Advance text rendering in i os

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Advance Text Rendering In iOS
Sohail Mohabbat Ali| iOS Mentor

Advance Text Rendering In iOS
Topics covered in the presentation

• Back Ground
• Core Text
• How to Do It?
• How to Fix IT

or
Sohail Mohabbat Ali | iOS Mentor

Advance text Rendering in iOS

Text Rendering in iOS

• UIKit

• Core Graphics/Quartz

• Core Text



Text Rendering in iOS Cont..

UIKit:

In UIKit you have and you add a word or a text line on
the screen by simple Drag-and-Drop in IB, but you cannot do
many things like strikethrough and custom formatting.




Core Graphics/Quartz:

In you can do pretty much everything the
system is capable of, but you need to calculate the position of each
glyph in your text and draw it on the screen.




Core Text:

lies right between the two! You have complete control over
position, layout, attributes like color and size, but Core Text takes care
of everything else for you – from word wrap to font rendering and more.



Back Ground

A tale of two Apples
• The original Apple development team created “Classic” APIs
and

• The NeXT team created NS* APIs which we later called
“ ”

• Since the merge of the two company, solutions like
and were created to close the gap

• For modern, Unicode-aware text layout, there is which
is still a popular choice for now



Background

More about ATSUI

• Short for “ ”

Like API (OSErr, Fixed, Pascal String, etc.)

• Fast, robust, powerful, but the API is bit complicate to use

(for font enumeration and selection) still exists, but ATSUI
is now , no 64-bit support



Why Core Text ?

• Simpler, Core Foundation style API, much easier to call from
Cocoa apps

• Minimize between different data formats, improve
performance (up to 2 times faster according to Apple)

• Supported behavior (like font traits) closely matches with
Cocoa Text System



What is easy with Core Text

• Lay formatted text down on the screen

• Fine tune the text’s appearance

• Add images inside the text content

• Display data in columns

• Display text with different transformations



How to do it ?

Step 1: Prepare Attributed String

• First, you prepare a with all the parameters set
(to the whole string or part of the string):

NSAttributedString * str = [[NSAttributedString alloc]
initWithString:@”Hello core text world!”
attributes:[NSDictionary
dictionaryWithObjectsAndKeys:
[UIFont fontWithName:@"Helvetive" size:12.0],
(NSString *) kCTFontAttributeName]];

CFAttributedStringRef attrString =
(CFAttributedStringRef) str;



Step 2: Create a CTFramesetter
• Now you can create a central object for Core Text typesetting:
, you will use it through the entire layout
process:

CTFramesetterRef framesetter =
CTFramesetterCreateWithAttributedString(attrString);




Step 3: Create a CGPath

• Third, you add one or more (or other shapes) to form
a complete :

CGMutablePathRef path =
CGPathCreateMutable();

CGRect bounds = self.bounds;

CGPathAddRect(path, NULL, bounds);




Step 4: Get the Frame

Use the and to create (s), then draw it in
current context

CGContextRef context = UIGraphicsGetCurrentContext();

CTFrameRef frame =
CTFramesetterCreateFrame(framesetter,
CFRangeMake(0, 0),
path, NULL);

CTFrameDraw(frame , context);




Step 5: Don’t forget to release them

Release everything you created with CGRelease.

CFRelease(attrString);

CFRelease(framesetter);

CFRelease(frame);

CFRelease(path);



How to it ?

CGContextSetTextMatrix(context, CGAffineTransformIdentity);

CGContextTranslateCTM(context, 0, self.bounds.size.height);

CGContextScaleCTM(context, 1.0, -1.0);



Writing on Shapes

CGMutablePathRef path = CGPathCreateMutable();

CTFramesetterRef framesetter =
CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attString);

CTFrameRef theFrame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0,
[attString length]), path, NULL);

CFRelease(framesetter);

CFRelease(path);

CTFrameDraw(theFrame, context);

CFRelease(theFrame);


Writing on Shapes (Output)



Playing with NSA Tributed String

With the help of function

we can format different chunks
of strings with different
attributes


Advance text rendering in i os

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