. Specifically: when an attribute is set on an HTML element using Element.setAttribute(), the name argument must be converted to ASCII lowercase before the element is affected; and when an Attr node is set on an HTML element using Element. setAttributeNode(), it must have its name converted to ASCII lowercase before the element is affected. This doesn't apply to Document.setAttributeNS() and Document.setAttributeNodeNS(). Element.getAttribute() Element.getAttributeNode() Attribute names are converted to ASCII lowercase. Specifically: When the Element.getAttribute() method or the Element.getAttributeNode() method is invoked on an HTML element, the name argument must be converted to ASCII lowercase before the element's attributes are examined. This doesn't apply to Document.getAttributeNS() and Document.getAttributeNodeNS(). Document.getElementsByTagName() Element.getElementsByTagName() HTML elements match by lower-casing the argument before comparison, elements from other namespaces are treated as in XML (case-sensitively). Specifically, these methods (but not their namespaced counterparts) must compare the given argument in a case-sensitive manner, but when looking at HTML elements, the argument must first be converted to ASCII lowercase. Thus, in an HTML document with nodes in multiple namespaces, these methods will effectively be both case-sensitive and case-insensitive at the same time. 3.7 Interactions with XPath and XSLT Implementations of XPath 1.0 that operate on HTML documents parsed or created in the manners described in this specification (e.g. as part of the document.evaluate() API) are affected as follows: In addition to the cases where a name expression would match a node per XPath 1.0, a name expression must evaluate to matching a node when all the following conditions are also met: q The name expression has no namespace. q The name expression has local name that is a match for local. q The expression is being tested against an element node. q The element has local name local. q The element is in the HTML namespace. q The element's document is an HTML document. http://dev.w3.org/html5/spec/Overview.html (81 de 570)01-08-2009 6:55:55
- 82. HTML 5 These requirements are a willful violation of the XPath 1.0 specification, motivated by desire to have implementations be compatible with legacy content while still supporting the changes that this specification introduces to HTML regarding which namespace is used for HTML elements. [XPATH10] XSLT 1.0 processors outputting to a DOM when the output method is "html" (either explicitly or via the defaulting rule in XSLT 1.0) are affected as follows: If the transformation program outputs an element in no namespace, the processor must, prior to constructing the corresponding DOM element node, change the namespace of the element to the HTML namespace, ASCII-lowercase the element's local name, and ASCII- lowercase the names of any non-namespaced attributes on the element. This requirement is a willful violation of the XSLT 1.0 specification, required because this specification changes the namespaces and case-sensitivity rules of HTML in a manner that would otherwise be incompatible with DOM-based XSLT transformations. (Processors that serialize the output are unaffected.) [XSLT10] 3.8 Dynamic markup insertion APIs for dynamically inserting markup into the document interact with the parser, and thus their behavior, varies depending on whether they are used with HTML documents (and the HTML parser) or XHTML in XML documents (and the XML parser). 3.8.1 Controlling the input stream The open() method comes in several variants with different numbers of arguments. document = document . open( [ type [, replace ] ] ) Causes the Document to be replaced in-place, as if it was a new Document object, but reusing the previous object, which is then returned. If the type argument is omitted or has the value "text/html", then the resulting Document has an HTML parser associated with it, which can be given data to parse using document.write(). Otherwise, all content passed to document.write() will be parsed as plain text. If the replace argument is absent or false, a new entry is added to the session history to represent this entry, and the previous entries for this Document are all collapsed into one entry with a new Document object. The method has no effect if the Document is still being parsed. window = document . open( url, name, features [, replace ] ) Works like the window.open() method. document . close() Closes the input stream that was opened by the document.open() method. When called with two or fewer arguments, the method must act as follows: 1. Let type be the value of the first argument, if there is one, or "text/html" otherwise. 2. Let replace be true if there is a second argument and it is an ASCII case-insensitive match for the value "replace", and false otherwise. 3. If the document has an active parser that isn't a script-created parser, and the insertion point associated with that parser's input stream is not undefined (that is, it does point to somewhere in the input stream), then the method does nothing. Abort these steps and return the Document object on which the method was invoked. This basically causes document.open() to be ignored when it's called in an inline script found during the parsing of data sent over the network, while still letting it have an effect when called asynchronously or on a document that is itself being spoon- fed using these APIs. 4. Unload the Document object, with the recycle parameter set to true. If the user refused to allow the document to be unloaded, then these steps must be aborted. 5. If the document has an active parser, then abort that parser, and throw away any pending content in the input stream. 6. Unregister all event listeners registered on the Document node and its descendants. 7. Remove any tasks associated with the Document in any task source. http://dev.w3.org/html5/spec/Overview.html (82 de 570)01-08-2009 6:55:55
- 83. HTML 5 8. Remove all child nodes of the document, without firing any mutation events. 9. Replace the Document's singleton objects with new instances of those objects. (This includes in particular the Window, Location, History, ApplicationCache, UndoManager, Navigator, and Selection objects, the various BarProp objects, the two Storage objects, and the various HTMLCollection objects. It also includes all the Web IDL prototypes in the JavaScript binding, including the Document object's prototype.) 10. Change the document's character encoding to UTF-16. 11. Change the document's address to the first script's browsing context's active document's address. 12. Create a new HTML parser and associate it with the document. This is a script-created parser (meaning that it can be closed by the document.open() and document.close() methods, and that the tokenizer will wait for an explicit call to document.close () before emitting an end-of-file token). The encoding confidence is irrelevant. 13. Mark the document as being an HTML document (it might already be so-marked). 14. If the type string contains a U+003B SEMICOLON (;) character, remove the first such character and all characters from it up to the end of the string. Strip all leading and trailing space characters from type. If type is not now an ASCII case-insensitive match for the string "text/html", then act as if the tokenizer had emitted a start tag token with the tag name "pre", then set the HTML parser's tokenization stage's content model flag to PLAINTEXT. 15. If replace is false, then: 1. Remove all the entries in the browsing context's session history after the current entry in its Document's History object 2. Remove any earlier entries that share the same Document 3. Add a new entry just before the last entry that is associated with the text that was parsed by the previous parser associated with the Document object, as well as the state of the document at the start of these steps. (This allows the user to step backwards in the session history to see the page before it was blown away by the document.open() call.) 16. Finally, set the insertion point to point at just before the end of the input stream (which at this point will be empty). 17. Return the Document on which the method was invoked. When called with three or more arguments, the open() method on the HTMLDocument object must call the open() method on the Window object of the HTMLDocument object, with the same arguments as the original call to the open() method, and return whatever that method returned. If the HTMLDocument object has no Window object, then the method must raise an INVALID_ACCESS_ERR exception. The close() method must do nothing if there is no script-created parser associated with the document. If there is such a parser, then, when the method is called, the user agent must insert an explicit "EOF" character at the end of the parser's input stream. 3.8.2 document.write() document . write(text...) Adds the given string(s) to the Document's input stream. If necessary, calls the open() method implicitly first. This method throws an INVALID_ACCESS_ERR exception when invoked on XML documents. The document.write(...) method must act as follows: 1. If the method was invoked on an XML document, throw an INVALID_ACCESS_ERR exception and abort these steps. 2. If the insertion point is undefined, the open() method must be called (with no arguments) on the document object. If the user refused to allow the document to be unloaded, then these steps must be aborted. Otherwise, the insertion point will point at just before the end of the (empty) input stream. 3. The string consisting of the concatenation of all the arguments to the method must be inserted into the input stream just before the insertion point. 4. If there is a pending external script, then the method must now return without further processing of the input stream. 5. Otherwise, the tokenizer must process the characters that were inserted, one at a time, processing resulting tokens as they are emitted, and stopping when the tokenizer reaches the insertion point or when the processing of the tokenizer is aborted by the tree construction stage (this can happen if a script end tag token is emitted by the tokenizer). If the document.write() method was called from script executing inline (i.e. executing because the parser parsed a set of script tags), then this is a reentrant invocation of the parser. http://dev.w3.org/html5/spec/Overview.html (83 de 570)01-08-2009 6:55:55
- 84. HTML 5 6. Finally, the method must return. 3.8.3 document.writeln() document . writeln(text...) Adds the given string(s) to the Document's input stream, followed by a newline character. If necessary, calls the open() method implicitly first. This method throws an INVALID_ACCESS_ERR exception when invoked on XML documents. The document.writeln(...) method, when invoked, must act as if the document.write() method had been invoked with the same argument(s), plus an extra argument consisting of a string containing a single line feed character (U+000A). 3.8.4 innerHTML The innerHTML DOM attribute represents the markup of the node's contents. document . innerHTML [ = value ] Returns a fragment of HTML or XML that represents the Document. Can be set, to replace the Document's contents with the result of parsing the given string. In the case of XML documents, will throw a SYNTAX_ERR if the Document cannot be serialized to XML, or if the given string is not well-formed. element . innerHTML [ = value ] Returns a fragment of HTML or XML that represents the element's contents. Can be set, to replace the contents of the element with nodes parsed from the given string. In the case of XML documents, will throw a SYNTAX_ERR if the element cannot be serialized to XML, or if the given string is not well-formed. On getting, if the node's document is an HTML document, then the attribute must return the result of running the HTML fragment serialization algorithm on the node; otherwise, the node's document is an XML document, and the attribute must return the result of running the XML fragment serialization algorithm on the node instead (this might raise an exception instead of returning a string). On setting, the following steps must be run: 1. If the node is an Element node, and the node's document is an HTML document, and the node is in a Document, and the node's document has an active parser, and the insertion point associated with that parser's input stream is not undefined (that is, it does point to somewhere in the input stream), and the list of scripts that will execute when the document has finished parsing is not empty, then run the following substeps: 1. Let the script be the first element in the list of scripts that will execute when the document has finished parsing. 2. Loop: If the script is a script element without a src attribute, then execute the script. 3. If the script is not the last script in the list of scripts that will execute when the document has finished parsing, then let the script be the next script in that list, and return to the step marked loop. 4. Remove any scripts that were executed as part of this algorithm from the list of scripts that will execute when the document has finished parsing. 2. If the node's document is an HTML document: Invoke the HTML fragment parsing algorithm. If the node's document is an XML document: Invoke the XML fragment parsing algorithm. In either case, the algorithm must be invoked with the string being assigned into the innerHTML attribute as the input. If the node is an Element node, then, in addition, that element must be passed as the context element. If this raises an exception, then abort these steps. Otherwise, let new children be the nodes returned. 3. If the attribute is being set on a Document node, and that document has an active parser, then abort that parser. 4. Remove the child nodes of the node whose innerHTML attribute is being set, firing appropriate mutation events. http://dev.w3.org/html5/spec/Overview.html (84 de 570)01-08-2009 6:55:55
- 85. HTML 5 5. If the attribute is being set on a Document node, let target document be that Document node. Otherwise, the attribute is being set on an Element node; let target document be the ownerDocument of that Element. 6. Set the ownerDocument of all the nodes in new children to the target document. 7. Append all the new children nodes to the node whose innerHTML attribute is being set, preserving their order, and firing mutation events as appropriate. 3.8.5 outerHTML The outerHTML DOM attribute represents the markup of the element and its contents. element . outerHTML [ = value ] Returns a fragment of HTML or XML that represents the element and its contents. Can be set, to replace the element with nodes parsed from the given string. In the case of XML documents, will throw a SYNTAX_ERR if the element cannot be serialized to XML, or if the given string is not well-formed. On getting, if the node's document is an HTML document, then the attribute must return the result of running the HTML fragment serialization algorithm on a fictional node whose only child is the node on which the attribute was invoked; otherwise, the node's document is an XML document, and the attribute must return the result of running the XML fragment serialization algorithm on that fictional node instead (this might raise an exception instead of returning a string). On setting, the following steps must be run: 1. Let target be the element whose outerHTML attribute is being set. 2. If target has no parent node, then abort these steps. There would be no way to obtain a reference to the nodes created even if the remaining steps were run. 3. If target's parent node is a Document object, throw a NO_MODIFICATION_ALLOWED_ERR exception and abort these steps. 4. Let parent be target's parent node, unless that is a DocumentFragment node, in which case let parent be an arbitrary body element. 5. If target's document is an HTML document: Invoke the HTML fragment parsing algorithm. If target's document is an XML document: Invoke the XML fragment parsing algorithm. In either case, the algorithm must be invoked with the string being assigned into the outerHTML attribute as the input, and parent as the context element. If this raises an exception, then abort these steps. Otherwise, let new children be targets returned. 6. Set the ownerDocument of all the nodes in new children to target's document. 7. Remove target from its parent node, firing mutation events as appropriate, and then insert in its place all the new children nodes, preserving their order, and again firing mutation events as appropriate. 3.8.6 insertAdjacentHTML() element . insertAdjacentHTML(position, text) Parsed the given string text as HTML or XML and inserts the resulting nodes into the tree in the position given by the position argument, as follows: "beforebegin" Before the element itself. "afterbegin" Just inside the element, before its first child. "beforeend" Just inside the element, after its last child. "afterend" After the element itself. Throws a SYNTAX_ERR exception the arguments have invalid values (e.g., in the case of XML documents, if the given string is not well-formed). Throws a NO_MODIFICATION_ALLOWED_ERR exception if the given position isn't possible (e.g. inserting elements after the root element of a Document). http://dev.w3.org/html5/spec/Overview.html (85 de 570)01-08-2009 6:55:55
- 86. HTML 5 The insertAdjacentHTML(position, text) method, when invoked, must run the following algorithm: 1. Let position and text be the method's first and second arguments, respectively. 2. Let target be the element on which the method was invoked. 3. Use the first matching item from this list: If position is an ASCII case-insensitive match for the string "beforebegin" If position is an ASCII case-insensitive match for the string "afterend" If target has no parent node, then abort these steps. If target's parent node is a Document object, then throw a NO_MODIFICATION_ALLOWED_ERR exception and abort these steps. Otherwise, let context be the parent node of target. If position is an ASCII case-insensitive match for the string "afterbegin" If position is an ASCII case-insensitive match for the string "beforeend" Let context be the same as target. Otherwise Throw a SYNTAX_ERR exception. 4. If target's document is an HTML document: Invoke the HTML fragment parsing algorithm. If target's document is an XML document: Invoke the XML fragment parsing algorithm. In either case, the algorithm must be invoked with text as the input, and the element selected in by the previous step as the context element. If this raises an exception, then abort these steps. Otherwise, let new children be targets returned. 5. Set the ownerDocument of all the nodes in new children to target's document. 6. Use the first matching item from this list: If position is an ASCII case-insensitive match for the string "beforebegin" Insert all the new children nodes immediately before target. If position is an ASCII case-insensitive match for the string "afterbegin" Insert all the new children nodes before the first child of target, if there is one. If there is no such child, append them all to target. If position is an ASCII case-insensitive match for the string "beforeend" Append all the new children nodes to target. If position is an ASCII case-insensitive match for the string "afterend" Insert all the new children nodes immediately after target. The new children nodes must be inserted in a manner that preserves their order and fires mutation events as appropriate. http://dev.w3.org/html5/spec/Overview.html (86 de 570)01-08-2009 6:55:55
- 87. HTML 5 4 The elements of HTML 4.1 The root element 4.1.1 The html element Categories None. Contexts in which this element may be used: As the root element of a document. Wherever a subdocument fragment is allowed in a compound document. Content model: A head element followed by a body element. Content attributes: Global attributes manifest DOM interface: interface HTMLHtmlElement : HTMLElement {}; The html element represents the root of an HTML document. The manifest attribute gives the address of the document's application cache manifest, if there is one. If the attribute is present, the attribute's value must be a valid URL. The manifest attribute only has an effect during the early stages of document load. Changing the attribute dynamically thus has no effect (and thus, no DOM API is provided for this attribute). For the purposes of application cache selection, later base elements cannot affect the resolving of relative URLs in manifest attributes, as the attributes are processed before those elements are seen. 4.2 Document metadata 4.2.1 The head element Categories None. Contexts in which this element may be used: As the first element in an html element. Content model: One or more elements of metadata content, of which exactly one is a title element. Content attributes: Global attributes DOM interface: interface HTMLHeadElement : HTMLElement {}; The head element represents a collection of metadata for the Document. 4.2.2 The title element Categories Metadata content. Contexts in which this element may be used: In a head element containing no other title elements. http://dev.w3.org/html5/spec/Overview.html (87 de 570)01-08-2009 6:55:55
- 88. HTML 5 Content model: Text. Content attributes: Global attributes DOM interface: interface HTMLTitleElement : HTMLElement { attribute DOMString text; }; The title element represents the document's title or name. Authors should use titles that identify their documents even when they are used out of context, for example in a user's history or bookmarks, or in search results. The document's title is often different from its first heading, since the first heading does not have to stand alone when taken out of context. There must be no more than one title element per document. The title element must not contain any elements. The text DOM attribute must return the same value as the textContent DOM attribute on the element. Here are some examples of appropriate titles, contrasted with the top-level headings that might be used on those same pages. <title>Introduction to The Mating Rituals of Bees</title> ... <h1>Introduction</h1> <p>This companion guide to the highly successful <cite>Introduction to Medieval Bee-Keeping</cite> book is... The next page might be a part of the same site. Note how the title describes the subject matter unambiguously, while the first heading assumes the reader knows what the context is and therefore won't wonder if the dances are Salsa or Waltz: <title>Dances used during bee mating rituals</title> ... <h1>The Dances</h1> The string to use as the document's title is given by the document.title DOM attribute. User agents should use the document's title when referring to the document in their user interface. 4.2.3 The base element Categories Metadata content. Contexts in which this element may be used: In a head element containing no other base elements. Content model: Empty. Content attributes: Global attributes href target DOM interface: interface HTMLBaseElement : HTMLElement { attribute DOMString href; attribute DOMString target; }; The base element allows authors to specify the document base URL for the purposes of resolving relative URLs, and the name of the default browsing context for the purposes of following hyperlinks. The element does not represent any content beyond this information. There must be no more than one base element per document. A base element must have either an href attribute, a target attribute, or both. http://dev.w3.org/html5/spec/Overview.html (88 de 570)01-08-2009 6:55:55
- 89. HTML 5 The href content attribute, if specified, must contain a valid URL. A base element, if it has an href attribute, must come before any other elements in the tree that have attributes defined as taking URLs, except the html element (its manifest attribute isn't affected by base elements). If there are multiple base elements with href attributes, all but the first are ignored. The target attribute, if specified, must contain a valid browsing context name or keyword, which specifies which browsing context is to be used as the default when hyperlinks and forms in the Document cause navigation. A base element, if it has a target attribute, must come before any elements in the tree that represent hyperlinks. If there are multiple base elements with target attributes, all but the first are ignored. The href and target DOM attributes must reflect the respective content attributes of the same name. 4.2.4 The link element Categories Metadata content. If the itemprop attribute is present: flow content. If the itemprop attribute is present: phrasing content. Contexts in which this element may be used: Where metadata content is expected. In a noscript element that is a child of a head element. If the itemprop attribute is present: where phrasing content is expected. Content model: Empty. Content attributes: Global attributes href rel media hreflang type sizes Also, the title attribute has special semantics on this element. DOM interface: interface HTMLLinkElement : HTMLElement { attribute boolean disabled; attribute DOMString href; attribute DOMString rel; readonly attribute DOMTokenList relList; attribute DOMString media; attribute DOMString hreflang; attribute DOMString type; attribute DOMString sizes; }; The LinkStyle interface must also be implemented by this element; the styling processing model defines how. [CSSOM] The link element allows authors to link their document to other resources. The destination of the link(s) is given by the href attribute, which must be present and must contain a valid URL. If the href attribute is absent, then the element does not define a link. The types of link indicated (the relationships) are given by the value of the rel attribute, which must be present, and must have a value that is a set of space-separated tokens. The allowed values and their meanings are defined in a later section. If the rel attribute is absent, or if the values used are not allowed according to the definitions in this specification, then the element does not define a link. Two categories of links can be created using the link element. Links to external resources are links to resources that are to be used to augment the current document, and hyperlink links are links to other documents. The link types section defines whether a particular link type is an external resource or a hyperlink. One element can create multiple links (of which some might be external resource links and some might be hyperlinks); exactly which and how many links are created depends on the keywords given in the rel http://dev.w3.org/html5/spec/Overview.html (89 de 570)01-08-2009 6:55:55
- 90. HTML 5 attribute. User agents must process the links on a per-link basis, not a per-element basis. Each link is handled separately. For instance, if there are two link elements with rel="stylesheet", they each count as a separate external resource, and each is affected by its own attributes independently. The exact behavior for links to external resources depends on the exact relationship, as defined for the relevant link type. Some of the attributes control whether or not the external resource is to be applied (as defined below). For external resources that are represented in the DOM (for example, style sheets), the DOM representation must be made available even if the resource is not applied. To obtain the resource, the user agent must resolve the URL given by the href attribute, relative to the element, and then fetch the resulting absolute URL. User agents may opt to only fetch such resources when they are needed, instead of pro-actively fetching all the external resources that are not applied. The semantics of the protocol used (e.g. HTTP) must be followed when fetching external resources. (For example, redirects must be followed and 404 responses must cause the external resource to not be applied.) Fetching external resources must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined below) has been run. The task that is queued by the networking task source once the resource has been fetched must, if the loads were successful, queue a task to fire a simple event called load at the link element; otherwise, if the resource or one of its subresources failed to completely load for any reason (e.g. DNS error, HTTP 404 response, a connection being prematurely closed, unsupported Content-Type), it must instead queue a task to fire a simple event called error at the link element. Non-network errors in processing the resource or its subresources (e.g. CSS parse errors, PNG decoding errors) are not failures for the purposes of this paragraph. The task source for these tasks is the DOM manipulation task source. Interactive user agents should provide users with a means to follow the hyperlinks created using the link element, somewhere within their user interface. The exact interface is not defined by this specification, but it should include the following information (obtained from the element's attributes, again as defined below), in some form or another (possibly simplified), for each hyperlink created with each link element in the document: q The relationship between this document and the resource (given by the rel attribute) q The title of the resource (given by the title attribute). q The address of the resource (given by the href attribute). q The language of the resource (given by the hreflang attribute). q The optimum media for the resource (given by the media attribute). User agents may also include other information, such as the type of the resource (as given by the type attribute). Hyperlinks created with the link element and its rel attribute apply to the whole page. This contrasts with the rel attribute of a and area elements, which indicates the type of a link whose context is given by the link's location within the document. The media attribute says which media the resource applies to. The value must be a valid media query. [MQ] If the link is a hyperlink then the media attribute is purely advisory, and describes for which media the document in question was designed. However, if the link is an external resource link, then the media attribute is prescriptive. The user agent must apply the external resource to views while their state match the listed media and the other relevant conditions apply, and must not apply them otherwise. The external resource might have further restrictions defined within that limit its applicability. For example, a CSS style sheet might have some @media blocks. This specification does not override such further restrictions or requirements. The default, if the media attribute is omitted, is all, meaning that by default links apply to all media. The hreflang attribute on the link element has the same semantics as the hreflang attribute on hyperlink elements. The type attribute gives the MIME type of the linked resource. It is purely advisory. The value must be a valid MIME type, optionally with parameters. [RFC2046] For external resource links, the type attribute is used as a hint to user agents so that they can avoid fetching resources they do not support. If the attribute is present, then the user agent must assume that the resource is of the given type. If the attribute is omitted, but the external resource link type has a default type defined, then the user agent must assume that the resource is of that type. If the UA does not support the given MIME type for the given link relationship, then the UA should not fetch the resource; if the UA does support the given MIME type for the given link relationship, then the UA should fetch the resource. If the attribute is omitted, and the external resource link type does not have a default type defined, but the user agent would fetch the resource if the type was known and supported, then the user agent should fetch the resource under the assumption that it will be supported. User agents must not consider the type attribute authoritative — upon fetching the resource, user agents must not use the type attribute to determine its actual type. Only the actual type (as defined in the next paragraph) is used to determine whether to apply the resource, not the aforementioned assumed type. If the external resource link type defines rules for processing the resource's Content-Type metadata, then those rules apply. Otherwise, if the resource is expected to be an image, user agents may apply the image sniffing rules, with the official type being the type determined from the resource's Content-Type metadata, and use the resulting sniffed type of the resource as if it was the actual type. Otherwise, if neither of these conditions apply or if the user agent opts not to apply the image sniffing rules, then the user agent must use the resource's Content-Type metadata to determine the type of the resource. If there is no type metadata, but the external resource link type has a default type defined, then the user agent must assume that the resource is of that type. http://dev.w3.org/html5/spec/Overview.html (90 de 570)01-08-2009 6:55:55
- 91. HTML 5 The stylesheet link type defines rules for processing the resource's Content-Type metadata. Once the user agent has established the type of the resource, the user agent must apply the resource if it is of a supported type and the other relevant conditions apply, and must ignore the resource otherwise. If a document contains style sheet links labeled as follows: <link rel="stylesheet" href="A" type="text/plain"> <link rel="stylesheet" href="B" type="text/css"> <link rel="stylesheet" href="C"> ...then a compliant UA that supported only CSS style sheets would fetch the B and C files, and skip the A file (since text/plain is not the MIME type for CSS style sheets). For files B and C, it would then check the actual types returned by the server. For those that are sent as text/css, it would apply the styles, but for those labeled as text/plain, or any other type, it would not. If one the two files was returned without a Content-Type metadata, or with a syntactically incorrect type like Content-Type: "null", then the default type for stylesheet links would kick in. Since that default type is text/css, the style sheet would nonetheless be applied. The title attribute gives the title of the link. With one exception, it is purely advisory. The value is text. The exception is for style sheet links, where the title attribute defines alternative style sheet sets. The title attribute on link elements differs from the global title attribute of most other elements in that a link without a title does not inherit the title of the parent element: it merely has no title. The sizes attribute is used with the icon link type. The attribute must not be specified on link elements that do not have a rel attribute that specifies the icon keyword. Some versions of HTTP defined a Link: header, to be processed like a series of link elements. If supported, for the purposes of ordering links defined by HTTP headers must be assumed to come before any links in the document, in the order that they were given in the HTTP entity header. (URIs in these headers are to be processed and resolved according to the rules given in HTTP; the rules of this specification don't apply.) [HTTP] [RFC2068] The DOM attributes href, rel, media, hreflang, and type, and sizes each must reflect the respective content attributes of the same name. The DOM attribute relList must reflect the rel content attribute. The DOM attribute disabled only applies to style sheet links. When the link element defines a style sheet link, then the disabled attribute behaves as defined for the alternative style sheets DOM. For all other link elements it always return false and does nothing on setting. 4.2.5 The meta element Categories Metadata content. If the itemprop attribute is present: flow content. If the itemprop attribute is present: phrasing content. Contexts in which this element may be used: If the charset attribute is present, or if the element's http-equiv attribute is in the Encoding declaration state: in a head element. If the http-equiv attribute is present and in the Encoding declaration state: in a head element. If the http-equiv attribute is present but not in the Encoding declaration state: in a noscript element that is a child of a head element. If the name attribute is present: where metadata content is expected. If the itemprop attribute is present: where phrasing content is expected. Content model: Empty. Content attributes: Global attributes name http-equiv content charset DOM interface: interface HTMLMetaElement : HTMLElement { attribute DOMString name; attribute DOMString httpEquiv; }; The meta element represents various kinds of metadata that cannot be expressed using the title, base, link, style, and script elements. http://dev.w3.org/html5/spec/Overview.html (91 de 570)01-08-2009 6:55:55
- 92. HTML 5 The meta element can represent document-level metadata with the name attribute, pragma directives with the http-equiv attribute, and the file's character encoding declaration when an HTML document is serialized to string form (e.g. for transmission over the network or for disk storage) with the charset attribute. Exactly one of the name, http-equiv, charset, and itemprop attributes must be specified. If either name, http-equiv, or itemprop is specified, then the content attribute must also be specified. Otherwise, it must be omitted. The charset attribute specifies the character encoding used by the document. This is a character encoding declaration. If the attribute is present in an XML document, its value must be an ASCII case-insensitive match for the string "UTF-8" (and the document is therefore required to use UTF-8 as its encoding). The charset attribute on the meta element has no effect in XML documents, and is only allowed in order to facilitate migration to and from XHTML. There must not be more than one meta element with a charset attribute per document. The content attribute gives the value of the document metadata or pragma directive when the element is used for those purposes. The allowed values depend on the exact context, as described in subsequent sections of this specification. If a meta element has a name attribute, it sets document metadata. Document metadata is expressed in terms of name/value pairs, the name attribute on the meta element giving the name, and the content attribute on the same element giving the value. The name specifies what aspect of metadata is being set; valid names and the meaning of their values are described in the following sections. If a meta element has no content attribute, then the value part of the metadata name/value pair is the empty string. The name DOM attribute must reflect the content attribute of the same name. The DOM attribute httpEquiv must reflect the content attribute http-equiv. 4.2.5.1 Standard metadata names This specification defines a few names for the name attribute of the meta element. application-name The value must be a short free-form string that giving the name of the Web application that the page represents. If the page is not a Web application, the application-name metadata name must not be used. User agents may use the application name in UI in preference to the page's title, since the title might include status messages and the like relevant to the status of the page at a particular moment in time instead of just being the name of the application. description The value must be a free-form string that describes the page. The value must be appropriate for use in a directory of pages, e.g. in a search engine. generator The value must be a free-form string that identifies the software used to generate the document. This value must not be used on hand-authored pages. 4.2.5.2 Other metadata names Extensions to the predefined set of metadata names may be registered in the WHATWG Wiki MetaExtensions page. Anyone is free to edit the WHATWG Wiki MetaExtensions page at any time to add a type. These new names must be specified with the following information: Keyword The actual name being defined. The name should not be confusingly similar to any other defined name (e.g. differing only in case). Brief description A short description of what the metadata name's meaning is, including the format the value is required to be in. Link to more details A link to a more detailed description of the metadata name's semantics and requirements. It could be another page on the Wiki, or a link to an external page. Synonyms A list of other names that have exactly the same processing requirements. Authors should not use the names defined to be synonyms, they are only intended to allow user agents to support legacy content. Status One of the following: Proposal The name has not received wide peer review and approval. Someone has proposed it and is using it. Accepted The name has received wide peer review and approval. It has a specification that unambiguously defines how to handle pages that use the name, including when they use it in incorrect ways. Unendorsed The metadata name has received wide peer review and it has been found wanting. Existing pages are using this keyword, but new pages should avoid it. The "brief description" and "link to more details" entries will give details of what authors should use instead, if anything. If a metadata name is added with the "proposal" status and found to be redundant with existing values, it should be removed and listed as a synonym for the existing value. Conformance checkers must use the information given on the WHATWG Wiki MetaExtensions page to establish if a value not explicitly defined in this specification is allowed or not. Conformance checkers may cache this information (e.g. for performance reasons or to avoid the use of unreliable network connectivity). http://dev.w3.org/html5/spec/Overview.html (92 de 570)01-08-2009 6:55:55
- 93. HTML 5 When an author uses a new type not defined by either this specification or the Wiki page, conformance checkers should offer to add the value to the Wiki, with the details described above, with the "proposal" status. This specification does not define how new values will get approved. It is expected that the Wiki will have a community that addresses this. Metadata names whose values are to be URLs must not be proposed or accepted. Links must be represented using the link element, not the meta element. 4.2.5.3 Pragma directives When the http-equiv attribute is specified on a meta element, the element is a pragma directive. The http-equiv attribute is an enumerated attribute. The following table lists the keywords defined for this attribute. The states given in the first cell of the rows with keywords give the states to which those keywords map. Some of the keywords are non-conforming, as noted in the last column. State Keywords Notes Content Language content-language Non-conforming Encoding declaration content-type Default style default-style Refresh refresh When a meta element is inserted into the document, if its http-equiv attribute is present and represents one of the above states, then the user agent must run the algorithm appropriate for that state, as described in the following list: Content language state (http-equiv="content-language") This non-conforming pragma sets the document-wide default language. Until the pragma is successfully processed, there is no document-wide default language. 1. If another meta element with an http-equiv attribute in the Content Language state has already been successfully processed (i.e. when it was inserted the user agent processed it and reached the last step of this list of steps), then abort these steps. 2. If the meta element has no content attribute, or if that attribute's value is the empty string, then abort these steps. 3. Let input be the value of the element's content attribute. 4. Let position point at the first character of input. 5. Skip whitespace. 6. Collect a sequence of characters that are neither space characters nor a U+002C COMMA character (","). 7. Let the document-wide default language be the string that resulted from the previous step. For meta elements with an http-equiv attribute in the Content Language state, the content attribute must have a value consisting of a valid RFC 3066 language code. [RFC3066] This pragma is not exactly equivalent to the HTTP Content-Language header, for instance it only supports one language. [HTTP] Encoding declaration state (http-equiv="content-type") The Encoding declaration state is just an alternative form of setting the charset attribute: it is a character encoding declaration. This state's user agent requirements are all handled by the parsing section of the specification. For meta elements with an http-equiv attribute in the Encoding declaration state, the content attribute must have a value that is an ASCII case-insensitive match for a string that consists of: the literal string "text/html;", optionally followed by any number of space characters, followed by the literal string "charset=", followed by the character encoding name of the character encoding declaration. If the document contains a meta element with an http-equiv attribute in the Encoding declaration state, then the document must not contain a meta element with the charset attribute present. The Encoding declaration state may be used in HTML documents, but elements with an http-equiv attribute in that state must not be used in XML documents. Default style state (http-equiv="default-style") This pragma sets the name of the default alternative style sheet set. 1. If the meta element has no content attribute, or if that attribute's value is the empty string, then abort these steps. 2. Set the preferred style sheet set to the value of the element's content attribute. [CSSOM] Refresh state (http-equiv="refresh") This pragma acts as timed redirect. 1. If another meta element with an http-equiv attribute in the Refresh state has already been successfully processed (i.e. when it was inserted the user agent processed it and reached the last step of this list of steps), then abort these steps. 2. If the meta element has no content attribute, or if that attribute's value is the empty string, then abort these steps. 3. Let input be the value of the element's content attribute. 4. Let position point at the first character of input. 5. Skip whitespace. 6. Collect a sequence of characters in the range U+0030 DIGIT ZERO to U+0039 DIGIT NINE, and parse the resulting string using the rules for parsing non-negative integers. If the sequence of characters collected is the empty string, then no number will have been parsed; abort these steps. Otherwise, let time be the parsed number. 7. Collect a sequence of characters in the range U+0030 DIGIT ZERO to U+0039 DIGIT NINE and U+002E FULL STOP ("."). Ignore any collected characters. 8. Skip whitespace. http://dev.w3.org/html5/spec/Overview.html (93 de 570)01-08-2009 6:55:55
- 94. HTML 5 9. Let url be the address of the current page. 10. If the character in input pointed to by position is a U+003B SEMICOLON (";"), then advance position to the next character. Otherwise, jump to the last step. 11. Skip whitespace. 12. If the character in input pointed to by position is one of U+0055 LATIN CAPITAL LETTER U or U+0075 LATIN SMALL LETTER U, then advance position to the next character. Otherwise, jump to the last step. 13. If the character in input pointed to by position is one of U+0052 LATIN CAPITAL LETTER R or U+0072 LATIN SMALL LETTER R, then advance position to the next character. Otherwise, jump to the last step. 14. If the character in input pointed to by position is one of U+004C LATIN CAPITAL LETTER L or U+006C LATIN SMALL LETTER L, then advance position to the next character. Otherwise, jump to the last step. 15. Skip whitespace. 16. If the character in input pointed to by position is a U+003D EQUALS SIGN ("="), then advance position to the next character. Otherwise, jump to the last step. 17. Skip whitespace. 18. If the character in input pointed to by position is either a U+0027 APOSTROPHE character (') or U+0022 QUOTATION MARK character ("), then let quote be that character, and advance position to the next character. Otherwise, let quote be the empty string. 19. Let url be equal to the substring of input from the character at position to the end of the string. 20. If quote is not the empty string, and there is a character in url equal to quote, then truncate url at that character, so that it and all subsequent characters are removed. 21. Strip any trailing space characters from the end of url. 22. Strip any U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), and U+000D CARRIAGE RETURN (CR) characters from url. 23. Resolve the url value to an absolute URL, relative to the meta element. If this fails, abort these steps. 24. Perform one or more of the following steps: s Set a timer so that in time seconds, adjusted to take into account user or user agent preferences, if the user has not canceled the redirect, the user agent navigates the document's browsing context to url, with replacement enabled, and with the document's browsing context as the source browsing context. s Provide the user with an interface that, when selected, navigates a browsing context to url, with the document's browsing context as the source browsing context. s Do nothing. In addition, the user agent may, as with anything, inform the user of any and all aspects of its operation, including the state of any timers, the destinations of any timed redirects, and so forth. For meta elements with an http-equiv attribute in the Refresh state, the content attribute must have a value consisting either of: r just a valid non-negative integer, or r a valid non-negative integer, followed by a U+003B SEMICOLON (;), followed by one or more space characters, followed by either a U+0055 LATIN CAPITAL LETTER U or a U+0075 LATIN SMALL LETTER U, a U+0052 LATIN CAPITAL LETTER R or a U +0072 LATIN SMALL LETTER R, a U+004C LATIN CAPITAL LETTER L or a U+006C LATIN SMALL LETTER L, a U+003D EQUALS SIGN (=), and then a valid URL. In the former case, the integer represents a number of seconds before the page is to be reloaded; in the latter case the integer represents a number of seconds before the page is to be replaced by the page at the given URL. There must not be more than one meta element with any particular state in the document at a time. 4.2.5.4 Other pragma directives Extensions to the predefined set of pragma directives may, under certain conditions, be registered in the WHATWG Wiki PragmaExtensions page. Such extensions must use a name that is identical to a previously-registered HTTP header defined in an RFC, and must have behavior identical to that described for the HTTP header. Pragma directions corresponding to headers describing metadata, or not requiring specific user agent processing, must not be registered; instead, use metadata names. Pragma directions corresponding to headers that affect the HTTP processing model (e.g. caching) must not be registered, as they would result in HTTP-level behavior being different for user agents that implement HTML than for user agents that do not. Anyone is free to edit the WHATWG Wiki PragmaExtensions page at any time to add a pragma directive satisfying these conditions. Such registrations must specify the following information: Keyword The actual name being defined. Brief description A short description of the purpose of the pragma directive. Specification A link to an IETF RFC defining the corresponding HTTP header. Conformance checkers must use the information given on the WHATWG Wiki PragmaExtensions page to establish if a value not explicitly defined in this specification is allowed or not. Conformance checkers may cache this information (e.g. for performance reasons or to avoid the use of unreliable network connectivity). 4.2.5.5 Specifying the document's character encoding A character encoding declaration is a mechanism by which the character encoding used to store or transmit a document is specified. The following restrictions apply to character encoding declarations: q The character encoding name given must be the name of the character encoding used to serialize the file. http://dev.w3.org/html5/spec/Overview.html (94 de 570)01-08-2009 6:55:55
- 95. HTML 5 q The value must be a valid character encoding name, and must be the preferred name for that encoding. [IANACHARSET] q The character encoding declaration must be serialized without the use of character references or character escapes of any kind. q The element containing the character encoding declaration must be serialized completely within the first 512 bytes of the document. q There can only be one character encoding declaration in the document. If an HTML document does not start with a BOM, and if its encoding is not explicitly given by Content-Type metadata, then the character encoding used must be an ASCII-compatible character encoding, and, in addition, if that encoding isn't US-ASCII itself, then the encoding must be specified using a meta element with a charset attribute or a meta element with an http-equiv attribute in the Encoding declaration state. If an HTML document contains a meta element with a charset attribute or a meta element with an http-equiv attribute in the Encoding declaration state, then the character encoding used must be an ASCII-compatible character encoding. Authors should not use JIS-X-0208 (JIS_C6226-1983), JIS-X-0212 (JIS_X0212-1990), encodings based on ISO-2022, and encodings based on EBCDIC. Authors should not use UTF-32. Authors must not use the CESU-8, UTF-7, BOCU-1 and SCSU encodings. [RFC1345] [RFC1468] [RFC2237] [RFC1554] [RFC1922] [RFC1557] [UTF32] [CESU8] [UTF7] [BOCU1] [SCSU] Authors are encouraged to use UTF-8. Conformance checkers may advise against authors using legacy encodings. Authoring tools should default to using UTF-8 for newly-created documents. Using non-UTF-8 encodings can have unexpected results on form submission and URL encodings, which use the document's character encoding by default. In XHTML, the XML declaration should be used for inline character encoding information, if necessary. 4.2.6 The style element Categories Metadata content. If the scoped attribute is present: flow content. Contexts in which this element may be used: If the scoped attribute is absent: where metadata content is expected. If the scoped attribute is absent: in a noscript element that is a child of a head element. If the scoped attribute is present: where flow content is expected, but before any other flow content other than other style elements and inter-element whitespace. Content model: Depends on the value of the type attribute. Content attributes: Global attributes media type scoped Also, the title attribute has special semantics on this element. DOM interface: interface HTMLStyleElement : HTMLElement { attribute boolean disabled; attribute DOMString media; attribute DOMString type; attribute boolean scoped; }; The LinkStyle interface must also be implemented by this element; the styling processing model defines how. [CSSOM] The style element allows authors to embed style information in their documents. The style element is one of several inputs to the styling processing model. The element does not represent content for the user. If the type attribute is given, it must contain a valid MIME type, optionally with parameters, that designates a styling language. [RFC2046] If the attribute is absent, the type defaults to text/css. [RFC2138] When examining types to determine if they support the language, user agents must not ignore unknown MIME parameters — types with unknown parameters must be assumed to be unsupported. The media attribute says which media the styles apply to. The value must be a valid media query. [MQ] User agents must apply the styles to views while their state match the listed media, and must not apply them otherwise. http://dev.w3.org/html5/spec/Overview.html (95 de 570)01-08-2009 6:55:55
- 96. HTML 5 The styles might be further limited in scope, e.g. in CSS with the use of @media blocks. This specification does not override such further restrictions or requirements. The default, if the media attribute is omitted, is all, meaning that by default styles apply to all media. The scoped attribute is a boolean attribute. If set, it indicates that the styles are intended just for the subtree rooted at the style element's parent element, as opposed to the whole Document. If the scoped attribute is present, then the user agent must apply the specified style information only to the style element's parent element (if any), and that element's child nodes. Otherwise, the specified styles must, if applied, be applied to the entire document. The title attribute on style elements defines alternative style sheet sets. If the style element has no title attribute, then it has no title; the title attribute of ancestors does not apply to the style element. [CSSOM] The title attribute on style elements, like the title attribute on link elements, differs from the global title attribute in that a style block without a title does not inherit the title of the parent element: it merely has no title. All descendant elements must be processed, according to their semantics, before the style element itself is evaluated. For styling languages that consist of pure text, user agents must evaluate style elements by passing the concatenation of the contents of all the text nodes that are direct children of the style element (not any other nodes such as comments or elements), in tree order, to the style system. For XML-based styling languages, user agents must pass all the child nodes of the style element to the style system. All URLs found by the styling language's processor must be resolved, relative to the element (or as defined by the styling language), when the processor is invoked. Once the element has been evaluated, if it had no subresources or once all the subresources it uses have been fetched, the user agent must queue a task to fire a simple event called load at the style element. If the resource has a subresource that fails to completely load for any reason (e.g. DNS error, HTTP 404 response, the connection being prematurely closed, unsupported Content-Type), the user agent must instead queue a task to fire a simple event called error at the style element. Non-network errors in the processing of the element's contents or its subresources (e.g. CSS parse errors) are not failures for the purposes of this paragraph. The style element must delay the load event of the element's document until one of these tasks has been queued. The task source for these tasks is the DOM manipulation task source. This specification does not specify a style system, but CSS is expected to be supported by most Web browsers. [CSS] The media, type and scoped DOM attributes must reflect the respective content attributes of the same name. The DOM disabled attribute behaves as defined for the alternative style sheets DOM. 4.2.7 Styling The link and style elements can provide styling information for the user agent to use when rendering the document. The DOM Styling specification specifies what styling information is to be used by the user agent and how it is to be used. [CSSOM] The style and link elements implement the LinkStyle interface. [CSSOM] For style elements, if the user agent does not support the specified styling language, then the sheet attribute of the element's LinkStyle interface must return null. Similarly, link elements that do not represent external resource links that contribute to the styling processing model (i.e. that do not have a stylesheet keyword in their rel attribute), and link elements whose specified resource has not yet been fetched, or is not in a supported styling language, must have their LinkStyle interface's sheet attribute return null. Otherwise, the LinkStyle interface's sheet attribute must return a StyleSheet object with the following properties: [CSSOM] The style sheet type The style sheet type must be the same as the style's specified type. For style elements, this is the same as the type content attribute's value, or text/css if that is omitted. For link elements, this is the Content-Type metadata of the specified resource. The style sheet location For link elements, the location must be the result of resolving the URL given by the element's href content attribute, relative to the element, or the empty string if that fails. For style elements, there is no location. The style sheet media The media must be the same as the value of the element's media content attribute, or the empty string, if the attribute is omitted. The style sheet title The title must be the same as the value of the element's title content attribute, if the attribute is present and has a non-empty value. If the attribute is absent or its value is the empty string, then the style sheet does not have a title (it is the empty string). The title is used for defining alternative style sheet sets. The style sheet alternate flag For link elements, true if the link is an alternative stylesheet. In all other cases, false. The disabled DOM attribute on link and style elements must return false and do nothing on setting, if the sheet attribute of their LinkStyle interface is null. Otherwise, it must return the value of the StyleSheet interface's disabled attribute on getting, and forward the new value to that same attribute on setting. The rules for handling alternative style sheets are defined in the CSS object model specification. [CSSOM] 4.3 Scripting Scripts allow authors to add interactivity to their documents. http://dev.w3.org/html5/spec/Overview.html (96 de 570)01-08-2009 6:55:55
