Petri Niemi Qt Web Kit
3 likes1,681 views
QtWebKit provides a web browser engine that allows rendering of HTML, XHTML, SVG, and scripting with JavaScript. It is based on the open source WebKit engine. QtWebKit enables embedding web content and full AJAX functionality anywhere in Qt applications. Custom Qt GUI components and QObjects can be exposed to the web environment through HTML tags and subclassing. This allows interaction between web content and native application interfaces and services.
Petri Niemi Qt Web Kit
- 1. QtWebKit 1
- 2. Contents • Classes • Features • Exposing Widgets • W ki with J Working i h JavaScript S i 2
- 3. WebKit • Provides a Web browser engine • Easy to embed WWW content into an application • Content may be enhanced with native controls • QtWebKit module provides facilities for rendering of • HyperText Markup Language (HTML), • Extensible HyperText Markup Language (XHTML) and • Scalable Vector Graphics (SVG) documents, • Styled using Cascading Style Sheets (CSS) and scripted with JavaScript • Based on the Open Source WebKit engine • www.webkit.org ebkit org 3
- 4. High-Level Architecture QWebView, QW bVi QtWebKit API QWebPage, QWebFrame, … WebCore WebKit Engine JavaScript Core Platform/Network QtCore, QtXml, Adaptation QtNetwork 4
- 5. QWebView and QWebPage Classes • QWebView inherited from QWidget QWebView • R d Renders th contents of a QWebPage the t t f • Easy to embed wherever a widget could be used QWebPage QWebView *view = new QWebView( parent ); QWebFrame view->load(QUrl(“http://www.nokia.com”)); view >show(); view->show(); • QWebPage provides access to the document structure in a page • F Frames • Navigation history • Undo/redo stack for editable content • Each QWebPage has one QWebFrame object as its main frame • HTML documents can be nested using multiple frames 5
- 6. QWebView • All Allows viewing and editing of Web documents i i d diti fW bd t • view.back(); view.forward(); view.reload(); • Easy to embed Web content anywhere y y • Three essential signals • loadStarted() • loadProgress() – emits a value b t it l between 0 100 0…100 • loadFinished() – view loaded completely • Settings can be specified with QWebSettings g p Q g • Font, is JavaScript enabled, are plugins enabled, auto load images, etc. • Use QWebSettings::globalSettings() to modify global settings, and QWebPage::settings() to modify page specific settings (overrides • QW bP tti () modif page-specific (o errides global settings for the given page) 6
- 7. QGraphicsWebView • Counterpart of QWebView in the Graphics View Framework • Enables displaying web content in a graphics view • Many of the functions and signals are the same as in QWebView • M k porting existing QWebView-using code t QGraphicsWebView easy Makes ti i ti b i i d to hi b i • Classes like QWebPage, QWebFrame etc. are used in the background here as well 7
- 8. Basic Services - Examples • HTML to PDF QPrinter p(QPrinter::HighResolution); p.setOutputFormat(QPrinter::PdfFormat); p.setOutputFileName(outputFile); webview->print(&p); • HTML to image QImage img(size(), QImage Fo mat ARGB32) img(si e() QImage::Format_ARGB32); img.fill(Qt::transparent); QPainter p(&img); webview->page()->mainFrame()->render(&p); img.scale(0.5, 0.5); 8
- 9. Exposing Widgets – 1(3) • QtWebKit can place QWidgets and QGraphicsWidgets in the Web environment i t • Use HTML/JavaScript to control UI and infrastructure • Approaches • Host widget inside Web environment • Expose a C++ object to JavaScript environment • …or execute JavaScript from C++ side • Why would you want to do this? • Simple updates (redeploy a script file) • Easy to reuse Web design for Look & Feel • Easier interaction with web services 9
- 10. Exposing Widgets – 2(3) • QWidgets can be exposed to the Web environment by • Using the HTML tag <object> with a specific MIME-type in the Web page, and • Subclassing QWebPage and implementing QWebPage::createPlugin() <!-- mywebsite html --> mywebsite.html <object type="application/x-qt-plugin" classid="mylabel“ width="300" height=“300“/> // mywebpage.cpp QObject* MyWebPage::createPlugin(const QString& classid, const QU l& url, const QSt i Li t& paramNames, t QUrl& l t QStringList& N const QStringList& paramValues ) { if (classid == “mylabel”) return new QLabel(“Test Label”); mylabel ) QLabel( Test Label ); return 0; } 10
- 11. Exposing Widgets – 3(3) • The same effect as in the previous slide can also be achieved by • Using the HTML tag <object> with any custom MIME-type, and • Subclassing QWebPluginFactory and implementing functions create() and plugins() • Note that in this case there is no need to subclass QWebPage! • Just tell the page which factory to use: QWebPage::setPluginFactory() • The same plugin can be reused with multiple QWebPages • N t also that plugins() i currently only called when J Note l th t is tl l ll d h JavaScript programs S i t access global plugins or mimetypes objects • Still, implement it p p y to g , p properly guarantee compatibility in the future p y 11
- 12. Working with Exposed Objects 1(2) • QObjects can expose meta-object information to the JavaScript environment • P Properties can b read and altered ti be d d lt d • Slots can be called • Connect statements can be made • Use QWebFrame::addToJavaScriptWindowObject() to make your object accessible from JavaScript • This should be done each time the JavaScript context is cleared, i.e. just before a new URL is loaded • A useful signal t monitor: f l i l to it QWebFrame::javaScriptWindowObjectCleared() 12
- 13. Working with Exposed Objects 2(2) // SomeFile.cpp pp // MyTwitObject derives from Qobject and has a slot function // called updateStatus(QString s) MyTwitObject* myTwit = new MyTwitObject(); frame->addToJavaScriptWindowObject(“twit”, myTwit); // MyWebSite.html <script type=”text/javascript”> function setStatus() { twit.updateStatus(“Some status”); // Slot function call } </script> 13
- 14. Interoperating with JavaScript • We already know that each Web frame has a JavaScript context • JavaScript code can be executed from C++ using QWebFrame::evaluateJavaScript() • Returns a QVariant • Can be used to dynamically manipulate the contents of a Web page! // A simple calculation, result.toInt() == 2 QVariant result = frame->evaluateJavaScript(“1+1;”); // Parse information from an HTML element on a Web page, p g // userName.toString() == ”Bugs Bunny” QWebFrame *frame = view->currentFrame(); QVariant userName = frame->evaluateJavaScript( “document.getElementById(“userName”).value”); 14
- 15. QWebElement • A convenience class for accessing and traversing DOM elements in a QWebFrame • Provides pretty much the same functionality as JavaScript functions such as getElementById() etc. • G t a reference to a QWebElement i t Get f t instance using i QWebFrame::documentElement() in your code • Contains plenty of useful functions: firstChild(), nextSibling(), findAll()… i • Argument to findAll() is a CSS selector statement • Convenience class QWebElementCollection can also be used; simply a list class ; py that contains QWebElements QWebElement document = frame->documentElement(); // Find all <span> elements QWebElementCollection allSpans = document.findAll("span"); // Find all <span> elements within a <p class=intro> element QWebElementCollection introSpans = document.findAll( p.intro span"); document findAll("p intro span ); 15
- 16. Summary • QtWebKit enables full AJAX application functionality and embedding Web content anywhere i th Qt application h in the li ti • Exposing custom Qt GUI components is easy • QObjects can be exposed too! exposed, 16