Working with Core Text by Roman Ilchyshyn

Working with Core Text by Roman Ilchyshyn

Transcript

1. Working with Core Text Roman Ilchyshyh
2. Core Text is an advanced, low-level technology for laying out text and handling fonts.
3. Do not to use it. Use Text Kit in iOS or the Cocoa text system in OS X. Core Text is the technology underlying those text systems, so they share in its speed and efficiency. When to use Core Text?
4. 2 cases when you really need Core Text When building your own custom layout manager (e. g. buiding rich text editor) When drawing directly from Core Graphics and need to draw text
5. We want to draw “Hello world!” on CALayer OK, but not so quick! A few words about typography first. “Hello world!” - is only the set of characters. It is not drawable
6. Why? A character is the smallest unit of written language that carries meaning. Characters can correspond to a particular sound in the spoken form of the language. In every case, however, a character is an abstract concept. Computers store characters as numbers mapped by encoding tables to their corresponding characters. But this is not about drawing. “A” “a” “b” “B” … and other friends in encoding table.
7. So what we need to draw? Although characters must be represented in a display area by a recognizable shape. A character can be drawn in various forms and remain the same character. Any one of these various concrete forms of a character is called a glyph. The glyphs used to depict characters are selected by layout manager during composition and layout processing.
8. So what we need to draw? To draw some set of characters we need to apply a font to it. A font is a series of glyphs depicting the characters in a consistent size, typeface, and typestyle. To bind font to text as always we use NSAttributedString.
9. Core Text is a C-baced API CFStringRef keys[] = { kCTFontAttributeName }; CFTypeRef values[] = { font }; CFDictionaryRef attributes = CFDictionaryCreate(kCFAllocatorDefault, (const void**)&keys, (const void**)&values, sizeof(keys) / sizeof(keys[0]), &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
11. Core Text is a C-baced API CFStringRef keys[] = { kCTFontAttributeName }; CFTypeRef values[] = { font }; CFDictionaryRef attributes = CFDictionaryCreate(kCFAllocatorDefault, (const void**)&keys, (const void**)&values, sizeof(keys) / sizeof(keys[0]), &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
12. Core Text is a C-based API The NSDictionary class is “toll-free bridged” with its Core Foundation counterpart, CFDictionaryRef. CFDictionaryRef attributes = (__bridge CFDictionaryRef) @{ NSFontAttributeName : [NSFont systemFontOfSize:13] };
13. In Core Text we use For text layout: CTTypesetter CTFrame CTFramesetter CTLine CTRun For font setup: CTFont CTFontCollection CTFontDescriptor
14. CTFramesetter - Describes an opaque type that generates text frames. CTFrame - Describes a multiline text frame.
15. NSDictionary *stringAttributes = @{ NSFontAttributeName : [NSFont systemFontOfSize:12], NSForegroundColorAttributeName : (id)[NSColor redColor].CGColor}; CFAttributedStringRef stringToDraw = CFAttributedStringCreate(NULL, (__bridge CFStringRef)str, (__bridge CFDictionaryRef)stringAttributes); CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(stringToDraw); CTFrameRef frame = CTFramesetterCreateFrame (framesetter, CFRangeMake(0, str.length), path, NULL); CTFrameDraw(frame, ctx);
16. CTLine - Describes a line of text. It is possible get lines of CTFrame NSArray *lines = ( id)CTFrameGetLines(frame); for (NSUInteger i = 0; i < lines.count; i++) { CGContextSetTextPosition(ctx, 5*i, 10*i); CTLineDraw((__bridge CTLineRef)[lines objectAtIndex:i], ctx); }
17. CTLine … or create brand new CFAttributedStringRef ctLineAttrStr = CFAttributedStringCreate (NULL, (__bridge CFStringRef)@"CTLine text" , (__bridge CFDictionaryRef )stringAttributes); CTLineRef line = CTLineCreateWithAttributedString (ctLineAttrStr); CGContextSetTextPosition (ctx, 50, 50); CTLineDraw(line, ctx); // Do not forget to release! CFRelease(line); CFRelease(ctLineAttrStr);
18. CTRun - Describes a set of consecutive glyphs sharing the same attributes and direction. СTRun is like subline of CTLine. Glyph runs can draw themselves into a graphic context, if desired, although most users have no need to interact directly with glyph runs.
19. Use CGContext to customize layout // ... CGContextRotateCTM(ctx, 15 * M_PI/180); // Code drawing frame // ... CGContextSetTextMatrix(ctx, CGAffineTransformMakeRotation(25)); // Code drawing line
20. About layer’s contentScale 1.0 2.0
21. Tanks! Q&A