- 97. HTML 5 Authors are encouraged to use declarative alternatives to scripting where possible, as declarative mechanisms are often more maintainable, and many users disable scripting. For example, instead of using script to show or hide a section to show more details, the details element could be used. Authors are also encouraged to make their applications degrade gracefully in the absence of scripting support. For example, if an author provides a link in a table header to dynamically resort the table, the link could also be made to function without scripts by requesting the sorted table from the server. 4.3.1 The script element Categories Metadata content. Flow content. Phrasing content. Contexts in which this element may be used: Where metadata content is expected. Where phrasing content is expected. Content model: If there is no src attribute, depends on the value of the type attribute. If there is a src attribute, the element must be either empty or contain only script documentation. Content attributes: Global attributes src async defer type charset DOM interface: interface HTMLScriptElement : HTMLElement { attribute DOMString src; attribute boolean async; attribute boolean defer; attribute DOMString type; attribute DOMString charset; attribute DOMString text; }; The script element allows authors to include dynamic script and data blocks in their documents. The element does not represent content for the user. When used to include dynamic scripts, the scripts may either be embedded inline or may be imported from an external file using the src attribute. If the language is not that described by "text/javascript", then the type attribute must be present. If the type attribute is present, its value must be the type of the script's language. When used to include data blocks, the data must be embedded inline, the format of the data must be given using the type attribute, and the src attribute must not be specified. The type attribute gives the language of the script or format of the data. If the attribute is present, its value must be a valid MIME type, optionally with parameters. The charset parameter must not be specified. (The default, which is used if the attribute is absent, is "text/javascript".) [RFC2046] The src attribute, if specified, gives the address of the external script resource to use. The value of the attribute must be a valid URL identifying a script resource of the type given by the type attribute, if the attribute is present, or of the type "text/javascript", if the attribute is absent. The charset attribute gives the character encoding of the external script resource. The attribute must not be specified if the src attribute is not present. If the attribute is set, its value must be a valid character encoding name, must be the preferred name for that encoding, and must match the encoding given in the charset parameter of the Content-Type metadata of the external file, if any. [IANACHARSET] The async and defer attributes are boolean attributes that indicate how the script should be executed. There are three possible modes that can be selected using these attributes. If the async attribute is present, then the script will be executed asynchronously, as soon as it is available. If the async attribute is not present but the defer attribute is present, then the script is executed when the page has finished parsing. If neither attribute is present, then the script is fetched and executed immediately, before the user agent continues parsing the page. The exact processing details for these attributes is described below. The defer attribute may be specified even if the async attribute is specified, to cause legacy Web browsers that only support defer (and not async) to fall back to the defer behavior instead of the synchronous blocking behavior that is the default. Changing the src, type, charset, async, and defer attributes dynamically has no direct effect; these attribute are only used at specific times described below (namely, when the element is inserted into the document). http://dev.w3.org/html5/spec/Overview.html (97 de 570)01-08-2009 6:55:55
- 98. HTML 5 script elements have four associated pieces of metadata. The first is a flag indicating whether or not the script block has been "already executed". Initially, script elements must have this flag unset (script blocks, when created, are not "already executed"). When a script element is cloned, the "already executed" flag, if set, must be propagated to the clone when it is created. The second is a flag indicating whether the element was "parser-inserted". This flag is set by the HTML parser and is used to handle document. write() calls. The third and fourth pieces of metadata are the script block's type and the script block's character encoding. They are determined when the script is run, based on the attributes on the element at that time. When a script element that is neither marked as having "already executed" nor marked as being "parser-inserted" experiences one of the events listed in the following list, the user agent must run the script element: q The script element gets inserted into a document. q The script element's child nodes are changed. q The script element has a src attribute set where previously the element had no such attribute. Running a script: When a script element is to be run, the user agent must act as follows: 1. If either: r the script element has a type attribute and its value is the empty string, or r the script element has no type attribute but it has a language attribute and that attribute's value is the empty string, or r the script element has neither a type attribute nor a language attribute, then ...let the script block's type for this script element be "text/javascript". Otherwise, if the script element has a type attribute, let the script block's type for this script element be the value of that attribute. Otherwise, the element has a non-empty language attribute; let the script block's type for this script element be the concatenation of the string "text/" followed by the value of the language attribute. The language attribute is never conforming, and is always ignored if there is a type attribute present. 2. If the script element has a charset attribute, then let the script block's character encoding for this script element be the encoding given by the charset attribute. Otherwise, let the script block's character encoding for this script element be the same as the encoding of the document itself. 3. If scripting is disabled for the script element, or if the user agent does not support the scripting language given by the script block's type for this script element, then the user agent must abort these steps at this point. The script is not executed. 4. If the element has no src attribute, and its child nodes consist only of comment nodes and empty text nodes, then the user agent must abort these steps at this point. The script is not executed. 5. The user agent must set the element's "already executed" flag. 6. If the element has a src attribute, then the value of that attribute must be resolved relative to the element, and if that is successful, the specified resource must then be fetched. For historical reasons, if the URL is a javascript: URL, then the user agent must not, despite the requirements in the definition of the fetching algorithm, actually execute the given script; instead the user agent must act as if it had received an empty HTTP 400 response. Once the resource's Content Type metadata is available, if it ever is, apply the algorithm for extracting an encoding from a Content-Type to it. If this returns an encoding, and the user agent supports that encoding, then let the script block's character encoding be that encoding. Once the fetching process has completed, and the script has completed loading, the user agent will have to complete the steps described below. (If the parser is still active at that time, those steps defer to the parser to handle the execution of pending scripts.) For performance reasons, user agents may start fetching the script as soon as the attribute is set, instead, in the hope that the element will be inserted into the document. Either way, once the element is inserted into the document, the load must have started. If the UA performs such prefetching, but the element is never inserted in the document, or the src attribute is dynamically changed, then the user agent will not execute the script, and the fetching process will have been effectively wasted. 7. Then, the first of the following options that describes the situation must be followed: If the document is still being parsed, and the element has a defer attribute, and the element does not have an async attribute The element must be added to the end of the list of scripts that will execute when the document has finished parsing. If the element has an async attribute and a src attribute The element must be added to the end of the list of scripts that will execute asynchronously. If the element has an async attribute but no src attribute, and the list of scripts that will execute asynchronously is not empty The element must be added to the end of the list of scripts that will execute asynchronously. If the element has a src attribute and has been flagged as "parser-inserted" The element is the pending external script. (There can only be one such script at a time.) If the element has a src attribute The element must be added to the end of the list of scripts that will execute as soon as possible. Otherwise http://dev.w3.org/html5/spec/Overview.html (98 de 570)01-08-2009 6:55:55
- 99. HTML 5 The user agent must immediately execute the script block, even if other scripts are already executing. Fetching an external script must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined below) has been run. When a script completes loading: If the script element was added to one of the lists mentioned above and the document is still being parsed, then the parser handles it. Otherwise, the UA must run the following steps as the task that the networking task source places on the task queue: If the script element was added to the list of scripts that will execute when the document has finished parsing: 1. If the script element is not the first element in the list, then do nothing yet. Stop going through these steps. 2. Otherwise, execute the script block (the first element in the list). 3. Remove the script element from the list (i.e. shift out the first entry in the list). 4. If there are any more entries in the list, and if the script associated with the element that is now the first in the list is already loaded, then jump back to step 2 to execute it. The scripts in the list of scripts that will execute when the document has finished parsing can also get executed prematurely if the innerHTML attribute is set on a node in the document. If the script element was added to the list of scripts that will execute asynchronously: 1. If the script is not the first element in the list, then do nothing yet. Stop going through these steps. 2. Execute the script block (the first element in the list). 3. Remove the script element from the list (i.e. shift out the first entry in the list). 4. If there are any more scripts in the list, and the element now at the head of the list had no src attribute when it was added to the list, or had one, but its associated script has finished loading, then jump back to step 2 to execute the script associated with this element. If the script element was added to the list of scripts that will execute as soon as possible: 1. Execute the script block. 2. Remove the script element from the list. Executing a script block: When the steps above require that the script block be executed, the user agent must act as follows: If the load resulted in an error (for example a DNS error, or an HTTP 404 error) Executing the script block must just consist of firing a simple event called error at the element. If the load was successful 1. Initialize the script block's source as follows: If the script is from an external file The contents of that file, interpreted as string of Unicode characters, are the script source. For each of the rows in the following table, starting with the first one and going down, if the file has as many or more bytes available than the number of bytes in the first column, and the first bytes of the file match the bytes given in the first column, then set the script block's character encoding to the encoding given in the cell in the second column of that row, irrespective of any previous value: Bytes in Hexadecimal Encoding FE FF UTF-16BE FF FE UTF-16LE EF BB BF UTF-8 This step looks for Unicode Byte Order Marks (BOMs). The file must then be converted to Unicode using the character encoding given by the script block's character encoding. If the script is inline and the script block's type is a text-based language The value of the DOM text attribute at the time the "running a script" algorithm was first invoked is the script source. If the script is inline and the script block's type is an XML-based language The child nodes of the script element at the time the "running a script" algorithm was first invoked are the script source. 2. Create a script from the script element node, using the the script block's source and the the script block's type. http://dev.w3.org/html5/spec/Overview.html (99 de 570)01-08-2009 6:55:55
- 100. HTML 5 This is where the script is compiled and actually executed. 3. Fire a simple event called load at the script element. The DOM attributes src, type, charset, async, and defer, each must reflect the respective content attributes of the same name. script . text [ = value ] Returns the contents of the element, ignoring child nodes that aren't text nodes. Can be set, to replace the element's children with the given value. The DOM attribute text must return a concatenation of the contents of all the text nodes that are direct children of the script element (ignoring any other nodes such as comments or elements), in tree order. On setting, it must act the same way as the textContent DOM attribute. In this example, two script elements are used. One embeds an external script, and the other includes some data. <script src="game-engine.js"></script> <script type="text/x-game-map"> ........U.........e o............A....e .....A.....AAA....e .A..AAA...AAAAA...e </script> The data in this case might be used by the script to generate the map of a video game. The data doesn't have to be used that way, though; maybe the map data is actually embedded in other parts of the page's markup, and the data block here is just used by the site's search engine to help users who are looking for particular features in their game maps. When inserted using the document.write() method, script elements execute (typically synchronously), but when inserted using innerHTML and outerHTML attributes, they do not execute at all. 4.3.1.1 Scripting languages A user agent is said to support the scripting language if the script block's type matches the MIME type of a scripting language that the user agent implements. The following lists some MIME types and the languages to which they refer: application/ecmascript application/javascript application/x-ecmascript application/x-javascript text/ecmascript text/javascript text/javascript1.0 text/javascript1.1 text/javascript1.2 text/javascript1.3 text/javascript1.4 text/javascript1.5 text/jscript text/livescript text/x-ecmascript text/x-javascript JavaScript. [ECMA262] text/javascript;e4x=1 JavaScript with ECMAScript for XML. [ECMA357] User agents may support other MIME types and other languages. When examining types to determine if they support the language, user agents must not ignore unknown MIME parameters — types with unknown parameters must be assumed to be unsupported. 4.3.1.2 Inline documentation for external scripts http://dev.w3.org/html5/spec/Overview.html (100 de 570)01-08-2009 6:55:55
- 101. HTML 5 If a script element's src attribute is specified, then the contents of the script element, if any, must be such that the value of the DOM text attribute, which is derived from the element's contents, matches the documentation production in the following ABNF, the character set for which is Unicode. [ABNF] documentation = *( *( space / tab / comment ) [ line-comment ] newline ) comment = slash star *( not-star / star not-slash ) 1*star slash line-comment = slash slash *not-newline ; characters tab = %x0009 ; U+0009 TAB newline = %x000A ; U+000A LINE FEED space = %x0020 ; U+0020 SPACE star = %x002A ; U+002A ASTERISK slash = %x002F ; U+002F SOLIDUS not-newline = %x0000-0009 / %x000B-10FFFF ; a Unicode character other than U+000A LINE FEED not-star = %x0000-0029 / %x002B-10FFFF ; a Unicode character other than U+002A ASTERISK not-slash = %x0000-002E / %x0030-10FFFF ; a Unicode character other than U+002F SOLIDUS This allows authors to include documentation, such as license information or API information, inside their documents while still referring to external script files. The syntax is constrained so that authors don't accidentally include what looks like valid script while also providing a src attribute. <script src="cool-effects.js"> // create new instances using: // var e = new Effect(); // start the effect using .play, stop using .stop: // e.play(); // e.stop(); </script> 4.3.2 The noscript element Categories Metadata content. Flow content. Phrasing content. Contexts in which this element may be used: In a head element of an HTML document, if there are no ancestor noscript elements. Where phrasing content is expected in HTML documents, if there are no ancestor noscript elements. Content model: When scripting is disabled, in a head element: in any order, zero or more link elements, zero or more style elements, and zero or more meta elements. When scripting is disabled, not in a head element: transparent, but there must be no noscript element descendants. Otherwise: text that conforms to the requirements given in the prose. Content attributes: Global attributes DOM interface: Uses HTMLElement. The noscript element represents nothing if scripting is enabled, and represents its children if scripting is disabled. It is used to present different markup to user agents that support scripting and those that don't support scripting, by affecting how the document is parsed. When used in HTML documents, the allowed content model is as follows: In a head element, if scripting is disabled for the noscript element The noscript element must contain only link, style, and meta elements. In a head element, if scripting is enabled for the noscript element The noscript element must contain only text, except that invoking the HTML fragment parsing algorithm with the noscript element as the context element and the text contents as the input must result in a list of nodes that consists only of link, style, and meta elements, and no parse errors. Outside of head elements, if scripting is disabled for the noscript element The noscript element's content model is transparent, with the additional restriction that a noscript element must not have a noscript element as an ancestor (that is, noscript can't be nested). Outside of head elements, if scripting is enabled for the noscript element The noscript element must contain only text, except that the text must be such that running the following algorithm results in a conforming document with no noscript elements and no script elements, and such that no step in the algorithm causes an HTML parser to flag a parse error: http://dev.w3.org/html5/spec/Overview.html (101 de 570)01-08-2009 6:55:55
- 102. HTML 5 1. Remove every script element from the document. 2. Make a list of every noscript element in the document. For every noscript element in that list, perform the following steps: 1. Let the parent element be the parent element of the noscript element. 2. Take all the children of the parent element that come before the noscript element, and call these elements the before children. 3. Take all the children of the parent element that come after the noscript element, and call these elements the after children. 4. Let s be the concatenation of all the text node children of the noscript element. 5. Set the innerHTML attribute of the parent element to the value of s. (This, as a side-effect, causes the noscript element to be removed from the document.) 6. Insert the before children at the start of the parent element, preserving their original relative order. 7. Insert the after children at the end of the parent element, preserving their original relative order. All these contortions are required because, for historical reasons, the noscript element is handled differently by the HTML parser based on whether scripting was enabled or not when the parser was invoked. The element is not allowed in XML, because in XML the parser is not affected by such state, and thus the element would not have the desired effect. The noscript element must not be used in XML documents. The noscript element is only effective in the the HTML syntax, it has no effect in the the XHTML syntax. The noscript element has no other requirements. In particular, children of the noscript element are not exempt from form submission, scripting, and so forth, even when scripting is enabled for the element. 4.4 Sections 4.4.1 The body element Categories Sectioning root. Contexts in which this element may be used: As the second element in an html element. Content model: Flow content. Content attributes: Global attributes onafterprint onbeforeprint onbeforeunload onblur onerror onfocus onhashchange onload onmessage onoffline ononline onpopstate onredo onresize onstorage onundo onunload DOM interface: interface HTMLBodyElement : HTMLElement { attribute Function onafterprint; attribute Function onbeforeprint; attribute Function onbeforeunload; attribute Function onblur; attribute Function onerror; attribute Function onfocus; attribute Function onhashchange; http://dev.w3.org/html5/spec/Overview.html (102 de 570)01-08-2009 6:55:55
- 103. HTML 5 attribute Function onload; attribute Function onmessage; attribute Function onoffline; attribute Function ononline; attribute Function onpopstate; attribute Function onredo; attribute Function onresize; attribute Function onstorage; attribute Function onundo; attribute Function onunload; }; The body element represents the main content of the document. In conforming documents, there is only one body element. The document.body DOM attribute provides scripts with easy access to a document's body element. Some DOM operations (for example, parts of the drag and drop model) are defined in terms of "the body element". This refers to a particular element in the DOM, as per the definition of the term, and not any arbitrary body element. The body element exposes as event handler content attributes a number of the event handler attributes of the Window object. It also mirrors their event handler DOM attributes. The onblur, onerror, onfocus, and onload event handler attributes of the Window object, exposed on the body element, shadow the generic event handler attributes with the same names normally supported by HTML elements. Thus, for example, a bubbling error event fired on a child of the body element of a Document would first trigger the onerror event handler content attributes of that element, then that of the root html element, and only then would it trigger the onerror event handler content attribute on the body element. This is because the event would bubble from the target, to the body, to the html, to the Document, to the Window, and the event handler attribute on the body is watching the Window not the body. A regular event listener attached to the body using addEventListener(), however, would fire when the event bubbled through the body and not when it reaches the Window object. 4.4.2 The section element Categories Flow content. Sectioning content. formatBlock candidate. Contexts in which this element may be used: Where flow content is expected. Content model: Flow content. Content attributes: Global attributes cite DOM interface: interface HTMLSectionElement : HTMLElement { attribute DOMString cite; }; The section element represents a generic document or application section. A section, in this context, is a thematic grouping of content, typically with a heading, possibly with a footer. Examples of sections would be chapters, the various tabbed pages in a tabbed dialog box, or the numbered sections of a thesis. A Web site's home page could be split into sections for an introduction, news items, contact information. The cite attribute may be used if the content of the section was taken from another page (e.g. syndicating content from multiple sources on one page). The attribute, if present, must contain a valid URL referencing the original source. To obtain the corresponding citation link, the value of the attribute must be resolved relative to the element. User agents should allow users to follow such citation links. The cite DOM attribute must reflect the element's cite content attribute. The section element is not a generic container element. When an element is needed for styling purposes or as a convenience for scripting, authors are encouraged to use the div element instead. A general rule is that the section element is appropriate only if the element's contents would be listed explicitly in the document's outline. In the following example, we see an article (part of a larger Web page) about apples, containing two short sections. http://dev.w3.org/html5/spec/Overview.html (103 de 570)01-08-2009 6:55:55
- 104. HTML 5 <article> <hgroup> <h1>Apples</h1> <h2>Tasty, delicious fruit!</h2> </hgroup> <p>The apple is the pomaceous fruit of the apple tree.</p> <section> <h1>Red Delicious</h1> <p>These bright red apples are the most common found in many supermarkets.</p> </section> <section> <h1>Granny Smith</h1> <p>These juicy, green apples make a great filling for apple pies.</p> </section> </article> Notice how the use of section means that the author can use h1 elements throughout, without having to worry about whether a particular section is at the top level, the second level, the third level, and so on. 4.4.3 The nav element Categories Flow content. Sectioning content. formatBlock candidate. Contexts in which this element may be used: Where flow content is expected. Content model: Flow content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The nav element represents a section of a page that links to other pages or to parts within the page: a section with navigation links. Not all groups of links on a page need to be in a nav element — only sections that consist of major navigation blocks are appropriate for the nav element. In particular, it is common for footers to have a list of links to various key parts of a site, but the footer element is more appropriate in such cases, and no nav element is necessary for those links. In the following example, the page has several places where links are present, but only one of those places is considered a navigation section. <body> <header> <h1>Wake up sheeple!</h1> <p><a href="news.html">News</a> - <a href="blog.html">Blog</a> - <a href="forums.html">Forums</a></p> <p>Last Modified: <time>2009-04-01</time></p> <nav> <h1>Navigation</h1> <ul> <li><a href="articles.html">Index of all articles</a></li> <li><a href="today.html">Things sheeple need to wake up for today</a></li> <li><a href="successes.html">Sheeple we have managed to wake</a></li> </ul> </nav> </header> <article> <p>...page content would be here...</p> </article> <footer> <p>Copyright © 2006 The Example Company</p> <p><a href="about.html">About</a> - <a href="policy.html">Privacy Policy</a> - <a href="contact.html">Contact Us</a></p> </footer> </body> http://dev.w3.org/html5/spec/Overview.html (104 de 570)01-08-2009 6:55:55
- 105. HTML 5 In the following example, there are two nav elements, one for primary navigation around the site, and one for secondary navigation around the page itself. <body> <h1>The Wiki Center Of Exampland</h1> <nav> <ul> <li><a href="/">Home</a></li> <li><a href="/events">Current Events</a></li> ...more... </ul> </nav> <article> <header> <h1>Demos in Exampland</h1> <nav> <ul> <li><a href="#public">Public demonstrations</a></li> <li><a href="#destroy">Demolitions</a></li> ...more... </ul> </nav> </header> <section id="public"> <h1>Public demonstrations</h1> <p>...more...</p> </section> <section id="destroy"> <h1>Demolitions</h1> <p>...more...</p> </section> ...more... <footer> <p><a href="?edit">Edit</a> | <a href="?delete">Delete</a> | <a href="?Rename">Rename</a></p> </footer> </article> <footer> <p><small>© copyright 1998 Exampland Emperor</small></p> </footer> </body> 4.4.4 The article element Categories Flow content. Sectioning content. formatBlock candidate. Contexts in which this element may be used: Where flow content is expected. Content model: Flow content. Content attributes: Global attributes cite pubdate DOM interface: interface HTMLArticleElement : HTMLElement { attribute DOMString cite; attribute DOMString pubDate; }; The article element represents a section of a page that consists of a composition that forms an independent part of a document, page, or site. This could be a forum post, a magazine or newspaper article, a Web log entry, a user-submitted comment, or any other independent item of content. http://dev.w3.org/html5/spec/Overview.html (105 de 570)01-08-2009 6:55:55
- 106. HTML 5 An article element is "independent" in the sense that its contents could stand alone, for example in syndication. When article elements are nested, the inner article elements represent articles that are in principle related to the contents of the outer article. For instance, a Web log entry on a site that accepts user-submitted comments could represent the comments as article elements nested within the article element for the Web log entry. Author information associated with an article element (q.v. the address element) does not apply to nested article elements. The cite attribute may be used if the content of the article was taken from another page (e.g. syndicating content from multiple sources on one page). The attribute, if present, must contain a valid URL referencing the original source. To obtain the corresponding citation link, the value of the attribute must be resolved relative to the element. User agents should allow users to follow such citation links. The pubdate attribute may be used to specify the time and date that the article was first published. If present, the pubdate attribute must be a valid global date and time string value. The cite DOM attribute must reflect the element's cite content attribute. The pubDate DOM attribute must reflect the element's pubdate content attribute. 4.4.5 The aside element Categories Flow content. Sectioning content. formatBlock candidate. Contexts in which this element may be used: Where flow content is expected. Content model: Flow content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The aside element represents a section of a page that consists of content that is tangentially related to the content around the aside element, and which could be considered separate from that content. Such sections are often represented as sidebars in printed typography. The element can also be used for typographical effects like pull quotes. It's not appropriate to use the aside element just for parentheticals, since those are part of the main flow of the document. The following example shows how an aside is used to mark up background material on Switzerland in a much longer news story on Europe. <aside> <h1>Switzerland</h1> <p>Switzerland, a land-locked country in the middle of geographic Europe, has not joined the geopolitical European Union, though it is a signatory to a number of European treaties.</p> </aside> The following example shows how an aside is used to mark up a pull quote in a longer article. ... <p>He later joined a large company, continuing on the same work. <q>I love my job. People ask me what I do for fun when I'm not at work. But I'm paid to do my hobby, so I never know what to answer. Some people wonder what they would do if they didn't have to work... but I know what I would do, because I was unemployed for a year, and I filled that time doing exactly what I do now.</q></p> <aside> <q> People ask me what I do for fun when I'm not at work. But I'm paid to do my hobby, so I never know what to answer. </q> </aside> <p>Of course his work — or should that be hobby? — isn't his only passion. He also enjoys other pleasures.</p> http://dev.w3.org/html5/spec/Overview.html (106 de 570)01-08-2009 6:55:55
- 107. HTML 5 ... 4.4.6 The h1, h2, h3, h4, h5, and h6 elements Categories Flow content. Heading content. formatBlock candidate. Contexts in which this element may be used: Where flow content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: interface HTMLHeadingElement : HTMLElement {}; These elements represent headings for their sections. The semantics and meaning of these elements are defined in the section on headings and sections. These elements have a rank given by the number in their name. The h1 element is said to have the highest rank, the h6 element has the lowest rank, and two elements with the same name have equal rank. 4.4.7 The hgroup element Categories Flow content. Heading content. formatBlock candidate. Contexts in which this element may be used: Where flow content is expected. Content model: One or more h1, h2, h3, h4, h5, and/or h6 elements. Content attributes: Global attributes DOM interface: Uses HTMLElement. The hgroup element represents the heading of a section. The element is used to group a set of h1–h6 elements when the heading has multiple levels, such as subheadings, alternative titles, or taglines. The point of hgroup is to mask an h2 element (that acts as a secondary title) from the outline algorithm. For the purposes of document summaries, outlines, and the like, the text of hgroup elements is defined to be the text of the highest ranked h1–h6 element descendant of the hgroup element, if there are any such elements, and the first such element if there are multiple elements with that rank. If there are no such elements, then the text of the hgroup element is the empty string. Other elements of heading content in the hgroup element indicate subheadings or subtitles. The rank of an hgroup element is the rank of the highest-ranked h1–h6 element descendant of the hgroup element, if there are any such elements, or otherwise the same as for an h1 element (the highest rank). The section on headings and sections defines how hgroup elements are assigned to individual sections. Here are some examples of valid headings. In each case, the emphasized text represents the text that would be used as the heading in an application extracting heading data and ignoring subheadings. <hgroup> <h1>The reality dysfunction</h1> <h2>Space is not the only void</h2> http://dev.w3.org/html5/spec/Overview.html (107 de 570)01-08-2009 6:55:55
- 108. HTML 5 </hgroup> <hgroup> <h1>Dr. Strangelove</h1> <h2>Or: How I Learned to Stop Worrying and Love the Bomb</h2> </hgroup> 4.4.8 The header element Categories Flow content. formatBlock candidate. Contexts in which this element may be used: Where flow content is expected. Content model: Flow content, but with no header or footer element descendants. Content attributes: Global attributes DOM interface: Uses HTMLElement. The header element represents a group of introductory or navigational aids. A header element is intended to usually contain the section's heading (an h1–h6 element or an hgroup element), but this is not required. The header element can also be used to wrap a section's table of contents, a search form, or any relevant logos. Here are some sample headers. This first one is for a game: <header> <p>Welcome to...</p> <h1>Voidwars!</h1> </header> The following snippet shows how the element can be used to mark up a specification's header: <header> <hgroup> <h1>Scalable Vector Graphics (SVG) 1.2</h1> <h2>W3C Working Draft 27 October 2004</h2> </hgroup> <dl> <dt>This version:</dt> <dd><a href="http://www.w3.org/TR/2004/WD-SVG12-20041027/">http://www.w3.org/TR/2004/WD-SVG12-20041027/</a></dd> <dt>Previous version:</dt> <dd><a href="http://www.w3.org/TR/2004/WD-SVG12-20040510/">http://www.w3.org/TR/2004/WD-SVG12-20040510/</a></dd> <dt>Latest version of SVG 1.2:</dt> <dd><a href="http://www.w3.org/TR/SVG12/">http://www.w3.org/TR/SVG12/</a></dd> <dt>Latest SVG Recommendation:</dt> <dd><a href="http://www.w3.org/TR/SVG/">http://www.w3.org/TR/SVG/</a></dd> <dt>Editor:</dt> <dd>Dean Jackson, W3C, <a href="mailto:dean@w3.org">dean@w3.org</a></dd> <dt>Authors:</dt> <dd>See <a href="#authors">Author List</a></dd> </dl> <p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notic ... </header> The header element is not sectioning content; it doesn't introduce a new section. In this example, the page has a page heading given by the h1 element, and two subsections whose headings are given by h2 elements. The content after the header element is still part of the last subsection started in the header element, because the header element doesn't take part in the outline algorithm. <body> <header> http://dev.w3.org/html5/spec/Overview.html (108 de 570)01-08-2009 6:55:55
- 109. HTML 5 <h1>Little Green Guys With Guns</h1> <nav> <ul> <li><a href="/games">Games</a> | <li><a href="/forum">Forum</a> | <li><a href="/download">Download</a> </ul> </nav> <h2>Important News</h2> <!-- this starts a second subsection --> <!-- this is part of the subsection entitled "Important News" --> <p>To play today's games you will need to update your client.</p> <h2>Games</h2> <!-- this starts a third subsection --> </header> <p>You have three active games:</p> <!-- this is still part of the subsection entitled "Games" --> ... 4.4.9 The footer element Categories Flow content. formatBlock candidate. Contexts in which this element may be used: Where flow content is expected. Content model: Flow content, but with no heading content descendants, no sectioning content descendants, and no header or footer element descendants. Content attributes: Global attributes DOM interface: Uses HTMLElement. The footer element represents a footer for its nearest ancestor sectioning content. A footer typically contains information about its section such as who wrote it, links to related documents, copyright data, and the like. Contact information belongs in an address element, possibly itself inside a footer. Footers don't necessarily have to appear at the end of a section, though they usually do. The footer element is inappropriate for containing entire sections. For appendices, indexes, long colophons, verbose license agreements, and other such content which needs sectioning with headings and so forth, regular section elements should be used, not a footer. Here is a page with two footers, one at the top and one at the bottom, with the same content: <body> <footer><a href="../">Back to index...</a></footer> <hgroup> <h1>Lorem ipsum</h1> <h2>The ipsum of all lorems</h2> </hgroup> <p>A dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</p> <footer><a href="../">Back to index...</a></footer> </body> 4.4.10 The address element Categories http://dev.w3.org/html5/spec/Overview.html (109 de 570)01-08-2009 6:55:55
- 110. HTML 5 Flow content. formatBlock candidate. Contexts in which this element may be used: Where flow content is expected. Content model: Flow content, but with no heading content descendants, no sectioning content descendants, and no header, footer, or address element descendants. Content attributes: Global attributes DOM interface: Uses HTMLElement. The address element represents the contact information for its nearest article or body element ancestor. If that is the body element, then the contact information applies to the document as a whole. For example, a page at the W3C Web site related to HTML might include the following contact information: <ADDRESS> <A href="../People/Raggett/">Dave Raggett</A>, <A href="../People/Arnaud/">Arnaud Le Hors</A>, contact persons for the <A href="Activity">W3C HTML Activity</A> </ADDRESS> The address element must not be used to represent arbitrary addresses (e.g. postal addresses), unless those addresses are in fact the relevant contact information. (The p element is the appropriate element for marking up postal addresses in general.) The address element must not contain information other than contact information. For example, the following is non-conforming use of the address element: <ADDRESS>Last Modified: 1999/12/24 23:37:50</ADDRESS> Typically, the address element would be included along with other information in a footer element. The contact information for a node node is a collection of address elements defined by the first applicable entry from the following list: If node is an article element If node is a body element The contact information consists of all the address elements that have node as an ancestor and do not have another body or article element ancestor that is a descendant of node. If node has an ancestor element that is a article element If node has an ancestor element that is a body element The contact information of node is the same as the contact information of the nearest article or body element ancestor, whichever is nearest. If node's Document has a body element The contact information of node is the same as the contact information the body element of the Document. Otherwise There is no contact information for node. User agents may expose the contact information of a node to the user, or use it for other purposes, such as indexing sections based on the sections' contact information. Contact information for one sectioning content element, e.g. an aside element, does not apply to its ancestor elements, e.g. the page's body. 4.4.11 Headings and sections The h1–h6 elements and the hgroup element are headings. The first element of heading content in an element of sectioning content represents the heading for that section. Subsequent headings of equal or higher rank start new (implied) sections, headings of lower rank start implied subsections that are part of the previous one. In both cases, the element represents the heading of the implied section. Sectioning content elements are always considered subsections of their nearest ancestor element of sectioning content, regardless of what implied sections other headings may have created. Certain elements are said to be sectioning roots, including blockquote and td elements. These elements can have their own outlines, but the sections and headings inside these elements do not contribute to the outlines of their ancestors. blockquotebodydatagridfiguretd For the following fragment: <body> http://dev.w3.org/html5/spec/Overview.html (110 de 570)01-08-2009 6:55:55
- 111. HTML 5 <h1>Foo</h1> <h2>Bar</h2> <blockquote> <h3>Bla</h3> </blockquote> <p>Baz</p> <h2>Quux</h2> <section> <h3>Thud</h3> </section> <p>Grunt</p> </body> ...the structure would be: 1. Foo (heading of explicit body section, containing the "Grunt" paragraph) 1. Bar (heading starting implied section, containing a block quote and the "Baz" paragraph) 2. Quux (heading starting implied section) 3. Thud (heading of explicit section section) Notice how the section ends the earlier implicit section so that a later paragraph ("Grunt") is back at the top level. Sections may contain headings of any rank, but authors are strongly encouraged to either use only h1 elements, or to use elements of the appropriate rank for the section's nesting level. Authors are also encouraged to explicitly wrap sections in elements of sectioning content, instead of relying on the implicit sections generated by having multiple headings in one element of sectioning content. For example, the following is correct: <body> <h4>Apples</h4> <p>Apples are fruit.</p> <section> <h2>Taste</h2> <p>They taste lovely.</p> <h6>Sweet</h6> <p>Red apples are sweeter than green ones.</p> <h1>Color</h1> <p>Apples come in various colors.</p> </section> </body> However, the same document would be more clearly expressed as: <body> <h1>Apples</h1> <p>Apples are fruit.</p> <section> <h2>Taste</h2> <p>They taste lovely.</p> <section> <h3>Sweet</h3> <p>Red apples are sweeter than green ones.</p> </section> </section> <section> <h2>Color</h2> <p>Apples come in various colors.</p> </section> </body> Both of the documents above are semantically identical and would produce the same outline in compliant user agents. 4.4.11.1 Creating an outline This section defines an algorithm for creating an outline for a sectioning content element or a sectioning root element. It is defined in terms of a walk over the nodes of a DOM tree, in tree order, with each node being visited when it is entered and when it is exited during the walk. The outline for a sectioning content element or a sectioning root element consists of a list of one or more potentially nested sections. A section is a container that corresponds to some nodes in the original DOM tree. Each section can have one heading associated http://dev.w3.org/html5/spec/Overview.html (111 de 570)01-08-2009 6:55:55
- 112. HTML 5 with it, and can contain any number of further nested sections. The algorithm for the outline also associates each node in the DOM tree with a particular section and potentially a heading. (The sections in the outline aren't section elements, though some may correspond to such elements — they are merely conceptual sections.) The following markup fragment: <body> <h1>A</h1> <p>B</p> <h2>C</h2> <p>D</p> <h2>E</h2> <p>F</p> </body> ...results in the following outline being created for the body node (and thus the entire document): 1. Section created for body node. Associated with heading "A". Also associated with paragraph "B". Nested sections: 1. Section implied for first h2 element. Associated with heading "C". Also associated with paragraph "D". No nested sections. 2. Section implied for second h2 element. Associated with heading "E". Also associated with paragraph "F". No nested sections. The algorithm that must be followed during a walk of a DOM subtree rooted at a sectioning content element or a sectioning root element to determine that element's outline is as follows: 1. Let current outlinee be null. (It holds the element whose outline is being created.) 2. Let current section be null. (It holds a pointer to a section, so that elements in the DOM can all be associated with a section.) 3. Create a stack to hold elements, which is used to handle nesting. Initialize this stack to empty. 4. As you walk over the DOM in tree order, trigger the first relevant step below for each element as you enter and exit it. If the top of the stack is an element, and you are exiting that element The element being exited is a heading content element. Pop that element from the stack. If the top of the stack is a heading content element Do nothing. When entering a sectioning content element or a sectioning root element If current outlinee is not null, push current outlinee onto the stack. Let current outlinee be the element that is being entered. Let current section be a newly created section for the current outlinee element. Let there be a new outline for the new current outlinee, initialized with just the new current section as the only section in the outline. When exiting a sectioning content element, if the stack is not empty Pop the top element from the stack, and let the current outlinee be that element. Let current section be the last section in the outline of the current outlinee element. Append the outline of the sectioning content element being exited to the current section. (This does not change which section is the last section in the outline.) When exiting a sectioning root element, if the stack is not empty Run these steps: 1. Pop the top element from the stack, and let the current outlinee be that element. 2. Let current section be the last section in the outline of the current outlinee element. 3. Finding the deepest child: If current section has no child sections, stop these steps. http://dev.w3.org/html5/spec/Overview.html (112 de 570)01-08-2009 6:55:55
- 113. HTML 5 4. Let current section be the last child section of the current current section. 5. Go back to the substep labeled finding the deepest child. When exiting a sectioning content element or a sectioning root element The current outlinee is the element being exited. Let current section be the first section in the outline of the current outlinee element. Skip to the next step in the overall set of steps. (The walk is over.) If the current outlinee is null. Do nothing. When entering a heading content element If the current section has no heading, let the element being entered be the heading for the current section. Otherwise, if the element being entered has a rank equal to or greater than the heading of the last section of the outline of the current outlinee, then create a new section and append it to the outline of the current outlinee element, so that this new section is the new last section of that outline. Let current section be that new section. Let the element being entered be the new heading for the current section. Otherwise, run these substeps: 1. Let candidate section be current section. 2. If the element being entered has a rank lower than the rank of the heading of the candidate section, then create a new section, and append it to candidate section. (This does not change which section is the last section in the outline.) Let current section be this new section. Let the element being entered be the new heading for the current section. Abort these substeps. 3. Let new candidate section be the section that contains candidate section in the outline of current outlinee. 4. Let candidate section be new candidate section. 5. Return to step 2. Push the element being entered onto the stack. (This causes the algorithm to skip any descendants of the element.) Recall that h1 has the highest rank, and h6 has the lowest rank. Otherwise Do nothing. In addition, whenever you exit a node, after doing the steps above, if current section is not null, associate the node with the section current section. 5. If the current outlinee is null, then there was no sectioning content element or sectioning root element in the DOM. There is no outline. Abort these steps. 6. Associate any nodes that were not associated with a section in the steps above with current outlinee as their section. 7. Associate all nodes with the heading of the section with which they are associated, if any. 8. If current outlinee is the body element, then the outline created for that element is the outline of the entire document. The tree of sections created by the algorithm above, or a proper subset thereof, must be used when generating document outlines, for example when generating tables of contents. When creating an interactive table of contents, entries should jump the user to the relevant sectioning content element, if the section was created for a real element in the original document, or to the relevant heading content element, if the section in the tree was generated for a heading in the above process. Selecting the first section of the document therefore always takes the user to the top of the document, regardless of where the first heading in the body is to be found. The following JavaScript function shows how the tree walk could be implemented. The root argument is the root of the tree to walk, and the enter and exit arguments are callbacks that are called with the nodes as they are entered and exited. [ECMA262] function (root, enter, exit) { var node = root; start: while (node) { enter(node); if (node.firstChild) { node = node.firstChild; continue start; } while (node) { http://dev.w3.org/html5/spec/Overview.html (113 de 570)01-08-2009 6:55:55
- 114. HTML 5 exit(node); if (node.nextSibling) { node = node.nextSibling; continue start; } if (node == root) node = null; else node = node.parentNode; } } } 4.4.11.2 Distinguishing site-wide headings from page headings Given the outline of a document, but ignoring any sections created for nav and aside elements, and any of their descendants, if the only root of the tree is the body element's section, and it has only a single subsection which is created by an article element, then the heading of the body element should be assumed to be a site-wide heading, and the heading of the article element should be assumed to be the page's heading. If a page starts with a heading that is common to the whole site, the document must be authored such that, in the document's outline, ignoring any sections created for nav and aside elements and any of their descendants, the tree has only one root section, the body element's section, its heading is the site-wide heading, the body element has just one subsection, that subsection is created by an article element, and that article's heading is the page heading. If a page does not contain a site-wide heading, then the page must be authored such that, in the document's outline, ignoring any sections created for nav and aside elements and any of their descendants, either the body element has no subsections, or it has more than one subsection, or it has a single subsection but that subsection is not created by an article element, or there is more than one section at the root of the outline. Conceptually, a site is thus a document with many articles — when those articles are split into many pages, the heading of the original single page becomes the heading of the site, repeated on every page. 4.5 Grouping content 4.5.1 The p element Categories Flow content. formatBlock candidate. Contexts in which this element may be used: Where flow content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: interface HTMLParagraphElement : HTMLElement {}; The p element represents a paragraph. The following examples are conforming HTML fragments: <p>The little kitten gently seated himself on a piece of carpet. Later in his life, this would be referred to as the time the cat sat on the mat.</p> <fieldset> <legend>Personal information</legend> <p> <label>Name: <input name="n"></label> <label><input name="anon" type="checkbox"> Hide from other users</label> </p> <p><label>Address: <textarea name="a"></textarea></label></p> </fieldset> <p>There was once an example from Femley,<br> http://dev.w3.org/html5/spec/Overview.html (114 de 570)01-08-2009 6:55:55
- 115. HTML 5 Whose markup was of dubious quality.<br> The validator complained,<br> So the author was pained,<br> To move the error from the markup to the rhyming.</p> The p element should not be used when a more specific element is more appropriate. The following example is technically correct: <section> <!-- ... --> <p>Last modified: 2001-04-23</p> <p>Author: fred@example.com</p> </section> However, it would be better marked-up as: <section> <!-- ... --> <footer>Last modified: 2001-04-23</footer> <address>Author: fred@example.com</address> </section> Or: <section> <!-- ... --> <footer> <p>Last modified: 2001-04-23</p> <address>Author: fred@example.com</address> </footer> </section> 4.5.2 The hr element Categories Flow content. Contexts in which this element may be used: Where flow content is expected. Content model: Empty. Content attributes: Global attributes DOM interface: interface HTMLHRElement : HTMLElement {}; The hr element represents a paragraph-level thematic break, e.g. a scene change in a story, or a transition to another topic within a section of a reference book. 4.5.3 The br element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Empty. Content attributes: Global attributes DOM interface: http://dev.w3.org/html5/spec/Overview.html (115 de 570)01-08-2009 6:55:55
- 116. HTML 5 interface HTMLBRElement : HTMLElement {}; The br element represents a line break. br elements must be empty. Any content inside br elements must not be considered part of the surrounding text. br elements must be used only for line breaks that are actually part of the content, as in poems or addresses. The following example is correct usage of the br element: <p>P. Sherman<br> 42 Wallaby Way<br> Sydney</p> br elements must not be used for separating thematic groups in a paragraph. The following examples are non-conforming, as they abuse the br element: <p><a ...>34 comments.</a><br> <a ...>Add a comment.<a></p> <p><label>Name: <input name="name"></label><br> <label>Address: <input name="address"></label></p> Here are alternatives to the above, which are correct: <p><a ...>34 comments.</a></p> <p><a ...>Add a comment.<a></p> <p><label>Name: <input name="name"></label></p> <p><label>Address: <input name="address"></label></p> If a paragraph consists of nothing but a single br element, it represents a placeholder blank line (e.g. as in a template). Such blank lines must not be used for presentation purposes. 4.5.4 The pre element Categories Flow content. formatBlock candidate. Contexts in which this element may be used: Where flow content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: interface HTMLPreElement : HTMLElement {}; The pre element represents a block of preformatted text, in which structure is represented by typographic conventions rather than by elements. In the the HTML syntax, a leading newline character immediately following the pre element start tag is stripped. Some examples of cases where the pre element could be used: q Including an e-mail, with paragraphs indicated by blank lines, lists indicated by lines prefixed with a bullet, and so on. q Including fragments of computer code, with structure indicated according to the conventions of that language. http://dev.w3.org/html5/spec/Overview.html (116 de 570)01-08-2009 6:55:55
- 117. HTML 5 q Displaying ASCII art. Authors are encouraged to consider how preformatted text will be experienced when the formatting is lost, as will be the case for users of speech synthesizers, braille displays, and the like. For cases like ASCII art, it is likely that an alternative presentation, such as a textual description, would be more universally accessible to the readers of the document. To represent a block of computer code, the pre element can be used with a code element; to represent a block of computer output the pre element can be used with a samp element. Similarly, the kbd element can be used within a pre element to indicate text that the user is to enter. In the following snippet, a sample of computer code is presented. <p>This is the <code>Panel</code> constructor:</p> <pre><code>function Panel(element, canClose, closeHandler) { this.element = element; this.canClose = canClose; this.closeHandler = function () { if (closeHandler) closeHandler() }; }</code></pre> In the following snippet, samp and kbd elements are mixed in the contents of a pre element to show a session of Zork I. <pre><samp>You are in an open field west of a big white house with a boarded front door. There is a small mailbox here. ></samp> <kbd>open mailbox</kbd> <samp>Opening the mailbox reveals: A leaflet. ></samp></pre> The following shows a contemporary poem that uses the pre element to preserve its unusual formatting, which forms an intrinsic part of the poem itself. <pre> maxling it is with a heart heavy that i admit loss of a feline so loved a friend lost to the unknown (night) ~cdr 11dec07</pre> 4.5.5 The dialog element Categories Flow content. Contexts in which this element may be used: Where flow content is expected. Content model: Zero or more pairs of one dt element followed by one dd element. Content attributes: Global attributes DOM interface: Uses HTMLElement. The dialog element represents a conversation, meeting minutes, a chat transcript, a dialog in a screenplay, an instant message log, or some other construct in which different players take turns in discourse. Each part of the conversation must have an explicit talker (or speaker) given by a dt element, and a discourse (or quote) given by a dd element. This example demonstrates this using an extract from Abbot and Costello's famous sketch, Who's on first: http://dev.w3.org/html5/spec/Overview.html (117 de 570)01-08-2009 6:55:55
- 118. HTML 5 <dialog> <dt> Costello <dd> Look, you gotta first baseman? <dt> Abbott <dd> Certainly. <dt> Costello <dd> Who's playing first? <dt> Abbott <dd> That's right. <dt> Costello <dd> When you pay off the first baseman every month, who gets the money? <dt> Abbott <dd> Every dollar of it. </dialog> Text in a dt element in a dialog element is implicitly the source of the text given in the following dd element, and the contents of the dd element are implicitly a quote from that speaker. There is thus no need to include cite, q, or blockquote elements in this markup. Indeed, a q element inside a dd element in a conversation would actually imply the people talking were themselves quoting another work. See the cite, q, and blockquote elements for other ways to cite or quote. 4.5.6 The blockquote element Categories Flow content. Sectioning root. formatBlock candidate. Contexts in which this element may be used: Where flow content is expected. Content model: Flow content. Content attributes: Global attributes cite DOM interface: interface HTMLQuoteElement : HTMLElement { attribute DOMString cite; }; The HTMLQuoteElement interface is also used by the q element. The blockquote element represents a section that is quoted from another source. Content inside a blockquote must be quoted from another source, whose address, if it has one, should be cited in the cite attribute. If the cite attribute is present, it must be a valid URL. To obtain the corresponding citation link, the value of the attribute must be resolved relative to the element. User agents should allow users to follow such citation links. The cite DOM attribute must reflect the element's cite content attribute. The best way to represent a conversation is not with the cite and blockquote elements, but with the dialog element. This next example shows the use of cite alongside blockquote: <p>His next piece was the aptly named <cite>Sonnet 130</cite>:</p> <blockquote cite="http://quotes.example.org/s/sonnet130.html"> <p>My mistress' eyes are nothing like the sun,<br> Coral is far more red, than her lips red,<br> ... 4.5.7 The ol element http://dev.w3.org/html5/spec/Overview.html (118 de 570)01-08-2009 6:55:55
- 119. HTML 5 Categories Flow content. Contexts in which this element may be used: Where flow content is expected. Content model: Zero or more li elements. Content attributes: Global attributes reversed start DOM interface: interface HTMLOListElement : HTMLElement { attribute boolean reversed; attribute long start; }; The ol element represents a list of items, where the items have been intentionally ordered, such that changing the order would change the meaning of the document. The items of the list are the li element child nodes of the ol element, in tree order. The reversed attribute is a boolean attribute. If present, it indicates that the list is a descending list (..., 3, 2, 1). If the attribute is omitted, the list is an ascending list (1, 2, 3, ...). The start attribute, if present, must be a valid integer giving the ordinal value of the first list item. If the start attribute is present, user agents must parse it as an integer, in order to determine the attribute's value. The default value, used if the attribute is missing or if the value cannot be converted to a number according to the referenced algorithm, is 1 if the element has no reversed attribute, and is the number of child li elements otherwise. The first item in the list has the ordinal value given by the ol element's start attribute, unless that li element has a value attribute with a value that can be successfully parsed, in which case it has the ordinal value given by that value attribute. Each subsequent item in the list has the ordinal value given by its value attribute, if it has one, or, if it doesn't, the ordinal value of the previous item, plus one if the reversed is absent, or minus one if it is present. The reversed DOM attribute must reflect the value of the reversed content attribute. The start DOM attribute must reflect the value of the start content attribute. The following markup shows a list where the order matters, and where the ol element is therefore appropriate. Compare this list to the equivalent list in the ul section to see an example of the same items using the ul element. <p>I have lived in the following countries (given in the order of when I first lived there):</p> <ol> <li>Switzerland <li>United Kingdom <li>United States <li>Norway </ol> Note how changing the order of the list changes the meaning of the document. In the following example, changing the relative order of the first two items has changed the birthplace of the author: <p>I have lived in the following countries (given in the order of when I first lived there):</p> <ol> <li>United Kingdom <li>Switzerland <li>United States <li>Norway </ol> 4.5.8 The ul element Categories http://dev.w3.org/html5/spec/Overview.html (119 de 570)01-08-2009 6:55:55
- 120. HTML 5 Flow content. Contexts in which this element may be used: Where flow content is expected. Content model: Zero or more li elements. Content attributes: Global attributes DOM interface: interface HTMLUListElement : HTMLElement {}; The ul element represents a list of items, where the order of the items is not important — that is, where changing the order would not materially change the meaning of the document. The items of the list are the li element child nodes of the ul element. The following markup shows a list where the order does not matter, and where the ul element is therefore appropriate. Compare this list to the equivalent list in the ol section to see an example of the same items using the ol element. <p>I have lived in the following countries:</p> <ul> <li>Norway <li>Switzerland <li>United Kingdom <li>United States </ul> Note that changing the order of the list does not change the meaning of the document. The items in the snippet above are given in alphabetical order, but in the snippet below they are given in order of the size of their current account balance in 2007, without changing the meaning of the document whatsoever: <p>I have lived in the following countries:</p> <ul> <li>Switzerland <li>Norway <li>United Kingdom <li>United States </ul> 4.5.9 The li element Categories None. Contexts in which this element may be used: Inside ol elements. Inside ul elements. Inside menu elements. Content model: Flow content. Content attributes: Global attributes If the element is a child of an ol element: value DOM interface: interface HTMLLIElement : HTMLElement { attribute long value; }; The li element represents a list item. If its parent element is an ol, ul, or menu element, then the element is an item of the parent element's list, as defined for those elements. Otherwise, the list item has no defined list-related relationship to any other li element. The value attribute, if present, must be a valid integer giving the ordinal value of the list item. If the value attribute is present, user agents must parse it as an integer, in order to determine the attribute's value. If the attribute's value cannot be converted to a number, the attribute must be treated as if it was absent. The attribute has no default value. http://dev.w3.org/html5/spec/Overview.html (120 de 570)01-08-2009 6:55:55
- 121. HTML 5 The value attribute is processed relative to the element's parent ol element (q.v.), if there is one. If there is not, the attribute has no effect. The value DOM attribute must reflect the value of the value content attribute. The following example, the top ten movies are listed (in reverse order). Note the way the list is given a title by using a figure element and its legend. <figure> <legend>The top 10 movies of all time</legend> <ol> <li value="10"><cite>Josie and the Pussycats</cite>, 2001</li> <li value="9"><cite lang="sh">•••• •••••, •••• •••••</cite>, 1998</li> <li value="8"><cite>A Bug's Life</cite>, 1998</li> <li value="7"><cite>Toy Story</cite>, 1995</li> <li value="6"><cite>Monsters, Inc</cite>, 2001</li> <li value="5"><cite>Cars</cite>, 2006</li> <li value="4"><cite>Toy Story 2</cite>, 1999</li> <li value="3"><cite>Finding Nemo</cite>, 2003</li> <li value="2"><cite>The Incredibles</cite>, 2004</li> <li value="1"><cite>Ratatouille</cite>, 2007</li> </ol> </figure> The markup could also be written as follows, using the reversed attribute on the ol element: <figure> <legend>The top 10 movies of all time</legend> <ol reversed> <li><cite>Josie and the Pussycats</cite>, 2001</li> <li><cite lang="sh">•••• •••••, •••• •••••</cite>, 1998</li> <li><cite>A Bug's Life</cite>, 1998</li> <li><cite>Toy Story</cite>, 1995</li> <li><cite>Monsters, Inc</cite>, 2001</li> <li><cite>Cars</cite>, 2006</li> <li><cite>Toy Story 2</cite>, 1999</li> <li><cite>Finding Nemo</cite>, 2003</li> <li><cite>The Incredibles</cite>, 2004</li> <li><cite>Ratatouille</cite>, 2007</li> </ol> </figure> If the li element is the child of a menu element and itself has a child that defines a command, then the li element will match the :enabled and :disabled pseudo-classes in the same way as the first such child element does. 4.5.10 The dl element Categories Flow content. Contexts in which this element may be used: Where flow content is expected. Content model: Zero or more groups each consisting of one or more dt elements followed by one or more dd elements. Content attributes: Global attributes DOM interface: interface HTMLDListElement : HTMLElement {}; The dl element represents an association list consisting of zero or more name-value groups (a description list). Each group must consist of one or more names (dt elements) followed by one or more values (dd elements). Name-value groups may be terms and definitions, metadata topics and values, or any other groups of name-value data. The values within a group are alternatives; multiple paragraphs forming part of the same value must all be given within the same dd element. The order of the list of groups, and of the names and values within each group, may be significant. http://dev.w3.org/html5/spec/Overview.html (121 de 570)01-08-2009 6:55:55
- 122. HTML 5 If a dl element is empty, it contains no groups. If a dl element contains non-whitespace text nodes, or elements other than dt and dd, then those elements or text nodes do not form part of any groups in that dl. If a dl element contains only dt elements, then it consists of one group with names but no values. If a dl element contains only dd elements, then it consists of one group with values but no names. If a dl element starts with one or more dd elements, then the first group has no associated name. If a dl element ends with one or more dt elements, then the last group has no associated value. When a dl element doesn't match its content model, it is often due to accidentally using dd elements in the place of dt elements and vice versa. Conformance checkers can spot such mistakes and might be able to advise authors how to correctly use the markup. In the following example, one entry ("Authors") is linked to two values ("John" and "Luke"). <dl> <dt> Authors <dd> John <dd> Luke <dt> Editor <dd> Frank </dl> In the following example, one definition is linked to two terms. <dl> <dt lang="en-US"> <dfn>color</dfn> </dt> <dt lang="en-GB"> <dfn>colour</dfn> </dt> <dd> A sensation which (in humans) derives from the ability of the fine structure of the eye to distinguish three differently filtered analyses of a view. </dd> </dl> The following example illustrates the use of the dl element to mark up metadata of sorts. At the end of the example, one group has two metadata labels ("Authors" and "Editors") and two values ("Robert Rothman" and "Daniel Jackson"). <dl> <dt> Last modified time </dt> <dd> 2004-12-23T23:33Z </dd> <dt> Recommended update interval </dt> <dd> 60s </dd> <dt> Authors </dt> <dt> Editors </dt> <dd> Robert Rothman </dd> <dd> Daniel Jackson </dd> </dl> The following example shows the dl element used to give a set of instructions. The order of the instructions here is important (in the other examples, the order of the blocks was not important). <p>Determine the victory points as follows (use the first matching case):</p> <dl> <dt> If you have exactly five gold coins </dt> <dd> You get five victory points </dd> <dt> If you have one or more gold coins, and you have one or more silver coins </dt> <dd> You get two victory points </dd> <dt> If you have one or more silver coins </dt> <dd> You get one victory point </dd> <dt> Otherwise </dt> <dd> You get no victory points </dd> </dl> The following snippet shows a dl element being used as a glossary. Note the use of dfn to indicate the word being defined. <dl> <dt><dfn>Apartment</dfn>, n.</dt> http://dev.w3.org/html5/spec/Overview.html (122 de 570)01-08-2009 6:55:55
- 123. HTML 5 <dd>An execution context grouping one or more threads with one or more COM objects.</dd> <dt><dfn>Flat</dfn>, n.</dt> <dd>A deflated tire.</dd> <dt><dfn>Home</dfn>, n.</dt> <dd>The user's login directory.</dd> </dl> The dl element is inappropriate for marking up dialogue. For an example of how to mark up dialogue, see the dialog element. 4.5.11 The dt element Categories None. Contexts in which this element may be used: Before dd or dt elements inside dl elements. Before a dd element inside a dialog element. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The dt element represents the term, or name, part of a term-description group in a description list (dl element), and the talker, or speaker, part of a talker-discourse pair in a conversation (dialog element). The dt element itself, when used in a dl element, does not indicate that its contents are a term being defined, but this can be indicated using the dfn element. If the dt element is the child of a dialog element, and it further contains a time element, then that time element represents a timestamp for when the associated discourse (dd element) was said, and is not part of the name of the talker. The following extract shows how an IM conversation log could be marked up. <dialog> <dt> <time>14:22</time> egof <dd> I'm not that nerdy, I've only seen 30% of the star trek episodes <dt> <time>14:23</time> kaj <dd> if you know what percentage of the star trek episodes you have seen, you are inarguably nerdy <dt> <time>14:23</time> egof <dd> it's unarguably <dt> <time>14:24</time> kaj <dd> you are not helping your case </dialog> 4.5.12 The dd element Categories None. Contexts in which this element may be used: After dt or dd elements inside dl elements. After a dt element inside a dialog element. Content model: Flow content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The dd element represents the description, definition, or value, part of a term-description group in a description list (dl element), and the discourse, or quote, part in a conversation (dialog element). http://dev.w3.org/html5/spec/Overview.html (123 de 570)01-08-2009 6:55:55
- 124. HTML 5 A dl can be used to define a vocabulary list, like in a dictionary. In the following example, each entry, given by a dt with a dfn, has several dds, showing the various parts of the definition. <dl> <dt><dfn>happiness</dfn></dt> <dd class="pronunciation">/'hæ p. nes/</dd> <dd class="part-of-speech"><i><abbr>n.</abbr></i></dd> <dd>The state of being happy.</dd> <dd>Good fortune; success. <q>Oh <b>happiness</b>! It worked!</q></dd> <dt><dfn>rejoice</dfn></dt> <dd class="pronunciation">/ri jois'/</dd> <dd><i class="part-of-speech"><abbr>v.intr.</abbr></i> To be delighted oneself.</dd> <dd><i class="part-of-speech"><abbr>v.tr.</abbr></i> To cause one to be delighted.</dd> </dl> 4.5.13 Common grouping idioms 4.5.13.1 Tag clouds This specification does not define any markup specifically for marking up lists of keywords that apply to a group of pages (also known as tag clouds). In general, authors are encouraged to either mark up such lists using ul elements with explicit inline counts that are then hidden and turned into a presentational effect using a style sheet, or to use SVG. Here, three tags are included in a short tag cloud: <style> @media screen, print, handheld, tv { /* should be ignored by non-visual browsers */ .tag-cloud > li > span { display: none; } .tag-cloud > li { display: inline; } .tag-cloud-1 { font-size: 0.7em; } .tag-cloud-2 { font-size: 0.9em; } .tag-cloud-3 { font-size: 1.1em; } .tag-cloud-4 { font-size: 1.3em; } .tag-cloud-5 { font-size: 1.5em; } } </style> ... <ul class="tag-cloud"> <li class="tag-cloud-4"><a title="28 instances" href="/t/apple">apple</a> <span>(popular)</span> <li class="tag-cloud-2"><a title="6 instances" href="/t/kiwi">kiwi</a> <span>(rare)</span> <li class="tag-cloud-5"><a title="41 instances" href="/t/pear">pear</a> <span>(very popular)</span> </ul> The actual frequency of each tag is given using the title attribute. A CSS style sheet is provided to convert the markup into a cloud of differently-sized words, but for user agents that do not support CSS or are not visual, the markup contains annotations like "(popular)" or "(rare)" to categorize the various tags by frequency, thus enabling all users to benefit from the information. The ul element is used (rather than ol) because the order is not particular important: while the list is in fact ordered alphabetically, it would convey the same information if ordered by, say, the length of the tag. The tag rel-keyword is not used on these a elements because they do not represent tags that apply to the page itself; they are just part of an index listing the tags themselves. 4.6 Text-level semantics 4.6.1 The a element Categories Flow content. When the element only contains phrasing content: phrasing content. Interactive content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Transparent, but there must be no interactive content descendant. Content attributes: Global attributes href http://dev.w3.org/html5/spec/Overview.html (124 de 570)01-08-2009 6:55:55
- 125. HTML 5 target ping rel media hreflang type DOM interface: [Stringifies=href] interface HTMLAnchorElement : HTMLElement { attribute DOMString href; attribute DOMString target; attribute DOMString ping; attribute DOMString rel; readonly attribute DOMTokenList relList; attribute DOMString media; attribute DOMString hreflang; attribute DOMString type; // URL decomposition attributes attribute DOMString protocol; attribute DOMString host; attribute DOMString hostname; attribute DOMString port; attribute DOMString pathname; attribute DOMString search; attribute DOMString hash; }; If the a element has an href attribute, then it represents a hyperlink (a hypertext anchor). If the a element has no href attribute, then the element represents a placeholder for where a link might otherwise have been placed, if it had been relevant. The target, ping, rel, media, hreflang, and type attributes must be omitted if the href attribute is not present. If a site uses a consistent navigation tool bar on every page, then the link that would normally link to the page itself could be marked up using an a element: <nav> <ul> <li> <a href="/">Home</a> </li> <li> <a href="/news">News</a> </li> <li> <a>Examples</a> </li> <li> <a href="/legal">Legal</a> </li> </ul> </nav> Interactive user agents should allow users to follow hyperlinks created using the a element. The href, target and ping attributes decide how the link is followed. The rel, media, hreflang, and type attributes may be used to indicate to the user the likely nature of the target resource before the user follows the link. The activation behavior of a elements that represent hyperlinks is to run the following steps: 1. If the DOMActivate event in question is not trusted (i.e. a click() method call was the reason for the event being dispatched), and the a element's target attribute is such that applying the rules for choosing a browsing context given a browsing context name, using the value of the target attribute as the browsing context name, would result in there not being a chosen browsing context, then raise an INVALID_ACCESS_ERR exception and abort these steps. 2. If the target of the click event is an img element with an ismap attribute specified, then server-side image map processing must be performed, as follows: 1. If the DOMActivate event was dispatched as the result of a real pointing-device-triggered click event on the img element, then let x be the distance in CSS pixels from the left edge of the image's left border, if it has one, or the left edge of the image otherwise, to the location of the click, and let y be the distance in CSS pixels from the top edge of the image's top border, if it has one, or the top edge of the image otherwise, to the location of the click. Otherwise, let x and y be zero. 2. Let the hyperlink suffix be a U+003F QUESTION MARK character, the value of x expressed as a base-ten integer using ASCII digits (U+0030 DIGIT ZERO to U+0039 DIGIT NINE), a U+002C COMMA character, and the value of y expressed as a base- ten integer using ASCII digits. 3. Finally, the user agent must follow the hyperlink defined by the a element. If the steps above defined a hyperlink suffix, then take that into account when following the hyperlink. The DOM attributes href, ping, target, rel, media, hreflang, and type, must reflect the respective content attributes of the same name. http://dev.w3.org/html5/spec/Overview.html (125 de 570)01-08-2009 6:55:55
- 126. HTML 5 The DOM attribute relList must reflect the rel content attribute. The a element also suports the complement of URL decomposition attributes, protocol, host, port, hostname, pathname, search, and hash. These must follow the rules given for URL decomposition attributes, with the input being the result of resolving the element's href attribute relative to the element, if there is such an attribute and resolving it is successful, or the empty string otherwise; and the common setter action being the same as setting the element's href attribute to the new output value. The a element may be wrapped around entire paragraphs, lists, tables, and so forth, even entire sections, so long as there is no interactive content within (e.g. buttons or other links). This example shows how this can be used to make an entire advertising block into a link: <aside class="advertising"> <h1>Advertising</h1> <a href="http://ad.example.com/?adid=1929&pubid=1422"> <section> <h1>Mellblomatic 9000!</h1> <p>Turn all your widgets into mellbloms!</p> <p>Only $9.99 plus shipping and handling.</p> </section> </a> <a href="http://ad.example.com/?adid=375&pubid=1422"> <section> <h1>The Mellblom Browser</h1> <p>Web browsing at the speed of light.</p> <p>No other browser goes faster!</p> </section> </a> </aside> 4.6.2 The q element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes cite DOM interface: The q element uses the HTMLQuoteElement interface. The q element represents some phrasing content quoted from another source. Quotation punctuation (such as quotation marks) must not appear immediately before, after, or inside q elements; they will be inserted into the rendering by the user agent. Content inside a q element must be quoted from another source, whose address, if it has one, should be cited in the cite attribute. The source may be fictional, as when quoting characters in a novel or screenplay. If the cite attribute is present, it must be a valid URL. To obtain the corresponding citation link, the value of the attribute must be resolved relative to the element. User agents should allow users to follow such citation links. The q element must not be used in place of quotation marks that do not represent quotes; for example, it is inappropriate to use the q element for marking up sarcastic statements. The use of q elements to mark up quotations is entirely optional; using explicit quotation punctuation without q elements is just as correct. Here is a simple example of the use of the q element: <p>The man said <q>Things that are impossible just take longer</q>. I disagreed with him.</p> Here is an example with both an explicit citation link in the q element, and an explicit citation outside: <p>The W3C page <cite>About W3C</cite> says the W3C's mission is <q cite="http://www.w3.org/Consortium/">To lead the World Wide Web to its full potential by developing protocols and guidelines that ensure long-term growth for the Web</q>. I http://dev.w3.org/html5/spec/Overview.html (126 de 570)01-08-2009 6:55:55
- 127. HTML 5 disagree with this mission.</p> In the following example, the quotation itself contains a quotation: <p>In <cite>Example One</cite>, he writes <q>The man said <q>Things that are impossible just take longer</q>. I disagreed with him</q>. Well, I disagree even more!</p> In the following example, quotation marks are used instead of the q element: <p>His best argument was ™I disagreed, which I thought was laughable.</p> In the following example, there is no quote — the quotation marks are used to name a word. Use of the q element in this case would be inappropriate. <p>The word "ineffable" could have been used to describe the disaster resulting from the campaign's mismanagement.</p> 4.6.3 The cite element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The cite element represents the title of a work (e.g. a book, a paper, an essay, a poem, a score, a song, a script, a film, a TV show, a game, a sculpture, a painting, a theatre production, a play, an opera, a musical, an exhibition, etc). This can be a work that is being quoted or referenced in detail (i.e. a citation), or it can just be a work that is mentioned in passing. A person's name is not the title of a work — even if people call that person a piece of work — and the element must therefore not be used to mark up people's names. (In some cases, the b element might be appropriate for names; e.g. in a gossip article where the names of famous people are keywords rendered with a different style to draw attention to them. In other cases, if an element is really needed, the span element can be used.) A ship is similarly not a work, and the element must not be used to mark up ship names (the i element can be used for that purpose). This next example shows a typical use of the cite element: <p>My favorite book is <cite>The Reality Dysfunction</cite> by Peter F. Hamilton. My favorite comic is <cite>Pearls Before Swine</cite> by Stephan Pastis. My favorite track is <cite>Jive Samba</cite> by the Cannonball Adderley Sextet.</p> This is correct usage: <p>According to the Wikipedia article <cite>HTML</cite>, as it stood in mid-February 2008, leaving attribute values unquoted is unsafe. This is obviously an over-simplification.</p> The following, however, is incorrect usage, as the cite element here is containing far more than the title of the work: <!-- do not copy this example, it is an example of bad usage! --> <p>According to <cite>the Wikipedia article on HTML</cite>, as it stood in mid-February 2008, leaving attribute values unquoted is unsafe. This is obviously an over-simplification.</p> The cite element is obviously a key part of any citation in a bibliography, but it is only used to mark the title: <p><cite>Universal Declaration of Human Rights</cite>, United Nations, December 1948. Adopted by General Assembly resolution 217 A (III).</p> http://dev.w3.org/html5/spec/Overview.html (127 de 570)01-08-2009 6:55:55
- 128. HTML 5 A citation is not a quote (for which the q element is appropriate). This is incorrect usage, because cite is not for quotes: <p><cite>This is wrong!</cite>, said Ian.</p> This is also incorrect usage, because a person is not a work: <p><q>This is still wrong!</q>, said <cite>Ian</cite>.</p> The correct usage does not use a cite element: <p><q>This is correct</q>, said Ian.</p> As mentioned above, the b element might be relevant for marking names as being keywords in certain kinds of documents: <p>And then <b>Ian</b> said <q>this might be right, in a gossip column, maybe!</q>.</p> 4.6.4 The em element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The em element represents stress emphasis of its contents. The level of emphasis that a particular piece of content has is given by its number of ancestor em elements. The placement of emphasis changes the meaning of the sentence. The element thus forms an integral part of the content. The precise way in which emphasis is used in this way depends on the language. These examples show how changing the emphasis changes the meaning. First, a general statement of fact, with no emphasis: <p>Cats are cute animals.</p> By emphasizing the first word, the statement implies that the kind of animal under discussion is in question (maybe someone is asserting that dogs are cute): <p><em>Cats</em> are cute animals.</p> Moving the emphasis to the verb, one highlights that the truth of the entire sentence is in question (maybe someone is saying cats are not cute): <p>Cats <em>are</em> cute animals.</p> By moving it to the adjective, the exact nature of the cats is reasserted (maybe someone suggested cats were mean animals): <p>Cats are <em>cute</em> animals.</p> Similarly, if someone asserted that cats were vegetables, someone correcting this might emphasize the last word: <p>Cats are cute <em>animals</em>.</p> By emphasizing the entire sentence, it becomes clear that the speaker is fighting hard to get the point across. This kind of emphasis also typically affects the punctuation, hence the exclamation mark here. http://dev.w3.org/html5/spec/Overview.html (128 de 570)01-08-2009 6:55:55
- 129. HTML 5 <p><em>Cats are cute animals!</em></p> Anger mixed with emphasizing the cuteness could lead to markup such as: <p><em>Cats are <em>cute</em> animals!</em></p> The em element isn't a generic "italics" element. Sometimes, text is intended to stand out from the rest of the paragraph, as if it was in a different mood or voice. For this, the i element is more appropriate. The em element also isn't intended to convey importance; for that purpose, the strong element is more appropriate. 4.6.5 The strong element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The strong element represents strong importance for its contents. The relative level of importance of a piece of content is given by its number of ancestor strong elements; each strong element increases the importance of its contents. Changing the importance of a piece of text with the strong element does not change the meaning of the sentence. Here is an example of a warning notice in a game, with the various parts marked up according to how important they are: <p><strong>Warning.</strong> This dungeon is dangerous. <strong>Avoid the ducks.</strong> Take any gold you find. <strong><strong>Do not take any of the diamonds</strong>, they are explosive and <strong>will destroy anything within ten meters.</strong></strong> You have been warned.</p> 4.6.6 The small element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The small element represents small print or other side comments. Small print typically features disclaimers, caveats, legal restrictions, or copyrights. Small print is also sometimes used for attribution, or for satisfying licensing requirements. The small element does not "de-emphasize" or lower the importance of text emphasized by the em element or marked as important with the strong element. http://dev.w3.org/html5/spec/Overview.html (129 de 570)01-08-2009 6:55:56
- 130. HTML 5 In this example the footer contains contact information and a copyright notice. <footer> <address> For more details, contact <a href="mailto:js@example.com">John Smith</a>. </address> <p><small>© copyright 2038 Example Corp.</small></p> </footer> In this second example, the small element is used for a side comment in an article. <p>Example Corp today announced record profits for the second quarter <small>(Full Disclosure: Foo News is a subsidiary of Example Corp)</small>, leading to speculation about a third quarter merger with Demo Group.</p> This is distinct from a sidebar, which might be multiple paragraphs long and is removed from the main flow of text. In the following example, we see a sidebar from the same article. This sidebar also has small print, indicating the source of the information in the sidebar. <aside> <h1>Example Corp</h1> <p>This company mostly creates small software and Web sites.</p> <p>The Example Corp company mission is "To provide entertainment and news on a sample basis".</p> <p><small>Information obtained from <a href="http://example.com/about.html">example.com</a> home page.</small></p> </aside> In this last example, the small element is marked as being important small print. <p><strong><small>Continued use of this service will result in a kiss.</small></strong></p> 4.6.7 The mark element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The mark element represents a run of text in one document marked or highlighted for reference purposes, due to its relevance in another context. When used in a quotation or other block of text referred to from the prose, it indicates a highlight that was not originally present but which has been added to bring the reader's attention to a part of the text that might not have been considered important by the original author when the block was originally written, but which is now under previously unexpected scrutiny. When used in the main prose of a document, it indicates a part of the document that has been highlighted due to its likely relevance to the user's current activity. This example shows how the mark element can be used to bring attention to a particular part of a quotation: <p lang="en-US">Consider the following quote:</p> <blockquote lang="en-GB"> <p>Look around and you will find, no-one's really <mark>colour</mark> blind.</p> </blockquote> <p lang="en-US">As we can tell from the <em>spelling</em> of the word, the person writing this quote is clearly not American.</p> Another example of the mark element is highlighting parts of a document that are matching some search string. If someone looked at a document, and the server knew that the user was searching for the word "kitten", then the server might return the document with one paragraph modified as follows: http://dev.w3.org/html5/spec/Overview.html (130 de 570)01-08-2009 6:55:56
- 131. HTML 5 <p>I also have some <mark>kitten</mark>s who are visiting me these days. They're really cute. I think they like my garden! Maybe I should adopt a <mark>kitten</mark>.</p> In the following snippet, a paragraph of text refers to a specific part of a code fragment. <p>The highlighted part below is where the error lies:</p> <pre><code>var i: Integer; begin i := <mark>1.1</mark>; end.</code></pre> This is another example showing the use of mark to highlight a part of quoted text that was originally not emphasized. In this example, common typographic conventions have led the author to explicitly style mark elements in quotes to render in italics. <article> <style> blockquote mark, q mark { font: inherit; font-style: italic; text-decoration: none; background: transparent; color: inherit; } .bubble em { font: inherit; font-size: larger; text-decoration: underline; } </style> <h1>She knew</h1> <p>Did you notice the subtle joke in the joke on panel 4?</p> <blockquote> <p class="bubble">I didn't <em>want</em> to believe. <mark>Of course on some level I realized it was a known-plaintext attack.</mark> But I couldn't admit it until I saw for myself.</p> </blockquote> <p>(Emphasis mine.) I thought that was great. It's so pedantic, yet it explains everything neatly.</p> </article> Note, incidentally, the distinction between the em element in this example, which is part of the original text being quoted, and the mark element, which is highlighting a part for comment. The following example shows the difference between denoting the importance of a span of text (strong) as opposed to denoting the relevance of a span of text (mark). It is an extract from a textbook, where the extract has had the parts relevant to the exam highlighted. The safety warnings, important though they may be, are apparently not relevant to the exam. <h3>Wormhole Physics Introduction</h3> <p><mark>A wormhole in normal conditions can be held open for a maximum of just under 39 minutes.</mark> Conditions that can increase the time include a powerful energy source coupled to one or both of the gates connecting the wormhole, and a large gravity well (such as a black hole).</p> <p><mark>Momentum is preserved across the wormhole. Electromagnetic radiation can travel in both directions through a wormhole, but matter cannot.</mark></p> <p>When a wormhole is created, a vortex normally forms. <strong>Warning: The vortex caused by the wormhole opening will annihilate anything in its path.</strong> Vortexes can be avoided when using sufficiently advanced dialing technology.</p> <p><mark>An obstruction in a gate will prevent it from accepting a wormhole connection.</mark></p> 4.6.8 The dfn element Categories Flow content. http://dev.w3.org/html5/spec/Overview.html (131 de 570)01-08-2009 6:55:56
- 132. HTML 5 Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content, but there must be no descendant dfn elements. Content attributes: Global attributes Also, the title attribute has special semantics on this element. DOM interface: Uses HTMLElement. The dfn element represents the defining instance of a term. The paragraph, description list group, or section that is the nearest ancestor of the dfn element must also contain the definition(s) for the term given by the dfn element. Defining term: If the dfn element has a title attribute, then the exact value of that attribute is the term being defined. Otherwise, if it contains exactly one element child node and no child text nodes, and that child element is an abbr element with a title attribute, then the exact value of that attribute is the term being defined. Otherwise, it is the exact textContent of the dfn element that gives the term being defined. If the title attribute of the dfn element is present, then it must contain only the term being defined. The title attribute of ancestor elements does not affect dfn elements. An a element that links to a dfn element represents an instance of the term defined by the dfn element. In the following fragment, the term "GDO" is first defined in the first paragraph, then used in the second. <p>The <dfn><abbr title="Garage Door Opener">GDO</abbr></dfn> is a device that allows off-world teams to open the iris.</p> <!-- ... later in the document: --> <p>Teal'c activated his <abbr title="Garage Door Opener">GDO</abbr> and so Hammond ordered the iris to be opened.</p> With the addition of an a element, the reference can be made explicit: <p>The <dfn id=gdo><abbr title="Garage Door Opener">GDO</abbr></dfn> is a device that allows off-world teams to open the iris.</p> <!-- ... later in the document: --> <p>Teal'c activated his <a href=#gdo><abbr title="Garage Door Opener">GDO</abbr></a> and so Hammond ordered the iris to be opened.</p> 4.6.9 The abbr element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes Also, the title attribute has special semantics on this element. DOM interface: Uses HTMLElement. The abbr element represents an abbreviation or acronym, optionally with its expansion. The title attribute may be used to provide an expansion of the abbreviation. The attribute, if specified, must contain an expansion of the abbreviation, and nothing else. The paragraph below contains an abbreviation marked up with the abbr element. This paragraph defines the term "Web Hypertext Application Technology Working Group". <p>The <dfn id=whatwg><abbr title="Web Hypertext Application Technology Working Group">WHATWG</abbr></dfn> is a loose unofficial collaboration of Web browser manufacturers and interested parties who wish to develop new technologies designed to allow authors to write and deploy Applications over the World Wide Web.</p> http://dev.w3.org/html5/spec/Overview.html (132 de 570)01-08-2009 6:55:56
- 133. HTML 5 An alternative way to write this would be: <p>The <dfn id=whatwg>Web Hypertext Application Technology Working Group</dfn> (<abbr title="Web Hypertext Application Technology Working Group">WHATWG</abbr>) is a loose unofficial collaboration of Web browser manufacturers and interested parties who wish to develop new technologies designed to allow authors to write and deploy Applications over the World Wide Web.</p> This paragraph has two abbreviations. Notice how only one is defined; the other, with no expansion associated with it, does not use the abbr element. <p>The <abbr title="Web Hypertext Application Technology Working Group">WHATWG</abbr> started working on HTML 5 in 2004.</p> This paragraph links an abbreviation to its definition. <p>The <a href="#whatwg"><abbr title="Web Hypertext Application Technology Working Group">WHATWG</abbr></a> community does not have much representation from Asia.</p> This paragraph marks up an abbreviation without giving an expansion, possibly as a hook to apply styles for abbreviations (e.g. smallcaps). <p>Philip` and Dashiva both denied that they were going to get the issue counts from past revisions of the specification to backfill the <abbr>WHATWG</abbr> issue graph.</p> If an abbreviation is pluralized, the expansion's grammatical number (plural vs singular) must match the grammatical number of the contents of the element. Here the plural is outside the element, so the expansion is in the singular: <p>Two <abbr title="Working Group">WG</abbr>s worked on this specification: the <abbr>WHATWG</abbr> and the <abbr>HTMLWG</abbr>.</p> Here the plural is inside the element, so the expansion is in the plural: <p>Two <abbr title="Working Groups">WGs</abbr> worked on this specification: the <abbr>WHATWG</abbr> and the <abbr>HTMLWG</abbr>.</p> Abbreviations do not have to be marked up using this element. It is expected to be useful in the following cases: q Abbreviations for which the author wants to give expansions, where using the abbr element with a title attribute is an alternative to including the expansion inline (e.g. in parentheses). q Abbreviations that are likely to be unfamiliar to the document's readers, for which authors are encouraged to either mark up the abbreviation using a abbr element with a title attribute or include the expansion inline in the text the first time the abbreviation is used. q Abbreviations whose presence needs to be semantically annotated, e.g. so that they can be identified from a style sheet and given specific styles, for which the abbr element can be used without a title attribute. Providing an expansion in a title attribute once will not necessarily cause other abbr elements in the same document with the same contents but without a title attribute to behave as if they had the same expansion. Every abbr element is independent. 4.6.10 The time element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: http://dev.w3.org/html5/spec/Overview.html (133 de 570)01-08-2009 6:55:56
- 134. HTML 5 Global attributes datetime DOM interface: interface HTMLTimeElement : HTMLElement { attribute DOMString dateTime; readonly attribute Date date; readonly attribute Date time; readonly attribute Date timezone; }; The time element represents a precise date and/or a time in the proleptic Gregorian calendar. [GREGORIAN] This element is intended as a way to encode modern dates and times in a machine-readable way so that user agents can offer to add them to the user's calendar. For example, adding birthday reminders or scheduling events. The time element is not intended for encoding times for which a precise date or time cannot be established. For example, it would be inappropriate for encoding times like "one millisecond after the big bang", "the early part of the Jurassic period", or "a winter around 250 BCE". For dates before the introduction of the Gregorian calendar, authors are encouraged to not use the time element, or else to be very careful about converting dates and times from the period to the Gregorian calendar. This is complicated by the manner in which the Gregorian calendar was phased in, which occurred at different times in different countries, ranging from partway through the 16th century all the way to early in the 20th. The datetime attribute, if present, must contain a valid date or time string that identifies the date or time being specified. If the datetime attribute is not present, then the date or time must be specified in the content of the element, such that the element's textContent is a valid date or time string in content, and the date, if any, must be expressed using the Gregorian calendar. If the datetime attribute is present, then the element may be empty, in which case the user agent should convey the attribute's value to the user when rendering the element. The time element can be used to encode dates, for example in Microformats. The following shows a hypothetical way of encoding an event using a variant on hCalendar that uses the time element: <div class="vevent"> <a class="url" href="http://www.web2con.com/">http://www.web2con.com/</a> <span class="summary">Web 2.0 Conference</span>: <time class="dtstart" datetime="2007-10-05">October 5</time> - <time class="dtend" datetime="2007-10-20">19</time>, at the <span class="location">Argent Hotel, San Francisco, CA</span> </div> The time element is not necessary for encoding dates or times. In the following snippet, the time is encoded using time, so that it can be restyled (e.g. using XBL2) to match local conventions, while the year is not marked up at all, since marking it up would not be particularly useful. <p>I usually have a snack at <time>16:00</time>.</p> <p>I've liked model trains since at least 1983.</p> Using a styling technology that supports restyling times, the first paragraph from the above snippet could be rendered as follows: I usually have a snack at 4pm. Or it could be rendered as follows: I usually have a snack at 16h00. The dateTime DOM attribute must reflect the datetime content attribute. User agents, to obtain the date, time, and time zone represented by a time element, must follow these steps: 1. If the datetime attribute is present, then use the rules to parse a date or time string with the flag in attribute from the value of that attribute, and let the result be result. 2. Otherwise, use the rules to parse a date or time string with the flag in content from the element's textContent, and let the result be result. 3. If result is empty (because the parsing failed), then the date is unknown, the time is unknown, and the time zone is unknown. 4. Otherwise: if result contains a date, then that is the date; if result contains a time, then that is the time; and if result contains a time zone, then the time zone is the element's time zone. (A time zone can only be present if both a date and a time are also present.) http://dev.w3.org/html5/spec/Overview.html (134 de 570)01-08-2009 6:55:56
- 135. HTML 5 time . date Returns a Date object representing the date component of the element's value, at midnight in the UTC time zone. Returns null if there is no date. time . time Returns a Date object representing the time component of the element's value, on 1970-01-01 in the UTC time zone. Returns null if there is no time. time . timezone Returns a Date object representing the time corresponding to 1970-01-01 00:00 UTC in the time zone given by the element's value. Returns null if there is no time zone. The date DOM attribute must return null if the date is unknown, and otherwise must return the time corresponding to midnight UTC (i.e. the first second) of the given date. The time DOM attribute must return null if the time is unknown, and otherwise must return the time corresponding to the given time of 1970-01-01, with the time zone UTC. The timezone DOM attribute must return null if the time zone is unknown, and otherwise must return the time corresponding to 1970-01-01 00:00 UTC in the given time zone, with the time zone set to UTC (i.e. the time corresponding to 1970-01-01 at 00:00 UTC plus the offset corresponding to the time zone). In the following snippet: <p>Our first date was <time datetime="2006-09-23">a Saturday</time>.</p> ...the time element's date attribute would have the value 1,158,969,600,000ms, and the time and timezone attributes would return null. In the following snippet: <p>We stopped talking at <time datetime="2006-09-24T05:00-07:00">5am the next morning</time>.</p> ...the time element's date attribute would have the value 1,159,056,000,000ms, the time attribute would have the value 18,000,000ms, and the timezone attribute would return −25,200,000ms. To obtain the actual time, the three attributes can be added together, obtaining 1,159,048,800,000, which is the specified date and time in UTC. Finally, in the following snippet: <p>Many people get up at <time>08:00</time>.</p> ...the time element's date attribute would have the value null, the time attribute would have the value 28,800,000ms, and the timezone attribute would return null. 4.6.11 The progress element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes value max DOM interface: interface HTMLProgressElement : HTMLElement { attribute float value; attribute float max; readonly attribute float position; }; http://dev.w3.org/html5/spec/Overview.html (135 de 570)01-08-2009 6:55:56
- 136. HTML 5 The progress element represents the completion progress of a task. The progress is either indeterminate, indicating that progress is being made but that it is not clear how much more work remains to be done before the task is complete (e.g. because the task is waiting for a remote host to respond), or the progress is a number in the range zero to a maximum, giving the fraction of work that has so far been completed. There are two attributes that determine the current task completion represented by the element. The value attribute specifies how much of the task has been completed, and the max attribute specifies how much work the task requires in total. The units are arbitrary and not specified. Instead of using the attributes, authors are recommended to include the current value and the maximum value inline as text inside the element. Here is a snippet of a Web application that shows the progress of some automated task: <section> <h2>Task Progress</h2> <p>Progress: <progress><span id="p">0</span>%</progress></p> <script> var progressBar = document.getElementById('p'); function updateProgress(newValue) { progressBar.textContent = newValue; } </script> </section> (The updateProgress() method in this example would be called by some other code on the page to update the actual progress bar as the task progressed.) Author requirements: The max and value attributes, when present, must have values that are valid floating point numbers. The max attribute, if present, must have a value greater than zero. The value attribute, if present, must have a value equal to or greater than zero, and less than or equal to the value of the max attribute, if present, or 1, otherwise. The progress element is the wrong element to use for something that is just a gauge, as opposed to task progress. For instance, indicating disk space usage using progress would be inappropriate. Instead, the meter element is available for such use cases. User agent requirements: User agents must parse the max and value attributes' values according to the rules for parsing floating point number values. If the value attribute is omitted, then user agents must also parse the textContent of the progress element in question using the steps for finding one or two numbers of a ratio in a string. These steps will return nothing, one number, one number with a denominator punctuation character, or two numbers. Using the results of this processing, user agents must determine whether the progress bar is an indeterminate progress bar, or whether it is a determinate progress bar, and in the latter case, what its current and maximum values are, all as follows: 1. If the max attribute is omitted, and the value is omitted, and the results of parsing the textContent was nothing, then the progress bar is an indeterminate progress bar. Abort these steps. 2. Otherwise, it is a determinate progress bar. 3. If the max attribute is included, then, if a value could be parsed out of it, then the maximum value is that value. 4. Otherwise, if the max attribute is absent but the value attribute is present, or, if the max attribute is present but no value could be parsed from it, then the maximum is 1. 5. Otherwise, if neither attribute is included, then, if the textContent contained one number with an associated denominator punctuation character, then the maximum value is the value associated with that denominator punctuation character; otherwise, if the textContent contained two numbers, the maximum value is the higher of the two values; otherwise, the maximum value is 1. 6. If the value attribute is present on the element and a value could be parsed out of it, that value is the current value of the progress bar. Otherwise, if the attribute is present but no value could be parsed from it, the current value is zero. 7. Otherwise if the value attribute is absent and the max attribute is present, then, if the textContent was parsed and found to contain just one number, with no associated denominator punctuation character, then the current value is that number. Otherwise, if the value attribute is absent and the max attribute is present then the current value is zero. 8. Otherwise, if neither attribute is present, then the current value is the lower of the one or two numbers that were found in the textContent of the element. 9. If the maximum value is less than or equal to zero, then it is reset to 1. 10. If the current value is less than zero, then it is reset to zero. 11. Finally, if the current value is greater than the maximum value, then the current value is reset to the maximum value. UA requirements for showing the progress bar: When representing a progress element to the user, the UA should indicate whether it is a determinate or indeterminate progress bar, and in the former case, should indicate the relative position of the current value relative to the maximum value. The max and value DOM attributes must reflect the respective content attributes of the same name. When the relevant content attributes are absent, the DOM attributes must return zero. The value parsed from the textContent never affects the DOM values. http://dev.w3.org/html5/spec/Overview.html (136 de 570)01-08-2009 6:55:56
- 137. HTML 5 progress . position For a determinate progress bar (one with known current and maximum values), returns the result of dividing the current value by the maximum value. For an indeterminate progress bar, returns −1. If the progress bar is an indeterminate progress bar, then the position DOM attribute must return −1. Otherwise, it must return the result of dividing the current value by the maximum value. 4.6.12 The meter element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes value min low high max optimum DOM interface: interface HTMLMeterElement : HTMLElement { attribute float value; attribute float min; attribute float max; attribute float low; attribute float high; attribute float optimum; }; The meter element represents a scalar measurement within a known range, or a fractional value; for example disk usage, the relevance of a query result, or the fraction of a voting population to have selected a particular candidate. This is also known as a gauge. The meter element should not be used to indicate progress (as in a progress bar). For that role, HTML provides a separate progress element. The meter element also does not represent a scalar value of arbitrary range — for example, it would be wrong to use this to report a weight, or height, unless there is a known maximum value. There are six attributes that determine the semantics of the gauge represented by the element. The min attribute specifies the lower bound of the range, and the max attribute specifies the upper bound. The value attribute specifies the value to have the gauge indicate as the "measured" value. The other three attributes can be used to segment the gauge's range into "low", "medium", and "high" parts, and to indicate which part of the gauge is the "optimum" part. The low attribute specifies the range that is considered to be the "low" part, and the high attribute specifies the range that is considered to be the "high" part. The optimum attribute gives the position that is "optimum"; if that is higher than the "high" value then this indicates that the higher the value, the better; if it's lower than the "low" mark then it indicates that lower values are better, and naturally if it is in between then it indicates that neither high nor low values are good. Authoring requirements: The recommended way of giving the value is to include it as contents of the element, either as two numbers (the higher number represents the maximum, the other number the current value, and the minimum is assumed to be zero), or as a percentage or similar (using one of the characters such as "%"), or as a fraction. However, it is also possible to use the attributes to specify these values. One of the following conditions, along with all the requirements that are listed with that condition, must be met: There are exactly two numbers in the contents of the element, and the value, min, and max attributes are all omitted If specified, the low, high, and optimum attributes must have values greater than or equal to zero and less than or equal to the bigger of the two numbers in the contents of the element. http://dev.w3.org/html5/spec/Overview.html (137 de 570)01-08-2009 6:55:56
- 138. HTML 5 If both the low and high attributes are specified, then the low attribute's value must be less than or equal to the value of the high attribute. There is exactly one number followed by zero or more White_Space characters and a valid denominator punctuation character in the contents of the element, and the value, min, and max attributes are all omitted If specified, the low, high, and optimum attributes must have values greater than or equal to zero and less than or equal to the value associated with the denominator punctuation character. If both the low and high attributes are specified, then the low attribute's value must be less than or equal to the value of the high attribute. There is exactly one number in the contents of the element, and the value attribute is omitted There are no numbers in the contents of the element, and the value attribute is specified If the min attribute attribute is specified, then the minimum is that attribute's value; otherwise, it is 0. If the max attribute attribute is specified, then the maximum is that attribute's value; otherwise, it is 1. If there is exactly one number in the contents of the element, then value is that number; otherwise, value is the value of the value attribute. The following inequalities must hold, as applicable: r minimum ≤ value ≤ maximum r minimum ≤ low ≤ maximum (if low is specified) r minimum ≤ high ≤ maximum (if high is specified) r minimum ≤ optimum ≤ maximum (if optimum is specified) If both the low and high attributes are specified, then the low attribute's value must be less than or equal to the value of the high attribute. For the purposes of these requirements, a number is a sequence of characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), optionally including with a single U+002E FULL STOP character (.), and separated from other numbers by at least one character that isn't any of those; interpreted as a base ten number. The value, min, low, high, max, and optimum attributes, when present, must have values that are valid floating point numbers. If no minimum or maximum is specified, then the range is assumed to be 0..1, and the value thus has to be within that range. The following examples all represent a measurement of three quarters (of the maximum of whatever is being measured): <meter>75%</meter> <meter>750‰</meter> <meter>3/4</meter> <meter>6 blocks used (out of 8 total)</meter> <meter>max: 100; current: 75</meter> <meter><object data="graph75.png">0.75</object></meter> <meter min="0" max="100" value="75"></meter> The following example is incorrect use of the element, because it doesn't give a range (and since the default maximum is 1, both of the gauges would end up looking maxed out): <p>The grapefruit pie had a radius of <meter>12cm</meter> and a height of <meter>2cm</meter>.</p> <!-- BAD! --> Instead, one would either not include the meter element, or use the meter element with a defined range to give the dimensions in context compared to other pies: <p>The grapefruit pie had a radius of 12cm and a height of 2cm.</p> <dl> <dt>Radius: <dd> <meter min=0 max=20 value=12>12cm</meter> <dt>Height: <dd> <meter min=0 max=10 value=2>2cm</meter> </dl> There is no explicit way to specify units in the meter element, but the units may be specified in the title attribute in free-form text. The example above could be extended to mention the units: <dl> <dt>Radius: <dd> <meter min=0 max=20 value=12 title="centimeters">12cm</meter> <dt>Height: <dd> <meter min=0 max=10 value=2 title="centimeters">2cm</meter> </dl> User agent requirements: User agents must parse the min, max, value, low, high, and optimum attributes using the rules for parsing floating point number values. If the value attribute has been omitted, the user agent must also process the textContent of the element according to the steps for finding one or two numbers of a ratio in a string. These steps will return nothing, one number, one number with a denominator punctuation character, or two numbers. http://dev.w3.org/html5/spec/Overview.html (138 de 570)01-08-2009 6:55:56
- 139. HTML 5 User agents must then use all these numbers to obtain values for six points on the gauge, as follows. (The order in which these are evaluated is important, as some of the values refer to earlier ones.) The minimum value If the min attribute is specified and a value could be parsed out of it, then the minimum value is that value. Otherwise, the minimum value is zero. The maximum value If the max attribute is specified and a value could be parsed out of it, the maximum value is that value. Otherwise, if the max attribute is specified but no value could be parsed out of it, or if it was not specified, but either or both of the min or value attributes were specified, then the maximum value is 1. Otherwise, none of the max, min, and value attributes were specified. If the result of processing the textContent of the element was either nothing or just one number with no denominator punctuation character, then the maximum value is 1; if the result was one number but it had an associated denominator punctuation character, then the maximum value is the value associated with that denominator punctuation character; and finally, if there were two numbers parsed out of the textContent, then the maximum is the higher of those two numbers. If the above machinations result in a maximum value less than the minimum value, then the maximum value is actually the same as the minimum value. The actual value If the value attribute is specified and a value could be parsed out of it, then that value is the actual value. If the value attribute is not specified but the max attribute is specified and the result of processing the textContent of the element was one number with no associated denominator punctuation character, then that number is the actual value. If neither of the value and max attributes are specified, then, if the result of processing the textContent of the element was one number (with or without an associated denominator punctuation character), then that is the actual value, and if the result of processing the textContent of the element was two numbers, then the actual value is the lower of the two numbers found. Otherwise, if none of the above apply, the actual value is zero. If the above procedure results in an actual value less than the minimum value, then the actual value is actually the same as the minimum value. If, on the other hand, the result is an actual value greater than the maximum value, then the actual value is the maximum value. The low boundary If the low attribute is specified and a value could be parsed out of it, then the low boundary is that value. Otherwise, the low boundary is the same as the minimum value. If the low boundary is then less than the minimum value, then the low boundary is actually the same as the minimum value. Similarly, if the low boundary is greater than the maximum value, then it is actually the maximum value instead. The high boundary If the high attribute is specified and a value could be parsed out of it, then the high boundary is that value. Otherwise, the high boundary is the same as the maximum value. If the high boundary is then less than the low boundary, then the high boundary is actually the same as the low boundary. Similarly, if the high boundary is greater than the maximum value, then it is actually the maximum value instead. The optimum point If the optimum attribute is specified and a value could be parsed out of it, then the optimum point is that value. Otherwise, the optimum point is the midpoint between the minimum value and the maximum value. If the optimum point is then less than the minimum value, then the optimum point is actually the same as the minimum value. Similarly, if the optimum point is greater than the maximum value, then it is actually the maximum value instead. All of which will result in the following inequalities all being true: q minimum value ≤ actual value ≤ maximum value q minimum value ≤ low boundary ≤ high boundary ≤ maximum value q minimum value ≤ optimum point ≤ maximum value UA requirements for regions of the gauge: If the optimum point is equal to the low boundary or the high boundary, or anywhere in between them, then the region between the low and high boundaries of the gauge must be treated as the optimum region, and the low and high parts, if any, must be treated as suboptimal. Otherwise, if the optimum point is less than the low boundary, then the region between the minimum value and the low boundary must be treated as the optimum region, the region between the low boundary and the high boundary must be treated as a suboptimal region, and the region between the high boundary and the maximum value must be treated as an even less good region. Finally, if the optimum point is higher than the high boundary, then the situation is reversed; the region between the high boundary and the maximum value must be treated as the optimum region, the region between the high boundary and the low boundary must be treated as a suboptimal region, and the remaining region between the low boundary and the minimum value must be treated as an even less good region. UA requirements for showing the gauge: When representing a meter element to the user, the UA should indicate the relative position of the actual value to the minimum and maximum values, and the relationship between the actual value and the three regions of the gauge. The following markup: <h3>Suggested groups</h3> <menu type="toolbar"> <a href="?cmd=hsg" onclick="hideSuggestedGroups()">Hide suggested groups</a> </menu> <ul> <li> <p><a href="/group/comp.infosystems.www.authoring.stylesheets/view">comp.infosystems.www.authoring.stylesheets</a> - <a href="/group/comp.infosystems.www.authoring.stylesheets/subscribe">join</a></p> <p>Group description: <strong>Layout/presentation on the WWW.</strong></p> <p><meter value="0.5">Moderate activity,</meter> Usenet, 618 subscribers</p> </li> <li> http://dev.w3.org/html5/spec/Overview.html (139 de 570)01-08-2009 6:55:56
- 140. HTML 5 <p><a href="/group/netscape.public.mozilla.xpinstall/view">netscape.public.mozilla.xpinstall</a> - <a href="/group/netscape.public.mozilla.xpinstall/subscribe">join</a></p> <p>Group description: <strong>Mozilla XPInstall discussion.</strong></p> <p><meter value="0.25">Low activity,</meter> Usenet, 22 subscribers</p> </li> <li> <p><a href="/group/mozilla.dev.general/view">mozilla.dev.general</a> - <a href="/group/mozilla.dev.general/subscribe">join</a></p> <p><meter value="0.25">Low activity,</meter> Usenet, 66 subscribers</p> </li> </ul> Might be rendered as follows: User agents may combine the value of the title attribute and the other attributes to provide context-sensitive help or inline text detailing the actual values. For example, the following snippet: <meter min=0 max=60 value=23.2 title=seconds></meter> ...might cause the user agent to display a gauge with a tooltip saying "Value: 23.2 out of 60." on one line and "seconds" on a second line. The min, max, value, low, high, and optimum DOM attributes must reflect the respective content attributes of the same name. When the relevant content attributes are absent, the DOM attributes must return zero. The value parsed from the textContent never affects the DOM values. 4.6.13 The code element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The code element represents a fragment of computer code. This could be an XML element name, a filename, a computer program, or any other string that a computer would recognize. Although there is no formal way to indicate the language of computer code being marked up, authors who wish to mark code elements with the language used, e.g. so that syntax highlighting scripts can use the right rules, may do so by adding a class prefixed with "language-" to the element. The following example shows how the element can be used in a paragraph to mark up element names and computer code, including punctuation. <p>The <code>code</code> element represents a fragment of computer code.</p> <p>When you call the <code>activate()</code> method on the <code>robotSnowman</code> object, the eyes glow.</p> <p>The example below uses the <code>begin</code> keyword to indicate the start of a statement block. It is paired with an <code>end</code> http://dev.w3.org/html5/spec/Overview.html (140 de 570)01-08-2009 6:55:56
- 141. HTML 5 keyword, which is followed by the <code>.</code> punctuation character (full stop) to indicate the end of the program.</p> The following example shows how a block of code could be marked up using the pre and code elements. <pre><code class="language-pascal">var i: Integer; begin i := 1; end.</code></pre> A class is used in that example to indicate the language used. See the pre element for more details. 4.6.14 The var element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The var element represents a variable. This could be an actual variable in a mathematical expression or programming context, or it could just be a term used as a placeholder in prose. In the paragraph below, the letter "n" is being used as a variable in prose: <p>If there are <var>n</var> pipes leading to the ice cream factory then I expect at <em>least</em> <var>n</var> flavors of ice cream to be available for purchase!</p> For mathematics, in particular for anything beyond the simplest of expressions, MathML is more appropriate. However, the var element can still be used to refer to specific variables that are then mentioned in MathML expressions. In this example, an equation is shown, with a legend that references the variables in the equation. The expression itself is marked up with MathML, but the variables are mentioned in the figure's legend using var. <figure> <math> <mi>a</mi> <mo>=</mo> <msqrt> <msup><mi>b</mi><mn>2</mn></msup> <mi>+</mi> <msup><mi>c</mi><mn>2</mn></msup> </msqrt> </math> <legend> Using Pythagoras' theorem to solve for the hypotenuse <var>a</var> of a triangle with sides <var>b</var> and <var>c</var> </legend> </figure> 4.6.15 The samp element Categories Flow content. Phrasing content. http://dev.w3.org/html5/spec/Overview.html (141 de 570)01-08-2009 6:55:56
- 142. HTML 5 Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The samp element represents (sample) output from a program or computing system. See the pre and kbd elements for more details. This example shows the samp element being used inline: <p>The computer said <samp>Too much cheese in tray two</samp> but I didn't know what that meant.</p> This second example shows a block of sample output. Nested samp and kbd elements allow for the styling of specific elements of the sample output using a style sheet. <pre><samp><span class="prompt">jdoe@mowmow:~$</span> <kbd>ssh demo.example.com</kbd> Last login: Tue Apr 12 09:10:17 2005 from mowmow.example.com on pts/1 Linux demo 2.6.10-grsec+gg3+e+fhs6b+nfs+gr0501+++p3+c4a+gr2b-reslog-v6.189 #1 SMP Tue Feb 1 11:22:36 PST 2005 i686 unknown <span class="prompt">jdoe@demo:~$</span> <span class="cursor">_</span></samp></pre> 4.6.16 The kbd element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The kbd element represents user input (typically keyboard input, although it may also be used to represent other input, such as voice commands). When the kbd element is nested inside a samp element, it represents the input as it was echoed by the system. When the kbd element contains a samp element, it represents input based on system output, for example invoking a menu item. When the kbd element is nested inside another kbd element, it represents an actual key or other single unit of input as appropriate for the input mechanism. Here the kbd element is used to indicate keys to press: <p>To make George eat an apple, press <kbd><kbd>Shift</kbd>+<kbd>F3</kbd></kbd></p> In this second example, the user is told to pick a particular menu item. The outer kbd element marks up a block of input, with the inner kbd elements representing each individual step of the input, and the samp elements inside them indicating that the steps are input based on something being displayed by the system, in this case menu labels: <p>To make George eat an apple, select <kbd><kbd><samp>File</samp></kbd>|<kbd><samp>Eat Apple...</samp></kbd></kbd> </p> 4.6.17 The sub and sup elements http://dev.w3.org/html5/spec/Overview.html (142 de 570)01-08-2009 6:55:56
- 143. HTML 5 Categories Flow content. Phrasing content. Contexts in which these elements may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The sup element represents a superscript and the sub element represents a subscript. These elements must be used only to mark up typographical conventions with specific meanings, not for typographical presentation for presentation's sake. For example, it would be inappropriate for the sub and sup elements to be used in the name of the LaTeX document preparation system. In general, authors should use these elements only if the absence of those elements would change the meaning of the content. When the sub element is used inside a var element, it represents the subscript that identifies the variable in a family of variables. <p>The coordinate of the <var>i</var>th point is (<var>x<sub><var>i</var></sub></var>, <var>y<sub><var>i</var></sub></var>). For example, the 10th point has coordinate (<var>x<sub>10</sub></var>, <var>y<sub>10</sub></var>).</p> In certain languages, superscripts are part of the typographical conventions for some abbreviations. <p>The most beautiful women are <span lang="fr"><abbr>M<sup>lle</sup></abbr> Gwendoline</span> and <span lang="fr"><abbr>M<sup>me</sup></abbr> Denise</span>.</p> Mathematical expressions often use subscripts and superscripts. Authors are encouraged to use MathML for marking up mathematics, but authors may opt to use sub and sup if detailed mathematical markup is not desired. [MathML] <var>E</var>=<var>m</var><var>c</var><sup>2</sup> f(<var>x</var>, <var>n</var>) = log<sub>4</sub><var>x</var><sup><var>n</var></sup> 4.6.18 The span element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: interface HTMLSpanElement : HTMLElement {}; The span element doesn't mean anything on its own, but can be useful when used together with other attributes, e.g. class, lang, or dir. It represents its children. 4.6.19 The i element Categories Flow content. Phrasing content. http://dev.w3.org/html5/spec/Overview.html (143 de 570)01-08-2009 6:55:56
- 144. HTML 5 Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The i element represents a span of text in an alternate voice or mood, or otherwise offset from the normal prose, such as a taxonomic designation, a technical term, an idiomatic phrase from another language, a thought, a ship name, or some other prose whose typical typographic presentation is italicized. Terms in languages different from the main text should be annotated with lang attributes (or, in XML, lang attributes in the XML namespace). The examples below show uses of the i element: <p>The <i class="taxonomy">Felis silvestris catus</i> is cute.</p> <p>The term <i>prose content</i> is defined above.</p> <p>There is a certain <i lang="fr">je ne sais quoi</i> in the air.</p> In the following example, a dream sequence is marked up using i elements. <p>Raymond tried to sleep.</p> <p><i>The ship sailed away on Thursday</i>, he dreamt. <i>The ship had many people aboard, including a beautiful princess called Carey. He watched her, day-in, day-out, hoping she would notice him, but she never did.</i></p> <p><i>Finally one night he picked up the courage to speak with her—</i></p> <p>Raymond woke with a start as the fire alarm rang out.</p> Authors are encouraged to use the class attribute on the i element to identify why the element is being used, so that if the style of a particular use (e.g. dream sequences as opposed to taxonomic terms) is to be changed at a later date, the author doesn't have to go through the entire document (or series of related documents) annotating each use. Similarly, authors are encouraged to consider whether other elements might be more applicable than the i element, for instance the em element for marking up stress emphasis, or the dfn element to mark up the defining instance of a term. Style sheets can be used to format i elements, just like any other element can be restyled. Thus, it is not the case that content in i elements will necessarily be italicized. 4.6.20 The b element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The b element represents a span of text to be stylistically offset from the normal prose without conveying any extra importance, such as key words in a document abstract, product names in a review, or other spans of text whose typical typographic presentation is boldened. The following example shows a use of the b element to highlight key words without marking them up as important: <p>The <b>frobonitor</b> and <b>barbinator</b> components are fried.</p> In the following example, objects in a text adventure are highlighted as being special by use of the b element. <p>You enter a small room. Your <b>sword</b> glows brighter. A <b>rat</b> scurries past the corner wall.</p> http://dev.w3.org/html5/spec/Overview.html (144 de 570)01-08-2009 6:55:56
- 145. HTML 5 Another case where the b element is appropriate is in marking up the lede (or lead) sentence or paragraph. The following example shows how a BBC article about kittens adopting a rabbit as their own could be marked up: <article> <h2>Kittens 'adopted' by pet rabbit</h2> <p><b>Six abandoned kittens have found an unexpected new mother figure — a pet rabbit.</b></p> <p>Veterinary nurse Melanie Humble took the three-week-old kittens to her Aberdeen home.</p> [...] The b element should be used as a last resort when no other element is more appropriate. In particular, headings should use the h1 to h6 elements, stress emphasis should use the em element, importance should be denoted with the strong element, and text marked or highlighted should use the mark element. The following would be incorrect usage: <p><b>WARNING!</b> Do not frob the barbinator!</p> In the previous example, the correct element to use would have been strong, not b. Style sheets can be used to format b elements, just like any other element can be restyled. Thus, it is not the case that content in b elements will necessarily be boldened. 4.6.21 The bdo element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Phrasing content. Content attributes: Global attributes Also, the dir global attribute has special semantics on this element. DOM interface: Uses HTMLElement. The bdo element represents explicit text directionality formatting control for its children. It allows authors to override the Unicode bidi algorithm by explicitly specifying a direction override. [BIDI] Authors must specify the dir attribute on this element, with the value ltr to specify a left-to-right override and with the value rtl to specify a right-to-left override. If the element has the dir attribute set to the exact value ltr, then for the purposes of the bidi algorithm, the user agent must act as if there was a U+202D LEFT-TO-RIGHT OVERRIDE character at the start of the element, and a U+202C POP DIRECTIONAL FORMATTING at the end of the element. If the element has the dir attribute set to the exact value rtl, then for the purposes of the bidi algorithm, the user agent must act as if there was a U+202E RIGHT-TO-LEFT OVERRIDE character at the start of the element, and a U+202C POP DIRECTIONAL FORMATTING at the end of the element. The requirements on handling the bdo element for the bidi algorithm may be implemented indirectly through the style layer. For example, an HTML+CSS user agent should implement these requirements by implementing the CSS 'unicode-bidi' property. [CSS] 4.6.22 The ruby element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: One or more groups of: phrasing content followed either by a single rt element, or an rp element, an rt element, and another rp element. Content attributes: Global attributes http://dev.w3.org/html5/spec/Overview.html (145 de 570)01-08-2009 6:55:56
- 146. HTML 5 DOM interface: Uses HTMLElement. The ruby element allows one or more spans of phrasing content to be marked with ruby annotations. Ruby annotations are short runs of text presented alongside base text, primarily used in East Asian typography as a guide for pronunciation or to include other annotations. In Japanese, this form of typography is also known as furigana. A ruby element represents the spans of phrasing content it contains, ignoring all the child rt and rp elements and their descendants. Those spans of phrasing content have associated annotations created using the rt element. In this example, each ideograph in the Japanese text •• is annotated with its kanji reading. ... <ruby> • <rt> •• </rt> • <rt> •• </rt> </ruby> ... This might be rendered as: In this example, each ideograph in the traditional Chinese text •• is annotated with its bopomofo reading. <ruby> • <rt> ••• </rt> • <rt> ••• </rt> </ruby> This might be rendered as: In this example, each ideograph in the simplified Chinese text •• is annotated with its pinyin reading. ... <ruby> • <rt> hàn </rt> • <rt> zì </rt> </ruby> ... This might be rendered as: 4.6.23 The rt element Categories None. Contexts in which this element may be used: As a child of a ruby element. Content model: Phrasing content. Content attributes: http://dev.w3.org/html5/spec/Overview.html (146 de 570)01-08-2009 6:55:56
- 147. HTML 5 Global attributes DOM interface: Uses HTMLElement. The rt element marks the ruby text component of a ruby annotation. An rt element that is a child of a ruby element represents an annotation (given by its children) for the zero or more nodes of phrasing content that immediately precedes it in the ruby element, ignoring rp elements. An rt element that is not a child of a ruby element represents the same thing as its children. 4.6.24 The rp element Categories None. Contexts in which this element may be used: As a child of a ruby element, either immediately before or immediately after an rt element. Content model: Phrasing content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The rp element can be used to provide parentheses around a ruby text component of a ruby annotation, to be shown by user agents that don't support ruby annotations. An rp element that is a child of a ruby element represents nothing and its contents must be ignored. An rp element whose parent element is not a ruby element represents its children. The example above, in which each ideograph in the text •• is annotated with its kanji reading, could be expanded to use rp so that in legacy user agents the readings are in parentheses: ... <ruby> • <rp>(</rp><rt>••</rt><rp>)</rp> • <rp>(</rp><rt>•</rt><rp>)</rp> </ruby> ... In conforming user agents the rendering would be as above, but in user agents that do not support ruby, the rendering would be: ... • (••) • (•) ... 4.6.25 Usage summary We need to summarize the various elements, in particular to distinguish b/i/em/strong/var/q/mark/cite. 4.6.26 Footnotes HTML does not have a dedicated mechanism for marking up footnotes. Here are the recommended alternatives. For short inline annotations, the title attribute should be used. In this example, two parts of a dialog are annotated. <dialog> <dt>Customer <dd>Hello! I wish to register a complaint. Hello. Miss? <dt>Shopkeeper <dd><span title="Colloquial pronunciation of 'What do you'" >Watcha</span> mean, miss? <dt>Customer <dd>Uh, I'm sorry, I have a cold. I wish to make a complaint. http://dev.w3.org/html5/spec/Overview.html (147 de 570)01-08-2009 6:55:56
- 148. HTML 5 <dt>Shopkeeper <dd>Sorry, <span title="This is, of course, a lie.">we're closing for lunch</span>. </dialog> For longer annotations, the a element should be used, pointing to an element later in the document. The convention is that the contents of the link be a number in square brackets. In this example, a footnote in the dialog links to a paragraph below the dialog. The paragraph then reciprocally links back to the dialog, allowing the user to return to the location of the footnote. <dialog> <dt>Announcer <dd>Number 16: The <i>hand</i>. <dt>Interviewer <dd>Good evening. I have with me in the studio tonight Mr Norman St John Polevaulter, who for the past few years has been contradicting people. Mr Polevaulter, why <em>do</em> you contradict people? <dt>Norman <dd>I don't. <a href="#fn1" id="r1">[1]</a> <dt>Interviewer <dd>You told me you did! </dialog> <section> <p id="fn1"><a href="#r1">[1]</a> This is, naturally, a lie, but paradoxically if it were true he could not say so without contradicting the interviewer and thus making it false.</p> </section> For side notes, longer annotations that apply to entire sections of the text rather than just specific words or sentences, the aside element should be used. In this example, a sidebar is given after a dialog, giving some context to the dialog. <dialog> <dt>Customer <dd>I will not buy this record, it is scratched. <dt>Shopkeeper <dd>I'm sorry? <dt>Customer <dd>I will not buy this record, it is scratched. <dt>Shopkeeper <dd>No no no, this's'a tobacconist's. </dialog> <aside> <p>In 1970, the British Empire lay in ruins, and foreign nationalists frequented the streets — many of them Hungarians (not the streets — the foreign nationals). Sadly, Alexander Yalt has been publishing incompetently-written phrase books. </aside> For figures or tables, footnotes can be included in the relevant legend or caption element, or in surrounding prose. In this example, a table has cells with footnotes that are given in prose. A figure element is used to give a single legend to the combination of the table and its footnotes. <figure> <legend>Table 1. Alternative activities for knights.</legend> <table> <tr> <th> Activity <th> Location <th> Cost <tr> <td> Dance <td> Wherever possible <td> £0<sup><a href="#fn1">1</a></sup> <tr> <td> Routines, chorus scenes<sup><a href="#fn2">2</a></sup> <td> Undisclosed <td> Undisclosed <tr> <td> Dining<sup><a href="#fn3">3</a></sup> http://dev.w3.org/html5/spec/Overview.html (148 de 570)01-08-2009 6:55:56
- 149. HTML 5 <td> Camelot <td> Cost of ham, jam, and spam<sup><a href="#fn4">4</a></sup> </table> <p id="fn1">1. Assumed.</p> <p id="fn2">2. Footwork impeccable.</p> <p id="fn3">3. Quality described as "well".</p> <p id="fn4">4. A lot.</p> </figure> 4.7 Edits The ins and del elements represent edits to the document. 4.7.1 The ins element Categories Flow content. When the element only contains phrasing content: phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Transparent. Content attributes: Global attributes cite datetime DOM interface: Uses the HTMLModElement interface. The ins element represents an addition to the document. The following represents the addition of a single paragraph: <aside> <ins> <p> I like fruit. </p> </ins> </aside> As does this, because everything in the aside element here counts as phrasing content and therefore there is just one paragraph: <aside> <ins> Apples are <em>tasty</em>. </ins> <ins> So are pears. </ins> </aside> ins elements should not cross implied paragraph boundaries. The following example represents the addition of two paragraphs, the second of which was inserted in two parts. The first ins element in this example thus crosses a paragraph boundary, which is considered poor form. <aside> <ins datetime="2005-03-16T00:00Z"> <p> I like fruit. </p> Apples are <em>tasty</em>. </ins> <ins datetime="2007-12-19T00:00Z"> So are pears. </ins> </aside> http://dev.w3.org/html5/spec/Overview.html (149 de 570)01-08-2009 6:55:56
- 150. HTML 5 Here is a better way of marking this up. It uses more elements, but none of the elements cross implied paragraph boundaries. <aside> <ins datetime="2005-03-16T00:00Z"> <p> I like fruit. </p> </ins> <ins datetime="2005-03-16T00:00Z"> Apples are <em>tasty</em>. </ins> <ins datetime="2007-12-19T00:00Z"> So are pears. </ins> </aside> 4.7.2 The del element Categories Flow content. When the element only contains phrasing content: phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Transparent. Content attributes: Global attributes cite datetime DOM interface: Uses the HTMLModElement interface. The del element represents a removal from the document. del elements should not cross implied paragraph boundaries. 4.7.3 Attributes common to ins and del elements The cite attribute may be used to specify the address of a document that explains the change. When that document is long, for instance the minutes of a meeting, authors are encouraged to include a fragment identifier pointing to the specific part of that document that discusses the change. If the cite attribute is present, it must be a valid URL that explains the change. To obtain the corresponding citation link, the value of the attribute must be resolved relative to the element. User agents should allow users to follow such citation links. The datetime attribute may be used to specify the time and date of the change. If present, the datetime attribute must be a valid global date and time string value. User agents must parse the datetime attribute according to the parse a global date and time string algorithm. If that doesn't return a time, then the modification has no associated timestamp (the value is non-conforming; it is not a valid global date and time string). Otherwise, the modification is marked as having been made at the given datetime. User agents should use the associated time-zone information to determine which time zone to present the given datetime in. The ins and del elements must implement the HTMLModElement interface: interface HTMLModElement : HTMLElement { attribute DOMString cite; attribute DOMString dateTime; }; The cite DOM attribute must reflect the element's cite content attribute. The dateTime DOM attribute must reflect the element's datetime content attribute. 4.7.4 Edits and paragraphs Since the ins and del elements do not affect paragraphing, it is possible, in some cases where paragraphs are implied (without explicit p elements), for an ins or del element to span both an entire paragraph or other non-phrasing content elements and part of http://dev.w3.org/html5/spec/Overview.html (150 de 570)01-08-2009 6:55:56
- 151. HTML 5 another paragraph. For example: <section> <ins> <p> This is a paragraph that was inserted. </p> This is another paragraph whose first sentence was inserted at the same time as the paragraph above. </ins> This is a second sentence, which was there all along. </section> By only wrapping some paragraphs in p elements, one can even get the end of one paragraph, a whole second paragraph, and the start of a third paragraph to be covered by the same ins or del element (though this is very confusing, and not considered good practice): <section> This is the first paragraph. <ins>This sentence was inserted. <p>This second paragraph was inserted.</p> This sentence was inserted too.</ins> This is the third paragraph in this example. </section> However, due to the way implied paragraphs are defined, it is not possible to mark up the end of one paragraph and the start of the very next one using the same ins or del element. You instead have to use one (or two) p element(s) and two ins or del elements: For example: <section> <p>This is the first paragraph. <del>This sentence was deleted.</del></p> <p><del>This sentence was deleted too.</del> That sentence needed a separate <del> element.</p> </section> Partly because of the confusion described above, authors are strongly recommended to always mark up all paragraphs with the p element, and to not have any ins or del elements that cross across any implied paragraphs. 4.7.5 Edits and lists The content models of the ol and ul elements do not allow ins and del elements as children. Lists always represent all their items, including items that would otherwise have been marked as deleted. To indicate that an item is inserted or deleted, an ins or del element can be wrapped around the contents of the li element. To indicate that an item has been replaced by another, a single li element can have one or more del elements followed by one or more ins elements. In the following example, a list that started empty had items added and removed from it over time. The bits in the example that have been emphasized show the parts that are the "current" state of the list. The list item numbers don't take into account the edits, though. <h1>Stop-ship bugs</h1> <ol> <li><ins datetime="2008-02-12T15:20Z">Bug 225: Rain detector doesn't work in snow</ins></li> <li><del datetime="2008-03-01T20:22Z"><ins datetime="2008-02-14T12:02Z">Bug 228: Water buffer overflows in April</ins></del></li> <li><ins datetime="2008-02-16T13:50Z">Bug 230: Water heater doesn't use renewable fuels</ins></li> <li><del datetime="2008-02-20T21:15Z"><ins datetime="2008-02-16T14:25Z">Bug 232: Carbon dioxide emissions detected after startup</ins></del></li> </ol> In the following example, a list that started with just fruit was replaced by a list with just colors. <h1>List of <del>fruits</del><ins>colors</ins></h1> <ul> <li><del>Lime</del><ins>Green</ins></li> <li><del>Apple</del></li> <li>Orange</li> http://dev.w3.org/html5/spec/Overview.html (151 de 570)01-08-2009 6:55:56
- 152. HTML 5 <li><del>Pear</del></li> <li><ins>Teal</ins></li> <li><del>Lemon</del><ins>Yellow</ins></li> <li>Olive</li> <li><ins>Purple</ins> </ul> 4.8 Embedded content 4.8.1 The figure element Categories Flow content. Sectioning root. Contexts in which this element may be used: Where flow content is expected. Content model: Either: one legend element followed by flow content. Or: Flow content followed by one legend element. Or: Flow content. Content attributes: Global attributes DOM interface: Uses HTMLElement. The figure element represents some flow content, optionally with a caption, that is self-contained and is typically referenced as a single unit from the main flow of the document. The element can thus be used to annotate illustrations, diagrams, photos, code listings, etc, that are referred to from the main content of the document, but that could, without affecting the flow of the document, be moved away from that primary content, e.g. to the side of the page, to dedicated pages, or to an appendix. The first legend element child of the element, if any, represents the caption of the figure element's contents. If there is no child legend element, then there is no caption. The remainder of the element's contents, if any, represents the content. This example shows the figure element to mark up a code listing. <p>In <a href="#l4">listing 4</a> we see the primary core interface API declaration.</p> <figure id="l4"> <legend>Listing 4. The primary core interface API declaration.</legend> <pre><code>interface PrimaryCore { boolean verifyDataLine(); void sendData(in sequence<byte> data); void initSelfDestruct(); }</code></pre> </figure> <p>The API is designed to use UTF-8.</p> Here we see a figure element to mark up a photo. <figure> <img src="bubbles-work.jpeg" alt="Bubbles, sitting in his office chair, works on his latest project intently."> <legend>Bubbles at work</legend> </figure> In this example, we see an image that is not a figure, as well as an image and a video that are. <h2>Malinko's comics</h2> <p>This case centered on some sort of "intellectual property" infringement related to a comic (see Exhibit A). The suit started after a trailer ending with these words:</p> http://dev.w3.org/html5/spec/Overview.html (152 de 570)01-08-2009 6:55:56
- 153. HTML 5 <img src="promblem-packed-action.png" alt="ROUGH COPY! Promblem-Packed Action!"> <p>...was aired. A lawyer, armed with a Bigger Notebook, launched a preemptive strike using snowballs. A complete copy of the trailer is included with Exhibit B.</p> <figure> <img src="ex-a.png" alt="Two squiggles on a dirty piece of paper."> <legend>Exhibit A. The alleged <cite>rough copy</cite> comic.</legend> </figure> <figure> <video src="ex-b.mov"></video> <legend>Exhibit B. The <code>Rough Copy</cite> trailer.</legend> </figure> <p>The case was resolved out of court.</p> Here, a part of a poem is marked up using figure. <figure> <p>'Twas brillig, and the slithy toves<br> Did gyre and gimble in the wabe;<br> All mimsy were the borogoves,<br> And the mome raths outgrabe.</p> <legend><cite>Jabberwocky</cite> (first verse). Lewis Carroll, 1832-98</legend> </figure> In this example, which could be part of a much larger work discussing a castle, the figure has three images in it. <figure> <img src="castle1423.jpeg" title="Etching. Anonymous, ca. 1423." alt="The castle has one tower, and a tall wall around it."> <img src="castle1858.jpeg" title="Oil-based paint on canvas. Maria Towle, 1858." alt="The castle now has two towers and two walls."> <img src="castle1999.jpeg" title="Film photograph. Peter Jankle, 1999." alt="The castle lies in ruins, the original tower all that remains in one piece."> <legend>The castle through the ages: 1423, 1858, and 1999 respectively.</legend> </figure> 4.8.2 The img element Categories Flow content. Phrasing content. Embedded content. If the element has a usemap attribute: Interactive content. Contexts in which this element may be used: Where embedded content is expected. Content model: Empty. Content attributes: Global attributes alt src usemap ismap width height DOM interface: [NamedConstructor=Image(), NamedConstructor=Image(in unsigned long width), NamedConstructor=Image(in unsigned long width, in unsigned long height)] interface HTMLImageElement : HTMLElement { http://dev.w3.org/html5/spec/Overview.html (153 de 570)01-08-2009 6:55:56
- 154. HTML 5 attribute DOMString alt; attribute DOMString src; attribute DOMString useMap; attribute boolean isMap; attribute unsigned long width; attribute unsigned long height; readonly attribute boolean complete; }; An img element represents an image. The image given by the src attribute is the embedded content, and the value of the alt attribute is the img element's fallback content. The src attribute must be present, and must contain a valid URL referencing a non-interactive, optionally animated, image resource that is neither paged nor scripted. If the base URI of the element is the same as the document's address, then the src attribute's value must not be the empty string. Images can thus be static bitmaps (e.g. PNGs, GIFs, JPEGs), single-page vector documents (single-page PDFs, XML files with an SVG root element), animated bitmaps (APNGs, animated GIFs), animated vector graphics (XML files with an SVG root element that use declarative SMIL animation), and so forth. However, this also precludes SVG files with script, multipage PDF files, interactive MNG files, HTML documents, plain text documents, and so forth. The requirements on the alt attribute's value are described in the next section. The img must not be used as a layout tool. In particular, img elements should not be used to display transparent images, as they rarely convey meaning and rarely add anything useful to the document. Unless the user agent cannot support images, or its support for images has been disabled, or the user agent only fetches elements on demand, or the element's src attribute has a value that is an ignored self-reference, then, when an img is created with a src attribute, and whenever the src attribute is set subsequently, the user agent must resolve the value of that attribute, relative to the element, and if that is successful must then fetch that resource. The src attribute's value is an ignored self-reference if its value is the empty string, and the base URI of the element is the same as the document's address. Fetching the image must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined below) has been run. This, unfortunately, can be used to perform a rudimentary port scan of the user's local network (especially in conjunction with scripting, though scripting isn't actually necessary to carry out such an attack). User agents may implement cross-origin access control policies that mitigate this attack. If the image is in a supported image type and its dimensions are known, then the image is said to be available (this affects exactly what the element represents, as defined below). This can be true even before the image is completely downloaded, if the user agent supports incremental rendering of images; in such cases, each task that is queued by the networking task source while the image is being fetched must update the presentation of the image appropriately. It can also stop being true, e.g. if the user agent finds, after obtaining the image's dimensions, that the image data is actually fatally corrupted. If the image was not fetched (e.g. because the UA's image support is disabled, or because the src attribute's value is an ignored self-reference), or if the conditions in the previous paragraph are not met, then the image is not available. An image might be available in one view but not another. For instance, a Document could be rendered by a screen reader providing a speech synthesis view of the output of a Web browser using the screen media. In this case, the image would be available in the Web browser's screen view, but not available in the screen reader's view. Whether the image is fetched successfully or not (e.g. whether the response code was a 2xx code or equivalent) must be ignored when determining the image's type and whether it is a valid image. This allows servers to return images with error responses, and have them displayed. The user agents should apply the image sniffing rules to determine the type of the image, with the image's associated Content-Type headers giving the official type. If these rules are not applied, then the type of the image must be the type given by the image's associated Content-Type headers. User agents must not support non-image resources with the img element (e.g. XML files whose root element is an HTML element). User agents must not run executable code (e.g. scripts) embedded in the image resource. User agents must only display the first page of a multipage resource (e.g. a PDF file). User agents must not allow the resource to act in an interactive fashion, but should honor any animation in the resource. This specification does not specify which image types are to be supported. The task that is queued by the networking task source once the resource has been fetched, must act as appropriate given the following alternatives: If the download was successful and the image is available Queue a task to fire a simple event called load at the img element (this happens after complete starts returning true). Otherwise (the fetching process failed without a response from the remote server, or completed but the image is not a supported image) Queue a task to fire a simple event called error on the img element. http://dev.w3.org/html5/spec/Overview.html (154 de 570)01-08-2009 6:55:56
- 155. HTML 5 The task source for these tasks is the DOM manipulation task source. What an img element represents depends on the src attribute and the alt attribute. If the src attribute is set and the alt attribute is set to the empty string The image is either decorative or supplemental to the rest of the content, redundant with some other information in the document. If the image is available and the user agent is configured to display that image, then the element represents the image specified by the src attribute. Otherwise, the element represents nothing, and may be omitted completely from the rendering. User agents may provide the user with a notification that an image is present but has been omitted from the rendering. If the src attribute is set and the alt attribute is set to a value that isn't empty The image is a key part of the content; the alt attribute gives a textual equivalent or replacement for the image. If the image is available and the user agent is configured to display that image, then the element represents the image specified by the src attribute. Otherwise, the element represents the text given by the alt attribute. User agents may provide the user with a notification that an image is present but has been omitted from the rendering. If the src attribute is set and the alt attribute is not The image might be a key part of the content, and there is no textual equivalent of the image available. In a conforming document, the absence of the alt attribute indicates that the image is a key part of the content but that a textual replacement for the image was not available when the image was generated. If the image is available, the element represents the image specified by the src attribute. If the image is not available or if the user agent is not configured to display the image, then the user agent should display some sort of indicator that there is an image that is not being rendered, and may, if requested by the user, or if so configured, or when required to provide contextual information in response to navigation, provide caption information for the image, derived as follows: 1. If the image has a title attribute whose value is not the empty string, then the value of that attribute is the caption information; abort these steps. 2. If the image is the child of a figure element that has a child legend element, then the contents of the first such legend element are the caption information; abort these steps. 3. Run the algorithm to create the outline for the document. 4. If the img element did not end up associated with a heading in the outline, or if there are any other images that are lacking an alt attribute and that are associated with the same heading in the outline as the img element in question, then there is no caption information; abort these steps. 5. The caption information is the heading with which the image is associated according to the outline. If the src attribute is not set and either the alt attribute is set to the empty string or the alt attribute is not set at all The element represents nothing. Otherwise The element represents the text given by the alt attribute. The alt attribute does not represent advisory information. User agents must not present the contents of the alt attribute in the same way as content of the title attribute. User agents may always provide the user with the option to display any image, or to prevent any image from being displayed. User agents may also apply image analysis heuristics to help the user make sense of the image when the user is unable to make direct use of the image, e.g. due to a visual disability or because they are using a text terminal with no graphics capabilities. The contents of img elements, if any, are ignored for the purposes of rendering. The usemap attribute, if present, can indicate that the image has an associated image map. The ismap attribute, when used on an element that is a descendant of an a element with an href attribute, indicates by its presence that the element provides access to a server-side image map. This affects how events are handled on the corresponding a element. The ismap attribute is a boolean attribute. The attribute must not be specified on an element that does not have an ancestor a element with an href attribute. The img element supports dimension attributes. The DOM attributes alt, src, useMap, and isMap each must reflect the respective content attributes of the same name. image . width [ = value ] http://dev.w3.org/html5/spec/Overview.html (155 de 570)01-08-2009 6:55:56
- 156. HTML 5 image . height [ = value ] These attributes return the actual rendered dimensions of the image, or zero if the dimensions are not known. They can be set, to change the corresponding content attributes. image . complete Returns true if the image has been downloaded, decoded, and found to be valid; otherwise, returns false. image = new Image( [ width [, height ] ] ) Returns a new img element, with the width and height attributes set to the values passed in the relevant arguments, if applicable. The DOM attributes width and height must return the rendered width and height of the image, in CSS pixels, if the image is being rendered, and is being rendered to a visual medium; or else the intrinsic width and height of the image, in CSS pixels, if the image is available but not being rendered to a visual medium; or else 0, if the image is not available or its dimensions are not known. [CSS] On setting, they must act as if they reflected the respective content attributes of the same name. The DOM attribute complete must return true if the user agent has fetched the image specified in the src attribute, and it is in a supported image type (i.e. it was decoded without fatal errors), even if the final task queued by the networking task source for the fetching of the image resource has not yet been processed. Otherwise, the attribute must return false. The value of complete can thus change while a script is executing. Three constructors are provided for creating HTMLImageElement objects (in addition to the factory methods from DOM Core such as createElement()): Image(), Image(width), and Image(width, height). When invoked as constructors, these must return a new HTMLImageElement object (a new img element). If the width argument is present, the new object's width content attribute must be set to width. If the height argument is also present, the new object's height content attribute must be set to height. A single image can have different appropriate alternative text depending on the context. In each of the following cases, the same image is used, yet the alt text is different each time. The image is the coat of arms of the Canton Geneva in Switzerland. Here it is used as a supplementary icon: <p>I lived in <img src="carouge.svg" alt=""> Carouge.</p> Here it is used as an icon representing the town: <p>Home town: <img src="carouge.svg" alt="Carouge"></p> Here it is used as part of a text on the town: <p>Carouge has a coat of arms.</p> <p><img src="carouge.svg" alt="The coat of arms depicts a lion, sitting in front of a tree."></p> <p>It is used as decoration all over the town.</p> Here it is used as a way to support a similar text where the description is given as well as, instead of as an alternative to, the image: <p>Carouge has a coat of arms.</p> <p><img src="carouge.svg" alt=""></p> <p>The coat of arms depicts a lion, sitting in front of a tree. It is used as decoration all over the town.</p> Here it is used as part of a story: <p>He picked up the folder and a piece of paper fell out.</p> <p><img src="carouge.svg" alt="Shaped like a shield, the paper had a red background, a green tree, and a yellow lion with its tongue hanging out and whose tail was shaped like an S."></p> <p>He stared at the folder. S! The answer he had been looking for all this time was simply the letter S! How had he not seen that before? It all came together now. The phone call where Hector had referred to a lion's tail, the time Marco had stuck his tongue out...</p> Here it is not known at the time of publication what the image will be, only that it will be a coat of arms of some kind, and thus no replacement text can be provided, and instead only a brief caption for the image is provided, in the title attribute: <p>The last user to have uploaded a coat of arms uploaded this one:</p> <p><img src="last-uploaded-coat-of-arms.cgi" title="User-uploaded coat of arms."></p> http://dev.w3.org/html5/spec/Overview.html (156 de 570)01-08-2009 6:55:56
- 157. HTML 5 Ideally, the author would find a way to provide real replacement text even in this case, e.g. by asking the previous user. Not providing replacement text makes the document more difficult to use for people who are unable to view images, e.g. blind users, or users or very low-bandwidth connections or who pay by the byte, or users who are forced to use a text-only Web browser. Here are some more examples showing the same picture used in different contexts, with different appropriate alternate texts each time. <article> <h1>My cats</h1> <h2>Fluffy</h2> <p>Fluffy is my favorite.</p> <img src="fluffy.jpg" alt="She likes playing with a ball of yarn."> <p>She's just too cute.</p> <h2>Miles</h2> <p>My other cat, Miles just eats and sleeps.</p> </article> <article> <h1>Photography</h1> <h2>Shooting moving targets indoors</h2> <p>The trick here is to know how to anticipate; to know at what speed and what distance the subject will pass by.</p> <img src="fluffy.jpg" alt="A cat flying by, chasing a ball of yarn, can be photographed quite nicely using this technique."> <h2>Nature by night</h2> <p>To achieve this, you'll need either an extremely sensitive film, or immense flash lights.</p> </article> <article> <h1>About me</h1> <h2>My pets</h2> <p>I've got a cat named Fluffy and a dog named Miles.</p> <img src="fluffy.jpg" alt="Fluffy, my cat, tends to keep itself busy."> <p>My dog Miles and I like go on long walks together.</p> <h2>music</h2> <p>After our walks, having emptied my mind, I like listening to Bach.</p> </article> <article> <h1>Fluffy and the Yarn</h1> <p>Fluffy was a cat who liked to play with yarn. He also liked to jump.</p> <aside><img src="fluffy.jpg" alt="" title="Fluffy"></aside> <p>He would play in the morning, he would play in the evening.</p> </article> 4.8.2.1 Requirements for providing text to act as an alternative for images The requirements for the alt attribute depend on what the image is intended to represent, as described in the following sections. 4.8.2.1.1 A link or button containing nothing but the image When an a element that is a hyperlink, or a button element, has no textual content but contains one or more images, the alt attributes must contain text that together convey the purpose of the link or button. In this example, a user is asked to pick his preferred color from a list of three. Each color is given by an image, but for users who have configured their user agent not to display images, the color names are used instead: <h1>Pick your color</h1> <ul> <li><a href="green.html"><img src="green.jpeg" alt="Green"></a></li> <li><a href="blue.html"><img src="blue.jpeg" alt="Blue"></a></li> <li><a href="red.html"><img src="red.jpeg" alt="Red"></a></li> </ul> In this example, each button has a set of images to indicate the kind of color output desired by the user. The first image is used in each case to give the alternative text. <button name="rgb"><img src="red" alt="RGB"><img src="green" alt=""><img src="blue" alt=""></button> <button name="cmyk"><img src="cyan" alt="CMYK"><img src="magenta" alt=""><img src="yellow" alt=""><img src="black" alt=""></button> Since each image represents one part of the text, it could also be written like this: http://dev.w3.org/html5/spec/Overview.html (157 de 570)01-08-2009 6:55:56
- 158. HTML 5 <button name="rgb"><img src="red" alt="R"><img src="green" alt="G"><img src="blue" alt="B"></button> <button name="cmyk"><img src="cyan" alt="C"><img src="magenta" alt="M"><img src="yellow" alt="Y"><img src="black" alt="K"></button> However, with other alternative text, this might not work, and putting all the alternative text into one image in each case might make more sense: <button name="rgb"><img src="red" alt="sRGB profile"><img src="green" alt=""><img src="blue" alt=""></button> <button name="cmyk"><img src="cyan" alt="CMYK profile"><img src="magenta" alt=""><img src="yellow" alt=""><img src="black" alt=""></button> 4.8.2.1.2 A phrase or paragraph with an alternative graphical representation: charts, diagrams, graphs, maps, illustrations Sometimes something can be more clearly stated in graphical form, for example as a flowchart, a diagram, a graph, or a simple map showing directions. In such cases, an image can be given using the img element, but the lesser textual version must still be given, so that users who are unable to view the image (e.g. because they have a very slow connection, or because they are using a text-only browser, or because they are listening to the page being read out by a hands-free automobile voice Web browser, or simply because they are blind) are still able to understand the message being conveyed. The text must be given in the alt attribute, and must convey the same message as the image specified in the src attribute. It is important to realize that the alternative text is a replacement for the image, not a description of the image. In the following example we have a flowchart in image form, with text in the alt attribute rephrasing the flowchart in prose form: <p>In the common case, the data handled by the tokenization stage comes from the network, but it can also come from script.</p> <p><img src="images/parsing-model-overview.png" alt="The network passes data to the Tokenizer stage, which passes data to the Tree Construction stage. From there, data goes to both the DOM and to Script Execution. Script Execution is linked to the DOM, and, using document.write(), passes data to the Tokenizer."></p> Here's another example, showing a good solution and a bad solution to the problem of including an image in a description. First, here's the good solution. This sample shows how the alternative text should just be what you would have put in the prose if the image had never existed. <!-- This is the correct way to do things. --> <p> You are standing in an open field west of a house. <img src="house.jpeg" alt="The house is white, with a boarded front door."> There is a small mailbox here. </p> Second, here's the bad solution. In this incorrect way of doing things, the alternative text is simply a description of the image, instead of a textual replacement for the image. It's bad because when the image isn't shown, the text doesn't flow as well as in the first example. <!-- This is the wrong way to do things. --> <p> You are standing in an open field west of a house. <img src="house.jpeg" alt="A white house, with a boarded front door."> There is a small mailbox here. </p> Text such as "Photo of white house with boarded door" would be equally bad alternative text (though it could be suitable for the title attribute or in the legend element of a figure with this image). 4.8.2.1.3 A short phrase or label with an alternative graphical representation: icons, logos A document can contain information in iconic form. The icon is intended to help users of visual browsers to recognize features at a glance. In some cases, the icon is supplemental to a text label conveying the same meaning. In those cases, the alt attribute must be present but must be empty. Here the icons are next to text that conveys the same meaning, so they have an empty alt attribute: <nav> <p><a href="/help/"><img src="/icons/help.png" alt=""> Help</a></p> <p><a href="/configure/"><img src="/icons/configuration.png" alt=""> Configuration Tools</a></p> </nav> http://dev.w3.org/html5/spec/Overview.html (158 de 570)01-08-2009 6:55:56
- 159. HTML 5 In other cases, the icon has no text next to it describing what it means; the icon is supposed to be self-explanatory. In those cases, an equivalent textual label must be given in the alt attribute. Here, posts on a news site are labeled with an icon indicating their topic. <body> <article> <header> <h1>Ratatouille wins <i>Best Movie of the Year</i> award</h1> <p><img src="movies.png" alt="Movies"></p> </header> <p>Pixar has won yet another <i>Best Movie of the Year</i> award, making this its 8th win in the last 12 years.</p> </article> <article> <header> <h1>Latest TWiT episode is online</h1> <p><img src="podcasts.png" alt="Podcasts"></p> </header> <p>The latest TWiT episode has been posted, in which we hear several tech news stories as well as learning much more about the iPhone. This week, the panelists compare how reflective their iPhones' Apple logos are.</p> </article> </body> Many pages include logos, insignia, flags, or emblems, which stand for a particular entity such as a company, organization, project, band, software package, country, or some such. If the logo is being used to represent the entity, e.g. as a page heading, the alt attribute must contain the name of the entity being represented by the logo. The alt attribute must not contain text like the word "logo", as it is not the fact that it is a logo that is being conveyed, it's the entity itself. If the logo is being used next to the name of the entity that it represents, then the logo is supplemental, and its alt attribute must instead be empty. If the logo is merely used as decorative material (as branding, or, for example, as a side image in an article that mentions the entity to which the logo belongs), then the entry below on purely decorative images applies. If the logo is actually being discussed, then it is being used as a phrase or paragraph (the description of the logo) with an alternative graphical representation (the logo itself), and the first entry above applies. In the following snippets, all four of the above cases are present. First, we see a logo used to represent a company: <h1><img src="XYZ.gif" alt="The XYZ company"></h1> Next, we see a paragraph which uses a logo right next to the company name, and so doesn't have any alternative text: <article> <h2>News</h2> <p>We have recently been looking at buying the <img src="alpha.gif" alt=""> ΑΒΓ company, a small Greek company specializing in our type of product.</p> In this third snippet, we have a logo being used in an aside, as part of the larger article discussing the acquisition: <aside><p><img src="alpha-large.gif" alt=""></p></aside> <p>The ΑΒΓ company has had a good quarter, and our pie chart studies of their accounts suggest a much bigger blue slice than its green and orange slices, which is always a good sign.</p> </article> Finally, we have an opinion piece talking about a logo, and the logo is therefore described in detail in the alternative text. <p>Consider for a moment their logo:</p> <p><img src="/images/logo" alt="It consists of a green circle with a green question mark centered inside it."></p> <p>How unoriginal can you get? I mean, oooooh, a question mark, how <em>revolutionary</em>, how utterly <em>ground-breaking</em>, I'm sure everyone will rush to adopt those specifications now! They could at least have tried for some sort of, I don't know, sequence of rounded squares with varying shades of green and bold white outlines, at least that would look good on the cover of a blue book.</p> http://dev.w3.org/html5/spec/Overview.html (159 de 570)01-08-2009 6:55:56
- 160. HTML 5 This example shows how the alternative text should be written such that if the image isn't available, and the text is used instead, the text flows seamlessly into the surrounding text, as if the image had never been there in the first place. 4.8.2.1.4 Text that has been rendered to a graphic for typographical effect Sometimes, an image just consists of text, and the purpose of the image is not to highlight the actual typographic effects used to render the text, but just to convey the text itself. In such cases, the alt attribute must be present but must consist of the same text as written in the image itself. Consider a graphic containing the text "Earth Day", but with the letters all decorated with flowers and plants. If the text is merely being used as a heading, to spice up the page for graphical users, then the correct alternative text is just the same text "Earth Day", and no mention need be made of the decorations: <h1><img src="earthdayheading.png" alt="Earth Day"></h1> 4.8.2.1.5 A graphical representation of some of the surrounding text In many cases, the image is actually just supplementary, and its presence merely reinforces the surrounding text. In these cases, the alt attribute must be present but its value must be the empty string. In general, an image falls into this category if removing the image doesn't make the page any less useful, but including the image makes it a lot easier for users of visual browsers to understand the concept. A flowchart that repeats the previous paragraph in graphical form: <p>The network passes data to the Tokenizer stage, which passes data to the Tree Construction stage. From there, data goes to both the DOM and to Script Execution. Script Execution is linked to the DOM, and, using document.write(), passes data to the Tokenizer.</p> <p><img src="images/parsing-model-overview.png" alt=""></p> In these cases, it would be wrong to include alternative text that consists of just a caption. If a caption is to be included, then either the title attribute can be used, or the figure and legend elements can be used. In the latter case, the image would in fact be a phrase or paragraph with an alternative graphical representation, and would thus require alternative text. <!-- Using the title="" attribute --> <p>The network passes data to the Tokenizer stage, which passes data to the Tree Construction stage. From there, data goes to both the DOM and to Script Execution. Script Execution is linked to the DOM, and, using document.write(), passes data to the Tokenizer.</p> <p><img src="images/parsing-model-overview.png" alt="" title="Flowchart representation of the parsing model."></p> <!-- Using <figure> and <legend> --> <p>The network passes data to the Tokenizer stage, which passes data to the Tree Construction stage. From there, data goes to both the DOM and to Script Execution. Script Execution is linked to the DOM, and, using document.write(), passes data to the Tokenizer.</p> <figure> <img src="images/parsing-model-overview.png" alt="The Network leads to the Tokenizer, which leads to the Tree Construction. The Tree Construction leads to two items. The first is Script Execution, which leads via document.write() back to the Tokenizer. The second item from which Tree Construction leads is the DOM. The DOM is related to the Script Execution."> <legend>Flowchart representation of the parsing model.</legend> </figure> <!-- This is WRONG. Do not do this. Instead, do what the above examples do. --> <p>The network passes data to the Tokenizer stage, which passes data to the Tree Construction stage. From there, data goes to both the DOM and to Script Execution. Script Execution is linked to the DOM, and, using document.write(), passes data to the Tokenizer.</p> <p><img src="images/parsing-model-overview.png" alt="Flowchart representation of the parsing model."></p> <!-- Never put the image's caption in the alt="" attribute! --> http://dev.w3.org/html5/spec/Overview.html (160 de 570)01-08-2009 6:55:56
- 161. HTML 5 A graph that repeats the previous paragraph in graphical form: <p>According to a study covering several billion pages, about 62% of documents on the Web in 2007 triggered the Quirks rendering mode of Web browsers, about 30% triggered the Almost Standards mode, and about 9% triggered the Standards mode.</p> <p><img src="rendering-mode-pie-chart.png" alt=""></p> 4.8.2.1.6 A purely decorative image that doesn't add any information In general, if an image is decorative but isn't especially page-specific, for example an image that forms part of a site-wide design scheme, the image should be specified in the site's CSS, not in the markup of the document. However, a decorative image that isn't discussed by the surrounding text still has some relevance can be included in a page using the img element. Such images are decorative, but still form part of the content. In these cases, the alt attribute must be present but its value must be the empty string. Examples where the image is purely decorative despite being relevant would include things like a photo of the Black Rock City landscape in a blog post about an event at Burning Man, or an image of a painting inspired by a poem, on a page reciting that poem. The following snippet shows an example of the latter case (only the first verse is included in this snippet): <h1>The Lady of Shalott</h1> <p><img src="shalott.jpeg" alt=""></p> <p>On either side the river lie<br> Long fields of barley and of rye,<br> That clothe the wold and meet the sky;<br> And through the field the road run by<br> To many-tower'd Camelot;<br> And up and down the people go,<br> Gazing where the lilies blow<br> Round an island there below,<br> The island of Shalott.</p> 4.8.2.1.7 A group of images that form a single larger picture with no links When a picture has been sliced into smaller image files that are then displayed together to form the complete picture again, one of the images must have its alt attribute set as per the relevant rules that would be appropriate for the picture as a whole, and then all the remaining images must have their alt attribute set to the empty string. In the following example, a picture representing a company logo for XYZ Corp has been split into two pieces, the first containing the letters "XYZ" and the second with the word "Corp". The alternative text ("XYZ Corp") is all in the first image. <h1><img src="logo1.png" alt="XYZ Corp"><img src="logo2.png" alt=""></h1> In the following example, a rating is shown as three filled stars and two empty stars. While the alternative text could have been "555••", the author has instead decided to more helpfully give the rating in the form "3 out of 5". That is the alternative text of the first image, and the rest have blank alternative text. <p>Rating: <meter max=5 value=3><img src="1" alt="3 out of 5" ><img src="1" alt=""><img src="1" alt=""><img src="0" alt="" ><img src="0" alt=""></meter></p> 4.8.2.1.8 A group of images that form a single larger picture with links Generally, image maps should be used instead of slicing an image for links. However, if an image is indeed sliced and any of the components of the sliced picture are the sole contents of links, then one image per link must have alternative text in its alt attribute representing the purpose of the link. In the following example, a picture representing the flying spaghetti monster emblem, with each of the left noodly appendages and the right noodly appendages in different images, so that the user can pick the left side or the right side in an adventure. <h1>The Church</h1> <p>You come across a flying spaghetti monster. Which side of His Noodliness do you wish to reach out for?</p> <p><a href="?go=left" ><img src="fsm-left.png" alt="Left side. "></a ><img src="fsm-middle.png" alt="" ><a href="?go=right"><img src="fsm-right.png" alt="Right side."></a></p> 4.8.2.1.9 A key part of the content http://dev.w3.org/html5/spec/Overview.html (161 de 570)01-08-2009 6:55:56
- 162. HTML 5 In some cases, the image is a critical part of the content. This could be the case, for instance, on a page that is part of a photo gallery. The image is the whole point of the page containing it. How to provide alternative text for an image that is a key part of the content depends on the image's provenance. The general case When it is possible for detailed alternative text to be provided, for example if the image is part of a series of screenshots in a magazine review, or part of a comic strip, or is a photograph in a blog entry about that photograph, text that can serve as a substitute for the image must be given as the contents of the alt attribute. A screenshot in a gallery of screenshots for a new OS, with some alternative text: <figure> <img src="KDE%20Light%20desktop.png" alt="The desktop is blue, with icons along the left hand side in two columns, reading System, Home, K-Mail, etc. A window is open showing that menus wrap to a second line if they cannot fit in the window. The window has a list of icons along the top, with an address bar below it, a list of icons for tabs along the left edge, a status bar on the bottom, and two panes in the middle. The desktop has a bar at the bottom of the screen with a few buttons, a pager, a list of open applications, and a clock."> <legend>Screenshot of a KDE desktop.</legend> </figure> A graph in a financial report: <img src="sales.gif" title="Sales graph" alt="From 1998 to 2005, sales increased by the following percentages with each year: 624%, 75%, 138%, 40%, 35%, 9%, 21%"> Note that "sales graph" would be inadequate alternative text for a sales graph. Text that would be a good caption is not generally suitable as replacement text. Images that defy a complete description In certain cases, the nature of the image might be such that providing thorough alternative text is impractical. For example, the image could be indistinct, or could be a complex fractal, or could be a detailed topographical map. In these cases, the alt attribute must contain some suitable alternative text, but it may be somewhat brief. Sometimes there simply is no text that can do justice to an image. For example, there is little that can be said to usefully describe a Rorschach inkblot test. However, a description, even if brief, is still better than nothing: <figure> <img src="/commons/a/a7/Rorschach1.jpg" alt="A shape with left-right symmetry with indistinct edges, with a small gap in the center, two larger gaps offset slightly from the center, with two similar gaps under them. The outline is wider in the top half than the bottom half, with the sides extending upwards higher than the center, and the center extending below the sides."> <legend>A black outline of the first of the ten cards in the Rorschach inkblot test.</legend> </figure> Note that the following would be a very bad use of alternative text: <!-- This example is wrong. Do not copy it. --> <figure> <img src="/commons/a/a7/Rorschach1.jpg" alt="A black outline of the first of the ten cards in the Rorschach inkblot test."> <legend>A black outline of the first of the ten cards in the Rorschach inkblot test.</legend> </figure> Including the caption in the alternative text like this isn't useful because it effectively duplicates the caption for users who don't have images, taunting them twice yet not helping them any more than if they had only read or heard the caption once. Another example of an image that defies full description is a fractal, which, by definition, is infinite in complexity. The following example shows one possible way of providing alternative text for the full view of an image of the Mandelbrot set. <img src="ms1.jpeg" alt="The Mandelbrot set appears as a cardioid with its cusp on the real axis in the positive direction, with a smaller bulb aligned along the same center line, touching it in the negative http://dev.w3.org/html5/spec/Overview.html (162 de 570)01-08-2009 6:55:56
- 163. HTML 5 direction, and with these two shapes being surrounded by smaller bulbs of various sizes."> Images whose contents are not known In some unfortunate cases, there might be no alternative text available at all, either because the image is obtained in some automated fashion without any associated alternative text (e.g. a Webcam), or because the page is being generated by a script using user- provided images where the user did not provide suitable or usable alternative text (e.g. photograph sharing sites), or because the author does not himself know what the images represent (e.g. a blind photographer sharing an image on his blog). In such cases, the alt attribute's value may be omitted, but one of the following conditions must be met as well: r The title attribute is present and has a non-empty value. r The img element is in a figure element that contains a legend element that contains content other than inter-element whitespace. r The img element is part of the only paragraph directly in its section, and is the only img element without an alt attribute in its section, and its section has an associated heading. Such cases are to be kept to an absolute minimum. If there is even the slightest possibility of the author having the ability to provide real alternative text, then it would not be acceptable to omit the alt attribute. A photo on a photo-sharing site, if the site received the image with no metadata other than the caption: <figure> <img src="1100670787_6a7c664aef.jpg"> <legend>Bubbles traveled everywhere with us.</legend> </figure> It could also be marked up like this: <article> <h1>Bubbles traveled everywhere with us.</h1> <img src="1100670787_6a7c664aef.jpg"> </article> In either case, though, it would be better if a detailed description of the important parts of the image obtained from the user and included on the page. A blind user's blog in which a photo taken by the user is shown. Initially, the user might not have any idea what the photo he took shows: <article> <h1>I took a photo</h1> <p>I went out today and took a photo!</p> <figure> <img src="photo2.jpeg"> <legend>A photograph taken blindly from my front porch.</legend> </figure> </article> Eventually though, the user might obtain a description of the image from his friends and could then include alternative text: <article> <h1>I took a photo</h1> <p>I went out today and took a photo!</p> <figure> <img src="photo2.jpeg" alt="The photograph shows my hummingbird feeder hanging from the edge of my roof. It is half full, but there are no birds around. In the background, out-of-focus trees fill the shot. The feeder is made of wood with a metal grate, and it contains peanuts. The edge of the roof is wooden too, and is painted white with light blue streaks."> <legend>A photograph taken blindly from my front porch.</legend> </figure> </article> Sometimes the entire point of the image is that a textual description is not available, and the user is to provide the description. For instance, the point of a CAPTCHA image is to see if the user can literally read the graphic. Here is one way to mark up a CAPTCHA (note the title attribute): <p><label>What does this image say? <img src="captcha.cgi?id=8934" title="CAPTCHA"> <input type=text name=captcha></label> (If you cannot see the image, you can use an <a href="?audio">audio</a> test instead.)</p> http://dev.w3.org/html5/spec/Overview.html (163 de 570)01-08-2009 6:55:56
- 164. HTML 5 Another example would be software that displays images and asks for alternative text precisely for the purpose of then writing a page with correct alternative text. Such a page could have a table of images, like this: <table> <thead> <tr> <th> Image <th> Description <tbody> <tr> <td> <img src="2421.png" title="Image 640 by 100, filename 'banner.gif'"> <td> <input name="alt2421"> <tr> <td> <img src="2422.png" title="Image 200 by 480, filename 'ad3.gif'"> <td> <input name="alt2422"> </table> Notice that even in this example, as much useful information as possible is still included in the title attribute. Since some users cannot use images at all (e.g. because they have a very slow connection, or because they are using a text-only browser, or because they are listening to the page being read out by a hands-free automobile voice Web browser, or simply because they are blind), the alt attribute is only allowed to be omitted rather than being provided with replacement text when no alternative text is available and none can be made available, as in the above examples. Lack of effort from the part of the author is not an acceptable reason for omitting the alt attribute. 4.8.2.1.10 An image not intended for the user Generally authors should avoid using img elements for purposes other than showing images. If an img element is being used for purposes other than showing an image, e.g. as part of a service to count page views, then the alt attribute must be the empty string. In such cases, the width and height attributes should both be set to zero. 4.8.2.1.11 An image in an e-mail or private document intended for a specific person who is known to be able to view images This section does not apply to documents that are publicly accessible, or whose target audience is not necessarily personally known to the author, such as documents on a Web site, e-mails sent to public mailing lists, or software documentation. When an image is included in a private communication (such as an HTML e-mail) aimed at a specific person who is known to be able to view images, the alt attribute may be omitted. However, even in such cases it is strongly recommended that alternative text be included (as appropriate according to the kind of image involved, as described in the above entries), so that the e-mail is still usable should the user use a mail client that does not support images, or should the document be forwarded on to other users whose abilities might not include easily seeing images. 4.8.2.1.12 General guidelines The most general rule to consider when writing alternative text is the following: the intent is that replacing every image with the text of its alt attribute not change the meaning of the page. So, in general, alternative text can be written by considering what one would have written had one not been able to include the image. A corollary to this is that the alt attribute's value should never contain text that could be considered the image's caption, title, or legend. It is supposed to contain replacement text that could be used by users instead of the image; it is not meant to supplement the image. The title attribute can be used for supplemental information. One way to think of alternative text is to think about how you would read the page containing the image to someone over the phone, without mentioning that there is an image present. Whatever you say instead of the image is typically a good start for writing the alternative text. 4.8.2.1.13 Guidance for markup generators Markup generators (such as WYSIWYG authoring tools) should, wherever possible, obtain alternative text from their users. However, it is recognized that in many cases, this will not be possible. For images that are the sole contents of links, markup generators should examine the link target to determine the title of the target, or the URL of the target, and use information obtained in this manner as the alternative text. As a last resort, implementors should either set the alt attribute to the empty string, under the assumption that the image is a purely decorative image that doesn't add any information but is still specific to the surrounding content, or omit the alt attribute altogether, under the assumption that the image is a key part of the content. Markup generators should generally avoid using the image's own file name as the alternative text. http://dev.w3.org/html5/spec/Overview.html (164 de 570)01-08-2009 6:55:56
- 165. HTML 5 4.8.2.1.14 Guidance for conformance checkers Conformance checkers must report the lack of an alt attribute as an error unless the conditions listed above for images whose contents are not known or they have been configured to assume that the document is an e-mail or document intended for a specific person who is known to be able to view images. 4.8.3 The iframe element Categories Flow content. Phrasing content. Embedded content. Interactive content. Contexts in which this element may be used: Where embedded content is expected. Content model: Text that conforms to the requirements given in the prose. Content attributes: Global attributes src name sandbox seamless width height DOM interface: interface HTMLIFrameElement : HTMLElement { attribute DOMString src; attribute DOMString name; attribute DOMString sandbox; attribute boolean seamless; attribute DOMString width; attribute DOMString height; readonly attribute Document contentDocument; readonly attribute WindowProxy contentWindow; }; The iframe element represents a nested browsing context. The src attribute gives the address of a page that the nested browsing context is to contain. The attribute, if present, must be a valid URL. When the browsing context is created, if the attribute is present, the user agent must resolve the value of that attribute, relative to the element, and if that is successful, must then navigate the element's browsing context to the resulting absolute URL, with replacement enabled, and with the iframe element's document's browsing context as the source browsing context. If the user navigates away from this page, the iframe's corresponding WindowProxy object will proxy new Window objects for new Document objects, but the src attribute will not change. Whenever the src attribute is set, the user agent must resolve the value of that attribute, relative to the element, and if that is successful, the nested browsing context must be navigated to the resulting absolute URL, with the iframe element's document's browsing context as the source browsing context. If the src attribute is not set when the element is created, or if its value cannot be resolved, the browsing context will remain at the initial about:blank page. The name attribute, if present, must be a valid browsing context name. The given value is used to name the nested browsing context. When the browsing context is created, if the attribute is present, the browsing context name must be set to the value of this attribute; otherwise, the browsing context name must be set to the empty string. Whenever the name attribute is set, the nested browsing context's name must be changed to the new value. If the attribute is removed, the browsing context name must be set to the empty string. When content loads in an iframe, after any load events are fired within the content itself, the user agent must fire a simple event called load at the iframe element. When content fails to load (e.g. due to a network error), then the user agent must fire a simple event called error at the element instead. When there is an active parser in the iframe, and when anything in the iframe is delaying the load event of the iframe's browsing context's active document, the iframe must delay the load event of its document. If, during the handling of the load event, the browsing context in the iframe is again navigated, that will further delay the load event. http://dev.w3.org/html5/spec/Overview.html (165 de 570)01-08-2009 6:55:56
- 166. HTML 5 The sandbox attribute, when specified, enables a set of extra restrictions on any content hosted by the iframe. Its value must be an unordered set of unique space-separated tokens. The allowed values are allow-same-origin, allow-forms, and allow- scripts. When the attribute is set, the content is treated as being from a unique origin, forms and scripts are disabled, links are prevented from targeting other browsing contexts, and plugins are disabled. The allow-same-origin token allows the content to be treated as being from the same origin instead of forcing it into a unique origin, and the allow-forms and allow-scripts tokens re-enable forms and scripts respectively (though scripts are still prevented from creating popups). While the sandbox attribute is specified, the iframe element's nested browsing context, and all the browsing contexts nested within it (either directly or indirectly through other nested browsing contexts) must have the following flags set: The sandboxed navigation browsing context flag This flag prevents content from navigating browsing contexts other than the sandboxed browsing context itself (or browsing contexts further nested inside it). This flag also prevents content from creating new auxiliary browsing contexts, e.g. using the target attribute or the window.open() method. The sandboxed plugins browsing context flag This flag prevents content from instantiating plugins, whether using the embed element, the object element, the applet element, or through navigation of a nested browsing context. The sandboxed origin browsing context flag, unless the sandbox attribute's value, when split on spaces, is found to have the allow-same-origin keyword set This flag forces content into a unique origin for the purposes of the same-origin policy. This flag also prevents script from reading the document.cookie DOM attribute. The allow-same-origin attribute is intended for two cases. First, it can be used to allow content from the same site to be sandboxed to disable scripting, while still allowing access to the DOM of the sandboxed content. Second, it can be used to embed content from a third-party site, sandboxed to prevent that site from opening popup windows, etc, without preventing the embedded page from communicating back to its originating site, using the database APIs to store data, etc. This flag only takes effect when the nested browsing context of the iframe is navigated. The sandboxed forms browsing context flag, unless the sandbox attribute's value, when split on spaces, is found to have the allow-forms keyword set This flag blocks form submission. The sandboxed scripts browsing context flag, unless the sandbox attribute's value, when split on spaces, is found to have the allow-scripts keyword set This flag blocks script execution. If the sandbox attribute is dynamically added after the iframe has loaded a page, scripts already compiled by that page (whether in script elements, or in event handler attributes, or elsewhere) will continue to run. Only new scripts will be prevented from executing by this flag. These flags must not be set unless the conditions listed above define them as being set. In this example, some completely-unknown, potentially hostile, user-provided HTML content is embedded in a page. Because it is sandboxed, it is treated by the user agent as being from a unique origin, despite the content being served from the same site. Thus it is affected by all the normal cross-site restrictions. In addition, the embedded page has scripting disabled, plugins disabled, forms disabled, and it cannot navigate any frames or windows other than itself (or any frames or windows it itself embeds). <p>We're not scared of you! Here is your content, unedited:</p> <iframe sandbox src="getusercontent.cgi?id=12193"></iframe> Note that cookies are still sent to the server in the getusercontent.cgi request, though they are not visible in the document.cookie DOM attribute. In this example, a gadget from another site is embedded. The gadget has scripting and forms enabled, and the origin sandbox restrictions are lifted, allowing the gadget to communicate with its originating server. The sandbox is still useful, however, as it disables plugins and popups, thus reducing the risk of the user being exposed to malware and other annoyances. <iframe sandbox="allow-same-origin allow-forms allow-scripts" src="http://maps.example.com/embedded.html"></iframe> The seamless attribute is a boolean attribute. When specified, it indicates that the iframe element's browsing context is to be rendered in a manner that makes it appear to be part of the containing document (seamlessly included in the parent document). Specifically, when the attribute is set on an element and while the browsing context's active document has the same origin as the iframe element's document, or the browsing context's active document's address has the same origin as the iframe element's document, the following requirements apply: q The user agent must set the seamless browsing context flag to true for that browsing context. This will cause links to open in the parent browsing context. q In a CSS-supporting user agent: the user agent must add all the style sheets that apply to the iframe element to the cascade of the active document of the iframe element's nested browsing context, at the appropriate cascade levels, before any style sheets specified by the document itself. q In a CSS-supporting user agent: the user agent must, for the purpose of CSS property inheritance only, treat the root element of the active document of the iframe element's nested browsing context as being a child of the iframe element. (Thus inherited properties on the root element of the document in the iframe will inherit the computed values of those properties on the iframe element instead of taking their initial values.) q In visual media, in a CSS-supporting user agent: the user agent should set the intrinsic width of the iframe to the width that the element would have if it was a non-replaced block-level element with 'width: auto'. q In visual media, in a CSS-supporting user agent: the user agent should set the intrinsic height of the iframe to the height of the bounding box around the content rendered in the iframe at its current width (as given in the previous bullet point), as it would be if the scrolling position was such that the top of the viewport for the content rendered in the iframe was aligned with the origin of that content's canvas. http://dev.w3.org/html5/spec/Overview.html (166 de 570)01-08-2009 6:55:56
- 167. HTML 5 q In visual media, in a CSS-supporting user agent: the user agent must force the height of the initial containing block of the active document of the nested browsing context of the iframe to zero. This is intended to get around the otherwise circular dependency of percentage dimensions that depend on the height of the containing block, thus affecting the height of the document's bounding box, thus affecting the height of the viewport, thus affecting the size of the initial containing block. q In speech media, the user agent should render the nested browsing context without announcing that it is a separate document. q User agents should, in general, act as if the active document of the iframe's nested browsing context was part of the document that the iframe is in. For example if the user agent supports listing all the links in a document, links in "seamlessly" nested documents would be included in that list without being significantly distinguished from links in the document itself. If the attribute is not specified, or if the origin conditions listed above are not met, then the user agent should render the nested browsing context in a manner that is clearly distinguishable as a separate browsing context, and the seamless browsing context flag must be set to false for that browsing context. It is important that user agents recheck the above conditions whenever the active document of the nested browsing context of the iframe changes, such that the seamless browsing context flag gets unset if the nested browsing context is navigated to another origin. The attribute can be set or removed dynamically, with the rendering updating in tandem. In this example, the site's navigation is embedded using a client-side include using an iframe. Any links in the iframe will, in new user agents, be automatically opened in the iframe's parent browsing context; for legacy user agents, the site could also include a base element with a target attribute with the value _parent. Similarly, in new user agents the styles of the parent page will be automatically applied to the contents of the frame, but to support legacy user agents authors might wish to include the styles explicitly. <nav><iframe seamless src="nav.include.html"></iframe></nav> The iframe element supports dimension attributes for cases where the embedded content has specific dimensions (e.g. ad units have well-defined dimensions). An iframe element never has fallback content, as it will always create a nested browsing context, regardless of whether the specified initial contents are successfully used. Descendants of iframe elements represent nothing. (In legacy user agents that do not support iframe elements, the contents would be parsed as markup that could act as fallback content.) When used in HTML documents, the allowed content model of iframe elements is text, except that invoking the HTML fragment parsing algorithm with the iframe element as the context element and the text contents as the input must result in a list of nodes that are all phrasing content, with no parse errors having occurred, with no script elements being anywhere in the list or as descendants of elements in the list, and with all the elements in the list (including their descendants) being themselves conforming. The iframe element must be empty in XML documents. The HTML parser treats markup inside iframe elements as text. The DOM attributes src, name, sandbox, and seamless must reflect the respective content attributes of the same name. The contentDocument DOM attribute must return the Document object of the active document of the iframe element's nested browsing context. The contentWindow DOM attribute must return the WindowProxy object of the iframe element's nested browsing context. 4.8.4 The embed element Categories Flow content. Phrasing content. Embedded content. Interactive content. Contexts in which this element may be used: Where embedded content is expected. Content model: Empty. Content attributes: Global attributes src type width height http://dev.w3.org/html5/spec/Overview.html (167 de 570)01-08-2009 6:55:56
- 168. HTML 5 Any other attribute that has no namespace (see prose). DOM interface: interface HTMLEmbedElement : HTMLElement { attribute DOMString src; attribute DOMString type; attribute DOMString width; attribute DOMString height; }; Depending on the type of content instantiated by the embed element, the node may also support other interfaces. The embed element represents an integration point for an external (typically non-HTML) application or interactive content. The src attribute gives the address of the resource being embedded. The attribute, if present, must contain a valid URL. The type attribute, if present, gives the MIME type of the plugin to instantiate. The value must be a valid MIME type, optionally with parameters. If both the type attribute and the src attribute are present, then the type attribute must specify the same type as the explicit Content-Type metadata of the resource given by the src attribute. [RFC2046] When the element is created with neither a src attribute nor a type attribute, and when attributes are removed such that neither attribute is present on the element anymore, and when the element has a media element ancestor, and when the element has an ancestor object element that is not showing its fallback content, any plugins instantiated for the element must be removed, and the embed element represents nothing. When the sandboxed plugins browsing context flag is set on the browsing context for which the embed element's document is the active document, then the user agent must render the embed element in a manner that conveys that the plugin was disabled. The user agent may offer the user the option to override the sandbox and instantiate the plugin anyway; if the user invokes such an option, the user agent must act as if the sandboxed plugins browsing context flag was not set for the purposes of this element. Plugins are disabled in sandboxed browsing contexts because they might not honor the restrictions imposed by the sandbox (e.g. they might allow scripting even when scripting in the sandbox is disabled). User agents should convey the danger of overriding the sandbox to the user if an option to do so is provided. When the element is created with a src attribute, and whenever the src attribute is subsequently set, and whenever the type attribute is set or removed while the element has a src attribute, if the element is not in a sandboxed browsing context, not a descendant of a media element, and not a descendant of an object element that is not showing its fallback content, the user agent must resolve the value of the attribute, relative to the element, and if that is successful, should fetch the resulting absolute URL. The task that is queued by the networking task source once the resource has been fetched must find and instantiate an appropriate plugin based on the content's type, and hand that plugin the content of the resource, replacing any previously instantiated plugin for the element. Fetching the resource must delay the load event of the element's document. The type of the content being embedded is defined as follows: 1. If the element has a type attribute, and that attribute's value is a type that a plugin supports, then the value of the type attribute is the content's type. 2. Otherwise, if the <path> component of the URL of the specified resource (after any redirects) matches a pattern that a plugin supports, then the content's type is the type that that plugin can handle. For example, a plugin might say that it can handle resources with <path> components that end with the four character string ".swf". 3. Otherwise, if the specified resource has explicit Content-Type metadata, then that is the content's type. 4. Otherwise, the content has no type and there can be no appropriate plugin for it. Whether the resource is fetched successfully or not (e.g. whether the response code was a 2xx code or equivalent) must be ignored when determining the resource's type and when handing the resource to the plugin. This allows servers to return data for plugins even with error responses (e.g. HTTP 500 Internal Server Error codes can still contain plugin data). When the element is created with a type attribute and no src attribute, and whenever the type attribute is subsequently set, so long as no src attribute is set, and whenever the src attribute is removed when the element has a type attribute, if the element is not in a sandboxed browsing context, user agents should find and instantiate an appropriate plugin based on the value of the type attribute. Any (namespace-less) attribute may be specified on the embed element, so long as its name is XML-compatible and contains no characters in the range U+0041 .. U+005A (LATIN CAPITAL LETTER A LATIN CAPITAL LETTER Z). All attributes in HTML documents get lowercased automatically, so the restriction on uppercase letters doesn't affect such documents. The user agent should pass the names and values of all the attributes of the embed element that have no namespace to the plugin used, when it is instantiated. If the plugin instantiated for the embed element supports a scriptable interface, the HTMLEmbedElement object representing the element should expose that interface while the element is instantiated. The embed element has no fallback content. If the user agent can't find a suitable plugin, then the user agent must use a default plugin. (This default could be as simple as saying "Unsupported Format".) http://dev.w3.org/html5/spec/Overview.html (168 de 570)01-08-2009 6:55:56
- 169. HTML 5 The embed element supports dimension attributes. The DOM attributes src and type each must reflect the respective content attributes of the same name. 4.8.5 The object element Categories Flow content. Phrasing content. Embedded content. If the element has a usemap attribute: Interactive content. Listed, submittable, form-associated element. Contexts in which this element may be used: Where embedded content is expected. Content model: Zero or more param elements, then, transparent. Content attributes: Global attributes data type name usemap form width height DOM interface: interface HTMLObjectElement : HTMLElement { attribute DOMString data; attribute DOMString type; attribute DOMString name; attribute DOMString useMap; readonly attribute HTMLFormElement form; attribute DOMString width; attribute DOMString height; readonly attribute Document contentDocument; readonly attribute WindowProxy contentWindow; }; Depending on the type of content instantiated by the object element, the node may also support other interfaces. The object element can represent an external resource, which, depending on the type of the resource, will either be treated as an image, as a nested browsing context, or as an external resource to be processed by a plugin. The data attribute, if present, specifies the address of the resource. If present, the attribute must be a valid URL. The type attribute, if present, specifies the type of the resource. If present, the attribute must be a valid MIME type, optionally with parameters. [RFC2046] One or both of the data and type attributes must be present. The name attribute, if present, must be a valid browsing context name. The given value is used to name the nested browsing context, if applicable. When the element is created, and subsequently whenever the classid attribute changes or is removed, or, if the classid attribute is not present, whenever the data attribute changes or is removed, or, if neither classid attribute nor the data attribute are present, whenever the type attribute changes or is removed, the user agent must run the following steps to determine what the object element represents: 1. If the element has an ancestor media element, or has an ancestor object element that is not showing its fallback content, then jump to the last step in the overall set of steps (fallback). 2. If the classid attribute is present, and has a value that isn't the empty string, then: if the user agent can find a plugin suitable according to the value of the classid attribute, and plugins aren't being sandboxed, then that plugin should be used, and the value of the data attribute, if any, should be passed to the plugin. If no suitable plugin can be found, or if the plugin reports an error, jump to the last step in the overall set of steps (fallback). 3. If the data attribute is present, then: http://dev.w3.org/html5/spec/Overview.html (169 de 570)01-08-2009 6:55:56
- 170. HTML 5 1. If the type attribute is present and its value is not a type that the user agent supports, and is not a type that the user agent can find a plugin for, then the user agent may jump to the last step in the overall set of steps (fallback) without fetching the content to examine its real type. 2. Resolve the URL specified by the data attribute, relative to the element. If that is successful, fetch the resulting absolute URL. Fetching the resource must delay the load event of the element's document until the task that is queued by the networking task source once the resource has been fetched (defined next) has been run. 3. If the resource is not yet available (e.g. because the resource was not available in the cache, so that loading the resource required making a request over the network), then jump to the last step in the overall set of steps (fallback). The task that is queued by the networking task source once the resource is available must restart this algorithm from this step. Resources can load incrementally; user agents may opt to consider a resource "available" whenever enough data has been obtained to begin processing the resource. 4. If the load failed (e.g. the URL could not be resolved, there was an HTTP 404 error, there was a DNS error), fire a simple event called error at the element, then jump to the last step in the overall set of steps (fallback). 5. Determine the resource type, as follows: 1. Let the resource type be unknown. 2. If the resource has associated Content-Type metadata, then let the resource type be the type specified in the resource's Content-Type metadata. 3. If the resource type is unknown or "application/octet-stream" and there is a type attribute present on the object element, then change the resource type to instead be the type specified in that type attribute. Otherwise, if the resource type is "application/octet-stream" but there is no type attribute on the object element, then change the resource type to be unknown, so that the sniffing rules in the next step are invoked. 4. If the resource type is still unknown, then change the resource type to instead be the sniffed type of the resource. 6. Handle the content as given by the first of the following cases that matches: If the resource type can be handled by a plugin and plugins aren't being sandboxed The user agent should use that plugin and pass the content of the resource to that plugin. If the plugin reports an error, then jump to the last step in the overall set of steps (fallback). If the resource type is an XML MIME type If the resource type is HTML If the resource type does not start with "image/" The object element must be associated with a nested browsing context, if it does not already have one. The element's nested browsing context must then be navigated to the given resource, with replacement enabled, and with the object element's document's browsing context as the source browsing context. (The data attribute of the object element doesn't get updated if the browsing context gets further navigated to other locations.) The object element represents the nested browsing context. If the name attribute is present, the browsing context name must be set to the value of this attribute; otherwise, the browsing context name must be set to the empty string. It's possible that the navigation of the browsing context will actually obtain the resource from a different application cache. Even if the resource is then found to have a different type, it is still used as part of a nested browsing context; this algorithm doesn't restart with the new resource. If the resource type starts with "image/", and support for images has not been disabled Apply the image sniffing rules to determine the type of the image. The object element represents the specified image. The image is not a nested browsing context. If the image cannot be rendered, e.g. because it is malformed or in an unsupported format, jump to the last step in the overall set of steps (fallback). Otherwise The given resource type is not supported. Jump to the last step in the overall set of steps (fallback). 7. The element's contents are not part of what the object element represents. 8. Once the resource is completely loaded, queue a task to fire a simple event called load at the element. The task source for this task is the DOM manipulation task source. 4. If the data attribute is absent but the type attribute is present, plugins aren't being sandboxed, and the user agent can find a plugin suitable according to the value of the type attribute, then that plugin should be used. If no suitable plugin can be found, or if the plugin reports an error, jump to the next step (fallback). 5. (Fallback.) The object element represents the element's children, ignoring any leading param element children. This is the element's fallback content. When the algorithm above instantiates a plugin, the user agent should pass the names and values of all the attributes on the element, and all the names and values of parameters given by param elements that are children of the object element, in tree order, to the plugin used. If the plugin supports a scriptable interface, the HTMLObjectElement object representing the element should expose that interface. The object element represents the plugin. The plugin is not a nested browsing context. http://dev.w3.org/html5/spec/Overview.html (170 de 570)01-08-2009 6:55:56
- 171. HTML 5 If the sandboxed plugins browsing context flag is set on the browsing context for which the object element's document is the active document, then the steps above must always act as if they had failed to find a plugin, even if one would otherwise have been used. Due to the algorithm above, the contents of object elements act as fallback content, used only when referenced resources can't be shown (e.g. because it returned a 404 error). This allows multiple object elements to be nested inside each other, targeting multiple user agents with different capabilities, with the user agent picking the first one it supports. Whenever the name attribute is set, if the object element has a nested browsing context, its name must be changed to the new value. If the attribute is removed, if the object element has a browsing context, the browsing context name must be set to the empty string. The usemap attribute, if present while the object element represents an image, can indicate that the object has an associated image map. The attribute must be ignored if the object element doesn't represent an image. The form attribute is used to explicitly associate the object element with its form owner. Constraint validation: object elements are always barred from constraint validation. The object element supports dimension attributes. The DOM attributes data, type, name, and useMap each must reflect the respective content attributes of the same name. The contentDocument DOM attribute must return the Document object of the active document of the object element's nested browsing context, if it has one; otherwise, it must return null. The contentWindow DOM attribute must return the WindowProxy object of the object element's nested browsing context, if it has one; otherwise, it must return null. In the following example, a Java applet is embedded in a page using the object element. (Generally speaking, it is better to avoid using applets like these and instead use native JavaScript and HTML to provide the functionality, since that way the application will work on all Web browsers without requiring a third-party plugin. Many devices, especially embedded devices, do not support third-party technologies like Java.) <figure> <object type="application/x-java-applet"> <param name="code" value="MyJavaClass"> <p>You do not have Java available, or it is disabled.</p> </object> <legend>My Java Clock</legend> </figure> In this example, an HTML page is embedded in another using the object element. <figure> <object data="clock.html"></object> <legend>My HTML Clock</legend> </figure> 4.8.6 The param element Categories None. Contexts in which this element may be used: As a child of an object element, before any flow content. Content model: Empty. Content attributes: Global attributes name value DOM interface: interface HTMLParamElement : HTMLElement { attribute DOMString name; attribute DOMString value; }; The param element defines parameters for plugins invoked by object elements. It does not represent anything on its own. The name attribute gives the name of the parameter. http://dev.w3.org/html5/spec/Overview.html (171 de 570)01-08-2009 6:55:56
- 172. HTML 5 The value attribute gives the value of the parameter. Both attributes must be present. They may have any value. If both attributes are present, and if the parent element of the param is an object element, then the element defines a parameter with the given name/value pair. The DOM attributes name and value must both reflect the respective content attributes of the same name. 4.8.7 The video element Categories Flow content. Phrasing content. Embedded content. If the element has a controls attribute: Interactive content. Contexts in which this element may be used: Where embedded content is expected. Content model: If the element has a src attribute: transparent, but with no media element descendants. If the element does not have a src attribute: one or more source elements, then, transparent, but with no media element descendants. Content attributes: Global attributes src poster autobuffer autoplay loop controls width height DOM interface: interface HTMLVideoElement : HTMLMediaElement { attribute DOMString width; attribute DOMString height; readonly attribute unsigned long videoWidth; readonly attribute unsigned long videoHeight; attribute DOMString poster; }; A video element represents a video or movie. Content may be provided inside the video element. User agents should not show this content to the user; it is intended for older Web browsers which do not support video, so that legacy video plugins can be tried, or to show text to the users of these older browser informing them of how to access the video contents. In particular, this content is not fallback content intended to address accessibility concerns. To make video content accessible to the blind, deaf, and those with other physical or cognitive disabilities, authors are expected to provide alternative media streams and/or to embed accessibility aids (such as caption or subtitle tracks) into their media streams. The video element is a media element whose media data is ostensibly video data, possibly with associated audio data. The src, autobuffer, autoplay, loop, and controls attributes are the attributes common to all media elements. The poster attribute gives the address of an image file that the user agent can show while no video data is available. The attribute, if present, must contain a valid URL. If the specified resource is to be used, then, when the element is created or when the poster attribute is set, its value must be resolved relative to the element, and if that is successful, the resulting absolute URL must be fetched; this must delay the load event of the element's document. The poster frame is then the image obtained from that resource, if any. The image given by the poster attribute, the poster frame, is intended to be a representative frame of the video (typically one of the first non-blank frames) that gives the user an idea of what the video is like. The poster DOM attribute must reflect the poster content attribute. http://dev.w3.org/html5/spec/Overview.html (172 de 570)01-08-2009 6:55:56
- 173. HTML 5 When no video data is available (the element's readyState attribute is either HAVE_NOTHING, or HAVE_METADATA but no video data has yet been obtained at all), the video element represents either the poster frame, or nothing. When a video element is paused and the current playback position is the first frame of video, the element represents either the frame of video corresponding to the current playback position or the poster frame, at the discretion of the user agent. Notwithstanding the above, the poster frame should be preferred over nothing, but the poster frame should not be shown again after a frame of video has been shown. When a video element is paused at any other position, the element represents the frame of video corresponding to the current playback position, or, if that is not yet available (e.g. because the video is seeking or buffering), the last frame of the video to have been rendered. When a video element is potentially playing, it represents the frame of video at the continuously increasing "current" position. When the current playback position changes such that the last frame rendered is no longer the frame corresponding to the current playback position in the video, the new frame must be rendered. Similarly, any audio associated with the video must, if played, be played synchronized with the current playback position, at the specified volume with the specified mute state. When a video element is neither potentially playing nor paused (e.g. when seeking or stalled), the element represents the last frame of the video to have been rendered. Which frame in a video stream corresponds to a particular playback position is defined by the video stream's format. In addition to the above, the user agent may provide messages to the user (such as "buffering", "no video loaded", "error", or more detailed information) by overlaying text or icons on the video or other areas of the element's playback area, or in another appropriate manner. User agents that cannot render the video may instead make the element represent a link to an external video playback utility or to the video data itself. video . videoWidth video . videoHeight These attributes return the intrinsic dimensions of the video, or zero if the dimensions are not known. The intrinsic width and intrinsic height of the media resource are the dimensions of the resource in CSS pixels after taking into account the resource's dimensions, aspect ratio, clean aperture, resolution, and so forth, as defined for the format used by the resource. The videoWidth DOM attribute must return the intrinsic width of the video in CSS pixels. The videoHeight DOM attribute must return the intrinsic height of the video in CSS pixels. If the element's readyState attribute is HAVE_NOTHING, then the attributes must return 0. The video element supports dimension attributes. Video content should be rendered inside the element's playback area such that the video content is shown centered in the playback area at the largest possible size that fits completely within it, with the video content's aspect ratio being preserved. Thus, if the aspect ratio of the playback area does not match the aspect ratio of the video, the video will be shown letterboxed or pillarboxed. Areas of the element's playback area that do not contain the video represent nothing. The intrinsic width of a video element's playback area is the intrinsic width of the video resource, if that is available; otherwise it is the intrinsic width of the poster frame, if that is available; otherwise it is 300 CSS pixels. The intrinsic height of a video element's playback area is the intrinsic height of the video resource, if that is available; otherwise it is the intrinsic height of the poster frame, if that is available; otherwise it is 150 CSS pixels. User agents should provide controls to enable or disable the display of closed captions associated with the video stream, though such features should, again, not interfere with the page's normal rendering. User agents may allow users to view the video content in manners more suitable to the user (e.g. full-screen or in an independent resizable window). As for the other user interface features, controls to enable this should not interfere with the page's normal rendering unless the user agent is exposing a user interface. In such an independent context, however, user agents may make full user interfaces visible, with, e.g., play, pause, seeking, and volume controls, even if the controls attribute is absent. User agents may allow video playback to affect system features that could interfere with the user's experience; for example, user agents could disable screensavers while video playback is in progress. User agents should not provide a public API to cause videos to be shown full-screen. A script, combined with a carefully crafted video file, could trick the user into thinking a system-modal dialog had been shown, and prompt the user for a password. There is also the danger of "mere" annoyance, with pages launching full-screen videos when links are clicked or pages navigated. Instead, user-agent specific interface features may be provided to easily allow the user to obtain a full-screen playback mode. 4.8.8 The audio element Categories Flow content. Phrasing content. Embedded content. http://dev.w3.org/html5/spec/Overview.html (173 de 570)01-08-2009 6:55:56
- 174. HTML 5 If the element has a controls attribute: Interactive content. Contexts in which this element may be used: Where embedded content is expected. Content model: If the element has a src attribute: transparent, but with no media element descendants. If the element does not have a src attribute: one or more source elements, then, transparent, but with no media element descendants. Content attributes: Global attributes src autobuffer autoplay loop controls DOM interface: [NamedConstructor=Audio(), NamedConstructor=Audio(in DOMString src)] interface HTMLAudioElement : HTMLMediaElement { // no members }; An audio element represents a sound or audio stream. Content may be provided inside the audio element. User agents should not show this content to the user; it is intended for older Web browsers which do not support audio, so that legacy audio plugins can be tried, or to show text to the users of these older browser informing them of how to access the audio contents. In particular, this content is not fallback content intended to address accessibility concerns. To make audio content accessible to the deaf or to those with other physical or cognitive disabilities, authors are expected to provide alternative media streams and/ or to embed accessibility aids (such as transcriptions) into their media streams. The audio element is a media element whose media data is ostensibly audio data. The src, autobuffer, autoplay, loop, and controls attributes are the attributes common to all media elements. When an audio element is potentially playing, it must have its audio data played synchronized with the current playback position, at the specified volume with the specified mute state. When an audio element is not potentially playing, audio must not play for the element. audio = new Audio( [ url ] ) Returns a new audio element, with the src attribute set to the value passed in the argument, if applicable. Two constructors are provided for creating HTMLAudioElement objects (in addition to the factory methods from DOM Core such as createElement()): Audio() and Audio(src). When invoked as constructors, these must return a new HTMLAudioElement object (a new audio element). The element must have its autobuffer attribute set to the literal value "autobuffer". If the src argument is present, the object created must have its src content attribute set to the provided value, and the user agent must invoke the object's resource selection algorithm before returning. 4.8.9 The source element Categories None. Contexts in which this element may be used: As a child of a media element, before any flow content. Content model: Empty. Content attributes: Global attributes src type media http://dev.w3.org/html5/spec/Overview.html (174 de 570)01-08-2009 6:55:56
- 175. HTML 5 DOM interface: interface HTMLSourceElement : HTMLElement { attribute DOMString src; attribute DOMString type; attribute DOMString media; }; The source element allows authors to specify multiple media resources for media elements. It does not represent anything on its own. The src attribute gives the address of the media resource. The value must be a valid URL. This attribute must be present. The type attribute gives the type of the media resource, to help the user agent determine if it can play this media resource before fetching it. If specified, its value must be a MIME type. The codecs parameter may be specified and might be necessary to specify exactly how the resource is encoded. [RFC2046] [RFC4281] The following list shows some examples of how to use the codecs= MIME parameter in the type attribute. H.264 Simple baseline profile video (main and extended video compatible) level 3 and Low-Complexity AAC audio in MP4 container <source src='video.mp4' type='video/mp4; codecs="avc1.42E01E, mp4a.40.2"'> H.264 Extended profile video (baseline-compatible) level 3 and Low-Complexity AAC audio in MP4 container <source src='video.mp4' type='video/mp4; codecs="avc1.58A01E, mp4a.40.2"'> H.264 Main profile video level 3 and Low-Complexity AAC audio in MP4 container <source src='video.mp4' type='video/mp4; codecs="avc1.4D401E, mp4a.40.2"'> H.264 'High' profile video (incompatible with main, baseline, or extended profiles) level 3 and Low-Complexity AAC audio in MP4 container <source src='video.mp4' type='video/mp4; codecs="avc1.64001E, mp4a.40.2"'> MPEG-4 Visual Simple Profile Level 0 video and Low-Complexity AAC audio in MP4 container <source src='video.mp4' type='video/mp4; codecs="mp4v.20.8, mp4a.40.2"'> MPEG-4 Advanced Simple Profile Level 0 video and Low-Complexity AAC audio in MP4 container <source src='video.mp4' type='video/mp4; codecs="mp4v.20.240, mp4a.40.2"'> MPEG-4 Visual Simple Profile Level 0 video and AMR audio in 3GPP container <source src='video.3gp' type='video/3gpp; codecs="mp4v.20.8, samr"'> Theora video and Vorbis audio in Ogg container <source src='video.ogv' type='video/ogg; codecs="theora, vorbis"'> Theora video and Speex audio in Ogg container <source src='video.ogv' type='video/ogg; codecs="theora, speex"'> Vorbis audio alone in Ogg container <source src='audio.ogg' type='audio/ogg; codecs=vorbis'> Speex audio alone in Ogg container <source src='audio.spx' type='audio/ogg; codecs=speex'> FLAC audio alone in Ogg container <source src='audio.oga' type='audio/ogg; codecs=flac'> http://dev.w3.org/html5/spec/Overview.html (175 de 570)01-08-2009 6:55:56
- 176. HTML 5 Dirac video and Vorbis audio in Ogg container <source src='video.ogv' type='video/ogg; codecs="dirac, vorbis"'> Theora video and Vorbis audio in Matroska container <source src='video.mkv' type='video/x-matroska; codecs="theora, vorbis"'> The media attribute gives the intended media type of the media resource, to help the user agent determine if this media resource is useful to the user before fetching it. Its value must be a valid media query. [MQ] If a source element is inserted as a child of a media element that is in a Document and whose networkState has the value NETWORK_EMPTY, the user agent must invoke the media element's resource selection algorithm. The DOM attributes src, type, and media must reflect the respective content attributes of the same name. 4.8.10 Media elements Media elements implement the following interface: interface HTMLMediaElement : HTMLElement { // error state readonly attribute MediaError error; // network state attribute DOMString src; readonly attribute DOMString currentSrc; const unsigned short NETWORK_EMPTY = 0; const unsigned short NETWORK_IDLE = 1; const unsigned short NETWORK_LOADING = 2; const unsigned short NETWORK_LOADED = 3; const unsigned short NETWORK_NO_SOURCE = 4; readonly attribute unsigned short networkState; attribute boolean autobuffer; readonly attribute TimeRanges buffered; void load(); DOMString canPlayType(in DOMString type); // ready state const unsigned short HAVE_NOTHING = 0; const unsigned short HAVE_METADATA = 1; const unsigned short HAVE_CURRENT_DATA = 2; const unsigned short HAVE_FUTURE_DATA = 3; const unsigned short HAVE_ENOUGH_DATA = 4; readonly attribute unsigned short readyState; readonly attribute boolean seeking; // playback state attribute float currentTime; readonly attribute float startTime; readonly attribute float duration; readonly attribute boolean paused; attribute float defaultPlaybackRate; attribute float playbackRate; readonly attribute TimeRanges played; readonly attribute TimeRanges seekable; readonly attribute boolean ended; attribute boolean autoplay; attribute boolean loop; void play(); void pause(); // cue ranges void addCueRange(in DOMString className, in DOMString id, in float start, in float end, in boolean pauseOnExit, in CueRangeCallback enterCallback, in CueRangeCallback exitCallback); void removeCueRanges(in DOMString className); http://dev.w3.org/html5/spec/Overview.html (176 de 570)01-08-2009 6:55:56
- 177. HTML 5 // controls attribute boolean controls; attribute float volume; attribute boolean muted; }; [Callback=FunctionOnly, NoInterfaceObject] interface CueRangeCallback { void handleEvent(in DOMString id); }; The media element attributes, src, autobuffer, autoplay, loop, and controls, apply to all media elements. They are defined in this section. Media elements are used to present audio data, or video and audio data, to the user. This is referred to as media data in this section, since this section applies equally to media elements for audio or for video. The term media resource is used to refer to the complete set of media data, e.g. the complete video file, or complete audio file. Unless otherwise specified, the task source for all the tasks queued in this section and its subsections is the media element event task source. 4.8.10.1 Error codes media . error Returns a MediaError object representing the current error state of the element. Returns null if there is no error. All media elements have an associated error status, which records the last error the element encountered since its resource selection algorithm was last invoked. The error attribute, on getting, must return the MediaError object created for this last error, or null if there has not been an error. interface MediaError { const unsigned short MEDIA_ERR_ABORTED = 1; const unsigned short MEDIA_ERR_NETWORK = 2; const unsigned short MEDIA_ERR_DECODE = 3; const unsigned short MEDIA_ERR_SRC_NOT_SUPPORTED = 4; readonly attribute unsigned short code; }; media . error . code Returns the current error's error code, from the list below. The code attribute of a MediaError object must return the code for the error, which must be one of the following: MEDIA_ERR_ABORTED (numeric value 1) The fetching process for the media resource was aborted by the user agent at the user's request. MEDIA_ERR_NETWORK (numeric value 2) A network error of some description caused the user agent to stop fetching the media resource, after the resource was established to be usable. MEDIA_ERR_DECODE (numeric value 3) An error of some description occurred while decoding the media resource, after the resource was established to be usable. MEDIA_ERR_SRC_NOT_SUPPORTED (numeric value 4) The media resource indicated by the src attribute was not suitable. 4.8.10.2 Location of the media resource The src content attribute on media elements gives the address of the media resource (video, audio) to show. The attribute, if present, must contain a valid URL. If a src attribute of a media element that is in a Document and whose networkState has the value NETWORK_EMPTY is set or changed, the user agent must invoke the media element's resource selection algorithm. http://dev.w3.org/html5/spec/Overview.html (177 de 570)01-08-2009 6:55:56
- 178. HTML 5 The src DOM attribute on media elements must reflect the respective content attribute of the same name. media . currentSrc Returns the address of the current media resource. Returns the empty string when there is no media resource. The currentSrc DOM attribute is initially the empty string. Its value is changed by the resource selection algorithm defined below. There are two ways to specify a media resource, the src attribute, or source elements. The attribute overrides the elements. 4.8.10.3 MIME types A media resource can be described in terms of its type, specifically a MIME type, optionally with a codecs parameter. [RFC2046] [RFC4281]. Types are usually somewhat incomplete descriptions; for example "video/mpeg" doesn't say anything except what the container type is, and even a type like "video/mp4; codecs="avc1.42E01E, mp4a.40.2"" doesn't include information like the actual bitrate (only the maximum bitrate). Thus, given a type, a user agent can often only know whether it might be able to play media of that type (with varying levels of confidence), or whether it definitely cannot play media of that type. A type that the user agent knows it cannot render is one that describes a resource that the user agent definitely does not support, for example because it doesn't recognize the container type, or it doesn't support the listed codecs. The MIME type "application/octet-stream" is never a type that the user agent knows it cannot render. User agents must treat that type as equivalent to the lack of any explicit Content-Type metadata when it is used to label a potential media resource. media . canPlayType(type) Returns the empty string (a negative response), "maybe", or "probably" based on how confident the user agent is that it can play media resources of the given type. The canPlayType(type) method must return the empty string if type is a type that the user agent knows it cannot render; it must return "probably" if the user agent is confident that the type represents a media resource that it can render if used in with this audio or video element; and it must return "maybe" otherwise. Implementors are encouraged to return "maybe" unless the type can be confidently established as being supported or not. Generally, a user agent should never return "probably" if the type doesn't have a codecs parameter. This script tests to see if the user agent supports a (fictional) new format to dynamically decide whether to use a video element or a plugin: <section id="video"> <p><a href="playing-cats.nfv">Download video</a></p> </section> <script> var videoSection = document.getElementById('video'); var videoElement = document.createElement('video'); var support = videoElement.canPlayType('video/x-new-fictional-format;codecs="kittens,bunnies"'); if (support != "probably" && "New Fictional Video Plug-in" in navigator.plugins) { // not confident of browser support // but we have a plugin // so use plugin instead videoElement = document.createElement("embed"); } else if (support == "") { // no support from browser and no plugin // do nothing videoElement = null; } if (videoElement) { while (videoSection.hasChildNodes()) videoSection.removeChild(videoSection.firstChild); videoElement.setAttribute("src", "playing-cats.nfv"); videoSection.appendChild(videoElement); } </script> The type attribute of the source element allows the user agent to avoid downloading resources that use formats it cannot render. http://dev.w3.org/html5/spec/Overview.html (178 de 570)01-08-2009 6:55:56
- 179. HTML 5 4.8.10.4 Network states media . networkState Returns the current state of network activity for the element, from the codes in the list below. As media elements interact with the network, their current network activity is represented by the networkState attribute. On getting, it must return the current network state of the element, which must be one of the following values: NETWORK_EMPTY (numeric value 0) The element has not yet been initialized. All attributes are in their initial states. NETWORK_IDLE (numeric value 1) The element's resource selection algorithm is active and has selected a resource, but it is not actually using the network at this time. NETWORK_LOADING (numeric value 2) The user agent is actively trying to download data. NETWORK_LOADED (numeric value 3) The entire media resource has been obtained and is available to the user agent locally. Network connectivity could be lost without affecting the media playback. NETWORK_NO_SOURCE (numeric value 4) The element's resource selection algorithm is active, but it has failed to find a resource to use. The resource selection algorithm defined below describes exactly when the networkState attribute changes value and what events fire to indicate changes in this state. Some resources, e.g. streaming Web radio, can never reach the NETWORK_LOADED state. 4.8.10.5 Loading the media resource media . load() Causes the element to reset and start selecting and loading a new media resource from scratch. All media elements have an autoplaying flag, which must begin in the true state, and a delaying-the-load-event flag, which must begin in the false state. While the delaying-the-load-event flag is true, the element must delay the load event of its document. When the load() method on a media element is invoked, the user agent must run the following steps. Note that this algorithm might get aborted, e.g. if the load() method itself is invoked again. 1. If the load() method for this element is already being invoked, then abort these steps. 2. Abort any already-running instance of the resource selection algorithm for this element. 3. If there are any tasks from the media element's media element event task source in one of the task queues, then remove those tasks. Basically, pending events and callbacks for the media element are discarded when the media element starts loading a new resource. 4. If the media element's networkState is set to NETWORK_LOADING or NETWORK_IDLE, set the error attribute to a new MediaError object whose code attribute is set to MEDIA_ERR_ABORTED, and fire a progress event called abort at the media element. 5. Set the error attribute to null and the autoplaying flag to true. 6. Set the playbackRate attribute to the value of the defaultPlaybackRate attribute. 7. If the media element's networkState is not set to NETWORK_EMPTY, then run these substeps: 1. If a fetching process is in progress for the media element, the user agent should stop it. 2. Set the networkState attribute to NETWORK_EMPTY. 3. If readyState is not set to HAVE_NOTHING, then set it to that state. 4. If the paused attribute is false, then set to true. http://dev.w3.org/html5/spec/Overview.html (179 de 570)01-08-2009 6:55:56
- 180. HTML 5 5. If seeking is true, set it to false. 6. Set the current playback position to 0. 7. Fire a simple event called emptied at the media element. 8. Invoke the media element's resource selection algorithm. 9. Playback of any previously playing media resource for this element stops. The resource selection algorithm for a media element is as follows. This algorithm is always invoked synchronously, but one of the first steps in the algorithm is to return and continue running the remaining steps asynchronously, meaning that it runs in the background with scripts and other tasks running in parallel. 1. Set the networkState to NETWORK_NO_SOURCE. 2. Asynchronously await a stable state, allowing the task that invoked this algorithm to continue. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with •.) 3. • If the media element has a src attribute, then let mode be attribute. • Otherwise, if the media element does not have a src attribute but has a source element child, then let mode be children and let candidate be the first such source element child in tree order. • Otherwise the media element has neither a src attribute nor a source element child: set the networkState to NETWORK_EMPTY, and abort these steps; the synchronous section ends. 4. • Set the media element's delaying-the-load-event flag to true (this delays the load event), and set its networkState to NETWORK_LOADING. 5. • Queue a task to fire a progress event called loadstart at the media element. 6. If mode is attribute, then run these substeps: 1. • Let absolute URL be the absolute URL that would have resulted from resolving the URL specified by the src attribute's value relative to the media element when the src attribute was last changed. 2. End the synchronous section, continuing the remaining steps asynchronously. 3. If absolute URL was obtained successfully, run the resource fetch algorithm with absolute URL. If that algorithm returns without aborting this one, then the load failed. 4. Reaching this step indicates that the media resource failed to load or that the given URL could not be resolved. Set the error attribute to a new MediaError object whose code attribute is set to MEDIA_ERR_SRC_NOT_SUPPORTED. 5. Set the element's networkState attribute to the NETWORK_NO_SOURCE value. 6. Queue a task to fire a progress event called error at the media element. 7. Set the element's delaying-the-load-event flag to false. This stops delaying the load event. 8. Abort these steps. Until the load() method is invoked, the element won't attempt to load another resource. Otherwise, the source elements will be used; run these substeps: 1. • Let pointer be a position defined by two adjacent nodes in the media element's child list, treating the start of the list (before the first child in the list, if any) and end of the list (after the last child in the list, if any) as nodes in their own right. One node is the node before pointer, and the other node is the node after pointer. Initially, let pointer be the position between the candidate node and the next node, if there are any, or the end of the list, if it is the last node. As elements are inserted and removed into the media element, pointer must be updated as follows: If a new element is inserted between the two nodes that define pointer Let pointer be the point between the node before pointer and the new node. In other words, insertions at pointer go after pointer. If the node before pointer is removed Let pointer be the point between the node after pointer and the node before the node after pointer. In other words, pointer doesn't move relative to the remaining nodes. If the node after pointer is removed Let pointer be the point between the node before pointer and the node after the node before pointer. Just as with the previous case, pointer doesn't move relative to the remaining nodes. Other changes don't affect pointer. 2. • Process candidate: If candidate does not have a src attribute, then end the synchronous section, and jump down to the failed step below. 3. • Let absolute URL be the absolute URL that would have resulted from resolving the URL specified by candidate's src attribute's value relative to the candidate when the src attribute was last changed. http://dev.w3.org/html5/spec/Overview.html (180 de 570)01-08-2009 6:55:56
- 181. HTML 5 4. • If absolute URL was not obtained successfully, then end the synchronous section, and jump down to the failed step below. 5. • If candidate has a type attribute whose value, when parsed as a MIME type (including any codecs described by the codec parameter), represents a type that the user agent knows it cannot render, then end the synchronous section, and jump down to the failed step below. 6. • If candidate has a media attribute whose value, when processed according to the rules for media queries, does not match the current environment, then end the synchronous section, and jump down to the failed step below. [MQ] 7. End the synchronous section, continuing the remaining steps asynchronously. 8. Run the resource fetch algorithm with absolute URL. If that algorithm returns without aborting this one, then the load failed. 9. Failed: Queue a task to fire a simple event called error at the candidate element. 10. Asynchronously await a stable state. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with •.) 11. • Find next candidate: Let candidate be null. 12. • Search loop: If the node after pointer is the end of the list, then jump o the waiting step below. 13. • If the node after pointer is a source element, let candidate be that element. 14. • Advance pointer so that the node before pointer is now the node that was after pointer, and the node after pointer is the node after the node that used to be after pointer, if any. 15. • If candidate is null, jump back to the search loop step. Otherwise, jump back to the process candidate step. 16. • Waiting: Set the element's networkState attribute to the NETWORK_NO_SOURCE value. 17. • Set the element's delaying-the-load-event flag to false. This stops delaying the load event. 18. End the synchronous section, continuing the remaining steps asynchronously. 19. Wait until the node after pointer is a node other than the end of the list. (This step might wait forever.) 20. Asynchronously await a stable state. The synchronous section consists of all the remaining steps of this algorithm until the algorithm says the synchronous section has ended. (Steps in synchronous sections are marked with •.) 21. • Set the element's delaying-the-load-event flag back to true (this delays the load event again, in case it hasn't been fired yet). 22. • Set the networkState back to NETWORK_LOADING. 23. • Jump back to the find next candidate step above. The resource fetch algorithm for a media element and a given absolute URL is as follows: 1. Let the current media resource be the resource given by the absolute URL passed to this algorithm. This is now the element's media resource. 2. Set the currentSrc attribute to the absolute URL of the current media resource. 3. Begin to fetch the current media resource. Every 350ms (±200ms) or for every byte received, whichever is least frequent, queue a task to fire a progress event called progress at the element. If at any point the user agent has received no data for more than about three seconds, then queue a task to fire a progress event called stalled at the element. User agents may allow users to selectively block or slow media data downloads. When a media element's download has been blocked altogether, the user agent must act as if it was stalled (as opposed to acting as if the connection was closed). The rate of the download may also be throttled automatically by the user agent, e.g. to balance the download with other connections sharing the same bandwidth. User agents may decide to not download more content at any time, e.g. after buffering five minutes of a one hour media resource, while waiting for the user to decide whether to play the resource or not, or while waiting for user input in an interactive resource. When a media element's download has been suspended, the user agent must set the networkState to NETWORK_IDLE and queue a task to fire a progress event called suspend at the element. If and when downloading of the resource resumes, the user agent must set the networkState to NETWORK_LOADING. The autobuffer attribute provides a hint that the author expects that downloading the entire resource optimistically will be worth it, even in the absence of the autoplay attribute. In the absence of either attribute, the user agent is likely to find that waiting until the user starts playback before downloading any further content leads to a more efficient use of the network resources. When a user agent decides to completely stall a download, e.g. if it is waiting until the user starts playback before downloading any further content, the element's delaying-the-load-event flag must be set to false. This stops delaying the load event. The user agent may use whatever means necessary to fetch the resource (within the constraints put forward by this and other specifications); for example, reconnecting to the server in the face of network errors, using HTTP partial range requests, or switching to a streaming protocol. The user agent must consider a resource erroneous only if it has given up trying to fetch it. http://dev.w3.org/html5/spec/Overview.html (181 de 570)01-08-2009 6:55:56
- 182. HTML 5 The networking task source tasks to process the data as it is being fetched must, when appropriate, include the relevant substeps from the following list: If the media data cannot be fetched at all, due to network errors, causing the user agent to give up trying to fetch the resource If the media resource is found to have Content-Type metadata that, when parsed as a MIME type (including any codecs described by the codec parameter), represents a type that the user agent knows it cannot render (even if the actual media data is in a supported format) If the media data can be fetched but is found by inspection to be in an unsupported format, or can otherwise not be rendered at all DNS errors, HTTP 4xx and 5xx errors (and equivalents in other protocols), and other fatal network errors that occur before the user agent has established whether the current media resource is usable, as well as the file using an unsupported container format, or using unsupported codecs for all the data, must cause the user agent to execute the following steps: 1. The user agent should cancel the fetching process. 2. Abort this subalgorithm, returning to the resource selection algorithm. Once enough of the media data has been fetched to determine the duration of the media resource, its dimensions, and other metadata This indicates that the resource is usable. The user agent must follow these substeps: 1. Set the current playback position to the earliest possible position. 2. Set the readyState attribute to HAVE_METADATA. 3. For video elements, set the videoWidth and videoHeight attributes. 4. Set the duration attribute to the duration of the resource. The user agent will queue a task to fire a simple event called durationchange at the element at this point. 5. Queue a task to fire a simple event called loadedmetadata at the element. 6. If either the media resource or the address of the current media resource indicate a particular start time, then seek to that time. Ignore any resulting exceptions (if the position is out of range, it is effectively ignored). For example, a fragment identifier could be used to indicate a start position. 7. Once the readyState attribute reaches HAVE_CURRENT_DATA, after the loadeddata event has been fired, set the element's delaying-the-load-event flag to false. This stops delaying the load event. A user agent that is attempting to reduce network usage while still fetching the metadata for each media resource would also stop buffering at this point, causing the networkState attribute to switch to the NETWORK_IDLE value, if the media element did not have an autobuffer or autoplay attribute. The user agent is required to determine the duration of the media resource and go through this step before playing. If the connection is interrupted, causing the user agent to give up trying to fetch the resource Fatal network errors that occur after the user agent has established whether the current media resource is usable must cause the user agent to execute the following steps: 1. The user agent should cancel the fetching process. 2. Set the error attribute to a new MediaError object whose code attribute is set to MEDIA_ERR_NETWORK. 3. Queue a task to fire a progress event called error at the media element. 4. Set the element's networkState attribute to the NETWORK_EMPTY value and queue a task to fire a simple event called emptied at the element. 5. Set the element's delaying-the-load-event flag to false. This stops delaying the load event. 6. Abort the overall resource selection algorithm. If the media data is corrupted Fatal errors in decoding the media data that occur after the user agent has established whether the current media resource is usable must cause the user agent to execute the following steps: 1. The user agent should cancel the fetching process. 2. Set the error attribute to a new MediaError object whose code attribute is set to MEDIA_ERR_DECODE. 3. Queue a task to fire a progress event called error at the media element. 4. Set the element's networkState attribute to the NETWORK_EMPTY value and queue a task to fire a simple event called emptied at the element. http://dev.w3.org/html5/spec/Overview.html (182 de 570)01-08-2009 6:55:56
- 183. HTML 5 5. Set the element's delaying-the-load-event flag to false. This stops delaying the load event. 6. Abort the overall resource selection algorithm. If the media data fetching process is aborted by the user The fetching process is aborted by the user, e.g. because the user navigated the browsing context to another page, the user agent must execute the following steps. These steps are not followed if the load() method itself is invoked while these steps are running, as the steps above handle that particular kind of abort. 1. The user agent should cancel the fetching process. 2. Set the error attribute to a new MediaError object whose code attribute is set to MEDIA_ERR_ABORT. 3. Queue a task to fire a progress event called abort at the media element. 4. If the media element's readyState attribute has a value equal to HAVE_NOTHING, set the element's networkState attribute to the NETWORK_EMPTY value and queue a task to fire a simple event called emptied at the element. Otherwise, set the element's networkState attribute to the NETWORK_IDLE value. 5. Set the element's delaying-the-load-event flag to false. This stops delaying the load event. 6. Abort the overall resource selection algorithm. If the media data can be fetched but has non-fatal errors or uses, in part, codecs that are unsupported, preventing the user agent from rendering the content completely correctly but not preventing playback altogether The server returning data that is partially usable but cannot be optimally rendered must cause the user agent to render just the bits it can handle, and ignore the rest. When the networking task source has queued the last task as part of fetching the media resource (i.e. once the download has completed), the user agent must move on to the next step. This might never happen, e.g. when streaming an infinite resource such as Web radio. 4. If the fetching process completes without errors, then set the networkState attribute to NETWORK_LOADED, and queue a task to fire a progress event called load at the element. 5. Then, abort the overall resource selection algorithm. If a media element whose networkState has the value NETWORK_EMPTY is inserted into a document, the user agent must invoke the media element's resource selection algorithm. The autobuffer attribute is a boolean attribute. Its presence hints to the user agent that the author believes that the media element will likely be used, even though the element does not have an autoplay attribute. (The attribute has no effect if used in conjunction with the autoplay attribute, though including both is not an error.) This attribute may be ignored altogether. The attribute must be ignored if the autoplay attribute is present. The autobuffer DOM attribute must reflect the content attribute of the same name. media . buffered Returns a TimeRanges object that represents the ranges of the media resource that the user agent has buffered. The buffered attribute must return a new static normalized TimeRanges object that represents the ranges of the media resource, if any, that the user agent has buffered, at the time the attribute is evaluated. Users agents must accurately determine the ranges available, even for media streams where this can only be determined by tedious inspection. Typically this will be a single range anchored at the zero point, but if, e.g. the user agent uses HTTP range requests in response to seeking, then there could be multiple ranges. User agents may discard previously buffered data. Thus, a time position included within a range of the objects return by the buffered attribute at one time can end up being not included in the range(s) of objects returned by the same attribute at later times. 4.8.10.6 Offsets into the media resource media . duration Returns the length of the media resource, in seconds. Returns NaN if the duration isn't available. Returns Infinity for unbounded streams. http://dev.w3.org/html5/spec/Overview.html (183 de 570)01-08-2009 6:55:56
- 184. HTML 5 media . currentTime [ = value ] Returns the current playback position, in seconds. Can be set, to seek to the given time. Will throw an INVALID_STATE_ERR exception if there is no selected media resource. Will throw an INDEX_SIZE_ERR exception if the given time is not within the ranges to which the user agent can seek. media . startTime Returns the earliest possible position, in seconds. This is the time for the start of the current clip. It might not be zero if the clip's timeline is not zero-based, or if the resource is a streaming resource (in which case it gives the earliest time that the user agent is able to seek back to). The duration attribute must return the length of the media resource, in seconds. If no media data is available, then the attributes must return the Not-a-Number (NaN) value. If the media resource is known to be unbounded (e.g. a streaming radio), then the attribute must return the positive Infinity value. The user agent must determine the duration of the media resource before playing any part of the media data and before setting readyState to a value equal to or greater than HAVE_METADATA, even if doing so requires seeking to multiple parts of the resource. When the length of the media resource changes (e.g. from being unknown to known, or from a previously established length to a new length) the user agent must queue a task to fire a simple event called durationchange at the media element. If an "infinite" stream ends for some reason, then the duration would change from positive Infinity to the time of the last frame or sample in the stream, and the durationchange event would be fired. Similarly, if the user agent initially estimated the media resource's duration instead of determining it precisely, and later revises the estimate based on new information, then the duration would change and the durationchange event would be fired. Media elements have a current playback position, which must initially be zero. The current position is a time. The currentTime attribute must, on getting, return the current playback position, expressed in seconds. On setting, the user agent must seek to the new value (which might raise an exception). If the media resource is a streaming resource, then the user agent might be unable to obtain certain parts of the resource after it has expired from its buffer. Similarly, some media resources might have a timeline that doesn't start at zero. The earliest possible position is the earliest position in the stream or resource that the user agent can ever obtain again. The startTime attribute must, on getting, return the earliest possible position, expressed in seconds. When the earliest possible position changes, then: if the current playback position is before the earliest possible position, the user agent must seek to the earliest possible position; otherwise, if the user agent has not fired a timeupdate event at the element in the past 15 to 250ms, then the user agent must queue a task to fire a simple event called timeupdate at the element. User agents must act as if the timeline of the media resource increases linearly starting from the earliest possible position, even if the underling media data has out-of-order or even overlapping time codes. For example, if two clips have been concatenated into one video file, but the video format exposes the original times for the two clips, the video data might expose a timeline that goes, say, 00:15..00:29 and then 00:05..00:38. However, the user agent would not expose those times; it would instead expose the times as 00:15..00:29 and 00:29..01:02, as a single video. The loop attribute is a boolean attribute that, if specified, indicates that the media element is to seek back to the start of the media resource upon reaching the end. The loop DOM attribute must reflect the content attribute of the same name. 4.8.10.7 The ready states media . readyState Returns a value that expresses the current state of the element with respect to rendering the current playback position, from the codes in the list below. Media elements have a ready state, which describes to what degree they are ready to be rendered at the current playback position. The possible values are as follows; the ready state of a media element at any particular time is the greatest value describing the state of the element: HAVE_NOTHING (numeric value 0) No information regarding the media resource is available. No data for the current playback position is available. Media elements whose networkState attribute is NETWORK_EMPTY are always in the HAVE_NOTHING state. HAVE_METADATA (numeric value 1) Enough of the resource has been obtained that the duration of the resource is available. In the case of a video element, the dimensions of the video are also available. The API will no longer raise an exception when seeking. No media data is available for the immediate current playback position. HAVE_CURRENT_DATA (numeric value 2) Data for the immediate current playback position is available, but either not enough data is available that the user agent could successfully advance the current playback position in the direction of playback at all without immediately reverting to the HAVE_METADATA state, or there is no more data to obtain in the direction of playback. For example, in video this corresponds to the user agent having data from the current frame, but not the next frame; and to when playback has ended. HAVE_FUTURE_DATA (numeric value 3) http://dev.w3.org/html5/spec/Overview.html (184 de 570)01-08-2009 6:55:56
- 185. HTML 5 Data for the immediate current playback position is available, as well as enough data for the user agent to advance the current playback position in the direction of playback at least a little without immediately reverting to the HAVE_METADATA state. For example, in video this corresponds to the user agent having data for at least the current frame and the next frame. The user agent cannot be in this state if playback has ended, as the current playback position can never advanced in this case. HAVE_ENOUGH_DATA (numeric value 4) All the conditions described for the HAVE_FUTURE_DATA state are met, and, in addition, the user agent estimates that data is being fetched at a rate where the current playback position, if it were to advance at the rate given by the defaultPlaybackRate attribute, would not overtake the available data before playback reaches the end of the media resource. When the ready state of a media element whose networkState is not NETWORK_EMPTY changes, the user agent must follow the steps given below: If the previous ready state was HAVE_NOTHING, and the new ready state is HAVE_METADATA A loadedmetadata DOM event will be fired as part of the load() algorithm. If the previous ready state was HAVE_METADATA and the new ready state is HAVE_CURRENT_DATA or greater If this is the first time this occurs for this media element since the load() algorithm was last invoked, the user agent must queue a task to fire a simple event called loadeddata at the element. If the new ready state is HAVE_FUTURE_DATA or HAVE_ENOUGH_DATA, then the relevant steps below must then be run also. If the previous ready state was HAVE_FUTURE_DATA or more, and the new ready state is HAVE_CURRENT_DATA or less A waiting DOM event can be fired, depending on the current state of playback. If the previous ready state was HAVE_CURRENT_DATA or less, and the new ready state is HAVE_FUTURE_DATA The user agent must queue a task to fire a simple event called canplay. If the element is potentially playing, the user agent must queue a task to fire a simple event called playing. If the new ready state is HAVE_ENOUGH_DATA If the previous ready state was HAVE_CURRENT_DATA or less, the user agent must queue a task to fire a simple event called canplay, and, if the element is also potentially playing, queue a task to fire a simple event called playing. If the autoplaying flag is true, and the paused attribute is true, and the media element has an autoplay attribute specified, then the user agent may also set the paused attribute to false, queue a task to fire a simple event called play, and queue a task to fire a simple event called playing. User agents are not required to autoplay, and it is suggested that user agents honor user preferences on the matter. Authors are urged to use the autoplay attribute rather than using script to force the video to play, so as to allow the user to override the behavior if so desired. In any case, the user agent must finally queue a task to fire a simple event called canplaythrough. It is possible for the ready state of a media element to jump between these states discontinuously. For example, the state of a media element can jump straight from HAVE_METADATA to HAVE_ENOUGH_DATA without passing through the HAVE_CURRENT_DATA and HAVE_FUTURE_DATA states. The readyState DOM attribute must, on getting, return the value described above that describes the current ready state of the media element. The autoplay attribute is a boolean attribute. When present, the user agent (as described in the algorithm described herein) will automatically begin playback of the media resource as soon as it can do so without stopping. Authors are urged to use the autoplay attribute rather than using script to trigger automatic playback, as this allows the user to override the automatic playback when it is not desired, e.g. when using a screen reader. Authors are also encouraged to consider not using the automatic playback behavior at all, and instead to let the user agent wait for the user to start playback explicitly. The autoplay DOM attribute must reflect the content attribute of the same name. 4.8.10.8 Cue ranges media . addCueRange(className, id, start, end, pauseOnExit, enterCallback, exitCallback) Registers a range of time, given in seconds, and a pair of callbacks, the first of which will be invoked when the current playback position enters the range, and the second of which will be invoked when it exits the range. The callbacks are invoked with the given ID as their argument. In addition, if the pauseOnExit argument is true, then playback will pause when it reaches the end of the range. media . removeCueRange(className) Removes all the ranges that were registered with the given class name. Media elements have a set of cue ranges. Each cue range is made up of the following information: http://dev.w3.org/html5/spec/Overview.html (185 de 570)01-08-2009 6:55:56
- 186. HTML 5 A class name A group of related ranges can be given the same class name so that they can all be removed at the same time. An identifier A string can be assigned to each cue range for identification by script. The string need not be unique and can contain any value. A start time An end time The actual time range, using the same timeline as the media resource itself. A "pause" boolean A flag indicating whether to pause playback on exit. An "enter" callback A callback that is called when the current playback position enters the range. An "exit" callback A callback that is called when the current playback position exits the range. An "active" boolean A flag indicating whether the range is active or not. The addCueRange(className, id, start, end, pauseOnExit, enterCallback, exitCallback) method must, when called, add a cue range to the media element, that cue range having the class name className, the identifier id, the start time start (in seconds), the end time end (in seconds), the "pause" boolean with the same value as pauseOnExit, the "enter" callback enterCallback, the "exit" callback exitCallback, and an "active" boolean that is true if the current playback position is equal to or greater than the start time and less than the end time, and false otherwise. The removeCueRanges(className) method must, when called, remove all the cue ranges of the media element which have the class name className. 4.8.10.9 Playing the media resource media . paused Returns true if playback is paused; false otherwise. media . ended Returns true if playback has reached the end of the media resource. media . defaultPlaybackRate [ = value ] Returns the default rate of playback, for when the user is not fast-forwarding or reversing through the media resource. Can be set, to change the default rate of playback. The default rate has no direct effect on playback, but if the user switches to a fast-forward mode, when they return to the normal playback mode, it is expected that the rate of playback will be returned to the default rate of playback. media . playbackRate [ = value ] Returns the current rate playback, where 1.0 is normal speed. Can be set, to change the rate of playback. media . played Returns a TimeRanges object that represents the ranges of the media resource that the user agent has played. media . play() Sets the paused attribute to false, loading the media resource and beginning playback if necessary. If the playback had ended, will restart it from the start. media . pause() Sets the paused attribute to true, loading the media resource if necessary. The paused attribute represents whether the media element is paused or not. The attribute must initially be true. A media element is said to be potentially playing when its paused attribute is false, the readyState attribute is either HAVE_FUTURE_DATA or HAVE_ENOUGH_DATA, the element has not ended playback, playback has not stopped due to errors, and the element has not paused for user interaction. A media element is said to have ended playback when the element's readyState attribute is HAVE_METADATA or greater, and either the current playback position is the end of the media resource and the direction of playback is forwards and the media element does not have a loop attribute specified, or the current playback position is the earliest possible position and the direction of playback is backwards. The ended attribute must return true if the media element has ended playback and the direction of playback is forwards, and false otherwise. http://dev.w3.org/html5/spec/Overview.html (186 de 570)01-08-2009 6:55:56
- 187. HTML 5 A media element is said to have stopped due to errors when the element's readyState attribute is HAVE_METADATA or greater, and the user agent encounters a non-fatal error during the processing of the media data, and due to that error, is not able to play the content at the current playback position. A media element is said to have paused for user interaction when its paused attribute is false, the readyState attribute is either HAVE_FUTURE_DATA or HAVE_ENOUGH_DATA and the user agent has reached a point in the media resource where the user has to make a selection for the resource to continue. It is possible for a media element to have both ended playback and paused for user interaction at the same time. When a media element that is potentially playing stops playing because it has paused for user interaction, the user agent must queue a task to fire a simple event called timeupdate at the element. When a media element that is potentially playing stops playing because its readyState attribute changes to a value lower than HAVE_FUTURE_DATA, without the element having ended playback, or playback having stopped due to errors, or playback having paused for user interaction, or the seeking algorithm being invoked, the user agent must queue a task to fire a simple event called timeupdate at the element, and queue a task to fire a simple event called waiting at the element. When the current playback position reaches the end of the media resource when the direction of playback is forwards, then the user agent must follow these steps: 1. If the media element has a loop attribute specified, then seek to the earliest possible position of the media resource and abort these steps. 2. Stop playback. The ended attribute becomes true. 3. The user agent must queue a task to fire a simple event called timeupdate at the element. 4. The user agent must queue a task to fire a simple event called ended at the element. When the current playback position reaches the earliest possible position of the media resource when the direction of playback is backwards, then the user agent must follow these steps: 1. Stop playback. 2. The user agent must queue a task to fire a simple event called timeupdate at the element. The defaultPlaybackRate attribute gives the desired speed at which the media resource is to play, as a multiple of its intrinsic speed. The attribute is mutable: on getting it must return the last value it was set to, or 1.0 if it hasn't yet been set; on setting the attribute must be set to the new value. The playbackRate attribute gives the speed at which the media resource plays, as a multiple of its intrinsic speed. If it is not equal to the defaultPlaybackRate, then the implication is that the user is using a feature such as fast forward or slow motion playback. The attribute is mutable: on getting it must return the last value it was set to, or 1.0 if it hasn't yet been set; on setting the attribute must be set to the new value, and the playback must change speed (if the element is potentially playing). If the playbackRate is positive or zero, then the direction of playback is forwards. Otherwise, it is backwards. The "play" function in a user agent's interface must set the playbackRate attribute to the value of the defaultPlaybackRate attribute before invoking the play() method's steps. Features such as fast-forward or rewind must be implemented by only changing the playbackRate attribute. When the defaultPlaybackRate or playbackRate attributes change value (either by being set by script or by being changed directly by the user agent, e.g. in response to user control) the user agent must queue a task to fire a simple event called ratechange at the media element. The played attribute must return a new static normalized TimeRanges object that represents the ranges of the media resource, if any, that the user agent has so far rendered, at the time the attribute is evaluated. When the play() method on a media element is invoked, the user agent must run the following steps. 1. If the media element's networkState attribute has the value NETWORK_EMPTY, then the user agent must invoke the media element's resource selection algorithm. 2. If the playback has ended, then the user agent must seek to the earliest possible position of the media resource. This will cause the user agent to queue a task to fire a simple event called timeupdate at the media element. 3. If the media element's paused attribute is true, it must be set to false. If this changed the value of paused, the user agent must run the following substeps: 1. Queue a task to fire a simple event called play at the element. 2. If the media element's readyState attribute has the value HAVE_NOTHING, HAVE_METADATA, or HAVE_CURRENT_DATA, queue a task to fire a simple event called waiting at the element. http://dev.w3.org/html5/spec/Overview.html (187 de 570)01-08-2009 6:55:56
- 188. HTML 5 3. Otherwise, the media element's readyState attribute has the value HAVE_FUTURE_DATA or HAVE_ENOUGH_DATA; queue a task to fire a simple event called playing at the element. 4. The media element's autoplaying flag must be set to false. 5. The method must then return. When the pause() method is invoked, the user agent must run the following steps: 1. If the media element's networkState attribute has the value NETWORK_EMPTY, then the user agent must invoke the media element's resource selection algorithm. 2. If the media element's paused attribute is false, it must be set to true. 3. The media element's autoplaying flag must be set to false. 4. If the second step above changed the value of paused, then the user agent must queue a task to fire a simple event called timeupdate at the element, and queue a task to fire a simple event called pause at the element. When a media element is potentially playing and its Document is an active document, its current playback position must increase monotonically at playbackRate units of media time per unit time of wall clock time. This specification doesn't define how the user agent achieves the appropriate playback rate — depending on the protocol and media available, it is plausible that the user agent could negotiate with the server to have the server provide the media data at the appropriate rate, so that (except for the period between when the rate is changed and when the server updates the stream's playback rate) the client doesn't actually have to drop or interpolate any frames. When the playbackRate is negative (playback is backwards), any corresponding audio must be muted. When the playbackRate is so low or so high that the user agent cannot play audio usefully, the corresponding audio must also be muted. If the playbackRate is not 1.0, the user agent may apply pitch adjustments to the audio as necessary to render it faithfully. The playbackRate can be 0.0, in which case the current playback position doesn't move, despite playback not being paused (paused doesn't become true, and the pause event doesn't fire). Media elements that are potentially playing while not in a Document must not play any video, but should play any audio component. Media elements must not stop playing just because all references to them have been removed; only once a media element to which no references exist has reached a point where no further audio remains to be played for that element (e.g. because the element is paused, or because the end of the clip has been reached, or because its playbackRate is 0.0) may the element be garbage collected. When the current playback position of a media element changes (e.g. due to playback or seeking), the user agent must run the following steps. If the current playback position changes while the steps are running, then the user agent must wait for the steps to complete, and then must immediately rerun the steps. (These steps are thus run as often as possible or needed — if one iteration takes a long time, this can cause certain ranges to be skipped over as the user agent rushes ahead to "catch up".) 1. Let current ranges be an ordered list of cue ranges, initialized to contain all the cue ranges of the media element whose start times are less than or equal to the current playback position and whose end times are greater than the current playback position, in the order they were added to the element. 2. Let other ranges be an ordered list of cue ranges, initialized to contain all the cue ranges of the media element that are not present in current ranges, in the order they were added to the element. 3. If the time was reached through the usual monotonic increase of the current playback position during normal playback, and if the user agent has not fired a timeupdate event at the element in the past 15 to 250ms, then the user agent must queue a task to fire a simple event called timeupdate at the element. (In the other cases, such as explicit seeks, relevant events get fired as part of the overall process of changing the current playback position.) The event thus is not to be fired faster than about 66Hz or slower than 4Hz. User agents are encouraged to vary the frequency of the event based on the system load and the average cost of processing the event each time, so that the UI updates are not any more frequent than the user agent can comfortably handle while decoding the video. 4. If none of the cue ranges in current ranges have their "active" boolean set to "false" (inactive) and none of the cue ranges in other ranges have their "active" boolean set to "true" (active), then abort these steps. 5. If the time was reached through the usual monotonic increase of the current playback position during normal playback, and there are cue ranges in other ranges that have both their "active" boolean and their "pause" boolean set to "true", then immediately act as if the element's pause() method had been invoked. (In the other cases, such as explicit seeks, playback is not paused by exiting a cue range, even if that cue range has its "pause" boolean set to "true".) 6. For each non-null "exit" callback of the cue ranges in other ranges that have their "active" boolean set to "true" (active), in list order, queue a task that invokes the callback, passing the cue range's identifier as the callback's only argument. 7. For each non-null "enter" callback of the cue ranges in current ranges that have their "active" boolean set to "false" (inactive), in list order, queue a task that invokes the callback, passing the cue range's identifier as the callback's only argument. 8. Set the "active" boolean of all the cue ranges in the current ranges list to "true" (active), and the "active" boolean of all the cue ranges in the other ranges list to "false" (inactive). When a media element is removed from a Document, if the media element's networkState attribute has a value other than NETWORK_EMPTY then the user agent must act as if the pause() method had been invoked. If the media element's Document stops being a fully active document, then the playback will stop until the document is active again. http://dev.w3.org/html5/spec/Overview.html (188 de 570)01-08-2009 6:55:56
- 189. HTML 5 4.8.10.10 Seeking media . seeking Returns true if the user agent is currently seeking. media . seekable Returns a TimeRanges object that represents the ranges of the media resource to which it is possible for the user agent to seek. The seeking attribute must initially have the value false. When the user agent is required to seek to a particular new playback position in the media resource, it means that the user agent must run the following steps: 1. If the media element's readyState is HAVE_NOTHING, then the user agent must raise an INVALID_STATE_ERR exception (if the seek was in response to a DOM method call or setting of a DOM attribute), and abort these steps. 2. If the new playback position is later than the end of the media resource, then let it be the end of the media resource instead. 3. If the new playback position is less than the earliest possible position, let it be that position instead. 4. If the (possibly now changed) new playback position is not in one of the ranges given in the seekable attribute, then the user agent must raise an INDEX_SIZE_ERR exception (if the seek was in response to a DOM method call or setting of a DOM attribute), and abort these steps. 5. The current playback position must be set to the given new playback position. 6. The seeking DOM attribute must be set to true. 7. The user agent must queue a task to fire a simple event called timeupdate at the element. 8. If the media element was potentially playing immediately before it started seeking, but seeking caused its readyState attribute to change to a value lower than HAVE_FUTURE_DATA, the user agent must queue a task to fire a simple event called waiting at the element. 9. If, when it reaches this step, the user agent has still not established whether or not the media data for the new playback position is available, and, if it is, decoded enough data to play back that position, the user agent must queue a task to fire a simple event called seeking at the element. 10. If the seek was in response to a DOM method call or setting of a DOM attribute, then continue the script. The remainder of these steps must be run asynchronously. 11. The user agent must wait until it has established whether or not the media data for the new playback position is available, and, if it is, until it has decoded enough data to play back that position. 12. The seeking DOM attribute must be set to false. 13. The user agent must queue a task to fire a simple event called seeked at the element. The seekable attribute must return a new static normalized TimeRanges object that represents the ranges of the media resource, if any, that the user agent is able to seek to, at the time the attribute is evaluated. If the user agent can seek to anywhere in the media resource, e.g. because it a simple movie file and the user agent and the server support HTTP Range requests, then the attribute would return an object with one range, whose start is the time of the first frame (typically zero), and whose end is the same as the time of the first frame plus the duration attribute's value (which would equal the time of the last frame). The range might be continuously changing, e.g. if the user agent is buffering a sliding window on an infinite stream. This is the behavior seen with DVRs viewing live TV, for instance. Media resources might be internally scripted or interactive. Thus, a media element could play in a non-linear fashion. If this happens, the user agent must act as if the algorithm for seeking was used whenever the current playback position changes in a discontinuous fashion (so that the relevant events fire). 4.8.10.11 User interface The controls attribute is a boolean attribute. If present, it indicates that the author has not provided a scripted controller and would like the user agent to provide its own set of controls. If the attribute is present, or if scripting is disabled for the media element, then the user agent should expose a user interface to the user. This user interface should include features to begin playback, pause playback, seek to an arbitrary position in the content (if the content supports arbitrary seeking), change the volume, and show the media content in manners more suitable to the user (e.g. full-screen video or in an independent resizable window). Other controls may also be made available. http://dev.w3.org/html5/spec/Overview.html (189 de 570)01-08-2009 6:55:57
- 190. HTML 5 If the attribute is absent, then the user agent should avoid making a user interface available that could conflict with an author-provided user interface. User agents may make the following features available, however, even when the attribute is absent: User agents may provide controls to affect playback of the media resource (e.g. play, pause, seeking, and volume controls), but such features should not interfere with the page's normal rendering. For example, such features could be exposed in the media element's context menu. Where possible (specifically, for starting, stopping, pausing, and unpausing playback, for muting or changing the volume of the audio, and for seeking), user interface features exposed by the user agent must be implemented in terms of the DOM API described above, so that, e.g., all the same events fire. The controls DOM attribute must reflect the content attribute of the same name. media . volume [ = value ] Returns the current playback volume, as a number in the range 0.0 to 1.0, where 0.0 is the quietest and 1.0 the loudest. Can be set, to change the volume. Throws an INDEX_SIZE_ERR if the new value is not in the range 0.0 .. 1.0. media . muted [ = value ] Returns true if audio is muted, overriding the volume attribute, and false if the volume attribute is being honored. Can be set, to change whether the audio is muted or not. The volume attribute must return the playback volume of any audio portions of the media element, in the range 0.0 (silent) to 1.0 (loudest). Initially, the volume must be 1.0, but user agents may remember the last set value across sessions, on a per-site basis or otherwise, so the volume may start at other values. On setting, if the new value is in the range 0.0 to 1.0 inclusive, the attribute must be set to the new value and the playback volume must be correspondingly adjusted as soon as possible after setting the attribute, with 0.0 being silent, and 1.0 being the loudest setting, values in between increasing in loudness. The range need not be linear. The loudest setting may be lower than the system's loudest possible setting; for example the user could have set a maximum volume. If the new value is outside the range 0.0 to 1.0 inclusive, then, on setting, an INDEX_SIZE_ERR exception must be raised instead. The muted attribute must return true if the audio channels are muted and false otherwise. Initially, the audio channels should not be muted (false), but user agents may remember the last set value across sessions, on a per-site basis or otherwise, so the muted state may start as muted (true). On setting, the attribute must be set to the new value; if the new value is true, audio playback for this media resource must then be muted, and if false, audio playback must then be enabled. Whenever either the muted or volume attributes are changed, the user agent must queue a task to fire a simple event called volumechange at the media element. 4.8.10.12 Time ranges Objects implementing the TimeRanges interface represent a list of ranges (periods) of time. interface TimeRanges { readonly attribute unsigned long length; float start(in unsigned long index); float end(in unsigned long index); }; media . length Returns the number of ranges in the object. time = media . start(index) Returns the time for the start of the range with the given index. Throws an INDEX_SIZE_ERR if the index is out of range. time = media . end(index) Returns the time for the end of the range with the given index. Throws an INDEX_SIZE_ERR if the index is out of range. The length DOM attribute must return the number of ranges represented by the object. http://dev.w3.org/html5/spec/Overview.html (190 de 570)01-08-2009 6:55:57
- 191. HTML 5 The start(index) method must return the position of the start of the indexth range represented by the object, in seconds measured from the start of the timeline that the object covers. The end(index) method must return the position of the end of the indexth range represented by the object, in seconds measured from the start of the timeline that the object covers. These methods must raise INDEX_SIZE_ERR exceptions if called with an index argument greater than or equal to the number of ranges represented by the object. When a TimeRanges object is said to be a normalized TimeRanges object, the ranges it represents must obey the following criteria: q The start of a range must be greater than the end of all earlier ranges. q The start of a range must be less than the end of that same range. In other words, the ranges in such an object are ordered, don't overlap, aren't empty, and don't touch (adjacent ranges are folded into one bigger range). The timelines used by the objects returned by the buffered, seekable and played DOM attributes of media elements must be the same as that element's media resource's timeline. 4.8.10.13 Event summary The following events fire on media elements as part of the processing model described above: Event name Interface Dispatched when... Preconditions loadstart ProgressEvent [PROGRESS] The user agent begins looking for media data, as part of the resource selection algorithm. networkState equals NETWORK_LOADING progress ProgressEvent [PROGRESS] The user agent is fetching media data. networkState equals NETWORK_LOADING suspend ProgressEvent [PROGRESS] The user agent is intentionally not currently fetching media data, but does not have the entire media networkState equals NETWORK_IDLE resource downloaded. load ProgressEvent [PROGRESS] The user agent finishes fetching the entire media resource. networkState equals NETWORK_LOADED abort ProgressEvent [PROGRESS] The user agent stops fetching the media data before it is completely downloaded. error is an object with the code MEDIA_ERR_ABORTED. networkState equals either NETWORK_EMPTY or NETWORK_LOADED, depending on when the download was aborted. error ProgressEvent [PROGRESS] An error occurs while fetching the media data. error is an object with the code MEDIA_ERR_NETWORK or higher. networkState equals either NETWORK_EMPTY or NETWORK_LOADED, depending on when the download was aborted. emptied Event A media element whose networkState was previously not in the NETWORK_EMPTY state has just networkState is NETWORK_EMPTY; all the DOM attributes are in their initial states. switched to that state (either because of a fatal error during load that's about to be reported, or because the load() method was invoked while the resource selection algorithm was already running, in which case it is fired synchronously during the load() method call). stalled ProgressEvent The user agent is trying to fetch media data, but data is unexpectedly not forthcoming. networkState is NETWORK_LOADING. play Event Playback has begun. Fired after the play() method has returned. paused is newly false. pause Event Playback has been paused. Fired after the pause method has returned. paused is newly true. loadedmetadata Event The user agent has just determined the duration and dimensions of the media resource. readyState is newly equal to HAVE_METADATA or greater for the first time. loadeddata Event The user agent can render the media data at the current playback position for the first time. readyState newly increased to HAVE_CURRENT_DATA or greater for the first time. waiting Event Playback has stopped because the next frame is not available, but the user agent expects that frame to readyState is newly equal to or less than HAVE_CURRENT_DATA, and paused is false. Either become available in due course. seeking is true, or the current playback position is not contained in any of the ranges in buffered. It is possible for playback to stop for two other reasons without paused being false, but those two reasons do not fire this event: maybe playback ended, or playback stopped due to errors. playing Event Playback has started. readyState is newly equal to or greater than HAVE_FUTURE_DATA, paused is false, seeking is false, or the current playback position is contained in one of the ranges in buffered. canplay Event The user agent can resume playback of the media data, but estimates that if playback were to be started readyState newly increased to HAVE_FUTURE_DATA or greater. now, the media resource could not be rendered at the current playback rate up to its end without having to stop for further buffering of content. canplaythrough Event The user agent estimates that if playback were to be started now, the media resource could be rendered at readyState is newly equal to HAVE_ENOUGH_DATA. the current playback rate all the way to its end without having to stop for further buffering. seeking Event The seeking DOM attribute changed to true and the seek operation is taking long enough that the user agent has time to fire the event. seeked Event The seeking DOM attribute changed to false. timeupdate Event The current playback position changed as part of normal playback or in an especially interesting way, for example discontinuously. ended Event Playback has stopped because the end of the media resource was reached. currentTime equals the end of the media resource; ended is true. ratechange Event Either the defaultPlaybackRate or the playbackRate attribute has just been updated. http://dev.w3.org/html5/spec/Overview.html (191 de 570)01-08-2009 6:55:57
- 192. HTML 5 durationchange Event The duration attribute has just been updated. volumechange Event Either the volume attribute or the muted attribute has changed. Fired after the relevant attribute's setter has returned. 4.8.10.14 Security and privacy considerations The main security and privacy implications of the video and audio elements come from the ability to embed media cross-origin. There are two directions that threats can flow: from hostile content to a victim page, and from a hostile page to victim content. If a victim page embeds hostile content, the threat is that the content might contain scripted code that attempts to interact with the Document that embeds the content. To avoid this, user agents must ensure that there is no access from the content to the embedding page. In the case of media content that uses DOM concepts, the embedded content must be treated as if it was in its own unrelated top-level browsing context. For instance, if an SVG animation was embedded in a video element, the user agent would not give it access to the DOM of the outer page. From the perspective of scripts in the SVG resource, the SVG file would appear to be in a lone top-level browsing context with no parent. If a hostile page embeds victim content, the threat is that the embedding page could obtain information from the content that it would not otherwise have access to. The API does expose some information: the existence of the media, its type, its duration, its size, and the performance characteristics of its host. Such information is already potentially problematic, but in practice the same information can more or less be obtained using the img element, and so it has been deemed acceptable. However, significantly more sensitive information could be obtained if the user agent further exposes metadata within the content such as subtitles or chapter titles. This version of the API does not expose such information. Future extensions to this API will likely reuse a mechanism such as CORS to check that the embedded content's site has opted in to exposing such information. [CORS] An attacker could trick a user running within a corporate network into visiting a site that attempts to load a video from a previously leaked location on the corporation's intranet. If such a video included confidential plans for a new product, then being able to read the subtitles would present a confidentiality breach. 4.8.11 The canvas element Categories Flow content. Phrasing content. Embedded content. Contexts in which this element may be used: Where embedded content is expected. Content model: Transparent. Content attributes: Global attributes width height DOM interface: interface HTMLCanvasElement : HTMLElement { attribute unsigned long width; attribute unsigned long height; DOMString toDataURL([Optional] in DOMString type, [Variadic] in any args); Object getContext(in DOMString contextId); }; The canvas element represents a resolution-dependent bitmap canvas, which can be used for rendering graphs, game graphics, or other visual images on the fly. Authors should not use the canvas element in a document when a more suitable element is available. For example, it is inappropriate to use a canvas element to render a page heading: if the desired presentation of the heading is graphically intense, it should be marked up using appropriate elements (typically h1) and then styled using CSS and supporting technologies such as XBL. When authors use the canvas element, they must also provide content that, when presented to the user, conveys essentially the same function or purpose as the bitmap canvas. This content may be placed as content of the canvas element. The contents of the canvas element, if any, are the element's fallback content. http://dev.w3.org/html5/spec/Overview.html (192 de 570)01-08-2009 6:55:57
- 193. HTML 5 In interactive visual media, if scripting is enabled for the canvas element, the canvas element represents an embedded element with a dynamically created image. In non-interactive, static, visual media, if the canvas element has been previously painted on (e.g. if the page was viewed in an interactive visual medium and is now being printed, or if some script that ran during the page layout process painted on the element), then the canvas element represents embedded content with the current image and size. Otherwise, the element represents its fallback content instead. In non-visual media, and in visual media if scripting is disabled for the canvas element, the canvas element represents its fallback content instead. The canvas element has two attributes to control the size of the coordinate space: width and height. These attributes, when specified, must have values that are valid non-negative integers. The rules for parsing non-negative integers must be used to obtain their numeric values. If an attribute is missing, or if parsing its value returns an error, then the default value must be used instead. The width attribute defaults to 300, and the height attribute defaults to 150. The intrinsic dimensions of the canvas element equal the size of the coordinate space, with the numbers interpreted in CSS pixels. However, the element can be sized arbitrarily by a style sheet. During rendering, the image is scaled to fit this layout size. The size of the coordinate space does not necessarily represent the size of the actual bitmap that the user agent will use internally or during rendering. On high-definition displays, for instance, the user agent may internally use a bitmap with two device pixels per unit in the coordinate space, so that the rendering remains at high quality throughout. Whenever the width and height attributes are set (whether to a new value or to the previous value), the bitmap and any associated contexts must be cleared back to their initial state and reinitialized with the newly specified coordinate space dimensions. The width and height DOM attributes must reflect the respective content attributes of the same name. Only one square appears to be drawn in the following example: // canvas is a reference to a <canvas> element var context = canvas.getContext('2d'); context.fillRect(0,0,50,50); canvas.setAttribute('width', '300'); // clears the canvas context.fillRect(0,100,50,50); canvas.width = canvas.width; // clears the canvas context.fillRect(100,0,50,50); // only this square remains When the canvas is initialized it must be set to fully transparent black. To draw on the canvas, authors must first obtain a reference to a context using the getContext(contextId) method of the canvas element. context = canvas . getContext(contextId) Returns an object that exposes an API for drawing on the canvas. Returns null if the given context ID is not supported. This specification only defines one context, with the name "2d". If getContext() is called with that exact string for its contextId argument, then the UA must return a reference to an object implementing CanvasRenderingContext2D. Other specifications may define their own contexts, which would return different objects. Vendors may also define experimental contexts using the syntax vendorname-context, for example, moz-3d. When the UA is passed an empty string or a string specifying a context that it does not support, then it must return null. String comparisons must be case-sensitive. A future version of this specification will probably define a 3d context (probably based on the OpenGL ES API). url = canvas . toDataURL( [ type, ... ]) Returns a data: URL for the image in the canvas. The first argument, if provided, controls the type of the image to be returned (e.g. PNG or JPEG). The default is image/png; that type is also used if the given type isn't supported. The other arguments are specific to the type, and control the way that the image is generated, as given in the table below. The toDataURL() method must, when called with no arguments, return a data: URL containing a representation of the image as a PNG file. [PNG]. If the canvas has no pixels (i.e. either its horizontal dimension or its vertical dimension is zero) then the method must return the string "data:,". (This is the shortest data: URL; it represents the empty string in a text/plain resource.) When the toDataURL(type) method, when called with one or more arguments, must return a data: URL containing a representation of the image in the format given by type. The possible values are MIME types with no parameters, for example image/png, image/jpeg, or even maybe image/svg+xml if the implementation actually keeps enough information to reliably render an SVG image from the canvas. http://dev.w3.org/html5/spec/Overview.html (193 de 570)01-08-2009 6:55:57
- 194. HTML 5 For image types that do not support an alpha channel, the image must be composited onto a solid black background using the source-over operator, and the resulting image must be the one used to create the data: URL. Only support for image/png is required. User agents may support other types. If the user agent does not support the requested type, it must return the image using the PNG format. User agents must convert the provided type to ASCII lowercase before establishing if they support that type and before creating the data: URL. When trying to use types other than image/png, authors can check if the image was really returned in the requested format by checking to see if the returned string starts with one the exact strings "data:image/png," or "data:image/png;". If it does, the image is PNG, and thus the requested type was not supported. (The one exception to this is if the canvas has either no height or no width, in which case the result might simply be "data:,".) If the method is invoked with the first argument giving a type corresponding to one of the types given in the first column of the following table, and the user agent supports that type, then the subsequent arguments, if any, must be treated as described in the second cell of that row. Type Other arguments image/jpeg The second argument, if it is a number between 0.0 and 1.0, must be treated as the desired quality level. If it is not a number or is outside that range, the user agent must use its default value, as if the argument had been omitted. Other arguments must be ignored and must not cause the user agent to raise an exception. A future version of this specification will probably define other parameters to be passed to toDataURL() to allow authors to more carefully control compression settings, image metadata, etc. 4.8.11.1 The 2D context When the getContext() method of a canvas element is invoked with 2d as the argument, a CanvasRenderingContext2D object is returned. There is only one CanvasRenderingContext2D object per canvas, so calling the getContext() method with the 2d argument a second time must return the same object. The 2D context represents a flat Cartesian surface whose origin (0,0) is at the top left corner, with the coordinate space having x values increasing when going right, and y values increasing when going down. interface CanvasRenderingContext2D { // back-reference to the canvas readonly attribute HTMLCanvasElement canvas; // state void save(); // push state on state stack void restore(); // pop state stack and restore state // transformations (default transform is the identity matrix) void scale(in float x, in float y); void rotate(in float angle); void translate(in float x, in float y); void transform(in float m11, in float m12, in float m21, in float m22, in float dx, in float dy); void setTransform(in float m11, in float m12, in float m21, in float m22, in float dx, in float dy); // compositing attribute float globalAlpha; // (default 1.0) attribute DOMString globalCompositeOperation; // (default source-over) // colors and styles attribute any strokeStyle; // (default black) attribute any fillStyle; // (default black) CanvasGradient createLinearGradient(in float x0, in float y0, in float x1, in float y1); CanvasGradient createRadialGradient(in float x0, in float y0, in float r0, in float x1, in float y1, in float r1); CanvasPattern createPattern(in HTMLImageElement image, in DOMString repetition); CanvasPattern createPattern(in HTMLCanvasElement image, in DOMString repetition); CanvasPattern createPattern(in HTMLVideoElement image, in DOMString repetition); // line caps/joins attribute float lineWidth; // (default 1) attribute DOMString lineCap; // "butt", "round", "square" (default "butt") attribute DOMString lineJoin; // "round", "bevel", "miter" (default "miter") attribute float miterLimit; // (default 10) // shadows attribute float shadowOffsetX; // (default 0) http://dev.w3.org/html5/spec/Overview.html (194 de 570)01-08-2009 6:55:57
- 195. HTML 5 attribute float shadowOffsetY; // (default 0) attribute float shadowBlur; // (default 0) attribute DOMString shadowColor; // (default transparent black) // rects void clearRect(in float x, in float y, in float w, in float h); void fillRect(in float x, in float y, in float w, in float h); void strokeRect(in float x, in float y, in float w, in float h); // path API void beginPath(); void closePath(); void moveTo(in float x, in float y); void lineTo(in float x, in float y); void quadraticCurveTo(in float cpx, in float cpy, in float x, in float y); void bezierCurveTo(in float cp1x, in float cp1y, in float cp2x, in float cp2y, in float x, in float y); void arcTo(in float x1, in float y1, in float x2, in float y2, in float radius); void rect(in float x, in float y, in float w, in float h); void arc(in float x, in float y, in float radius, in float startAngle, in float endAngle, in boolean anticlockwise); void fill(); void stroke(); void clip(); boolean isPointInPath(in float x, in float y); // text attribute DOMString font; // (default 10px sans-serif) attribute DOMString textAlign; // "start", "end", "left", "right", "center" (default: "start") attribute DOMString textBaseline; // "top", "hanging", "middle", "alphabetic", "ideographic", "bottom" (default: "alphabetic") void fillText(in DOMString text, in float x, in float y, [Optional] in float maxWidth); void strokeText(in DOMString text, in float x, in float y, [Optional] in float maxWidth); TextMetrics measureText(in DOMString text); // drawing images void drawImage(in HTMLImageElement image, in float dx, in float dy, [Optional] in float dw, in float dh); void drawImage(in HTMLImageElement image, in float sx, in float sy, in float sw, in float sh, in float dx, in float dy, in float dw, in float dh); void drawImage(in HTMLCanvasElement image, in float dx, in float dy, [Optional] in float dw, in float dh); void drawImage(in HTMLCanvasElement image, in float sx, in float sy, in float sw, in float sh, in float dx, in float dy, in float dw, in float dh); void drawImage(in HTMLVideoElement image, in float dx, in float dy, [Optional] in float dw, in float dh); void drawImage(in HTMLVideoElement image, in float sx, in float sy, in float sw, in float sh, in float dx, in float dy, in float dw, in float dh); // pixel manipulation ImageData createImageData(in float sw, in float sh); ImageData createImageData(in ImageData imagedata); ImageData getImageData(in float sx, in float sy, in float sw, in float sh); void putImageData(in ImageData imagedata, in float dx, in float dy, [Optional] in float dirtyX, in float dirtyY, in float dirtyWidth, in float dirtyHeight); }; interface CanvasGradient { // opaque object void addColorStop(in float offset, in DOMString color); }; interface CanvasPattern { // opaque object }; interface TextMetrics { readonly attribute float width; }; interface ImageData { readonly attribute unsigned long width; readonly attribute unsigned long height; readonly attribute CanvasPixelArray data; }; http://dev.w3.org/html5/spec/Overview.html (195 de 570)01-08-2009 6:55:57
- 196. HTML 5 [IndexGetter, IndexSetter] interface CanvasPixelArray { readonly attribute unsigned long length; }; context . canvas Returns the canvas element. The canvas attribute must return the canvas element that the context paints on. Unless otherwise stated, for the 2D context interface, any method call with a numeric argument whose value is infinite or a NaN value must be ignored. Whenever the CSS value currentColor is used as a color in this API, the "computed value of the 'color' property" for the purposes of determining the computed value of the currentColor keyword is the computed value of the 'color' property on the element in question at the time that the color is specified (e.g. when the appropriate attribute is set, or when the method is called; not when the color is rendered or otherwise used). If the computed value of the 'color' property is undefined for a particular case (e.g. because the element is not in a Document), then the "computed value of the 'color' property" for the purposes of determining the computed value of the currentColor keyword is fully opaque black. [CSSCOLOR] 4.8.11.1.1 The canvas state Each context maintains a stack of drawing states. Drawing states consist of: q The current transformation matrix. q The current clipping region. q The current values of the following attributes: strokeStyle, fillStyle, globalAlpha, lineWidth, lineCap, lineJoin, miterLimit, shadowOffsetX, shadowOffsetY, shadowBlur, shadowColor, globalCompositeOperation, font, textAlign, textBaseline. The current path and the current bitmap are not part of the drawing state. The current path is persistent, and can only be reset using the beginPath() method. The current bitmap is a property of the canvas, not the context. context . save() Pushes the current state onto the stack. context . restore() Pops the top state on the stack, restoring the context to that state. The save() method must push a copy of the current drawing state onto the drawing state stack. The restore() method must pop the top entry in the drawing state stack, and reset the drawing state it describes. If there is no saved state, the method must do nothing. 4.8.11.1.2 Transformations The transformation matrix is applied to coordinates when creating shapes and paths. When the context is created, the transformation matrix must initially be the identity transform. It may then be adjusted using the transformation methods. The transformations must be performed in reverse order. For instance, if a scale transformation that doubles the width is applied, followed by a rotation transformation that rotates drawing operations by a quarter turn, and a rectangle twice as wide as it is tall is then drawn on the canvas, the actual result will be a square. context . scale(x, y) Changes the transformation matrix to apply a scaling transformation with the given characteristics. context . rotate(angle) Changes the transformation matrix to apply a rotation transformation with the given characteristics. context . translate(x, y) http://dev.w3.org/html5/spec/Overview.html (196 de 570)01-08-2009 6:55:57
- 197. HTML 5 Changes the transformation matrix to apply a translation transformation with the given characteristics. context . transform(m11, m12, m21, m22, dx, dy) Changes the transformation matrix to apply the matrix given by the arguments as described below. context . setTransform(m11, m12, m21, m22, dx, dy) Changes the transformation matrix to the matrix given by the arguments as described below. The scale(x, y) method must add the scaling transformation described by the arguments to the transformation matrix. The x argument represents the scale factor in the horizontal direction and the y argument represents the scale factor in the vertical direction. The factors are multiples. The rotate(angle) method must add the rotation transformation described by the argument to the transformation matrix. The angle argument represents a clockwise rotation angle expressed in radians. The translate(x, y) method must add the translation transformation described by the arguments to the transformation matrix. The x argument represents the translation distance in the horizontal direction and the y argument represents the translation distance in the vertical direction. The arguments are in coordinate space units. The transform(m11, m12, m21, m22, dx, dy) method must multiply the current transformation matrix with the matrix described by: m11 m21 dx m12 m22 dy 0 0 1 The setTransform(m11, m12, m21, m22, dx, dy) method must reset the current transform to the identity matrix, and then invoke the transform(m11, m12, m21, m22, dx, dy) method with the same arguments. 4.8.11.1.3 Compositing context . globalAlpha [ = value ] Returns the current alpha value applied to rendering operations. Can be set, to change the alpha value. Values outside of the range 0.0 .. 1.0 are ignored. context . globalCompositeOperation [ = value ] Returns the current composition operation, from the list below. Can be set, to change the composition operation. Unknown values are ignored. All drawing operations are affected by the global compositing attributes, globalAlpha and globalCompositeOperation. The globalAlpha attribute gives an alpha value that is applied to shapes and images before they are composited onto the canvas. The value must be in the range from 0.0 (fully transparent) to 1.0 (no additional transparency). If an attempt is made to set the attribute to a value outside this range (including Infinity and NaN values), the attribute must retain its previous value. When the context is created, the globalAlpha attribute must initially have the value 1.0. The globalCompositeOperation attribute sets how shapes and images are drawn onto the existing bitmap, once they have had globalAlpha and the current transformation matrix applied. It must be set to a value from the following list. In the descriptions below, the source image, A, is the shape or image being rendered, and the destination image, B, is the current state of the bitmap. source-atop A atop B. Display the source image wherever both images are opaque. Display the destination image wherever the destination image is opaque but the source image is transparent. Display transparency elsewhere. source-in A in B. Display the source image wherever both the source image and destination image are opaque. Display transparency elsewhere. source-out A out B. Display the source image wherever the source image is opaque and the destination image is transparent. Display transparency elsewhere. source-over (default) A over B. Display the source image wherever the source image is opaque. Display the destination image elsewhere. destination-atop B atop A. Same as source-atop but using the destination image instead of the source image and vice versa. destination-in B in A. Same as source-in but using the destination image instead of the source image and vice versa. destination-out B out A. Same as source-out but using the destination image instead of the source image and vice versa. destination-over B over A. Same as source-over but using the destination image instead of the source image and vice versa. lighter http://dev.w3.org/html5/spec/Overview.html (197 de 570)01-08-2009 6:55:57
- 198. HTML 5 A plus B. Display the sum of the source image and destination image, with color values approaching 1 as a limit. copy A (B is ignored). Display the source image instead of the destination image. xor A xor B. Exclusive OR of the source image and destination image. vendorName-operationName Vendor-specific extensions to the list of composition operators should use this syntax. These values are all case-sensitive — they must be used exactly as shown. User agents must not recognize values that are not a case-sensitive match for one of the values given above. The operators in the above list must be treated as described by the Porter-Duff operator given at the start of their description (e.g. A over B). [PORTERDUFF] On setting, if the user agent does not recognize the specified value, it must be ignored, leaving the value of globalCompositeOperation unaffected. When the context is created, the globalCompositeOperation attribute must initially have the value source-over. 4.8.11.1.4 Colors and styles context . strokeStyle [ = value ] Returns the current style used for stroking shapes. Can be set, to change the stroke style. The style can be either a string containing a CSS color, or a CanvasGradient or CanvasPattern object. Invalid values are ignored. context . fillStyle [ = value ] Returns the current style used for filling shapes. Can be set, to change the fill style. The style can be either a string containing a CSS color, or a CanvasGradient or CanvasPattern object. Invalid values are ignored. The strokeStyle attribute represents the color or style to use for the lines around shapes, and the fillStyle attribute represents the color or style to use inside the shapes. Both attributes can be either strings, CanvasGradients, or CanvasPatterns. On setting, strings must be parsed as CSS <color> values and the color assigned, and CanvasGradient and CanvasPattern objects must be assigned themselves. [CSSCOLOR] If the value is a string but is not a valid color, or is neither a string, a CanvasGradient, nor a CanvasPattern, then it must be ignored, and the attribute must retain its previous value. On getting, if the value is a color, then the serialization of the color must be returned. Otherwise, if it is not a color but a CanvasGradient or CanvasPattern, then the respective object must be returned. (Such objects are opaque and therefore only useful for assigning to other attributes or for comparison to other gradients or patterns.) The serialization of a color for a color value is a string, computed as follows: if it has alpha equal to 1.0, then the string is a lowercase six-digit hex value, prefixed with a "#" character (U+0023 NUMBER SIGN), with the first two digits representing the red component, the next two digits representing the green component, and the last two digits representing the blue component, the digits being in the range 0-9 a-f (U+0030 to U+0039 and U+0061 to U+0066). Otherwise, the color value has alpha less than 1.0, and the string is the color value in the CSS rgba() functional-notation format: the literal string rgba (U+0072 U+0067 U+0062 U+0061) followed by a U+0028 LEFT PARENTHESIS, a base-ten integer in the range 0-255 representing the red component (using digits 0-9, U+0030 to U +0039, in the shortest form possible), a literal U+002C COMMA and U+0020 SPACE, an integer for the green component, a comma and a space, an integer for the blue component, another comma and space, a U+0030 DIGIT ZERO, a U+002E FULL STOP (representing the decimal point), one or more digits in the range 0-9 (U+0030 to U+0039) representing the fractional part of the alpha value, and finally a U+0029 RIGHT PARENTHESIS. When the context is created, the strokeStyle and fillStyle attributes must initially have the string value #000000. There are two types of gradients, linear gradients and radial gradients, both represented by objects implementing the opaque CanvasGradient interface. Once a gradient has been created (see below), stops are placed along it to define how the colors are distributed along the gradient. The color of the gradient at each stop is the color specified for that stop. Between each such stop, the colors and the alpha component must be linearly interpolated over the RGBA space without premultiplying the alpha value to find the color to use at that offset. Before the first stop, the color must be the color of the first stop. After the last stop, the color must be the color of the last stop. When there are no stops, the gradient is transparent black. gradient . addColorStop(offset, color) Adds a color stop with the given color to the gradient at the given offset. 0.0 is the offset at one end of the gradient, 1.0 is the offset at the other end. Throws an INDEX_SIZE_ERR exception if the offset it out of range. Throws a SYNTAX_ERR exception if the color cannot be parsed. gradient = context . createLinearGradient(x0, y0, x1, y1) Returns a CanvasGradient object that represents a linear gradient that paints along the line given by the coordinates represented by the arguments. http://dev.w3.org/html5/spec/Overview.html (198 de 570)01-08-2009 6:55:57
- 199. HTML 5 If any of the arguments are not finite numbers, throws a NOT_SUPPORTED_ERR exception. gradient = context . createRadialGradient(x0, y0, r0, x1, y1, r1) Returns a CanvasGradient object that represents a radial gradient that paints along the cone given by the circles represented by the arguments. If any of the arguments are not finite numbers, throws a NOT_SUPPORTED_ERR exception. If either of the radii are negative throws an INDEX_SIZE_ERR exception. The addColorStop(offset, color) method on the CanvasGradient interface adds a new stop to a gradient. If the offset is less than 0, greater than 1, infinite, or NaN, then an INDEX_SIZE_ERR exception must be raised. If the color cannot be parsed as a CSS color, then a SYNTAX_ERR exception must be raised. Otherwise, the gradient must have a new stop placed, at offset offset relative to the whole gradient, and with the color obtained by parsing color as a CSS <color> value. If multiple stops are added at the same offset on a gradient, they must be placed in the order added, with the first one closest to the start of the gradient, and each subsequent one infinitesimally further along towards the end point (in effect causing all but the first and last stop added at each point to be ignored). The createLinearGradient(x0, y0, x1, y1) method takes four arguments that represent the start point (x0, y0) and end point (x1, y1) of the gradient. If any of the arguments to createLinearGradient() are infinite or NaN, the method must raise a NOT_SUPPORTED_ERR exception. Otherwise, the method must return a linear CanvasGradient initialized with the specified line. Linear gradients must be rendered such that all points on a line perpendicular to the line that crosses the start and end points have the color at the point where those two lines cross (with the colors coming from the interpolation and extrapolation described above). The points in the linear gradient must be transformed as described by the current transformation matrix when rendering. If x0 = x1 and y0 = y1, then the linear gradient must paint nothing. The createRadialGradient(x0, y0, r0, x1, y1, r1) method takes six arguments, the first three representing the start circle with origin (x0, y0) and radius r0, and the last three representing the end circle with origin (x1, y1) and radius r1. The values are in coordinate space units. If any of the arguments are infinite or NaN, a NOT_SUPPORTED_ERR exception must be raised. If either of r0 or r1 are negative, an INDEX_SIZE_ERR exception must be raised. Otherwise, the method must return a radial CanvasGradient initialized with the two specified circles. Radial gradients must be rendered by following these steps: 1. If x0 = x1 and y0 = y1 and r0 = r1, then the radial gradient must paint nothing. Abort these steps. 2. Let x(ω) = (x1-x0)ω + x0 Let y(ω) = (y1-y0)ω + y0 Let r(ω) = (r1-r0)ω + r0 Let the color at ω be the color at that position on the gradient (with the colors coming from the interpolation and extrapolation described above). 3. For all values of ω where r(ω) > 0, starting with the value of ω nearest to positive infinity and ending with the value of ω nearest to negative infinity, draw the circumference of the circle with radius r(ω) at position (x(ω), y(ω)), with the color at ω, but only painting on the parts of the canvas that have not yet been painted on by earlier circles in this step for this rendering of the gradient. This effectively creates a cone, touched by the two circles defined in the creation of the gradient, with the part of the cone before the start circle (0.0) using the color of the first offset, the part of the cone after the end circle (1.0) using the color of the last offset, and areas outside the cone untouched by the gradient (transparent black). Gradients must be painted only where the relevant stroking or filling effects requires that they be drawn. The points in the radial gradient must be transformed as described by the current transformation matrix when rendering. Patterns are represented by objects implementing the opaque CanvasPattern interface. pattern = context . createPattern(image, repetition) Returns a CanvasPattern object that uses the given image and repeats in the direction(s) given by the repetition argument. The allowed values for repeat are repeat (both directions), repeat-x (horizontal only), repeat-y (vertical only), and no-repeat (neither). If the repetition argument is empty or null, the value repeat is used. If the first argument isn't an img, canvas, or video element, throws a TYPE_MISMATCH_ERR exception. If the image is not fully decoded yet, or has no image data, throws an INVALID_STATE_ERR exception. If the second argument isn't one of the allowed values, throws a SYNTAX_ERR exception. To create objects of this type, the createPattern(image, repetition) method is used. The first argument gives the image to use as the pattern (either an HTMLImageElement or an HTMLCanvasElement). Modifying this image after calling the createPattern() method must not affect the pattern. The second argument must be a string with one of the following values: repeat, repeat-x, repeat-y, no-repeat. If the empty string or null is specified, repeat must be assumed. If an unrecognized value is given, then the user agent must raise a SYNTAX_ERR exception. User agents must recognize the four values described above exactly (e.g. they must not do case folding). The method must return a CanvasPattern object suitably initialized. http://dev.w3.org/html5/spec/Overview.html (199 de 570)01-08-2009 6:55:57
- 200. HTML 5 The image argument is an instance of either HTMLImageElement, HTMLCanvasElement, or HTMLVideoElement. If the image is of the wrong type or null, the implementation must raise a TYPE_MISMATCH_ERR exception. If the image argument is an HTMLImageElement object whose complete attribute is false, then the implementation must raise an INVALID_STATE_ERR exception. If the image argument is an HTMLVideoElement object whose readyState attribute is either HAVE_NOTHING or HAVE_METADATA, then the implementation must raise an INVALID_STATE_ERR exception. If the image argument is an HTMLCanvasElement object with either a horizontal dimension or a vertical dimension equal to zero, then the implementation must raise an INVALID_STATE_ERR exception. Patterns must be painted so that the top left of the first image is anchored at the origin of the coordinate space, and images are then repeated horizontally to the left and right (if the repeat-x string was specified) or vertically up and down (if the repeat-y string was specified) or in all four directions all over the canvas (if the repeat string was specified). The images are not scaled by this process; one CSS pixel of the image must be painted on one coordinate space unit. Of course, patterns must actually be painted only where the stroking or filling effect requires that they be drawn, and are affected by the current transformation matrix. When the createPattern() method is passed an animated image as its image argument, the user agent must use the poster frame of the animation, or, if there is no poster frame, the first frame of the animation. When the image argument is an HTMLVideoElement, then the frame at the current playback position must be used as the source image. 4.8.11.1.5 Line styles context . lineWidth [ = value ] Returns the current line width. Can be set, to change the line width. Values that are not finite values greater than zero are ignored. context . lineCap [ = value ] Returns the current line cap style. Can be set, to change the line cap style. The possible line cap styles are butt, round, and square. Other values are ignored. context . lineJoin [ = value ] Returns the current line join style. Can be set, to change the line join style. The possible line join styles are bevel, round, and miter. Other values are ignored. context . miterLimit [ = value ] Returns the current miter limit ratio. Can be set, to change the miter limit ratio. Values that are not finite values greater than zero are ignored. The lineWidth attribute gives the width of lines, in coordinate space units. On setting, zero, negative, infinite, and NaN values must be ignored, leaving the value unchanged. When the context is created, the lineWidth attribute must initially have the value 1.0. The lineCap attribute defines the type of endings that UAs will place on the end of lines. The three valid values are butt, round, and square. The butt value means that the end of each line has a flat edge perpendicular to the direction of the line (and that no additional line cap is added). The round value means that a semi-circle with the diameter equal to the width of the line must then be added on to the end of the line. The square value means that a rectangle with the length of the line width and the width of half the line width, placed flat against the edge perpendicular to the direction of the line, must be added at the end of each line. On setting, any other value than the literal strings butt, round, and square must be ignored, leaving the value unchanged. When the context is created, the lineCap attribute must initially have the value butt. The lineJoin attribute defines the type of corners that UAs will place where two lines meet. The three valid values are bevel, round, and miter. On setting, any other value than the literal strings bevel, round, and miter must be ignored, leaving the value unchanged. When the context is created, the lineJoin attribute must initially have the value miter. A join exists at any point in a subpath shared by two consecutive lines. When a subpath is closed, then a join also exists at its first point (equivalent to its last point) connecting the first and last lines in the subpath. In addition to the point where the join occurs, two additional points are relevant to each join, one for each line: the two corners found half the line width away from the join point, one perpendicular to each line, each on the side furthest from the other line. A filled triangle connecting these two opposite corners with a straight line, with the third point of the triangle being the join point, must be rendered at all joins. The lineJoin attribute controls whether anything else is rendered. The three aforementioned values have the following meanings: http://dev.w3.org/html5/spec/Overview.html (200 de 570)01-08-2009 6:55:57
- 201. HTML 5 The bevel value means that this is all that is rendered at joins. The round value means that a filled arc connecting the two aforementioned corners of the join, abutting (and not overlapping) the aforementioned triangle, with the diameter equal to the line width and the origin at the point of the join, must be rendered at joins. The miter value means that a second filled triangle must (if it can given the miter length) be rendered at the join, with one line being the line between the two aforementioned corners, abutting the first triangle, and the other two being continuations of the outside edges of the two joining lines, as long as required to intersect without going over the miter length. The miter length is the distance from the point where the join occurs to the intersection of the line edges on the outside of the join. The miter limit ratio is the maximum allowed ratio of the miter length to half the line width. If the miter length would cause the miter limit ratio to be exceeded, this second triangle must not be rendered. The miter limit ratio can be explicitly set using the miterLimit attribute. On setting, zero, negative, infinite, and NaN values must be ignored, leaving the value unchanged. When the context is created, the miterLimit attribute must initially have the value 10.0. 4.8.11.1.6 Shadows All drawing operations are affected by the four global shadow attributes. context . shadowColor [ = value ] Returns the current shadow color. Can be set, to change the shadow color. Values that cannot be parsed as CSS colors are ignored. context . shadowOffsetX [ = value ] context . shadowOffsetY [ = value ] Returns the current shadow offset. Can be set, to change the shadow offset. Values that are not finite numbers are ignored. context . shadowBlur [ = value ] Returns the current level of blur applied to shadows. Can be set, to change the blur level. Values that are not finite numbers greater than or equal to zero are ignored. The shadowColor attribute sets the color of the shadow. When the context is created, the shadowColor attribute initially must be fully-transparent black. On getting, the serialization of the color must be returned. On setting, the new value must be parsed as a CSS <color> value and the color assigned. If the value is not a valid color, then it must be ignored, and the attribute must retain its previous value. [CSSCOLOR] The shadowOffsetX and shadowOffsetY attributes specify the distance that the shadow will be offset in the positive horizontal and positive vertical distance respectively. Their values are in coordinate space units. They are not affected by the current transformation matrix. When the context is created, the shadow offset attributes must initially have the value 0. On getting, they must return their current value. On setting, the attribute being set must be set to the new value, except if the value is infinite or NaN, in which case the new value must be ignored. The shadowBlur attribute specifies the size of the blurring effect. (The units do not map to coordinate space units, and are not affected by the current transformation matrix.) When the context is created, the shadowBlur attribute must initially have the value 0. On getting, the attribute must return its current value. On setting the attribute must be set to the new value, except if the value is negative, infinite or NaN, in which case the new value must be ignored. Shadows are only drawn if the opacity component of the alpha component of the color of shadowColor is non-zero and either the shadowBlur is non-zero, or the shadowOffsetX is non-zero, or the shadowOffsetY is non-zero. When shadows are drawn, they must be rendered as follows: 1. Let A be the source image for which a shadow is being created. 2. Let B be an infinite transparent black bitmap, with a coordinate space and an origin identical to A. 3. Copy the alpha channel of A to B, offset by shadowOffsetX in the positive x direction, and shadowOffsetY in the positive y direction. http://dev.w3.org/html5/spec/Overview.html (201 de 570)01-08-2009 6:55:57
- 202. HTML 5 4. If shadowBlur is greater than 0: 1. If shadowBlur is less than 8, let σ be half the value of shadowBlur; otherwise, let σ be the square root of multiplying the value of shadowBlur by 2. 2. Perform a 2D Gaussian Blur on B, using σ as the standard deviation. User agents may limit values of σ to an implementation-specific maximum value to avoid exceeding hardware limitations during the Gaussian blur operation. 5. Set the red, green, and blue components of every pixel in B to the red, green, and blue components (respectively) of the color of shadowColor. 6. Multiply the alpha component of every pixel in B by the alpha component of the color of shadowColor. 7. The shadow is in the bitmap B, and is rendered as part of the drawing model described below. 4.8.11.1.7 Simple shapes (rectangles) There are three methods that immediately draw rectangles to the bitmap. They each take four arguments; the first two give the x and y coordinates of the top left of the rectangle, and the second two give the width w and height h of the rectangle, respectively. The current transformation matrix must be applied to the following four coordinates, which form the path that must then be closed to get the specified rectangle: (x, y), (x+w, y), (x+w, y+h), (x, y+h). Shapes are painted without affecting the current path, and are subject to the clipping region, and, with the exception of clearRect(), also shadow effects, global alpha, and global composition operators. context . clearRect(x, y, w, h) Clears all pixels on the canvas in the given rectangle to transparent black. context . fillRect(x, y, w, h) Paints the given rectangle onto the canvas, using the current fill style. context . strokeRect(x, y, w, h) Paints the box that outlines the given rectangle onto the canvas, using the current stroke style. The clearRect(x, y, w, h) method must clear the pixels in the specified rectangle that also intersect the current clipping region to a fully transparent black, erasing any previous image. If either height or width are zero, this method has no effect. The fillRect(x, y, w, h) method must paint the specified rectangular area using the fillStyle. If either height or width are zero, this method has no effect. The strokeRect(x, y, w, h) method must stroke the specified rectangle's path using the strokeStyle, lineWidth, lineJoin, and (if appropriate) miterLimit attributes. If both height and width are zero, this method has no effect, since there is no path to stroke (it's a point). If only one of the two is zero, then the method will draw a line instead (the path for the outline is just a straight line along the non-zero dimension). 4.8.11.1.8 Complex shapes (paths) The context always has a current path. There is only one current path, it is not part of the drawing state. A path has a list of zero or more subpaths. Each subpath consists of a list of one or more points, connected by straight or curved lines, and a flag indicating whether the subpath is closed or not. A closed subpath is one where the last point of the subpath is connected to the first point of the subpath by a straight line. Subpaths with fewer than two points are ignored when painting the path. context . beginPath() Resets the current path. context . moveTo(x, y) Creates a new subpath with the given point. context . closePath() Marks the current subpath as closed, and starts a new subpath with a point the same as the start and end of the newly closed subpath. context . lineTo(x, y) Adds the given point to the current subpath, connected to the previous one by a straight line. http://dev.w3.org/html5/spec/Overview.html (202 de 570)01-08-2009 6:55:57
- 203. HTML 5 context . quadraticCurveTo(cpx, cpy, x, y) Adds the given point to the current path, connected to the previous one by a quadratic Bézier curve with the given control point. context . bezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y) Adds the given point to the current path, connected to the previous one by a cubic Bézier curve with the given control points. context . arcTo(x1, y1, x2, y2, radius) Adds a point to the current path, connected to the previous one by a straight line, then adds a second point to the current path, connected to the previous one by an arc whose properties are described by the arguments. Throws an INDEX_SIZE_ERR exception if the given radius is negative. context . arc(x, y, radius, startAngle, endAngle, anticlockwise) Adds points to the subpath such that the arc described by the circumference of the circle described by the arguments, starting at the given start angle and ending at the given end angle, going in the given direction, is added to the path, connected to the previous point by a straight line. Throws an INDEX_SIZE_ERR exception if the given radius is negative. context . rect(x, y, w, h) Adds a new closed subpath to the path, representing the given rectangle. context . fill() Fills the subpaths with the current fill style. context . stroke() Strokes the subpaths with the current stroke style. context . clip() Further constrains the clipping region to the given path. context . isPointInPath(x, y) Returns true if the given point is in the current path. Initially, the context's path must have zero subpaths. The points and lines added to the path by these methods must be transformed according to the current transformation matrix as they are added. The beginPath() method must empty the list of subpaths so that the context once again has zero subpaths. The moveTo(x, y) method must create a new subpath with the specified point as its first (and only) point. When the user agent is to ensure there is a subpath for a coordinate (x, y), the user agent must check to see if the context has any subpaths, and if it does not, then the user agent must create a new subpath with the point (x, y) as its first (and only) point, as if the moveTo() method had been called. The closePath() method must do nothing if the context has no subpaths. Otherwise, it must mark the last subpath as closed, create a new subpath whose first point is the same as the previous subpath's first point, and finally add this new subpath to the path. If the last subpath had more than one point in its list of points, then this is equivalent to adding a straight line connecting the last point back to the first point, thus "closing" the shape, and then repeating the last (possibly implied) moveTo() call. New points and the lines connecting them are added to subpaths using the methods described below. In all cases, the methods only modify the last subpath in the context's paths. The lineTo(x, y) method must ensure there is a subpath for (x, y) if the context has no subpaths. Otherwise, it must connect the last point in the subpath to the given point (x, y) using a straight line, and must then add the given point (x, y) to the subpath. The quadraticCurveTo(cpx, cpy, x, y) method must ensure there is a subpath for (cpx, cpy), and then must connect the last point in the subpath to the given point (x, y) using a quadratic Bézier curve with control point (cpx, cpy), and must then add the given point (x, y) to the subpath. [BEZIER] The bezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y) method must ensure there is a subpath for (cp1x, cp1y), and then must connect the last point in the subpath to the given point (x, y) using a cubic Bézier curve with control points (cp1x, cp1y) and (cp2x, cp2y). Then, it must add the point (x, y) to the subpath. [BEZIER] The arcTo(x1, y1, x2, y2, radius) method must first ensure there is a subpath for (x1, y1). Then, the behavior depends on the arguments and the last point in the subpath, as described below. http://dev.w3.org/html5/spec/Overview.html (203 de 570)01-08-2009 6:55:57
- 204. HTML 5 Negative values for radius must cause the implementation to raise an INDEX_SIZE_ERR exception. Let the point (x0, y0) be the last point in the subpath. If the point (x0, y0) is equal to the point (x1, y1), or if the point (x1, y1) is equal to the point (x2, y2), or if the radius radius is zero, then the method must add the point (x1, y1) to the subpath, and connect that point to the previous point (x0, y0) by a straight line. Otherwise, if the points (x0, y0), (x1, y1), and (x2, y2) all lie on a single straight line, then the method must add the point (x1, y1) to the subpath, and connect that point to the previous point (x0, y0) by a straight line. Otherwise, let The Arc be the shortest arc given by circumference of the circle that has radius radius, and that has one point tangent to the half-infinite line that crosses the point (x0, y0) and ends at the point (x1, y1), and that has a different point tangent to the half- infinite line that ends at the point (x1, y1) and crosses the point (x2, y2). The points at which this circle touches these two lines are called the start and end tangent points respectively. The method must connect the point (x0, y0) to the start tangent point by a straight line, adding the start tangent point to the subpath, and then must connect the start tangent point to the end tangent point by The Arc, adding the end tangent point to the subpath. The arc(x, y, radius, startAngle, endAngle, anticlockwise) method draws an arc. If the context has any subpaths, then the method must add a straight line from the last point in the subpath to the start point of the arc. In any case, it must draw the arc between the start point of the arc and the end point of the arc, and add the start and end points of the arc to the subpath. The arc and its start and end points are defined as follows: Consider a circle that has its origin at (x, y) and that has radius radius. The points at startAngle and endAngle along this circle's circumference, measured in radians clockwise from the positive x-axis, are the start and end points respectively. If the anticlockwise argument is false and endAngle-startAngle is equal to or greater than 2π, or, if the anticlockwise argument is true and startAngle-endAngle is equal to or greater than 2π, then the arc is the whole circumference of this circle. Otherwise, the arc is the path along the circumference of this circle from the start point to the end point, going anti-clockwise if the anticlockwise argument is true, and clockwise otherwise. Since the points are on the circle, as opposed to being simply angles from zero, the arc can never cover an angle greater than 2π radians. If the two points are the same, or if the radius is zero, then the arc is defined as being of zero length in both directions. Negative values for radius must cause the implementation to raise an INDEX_SIZE_ERR exception. The rect(x, y, w, h) method must create a new subpath containing just the four points (x, y), (x+w, y), (x+w, y+h), (x, y+h), with those four points connected by straight lines, and must then mark the subpath as closed. It must then create a new subpath with the point (x, y) as the only point in the subpath. The fill() method must fill all the subpaths of the current path, using fillStyle, and using the non-zero winding number rule. Open subpaths must be implicitly closed when being filled (without affecting the actual subpaths). Thus, if two overlapping but otherwise independent subpaths have opposite windings, they cancel out and result in no fill. If they have the same winding, that area just gets painted once. The stroke() method must calculate the strokes of all the subpaths of the current path, using the lineWidth, lineCap, lineJoin, and (if appropriate) miterLimit attributes, and then fill the combined stroke area using the strokeStyle attribute. Since the subpaths are all stroked as one, overlapping parts of the paths in one stroke operation are treated as if their union was what was painted. Paths, when filled or stroked, must be painted without affecting the current path, and must be subject to shadow effects, global alpha, the clipping region, and global composition operators. (Transformations affect the path when the path is created, not when it is painted, though the stroke style is still affected by the transformation during painting.) Zero-length line segments must be pruned before stroking a path. Empty subpaths must be ignored. The clip() method must create a new clipping region by calculating the intersection of the current clipping region and the area described by the current path, using the non-zero winding number rule. Open subpaths must be implicitly closed when computing the clipping region, without affecting the actual subpaths. The new clipping region replaces the current clipping region. When the context is initialized, the clipping region must be set to the rectangle with the top left corner at (0,0) and the width and height of the coordinate space. The isPointInPath(x, y) method must return true if the point given by the x and y coordinates passed to the method, when treated as coordinates in the canvas coordinate space unaffected by the current transformation, is inside the current path as determined by the non-zero winding number rule; and must return false otherwise. Points on the path itself are considered to be inside the path. If either of the arguments is infinite or NaN, then the method must return false. 4.8.11.1.9 Text context . font [ = value ] Returns the current font settings. Can be set, to change the font. The syntax is the same as for the CSS 'font' property; values that cannot be parsed as CSS font values are ignored. Relative keywords and lengths are computed relative to the default font, 10px sans-serif. context . textAlign [ = value ] Returns the current text alignment settings. Can be set, to change the alignment. The possible values are start, end, left, right, and center. The default is start. Other values are ignored. http://dev.w3.org/html5/spec/Overview.html (204 de 570)01-08-2009 6:55:57
- 205. HTML 5 context . textBaseline [ = value ] Returns the current baseline alignment settings. Can be set, to change the baseline alignment. The possible values and their meanings are given below. The default is alphabetic. Other values are ignored. context . fillText(text, x, y [, maxWidth ] ) context . strokeText(text, x, y [, maxWidth ] ) Fills or strokes (respectively) the given text at the given position. If a maximum width is provided, the text will be scaled to fit that width if necessary. metrics = context . measureText(text) Returns a TextMetrics object with the metrics of the given text in the current font. metrics . width Returns the advance width of the text that was passed to the measureText() method. The font DOM attribute, on setting, must be parsed the same way as the 'font' property of CSS (but without supporting property-independent stylesheet syntax like 'inherit'), and the resulting font must be assigned to the context, with the 'line-height' component forced to 'normal'. If the new value is syntactically incorrect (including using property-independent stylesheet syntax like 'inherit' or 'initial'), then it must be ignored, without assigning a new font value. [CSS] Font names must be interpreted in the context of the canvas element's stylesheets; any fonts embedded using @font-face must therefore be available once they are loaded. (If a font is referenced before it is fully loaded, then it must be treated as if it was an unknown font, falling back to another as described by the relevant CSS specifications.) [CSSWEBFONTS] Only vector fonts should be used by the user agent; if a user agent were to use bitmap fonts then transformations would likely make the font look very ugly. On getting, the font attribute must return the serialized form of the current font of the context (with no 'line-height' component). [CSSOM] For example, after the following statement: context.font = 'italic 400 12px/2 Unknown Font, sans-serif'; ...the expression context.font would evaluate to the string "italic 12px Unknown Font, sans-serif". The "400" font-weight doesn't appear because that is the default value. The line-height doesn't appear because it is forced to "normal", the default value. When the context is created, the font of the context must be set to 10px sans-serif. When the 'font-size' component is set to lengths using percentages, 'em' or 'ex' units, or the 'larger' or 'smaller' keywords, these must be interpreted relative to the computed value of the 'font-size' property of the corresponding canvas element at the time that the attribute is set. When the 'font-weight' component is set to the relative values 'bolder' and 'lighter', these must be interpreted relative to the computed value of the 'font-weight' property of the corresponding canvas element at the time that the attribute is set. If the computed values are undefined for a particular case (e.g. because the canvas element is not in a Document), then the relative keywords must be interpreted relative to the normal-weight 10px sans-serif default. The textAlign DOM attribute, on getting, must return the current value. On setting, if the value is one of start, end, left, right, or center, then the value must be changed to the new value. Otherwise, the new value must be ignored. When the context is created, the textAlign attribute must initially have the value start. The textBaseline DOM attribute, on getting, must return the current value. On setting, if the value is one of top, hanging, middle, alphabetic, ideographic, or bottom, then the value must be changed to the new value. Otherwise, the new value must be ignored. When the context is created, the textBaseline attribute must initially have the value alphabetic. The textBaseline attribute's allowed keywords correspond to alignment points in the font: http://dev.w3.org/html5/spec/Overview.html (205 de 570)01-08-2009 6:55:57
- 206. HTML 5 The keywords map to these alignment points as follows: top The top of the em square hanging The hanging baseline middle The middle of the em square alphabetic The alphabetic baseline ideographic The ideographic baseline bottom The bottom of the em square The fillText() and strokeText() methods take three or four arguments, text, x, y, and optionally maxWidth, and render the given text at the given (x, y) coordinates ensuring that the text isn't wider than maxWidth if specified, using the current font, textAlign, and textBaseline values. Specifically, when the methods are called, the user agent must run the following steps: 1. Let font be the current font of the context, as given by the font attribute. 2. Replace all the space characters in text with U+0020 SPACE characters. 3. Form a hypothetical infinitely wide CSS line box containing a single inline box containing the text text, with all the properties at their initial values except the 'font' property of the inline box set to font and the 'direction' property of the inline box set to the directionality of the canvas element. [CSS] 4. If the maxWidth argument was specified and the hypothetical width of the inline box in the hypothetical line box is greater than maxWidth CSS pixels, then change font to have a more condensed font (if one is available or if a reasonably readable one can be synthesized by applying a horizontal scale factor to the font) or a smaller font, and return to the previous step. 5. Let the anchor point be a point on the inline box, determined by the textAlign and textBaseline values, as follows: Horizontal position: If textAlign is left If textAlign is start and the directionality of the canvas element is 'ltr' If textAlign is end and the directionality of the canvas element is 'rtl' Let the anchor point's horizontal position be the left edge of the inline box. If textAlign is right If textAlign is end and the directionality of the canvas element is 'ltr' If textAlign is start and the directionality of the canvas element is 'rtl' Let the anchor point's horizontal position be the right edge of the inline box. If textAlign is center Let the anchor point's horizontal position be half way between the left and right edges of the inline box. Vertical position: If textBaseline is top Let the anchor point's vertical position be the top of the em box of the first available font of the inline box. If textBaseline is hanging Let the anchor point's vertical position be the hanging baseline of the first available font of the inline box. If textBaseline is middle Let the anchor point's vertical position be half way between the bottom and the top of the em box of the first available font of the inline box. If textBaseline is alphabetic Let the anchor point's vertical position be the alphabetic baseline of the first available font of the inline box. If textBaseline is ideographic Let the anchor point's vertical position be the ideographic baseline of the first available font of the inline box. If textBaseline is bottom Let the anchor point's vertical position be the bottom of the em box of the first available font of the inline box. 6. Paint the hypothetical inline box as the shape given by the text's glyphs, as transformed by the current transformation matrix, and anchored and sized so that before applying the current transformation matrix, the anchor point is at (x, y) and each CSS pixel is mapped to one coordinate space unit. For fillText() fillStyle must be applied to the glyphs and strokeStyle must be ignored. For strokeText() the reverse holds and strokeStyle must be applied to the glyph outlines and fillStyle must be ignored. Text is painted without affecting the current path, and is subject to shadow effects, global alpha, the clipping region, and global composition operators. The measureText() method takes one argument, text. When the method is invoked, the user agent must replace all the space characters in text with U+0020 SPACE characters, and then must form a hypothetical infinitely wide CSS line box containing a single inline box containing the text text, with all the properties at their initial values except the 'font' property of the inline element set to the current font of the context, as given by the font attribute, and must then return a new TextMetrics object with its width attribute set to http://dev.w3.org/html5/spec/Overview.html (206 de 570)01-08-2009 6:55:57
- 207. HTML 5 the width of that inline box, in CSS pixels. [CSS] The TextMetrics interface is used for the objects returned from measureText(). It has one attribute, width, which is set by the measureText() method. Glyphs rendered using fillText() and strokeText() can spill out of the box given by the font size (the em square size) and the width returned by measureText() (the text width). This version of the specification does not provide a way to obtain the bounding box dimensions of the text. If the text is to be rendered and removed, care needs to be taken to replace the entire area of the canvas that the clipping region covers, not just the box given by the em square height and measured text width. A future version of the 2D context API may provide a way to render fragments of documents, rendered using CSS, straight to the canvas. This would be provided in preference to a dedicated way of doing multiline layout. 4.8.11.1.10 Images To draw images onto the canvas, the drawImage method can be used. This method can be invoked with three different sets of arguments: q drawImage(image, dx, dy) q drawImage(image, dx, dy, dw, dh) q drawImage(image, sx, sy, sw, sh, dx, dy, dw, dh) Each of those three can take either an HTMLImageElement, an HTMLCanvasElement, or an HTMLVideoElement for the image argument. context . drawImage(image, dx, dy) context . drawImage(image, dx, dy, dw, dh) context . drawImage(image, sx, sy, sw, sh, dx, dy, dw, dh) Draws the given image onto the canvas. The arguments are interpreted as follows: If the first argument isn't an img, canvas, or video element, throws a TYPE_MISMATCH_ERR exception. If the image is not fully decoded yet, or has no image data, throws an INVALID_STATE_ERR exception. If the second argument isn't one of the allowed values, throws a SYNTAX_ERR exception. If not specified, the dw and dh arguments must default to the values of sw and sh, interpreted such that one CSS pixel in the image is treated as one unit in the canvas coordinate space. If the sx, sy, sw, and sh arguments are omitted, they must default to 0, 0, the image's intrinsic width in image pixels, and the image's intrinsic height in image pixels, respectively. The image argument is an instance of either HTMLImageElement, HTMLCanvasElement, or HTMLVideoElement. If the image is of the wrong type or null, the implementation must raise a TYPE_MISMATCH_ERR exception. If the image argument is an HTMLImageElement object whose complete attribute is false, then the implementation must raise an INVALID_STATE_ERR exception. If the image argument is an HTMLVideoElement object whose readyState attribute is either HAVE_NOTHING or HAVE_METADATA, then the implementation must raise an INVALID_STATE_ERR exception. If the image argument is an HTMLCanvasElement object with either a horizontal dimension or a vertical dimension equal to zero, then the implementation must raise an INVALID_STATE_ERR exception. The source rectangle is the rectangle whose corners are the four points (sx, sy), (sx+sw, sy), (sx+sw, sy+sh), (sx, sy+sh). http://dev.w3.org/html5/spec/Overview.html (207 de 570)01-08-2009 6:55:57
- 208. HTML 5 If the source rectangle is not entirely within the source image, or if one of the sw or sh arguments is zero, the implementation must raise an INDEX_SIZE_ERR exception. The destination rectangle is the rectangle whose corners are the four points (dx, dy), (dx+dw, dy), (dx+dw, dy+dh), (dx, dy+dh). When drawImage() is invoked, the region of the image specified by the source rectangle must be painted on the region of the canvas specified by the destination rectangle, after applying the current transformation matrix to the points of the destination rectangle. The original image data of the source image must be used, not the image as it is rendered (e.g. width and height attributes on the source element have no effect). This specification does not define the algorithm to use when scaling the image, if necessary. When a canvas is drawn onto itself, the drawing model requires the source to be copied before the image is drawn back onto the canvas, so it is possible to copy parts of a canvas onto overlapping parts of itself. When the drawImage() method is passed an animated image as its image argument, the user agent must use the poster frame of the animation, or, if there is no poster frame, the first frame of the animation. When the image argument is an HTMLVideoElement, then the frame at the current playback position must be used as the source image. Images are painted without affecting the current path, and are subject to shadow effects, global alpha, the clipping region, and global composition operators. 4.8.11.1.11 Pixel manipulation imagedata = context . createImageData(sw, sh) Returns an ImageData object with the given dimensions in CSS pixels (which might map to a different number of actual device pixels exposed by the object itself). All the pixels in the returned object are transparent black. imagedata = context . createImageData(imagedata) Returns an ImageData object with the same dimensions as the argument. All the pixels in the returned object are transparent black. Throws a NOT_SUPPORTED_ERR exception if the argument is null. imagedata = context . getImageData(sx, sy, sw, sh) Returns an ImageData object containing the image data for the given rectangle of the canvas. Throws a NOT_SUPPORTED_ERR exception if any of the arguments are not finite. Throws an INDEX_SIZE_ERR exception if the either of the width or height arguments are zero. imagedata . width imagedata . height Returns the actual dimensions of the data in the ImageData object, in device pixels. imagedata . data Returns the one-dimensional array containing the data. context . putImageData(imagedata, dx, dy [, dirtyX, dirtyY, dirtyWidth, dirtyHeight ]) Paints the data from the given ImageData object onto the canvas. If a dirty rectangle is provided, only the pixels from that rectangle are painted. The globalAlpha and globalCompositeOperation attributes, as well as the shadow attributes, are ignored for the purposes of this method call; pixels in the canvas are replaced wholesale, with no composition, alpha blending, no shadows, etc. If the first argument isn't an ImageData object, throws a TYPE_MISMATCH_ERR exception. Throws a NOT_SUPPORTED_ERR exception if any of the other arguments are not finite. The createImageData() method is used to instantiate new blank ImageData objects. When the method is invoked with two arguments sw and sh, it must return an ImageData object representing a rectangle with a width in CSS pixels equal to the absolute magnitude of sw and a height in CSS pixels equal to the absolute magnitude of sh. When invoked with a single imagedata argument, it must return an ImageData object representing a rectangle with the same dimensions as the ImageData object passed as the argument. The ImageData object return must be filled with transparent black. The getImageData(sx, sy, sw, sh) method must return an ImageData object representing the underlying pixel data for the area of the canvas denoted by the rectangle whose corners are the four points (sx, sy), (sx+sw, sy), (sx+sw, sy+sh), (sx, sy+sh), in canvas coordinate space units. Pixels outside the canvas must be returned as transparent black. Pixels must be returned as non-premultiplied alpha values. If any of the arguments to createImageData() or getImageData() are infinite or NaN, or if the createImageData() method is invoked with only one argument but that argument is null, the method must instead raise a NOT_SUPPORTED_ERR exception. If either the sw or sh arguments are zero, the method must instead raise an INDEX_SIZE_ERR exception. ImageData objects must be initialized so that their width attribute is set to w, the number of physical device pixels per row in the image data, their height attribute is set to h, the number of rows in the image data, and their data attribute is initialized to a http://dev.w3.org/html5/spec/Overview.html (208 de 570)01-08-2009 6:55:57
- 209. HTML 5 CanvasPixelArray object holding the image data. At least one pixel's worth of image data must be returned. The CanvasPixelArray object provides ordered, indexed access to the color components of each pixel of the image data. The data must be represented in left-to-right order, row by row top to bottom, starting with the top left, with each pixel's red, green, blue, and alpha components being given in that order for each pixel. Each component of each device pixel represented in this array must be in the range 0..255, representing the 8 bit value for that component. The components must be assigned consecutive indices starting with 0 for the top left pixel's red component. The CanvasPixelArray object thus represents h×w×4 integers. The length attribute of a CanvasPixelArray object must return this number. The object's indices of the supported indexed properties are the numbers in the range 0 .. h×w×4-1. When a CanvasPixelArray object is indexed to retrieve an indexed property index, the value returned must be the value of the indexth component in the array. When a CanvasPixelArray object is indexed to modify an indexed property index with value value, the value of the indexth component in the array must be set to value. JS undefined values must be converted to zero. Other values must first be converted to numbers using JavaScript's ToNumber algorithm, and if the result is a NaN value, then the value must be converted to zero. If the result is less than 0, it must be clamped to zero. If the result is more than 255, it must be clamped to 255. If the number is not an integer, it should be rounded to the nearest integer using the IEEE 754r convertToIntegerTiesToEven rounding mode. [ECMA262] [IEEE754R] The width and height (w and h) might be different from the sw and sh arguments to the above methods, e.g. if the canvas is backed by a high-resolution bitmap, or if the sw and sh arguments are negative. The putImageData(imagedata, dx, dy, dirtyX, dirtyY, dirtyWidth, dirtyHeight) method writes data from ImageData structures back to the canvas. If any of the arguments to the method are infinite or NaN, the method must raise a NOT_SUPPORTED_ERR exception. If the first argument to the method is null or not an ImageData object then the putImageData() method must raise a TYPE_MISMATCH_ERR exception. When the last four arguments are omitted, they must be assumed to have the values 0, 0, the width member of the imagedata structure, and the height member of the imagedata structure, respectively. When invoked with arguments that do not, per the last few paragraphs, cause an exception to be raised, the putImageData() method must act as follows: 1. Let dxdevice be the x-coordinate of the device pixel in the underlying pixel data of the canvas corresponding to the dx coordinate in the canvas coordinate space. Let dydevice be the y-coordinate of the device pixel in the underlying pixel data of the canvas corresponding to the dy coordinate in the canvas coordinate space. 2. If dirtyWidth is negative, let dirtyX be dirtyX+dirtyWidth, and let dirtyWidth be equal to the absolute magnitude of dirtyWidth. If dirtyHeight is negative, let dirtyY be dirtyY+dirtyHeight, and let dirtyHeight be equal to the absolute magnitude of dirtyHeight. 3. If dirtyX is negative, let dirtyWidth be dirtyWidth+dirtyX, and let dirtyX be zero. If dirtyY is negative, let dirtyHeight be dirtyHeight+dirtyY, and let dirtyY be zero. 4. If dirtyX+dirtyWidth is greater than the width attribute of the imagedata argument, let dirtyWidth be the value of that width attribute, minus the value of dirtyX. If dirtyY+dirtyHeight is greater than the height attribute of the imagedata argument, let dirtyHeight be the value of that height attribute, minus the value of dirtyY. 5. If, after those changes, either dirtyWidth or dirtyHeight is negative or zero, stop these steps without affecting the canvas. 6. Otherwise, for all integer values of x and y where dirtyX ≤ x < dirtyX+dirtyWidth and dirtyY ≤ y < dirtyY+dirtyHeight, copy the four channels of the pixel with coordinate (x, y) in the imagedata data structure to the pixel with coordinate (dxdevice+x, dydevice+y) in the underlying pixel data of the canvas. The handling of pixel rounding when the specified coordinates do not exactly map to the device coordinate space is not defined by this specification, except that the following must result in no visible changes to the rendering: context.putImageData(context.getImageData(x, y, w, h), p, q); ...for any value of x, y, w, and h and where p is the smaller of x and the sum of x and w, and q is the smaller of y and the sum of y and h; and except that the following two calls: context.createImageData(w, h); context.getImageData(0, 0, w, h); ...must return ImageData objects with the same dimensions, for any value of w and h. In other words, while user agents may round the arguments of these methods so that they map to device pixel boundaries, any rounding performed must be performed consistently for all of the createImageData(), getImageData() and putImageData() operations. Due to the lossy nature of converting to and from premultiplied alpha color values, pixels that have just been set using putImageData() might be returned to an equivalent getImageData() as different values. The current path, transformation matrix, shadow attributes, global alpha, the clipping region, and global composition operator must not affect the getImageData() and putImageData() methods. http://dev.w3.org/html5/spec/Overview.html (209 de 570)01-08-2009 6:55:57
- 210. HTML 5 The data returned by getImageData() is at the resolution of the canvas backing store, which is likely to not be one device pixel to each CSS pixel if the display used is a high resolution display. In the following example, the script generates an ImageData object so that it can draw onto it. // canvas is a reference to a <canvas> element var context = canvas.getContext('2d'); // create a blank slate var data = context.createImageData(canvas.width, canvas.height); // create some plasma FillPlasma(data, 'green'); // green plasma // add a cloud to the plasma AddCloud(data, data.width/2, data.height/2); // put a cloud in the middle // paint the plasma+cloud on the canvas context.putImageData(data, 0, 0); // support methods function FillPlasma(data, color) { ... } function AddCloud(data, x, y) { ... } Here is an example of using getImageData() and putImageData() to implement an edge detection filter. <!DOCTYPE HTML> <html> <head> <title>Edge detection demo</title> <script> var image = new Image(); function init() { image.onload = demo; image.src = "image.jpeg"; } function demo() { var canvas = document.getElementsByTagName('canvas')[0]; var context = canvas.getContext('2d'); // draw the image onto the canvas context.drawImage(image, 0, 0); // get the image data to manipulate var input = context.getImageData(0, 0, canvas.width, canvas.height); // get an empty slate to put the data into var output = context.createImageData(canvas.width, canvas.height); // alias some variables for convenience // notice that we are using input.width and input.height here // as they might not be the same as canvas.width and canvas.height // (in particular, they might be different on high-res displays) var w = input.width, h = input.height; var inputData = input.data; var outputData = output.data; // edge detection for (var y = 1; y < h-1; y += 1) { for (var x = 1; x < w-1; x += 1) { for (var c = 0; c < 3; c += 1) { var i = (y*w + x)*4 + c; outputData[i] = 127 + -inputData[i - w*4 - 4] - inputData[i - w*4] - inputData[i - w*4 + 4] + -inputData[i - 4] + 8*inputData[i] - inputData[i + 4] + -inputData[i + w*4 - 4] - inputData[i + w*4] - inputData[i + w*4 + 4]; } outputData[(y*w + x)*4 + 3] = 255; // alpha } } // put the image data back after manipulation context.putImageData(output, 0, 0); http://dev.w3.org/html5/spec/Overview.html (210 de 570)01-08-2009 6:55:57
- 211. HTML 5 } </script> </head> <body onload="init()"> <canvas></canvas> </body> </html> 4.8.11.1.12 Drawing model When a shape or image is painted, user agents must follow these steps, in the order given (or act as if they do): 1. Render the shape or image, creating image A, as described in the previous sections. For shapes, the current fill, stroke, and line styles must be honored, and the stroke must itself also be subjected to the current transformation matrix. 2. When shadows are drawn, render the shadow from image A, using the current shadow styles, creating image B. 3. When shadows are drawn, multiply the alpha component of every pixel in B by globalAlpha. 4. When shadows are drawn, composite B within the clipping region over the current canvas bitmap using the current composition operator. 5. Multiply the alpha component of every pixel in A by globalAlpha. 6. Composite A within the clipping region over the current canvas bitmap using the current composition operator. 4.8.11.2 Color spaces and color correction The canvas APIs must perform color correction at only two points: when rendering images with their own gamma correction and color space information onto the canvas, to convert the image to the color space used by the canvas (e.g. using the drawImage() method with an HTMLImageElement object), and when rendering the actual canvas bitmap to the output device. Thus, in the 2D context, colors used to draw shapes onto the canvas will exactly match colors obtained through the getImageData() method. The toDataURL() method must not include color space information in the resource returned. Where the output format allows it, the color of pixels in resources created by toDataURL() must match those returned by the getImageData() method. In user agents that support CSS, the color space used by a canvas element must match the color space used for processing any colors for that element in CSS. The gamma correction and color space information of images must be handled in such a way that an image rendered directly using an img element would use the same colors as one painted on a canvas element that is then itself rendered. Furthermore, the rendering of images that have no color correction information (such as those returned by the toDataURL() method) must be rendered with no color correction. Thus, in the 2D context, calling the drawImage() method to render the output of the toDataURL() method to the canvas, given the appropriate dimensions, has no visible effect. 4.8.11.3 Security with canvas elements Information leakage can occur if scripts from one origin can access information (e.g. read pixels) from images from another origin (one that isn't the same). To mitigate this, canvas elements are defined to have a flag indicating whether they are origin-clean. All canvas elements must start with their origin-clean set to true. The flag must be set to false if any of the following actions occur: q The element's 2D context's drawImage() method is called with an HTMLImageElement or an HTMLVideoElement whose origin is not the same as that of the Document object that owns the canvas element. q The element's 2D context's drawImage() method is called with an HTMLCanvasElement whose origin-clean flag is false. q The element's 2D context's fillStyle attribute is set to a CanvasPattern object that was created from an HTMLImageElement or an HTMLVideoElement whose origin was not the same as that of the Document object that owns the canvas element when the pattern was created. q The element's 2D context's fillStyle attribute is set to a CanvasPattern object that was created from an HTMLCanvasElement whose origin-clean flag was false when the pattern was created. q The element's 2D context's strokeStyle attribute is set to a CanvasPattern object that was created from an HTMLImageElement or an HTMLVideoElement whose origin was not the same as that of the Document object that owns the canvas element when the pattern was created. q The element's 2D context's strokeStyle attribute is set to a CanvasPattern object that was created from an HTMLCanvasElement whose origin-clean flag was false when the pattern was created. http://dev.w3.org/html5/spec/Overview.html (211 de 570)01-08-2009 6:55:57
- 212. HTML 5 Whenever the toDataURL() method of a canvas element whose origin-clean flag is set to false is called, the method must raise a SECURITY_ERR exception. Whenever the getImageData() method of the 2D context of a canvas element whose origin-clean flag is set to false is called with otherwise correct arguments, the method must raise a SECURITY_ERR exception. Even resetting the canvas state by changing its width or height attributes doesn't reset the origin-clean flag. 4.8.12 The map element Categories Flow content. When the element only contains phrasing content: phrasing content. Contexts in which this element may be used: Where phrasing content is expected. Content model: Transparent. Content attributes: Global attributes name DOM interface: interface HTMLMapElement : HTMLElement { attribute DOMString name; readonly attribute HTMLCollection areas; readonly attribute HTMLCollection images; }; The map element, in conjunction with any area element descendants, defines an image map. The element represents its children. The name attribute gives the map a name so that it can be referenced. The attribute must be present and must have a non-empty value with no space characters. If the id attribute is also specified, both attributes must have the same value. map . areas Returns an HTMLCollection of the area elements in the map. map . images Returns an HTMLCollection of the img and object elements that use the map. The areas attribute must return an HTMLCollection rooted at the map element, whose filter matches only area elements. The images attribute must return an HTMLCollection rooted at the Document node, whose filter matches only img and object elements that are associated with this map element according to the image map processing model. The DOM attribute name must reflect the content attribute of the same name. 4.8.13 The area element Categories Flow content. Phrasing content. Contexts in which this element may be used: Where phrasing content is expected, but only if there is a map element ancestor. Content model: Empty. Content attributes: Global attributes alt http://dev.w3.org/html5/spec/Overview.html (212 de 570)01-08-2009 6:55:57
- 213. HTML 5 coords shape href target ping rel media hreflang type DOM interface: [Stringifies=href] interface HTMLAreaElement : HTMLElement { attribute DOMString alt; attribute DOMString coords; attribute DOMString shape; attribute DOMString href; attribute DOMString target; attribute DOMString ping; attribute DOMString rel; readonly attribute DOMTokenList relList; attribute DOMString media; attribute DOMString hreflang; attribute DOMString type; // URL decomposition attributes attribute DOMString protocol; attribute DOMString host; attribute DOMString hostname; attribute DOMString port; attribute DOMString pathname; attribute DOMString search; attribute DOMString hash; }; The area element represents either a hyperlink with some text and a corresponding area on an image map, or a dead area on an image map. If the area element has an href attribute, then the area element represents a hyperlink. In this case, the alt attribute must be present. It specifies the text of the hyperlink. Its value must be text that, when presented with the texts specified for the other hyperlinks of the image map, and with the alternative text of the image, but without the image itself, provides the user with the same kind of choice as the hyperlink would when used without its text but with its shape applied to the image. The alt attribute may be left blank if there is another area element in the same image map that points to the same resource and has a non-blank alt attribute. If the area element has no href attribute, then the area represented by the element cannot be selected, and the alt attribute must be omitted. In both cases, the shape and coords attributes specify the area. The shape attribute is an enumerated attribute. The following table lists the keywords defined for this attribute. The states given in the first cell of the rows with keywords give the states to which those keywords map. Some of the keywords are non-conforming, as noted in the last column. State Keywords Notes Circle state circle circ Non-conforming Default state default Polygon state poly polygon Non-conforming Rectangle state rect rectangle Non-conforming The attribute may be omitted. The missing value default is the rectangle state. The coords attribute must, if specified, contain a valid list of integers. This attribute gives the coordinates for the shape described by the shape attribute. The processing for this attribute is described as part of the image map processing model. In the circle state, area elements must have a coords attribute present, with three integers, the last of which must be non-negative. The first integer must be the distance in CSS pixels from the left edge of the image to the center of the circle, the second integer must be the distance in CSS pixels from the top edge of the image to the center of the circle, and the third integer must be the radius of the circle, again in CSS pixels. http://dev.w3.org/html5/spec/Overview.html (213 de 570)01-08-2009 6:55:57
- 214. HTML 5 In the default state state, area elements must not have a coords attribute. (The area is the whole image.) In the polygon state, area elements must have a coords attribute with at least six integers, and the number of integers must be even. Each pair of integers must represent a coordinate given as the distances from the left and the top of the image in CSS pixels respectively, and all the coordinates together must represent the points of the polygon, in order. In the rectangle state, area elements must have a coords attribute with exactly four integers, the first of which must be less than the third, and the second of which must be less than the fourth. The four points must represent, respectively, the distance from the left edge of the image to the left side of the rectangle, the distance from the top edge to the top side, the distance from the left edge to the right side, and the distance from the top edge to the bottom side, all in CSS pixels. When user agents allow users to follow hyperlinks created using the area element, as described in the next section, the href, target and ping attributes decide how the link is followed. The rel, media, hreflang, and type attributes may be used to indicate to the user the likely nature of the target resource before the user follows the link. The target, ping, rel, media, hreflang, and type attributes must be omitted if the href attribute is not present. The activation behavior of area elements is to run the following steps: 1. If the DOMActivate event in question is not trusted (i.e. a click() method call was the reason for the event being dispatched), and the area element's target attribute is such that applying the rules for choosing a browsing context given a browsing context name, using the value of the target attribute as the browsing context name, would result in there not being a chosen browsing context, then raise an INVALID_ACCESS_ERR exception and abort these steps. 2. Otherwise, the user agent must follow the hyperlink defined by the area element, if any. The DOM attributes alt, coords, href, target, ping, rel, media, hreflang, and type, each must reflect the respective content attributes of the same name. The DOM attribute shape must reflect the shape content attribute, limited to only known values. The DOM attribute relList must reflect the rel content attribute. The area element also suports the complement of URL decomposition attributes, protocol, host, port, hostname, pathname, search, and hash. These must follow the rules given for URL decomposition attributes, with the input being the result of resolving the element's href attribute relative to the element, if there is such an attribute and resolving it is successful, or the empty string otherwise; and the common setter action being the same as setting the element's href attribute to the new output value. 4.8.14 Image maps 4.8.14.1 Authoring An image map allows geometric areas on an image to be associated with hyperlinks. An image, in the form of an img element or an object element representing an image, may be associated with an image map (in the form of a map element) by specifying a usemap attribute on the img or object element. The usemap attribute, if specified, must be a valid hash-name reference to a map element. Consider an image that looks as follows: If we wanted just the colored areas to be clickable, we could do it as follows: <p> Please select a shape: <img src="shapes.png" usemap="#shapes" alt="Four shapes are available: a red hollow box, a green circle, a blue triangle, and a yellow four-pointed star."> <map name="shapes"> <area shape=rect coords="50,50,100,100"> <!-- the hole in the red box --> <area shape=rect coords="25,25,125,125" href="red.html" alt="Red box."> <area shape=circle coords="200,75,50" href="green.html" alt="Green circle."> <area shape=poly coords="325,25,262,125,388,125" href="blue.html" alt="Blue triangle."> <area shape=poly coords="450,25,435,60,400,75,435,90,450,125,465,90,500,75,465,60" href="yellow.html" alt="Yellow star."> </map> http://dev.w3.org/html5/spec/Overview.html (214 de 570)01-08-2009 6:55:57
- 215. HTML 5 </p> 4.8.14.2 Processing model If an img element or an object element representing an image has a usemap attribute specified, user agents must process it as follows: 1. First, rules for parsing a hash-name reference to a map element must be followed. This will return either an element (the map) or null. 2. If that returned null, then abort these steps. The image is not associated with an image map after all. 3. Otherwise, the user agent must collect all the area elements that are descendants of the map. Let those be the areas. Having obtained the list of area elements that form the image map (the areas), interactive user agents must process the list in one of two ways. If the user agent intends to show the text that the img element represents, then it must use the following steps. In user agents that do not support images, or that have images disabled, object elements cannot represent images, and thus this section never applies (the fallback content is shown instead). The following steps therefore only apply to img elements. 1. Remove all the area elements in areas that have no href attribute. 2. Remove all the area elements in areas that have no alt attribute, or whose alt attribute's value is the empty string, if there is another area element in areas with the same value in the href attribute and with a non-empty alt attribute. 3. Each remaining area element in areas represents a hyperlink. Those hyperlinks should all be made available to the user in a manner associated with the text of the img. In this context, user agents may represent area and img elements with no specified alt attributes, or whose alt attributes are the empty string or some other non-visible text, in a user-agent-defined fashion intended to indicate the lack of suitable author- provided text. If the user agent intends to show the image and allow interaction with the image to select hyperlinks, then the image must be associated with a set of layered shapes, taken from the area elements in areas, in reverse tree order (so the last specified area element in the map is the bottom-most shape, and the first element in the map, in tree order, is the top-most shape). Each area element in areas must be processed as follows to obtain a shape to layer onto the image: 1. Find the state that the element's shape attribute represents. 2. Use the rules for parsing a list of integers to parse the element's coords attribute, if it is present, and let the result be the coords list. If the attribute is absent, let the coords list be the empty list. 3. If the number of items in the coords list is less than the minimum number given for the area element's current state, as per the following table, then the shape is empty; abort these steps. State Minimum number of items Circle state 3 Default state 0 Polygon state 6 Rectangle state 4 4. Check for excess items in the coords list as per the entry in the following list corresponding to the shape attribute's state: Circle state Drop any items in the list beyond the third. Default state Drop all items in the list. Polygon state Drop the last item if there's an odd number of items. Rectangle state Drop any items in the list beyond the fourth. 5. If the shape attribute represents the rectangle state, and the first number in the list is numerically less than the third number in the list, then swap those two numbers around. 6. If the shape attribute represents the rectangle state, and the second number in the list is numerically less than the fourth number in the list, then swap those two numbers around. 7. If the shape attribute represents the circle state, and the third number in the list is less than or equal to zero, then the shape is empty; abort these steps. 8. Now, the shape represented by the element is the one described for the entry in the list below corresponding to the state of the shape attribute: http://dev.w3.org/html5/spec/Overview.html (215 de 570)01-08-2009 6:55:57
- 216. HTML 5 Circle state Let x be the first number in coords, y be the second number, and r be the third number. The shape is a circle whose center is x CSS pixels from the left edge of the image and x CSS pixels from the top edge of the image, and whose radius is r pixels. Default state The shape is a rectangle that exactly covers the entire image. Polygon state Let xi be the (2i)th entry in coords, and yi be the (2i+1)th entry in coords (the first entry in coords being the one with index 0). Let the coordinates be (xi, yi), interpreted in CSS pixels measured from the top left of the image, for all integer values of i from 0 to (N/2)-1, where N is the number of items in coords. The shape is a polygon whose vertices are given by the coordinates, and whose interior is established using the even-odd rule. [GRAPHICS] Rectangle state Let x1 be the first number in coords, y1 be the second number, x2 be the third number, and y2 be the fourth number. The shape is a rectangle whose top-left corner is given by the coordinate (x1, y1) and whose bottom right corner is given by the coordinate (x2, y2), those coordinates being interpreted as CSS pixels from the top left corner of the image. For historical reasons, the coordinates must be interpreted relative to the displayed image, even if it stretched using CSS or the image element's width and height attributes. Mouse clicks on an image associated with a set of layered shapes per the above algorithm must be dispatched to the top-most shape covering the point that the pointing device indicated (if any), and then, must be dispatched again (with a new Event object) to the image element itself. User agents may also allow individual area elements representing hyperlinks to be selected and activated (e.g. using a keyboard); events from this are not also propagated to the image. Because a map element (and its area elements) can be associated with multiple img and object elements, it is possible for an area element to correspond to multiple focusable areas of the document. Image maps are live; if the DOM is mutated, then the user agent must act as if it had rerun the algorithms for image maps. 4.8.15 MathML The math element from the MathML namespace falls into the embedded content category for the purposes of the content models in this specification. User agents must handle text other than inter-element whitespace found in MathML elements whose content models do not allow raw text by pretending for the purposes of MathML content models, layout, and rendering that that text is actually wrapped in an mtext element in the MathML namespace. (Such text is not, however, conforming.) User agents must act as if any MathML element whose contents does not match the element's content model was replaced, for the purposes of MathML layout and rendering, by an merror element in the MathML namespace containing some appropriate error message. To enable authors to use MathML tools that only accept MathML in its XML form, interactive HTML user agents are encouraged to provide a way to export any MathML fragment as a namespace-well-formed XML fragment. 4.8.16 SVG The svg element from the SVG namespace falls into the embedded content, phrasing content, and flow content categories for the purposes of the content models in this specification. To enable authors to use SVG tools that only accept SVG in its XML form, interactive HTML user agents are encouraged to provide a way to export any SVG fragment as a namespace-well-formed XML fragment. When the SVG foreignObject element contains elements from the HTML namespace, such elements must all be flow content. [SVG] The content model for title elements in the SVG namespace inside HTML documents is phrasing content. (This further constrains the requirements given in the SVG specification.) 4.8.17 Dimension attributes Author requirements: The width and height attributes on img, iframe, embed, object, video, and, when their type attribute is in the Image Button state, input elements may be specified to give the dimensions of the visual content of the element (the width and height respectively, relative to the nominal direction of the output medium), in CSS pixels. The attributes, if specified, must have values that are valid non-negative integers. The specified dimensions given may differ from the dimensions specified in the resource itself, since the resource may have a resolution that differs from the CSS pixel resolution. (On screens, CSS pixels have a resolution of 96ppi, but in general the CSS pixel resolution depends on the reading distance.) If both attributes are specified, then one of the following statements must be true: q specified width - 0.5 ≤ specified height * target ratio ≤ specified width + 0.5 q specified height - 0.5 ≤ specified width / target ratio ≤ specified height + 0.5 q specified height = specified width = 0 http://dev.w3.org/html5/spec/Overview.html (216 de 570)01-08-2009 6:55:57
- 217. HTML 5 The target ratio is the ratio of the intrinsic width to the intrinsic height in the resource. The specified width and specified height are the values of the width and height attributes respectively. The two attributes must be omitted if the resource in question does not have both an intrinsic width and an intrinsic height. If the two attributes are both zero, it indicates that the element is not intended for the user (e.g. it might be a part of a service to count page views). The dimension attributes are not intended to be used to stretch the image. User agent requirements: User agents are expected to use these attributes as hints for the rendering. The width and height DOM attributes on the iframe, embed, object, and video elements must reflect the respective content attributes of the same name. 4.9 Tabular data 4.9.1 Introduction This section is non-normative. ...examples, how to write tables accessibly, a brief mention of the table model, etc... 4.9.2 The table element Categories Flow content. Contexts in which this element may be used: Where flow content is expected. Content model: In this order: optionally a caption element, followed by either zero or more colgroup elements, followed optionally by a thead element, followed optionally by a tfoot element, followed by either zero or more tbody elements or one or more tr elements, followed optionally by a tfoot element (but there can only be one tfoot element child in total). Content attributes: Global attributes DOM interface: interface HTMLTableElement : HTMLElement { attribute HTMLTableCaptionElement caption; HTMLElement createCaption(); void deleteCaption(); attribute HTMLTableSectionElement tHead; HTMLElement createTHead(); void deleteTHead(); attribute HTMLTableSectionElement tFoot; HTMLElement createTFoot(); void deleteTFoot(); readonly attribute HTMLCollection tBodies; HTMLElement createTBody(); readonly attribute HTMLCollection rows; HTMLElement insertRow([Optional] in long index); void deleteRow(in long index); }; The table element represents data with more than one dimension, in the form of a table. The table element takes part in the table model. Tables must not be used as layout aids. Historically, some Web authors have misused tables in HTML as a way to control their page layout. This usage is non-conforming, because tools attempting to extract tabular data from such documents would obtain very confusing results. In particular, users of accessibility tools like screen readers are likely to find it very difficult to navigate pages with tables used for la