Session 226 - Core Text and Fonts

Transcript

1. These are confidential sessions—please refrain from streaming, blogging, or taking pictures Features and techniques Session 226 Core Text and Fonts Ned Holbrook Typographic Engineer
2. What You Will Learn •New features in Mountain Lion and iOS 6 ▪ Line bounds ▪ Baseline alignment •Techniques ▪ Vertical text ▪ Font names, fallbacks, emoji ▪ Avoiding common pitfalls
3. CoreText Overview •Fundamental framework for Unicode text layout and fonts •Available via: ▪ AppKit (OS X) ▪ Core Animation ▪ UIKit (iOS) ▪ WebKit
4. Availability CoreText Overview •Leopard and iOS 3.2 •Top-level framework on iOS and Mountain Lion
5. Deprecated OS X Frameworks CoreText Overview •ATSUI (text layout) •ATS (font management)
6. New Features
7. CTLineGetTypographicBounds(…) Line Bounds “Just the facts, ma’am.”
8. CTLineGetTypographicBounds(…) Line Bounds “Just the facts, ma’am.”
9. CTLineGetBoundsWithOptions(…, 0) Line Bounds “Just the facts, ma’am.”
10. CTLineGetBoundsWithOptions(…, kCTLineBoundsUseOpticalBounds) Line Bounds “Just the facts, ma’am.”
11. CTLineGetBoundsWithOptions(…, kCTLineBoundsUseHangingPunctuation) Line Bounds “Just the facts, ma’am.”
12. CTLineGetBoundsWithOptions(…, kCTLineBoundsUseHangingPunctuation | kCTLineBoundsUseOpticalBounds) Line Bounds “Just the facts, ma’am.”
13. CTLineGetBoundsWithOptions(…, kCTLineBoundsUseGlyphPathBounds) Line Bounds “Just the facts, ma’am.”
14. Line Bounds kCTParagraphStyleSpecifierLineBoundsOptions ▪ Affects line edges during frame filling
15. •Better handling of mixed scripts Baseline Alignment Hello ੈք
16. •Better handling of mixed scripts Baseline Alignment Hello ੈք
17. •Better handling of mixed scripts Baseline Alignment World नम#$
18. •Better handling of mixed scripts Baseline Alignment World नम#$
19. •Typographic effects Baseline Alignment rop aps D C
20. •Typographic effects Baseline Alignment rop aps D C
21. Basics Baseline Alignment •Each font has multiple baselines •Each baseline is a vertical offset •Each glyph has a default baseline •Alignment uses the same baseline from two sets
22. Basics, cont. Baseline Alignment •Parameters determined by string attributes •Reference established with kCTBaselineReferenceInfoAttributeName •Baselines to be moved use kCTBaselineInfoAttributeName •Baseline being aligned is kCTBaselineClassAttributeName
23. Font Fallbacks Baseline Alignment CTFontRef font; NSMutableAttributedString *attrString; NSRange range; NSDictionary *referenceInfo = @{ (id)kCTBaselineReferenceFont : (id)font }; [attrString addAttribute:(id)kCTBaselineReferenceInfoAttributeName value:referenceInfo range:range];
24. Specifying a Baseline Baseline Alignment CTFontRef font, hangingFont; NSMutableAttributedString *attrString; NSRange range, wordRange; NSDictionary *referenceInfo = @{ (id)kCTBaselineReferenceFont : (id)font }; [attrString addAttribute:(id)kCTBaselineReferenceInfoAttributeName value:referenceInfo range:range]; NSRange hangingRange = NSMakeRange(wordRange.location, 1); [attrString addAttribute:(id)kCTBaselineClassAttributeName value:(id)kCTBaselineClassHanging range:hangingRange]; [attrString addAttribute:(id)kCTFontAttributeName, value:(id)hangingFont range:hangingRange];
25. Specifying an Offset Baseline Alignment CTFontRef font; NSMutableAttributedString *attrString; NSRange range; NSDictionary *referenceInfo = @{ (id)kCTBaselineReferenceFont : (id)font, (id)kCTBaselineClassHanging : @5.0 }; [attrString addAttribute:(id)kCTBaselineReferenceInfoAttributeName value:referenceInfo range:range];
26. CTFontCollection •Lion improvements ▪ Mutable collections ▪ Easier to access font family members ▪ Toll-free bridged with NSFontCollection •Preferred way to enumerate fonts
27. AAT and OpenType Features •New AAT features correspond to common OT features ▪ For example, to enable ‘pcap’ feature CTFontRef font; CTFontDescriptorRef descriptor = CTFontCopyFontDescriptor(font); CTFontDescriptorRef pcapDescriptor = CTFontDescriptorCreateCopyWithFeature(descriptor, (CFNumberRef)[NSNumber numberWithInt:kLowerCaseType], (CFNumberRef)[NSNumber numberWithInt: kLowerCasePetiteCapsSelector]); CTFontRef pcapFont = CTFontCreateWithFontDescriptor(pcapDescriptor, 0.0, NULL);
28. Bidirectional Text kCTWritingDirectionAttributeName ▪ Embedding or override
29. “Advanced” Topics
30. Vertical Text αϯϑϥϯγεί
31. kCTVerticalFormsAttributeName = @YES Vertical Text αϯϑϥϯγεί
32. kCTVerticalFormsAttributeName = @YES Vertical Text α ϯ ϑ ϥ ϯ γ ε ί
33. α ϯ ϑ ϥ ϯ γ ε ί Vertical Text ▪ Rotate context
34. α ϯ ϑ ϥ ϯ γ ε ί Vertical Text ▪ Rotate context
35. Vertical Text •Use NSTextView or CTFramesetter if possible •Not using one of those? ▪ Layout process is same as with horizontal text ▪ Drawing is much, much different
36. Font Names •Fonts have many names ▪ Example: PostScript TimesNewRomanPS-ItalicMT Family Times New Roman Full/Display Times New Roman Italic Style Italic
37. PostScript TimesNewRomanPS-ItalicMT Family Times New Roman Full/Display Times New Roman Italic Style Italic Font Names •Fonts have many names ▪ Example:
38. PostScript TimesNewRomanPS-ItalicMT Family Times New Roman Full/Display Times New Roman Italic Style Italic Font Names •Fonts have many names ▪ Example:
39. Performance Font Names CTFontCreateWithName() is currently too lenient ▪ Will stop accepting non-PostScript names in future releases •iOS 6 adds logging to detect use of wrong name: June 13 08:50:59 YourDevice YourApp[237] <Notice>: CoreText performance note: Client requested font with PostScript name "HelveticaNeue" using name "Helvetica Neue" instead. June 13 08:50:59 YourDevice YourApp[237] <Notice>: CoreText performance note: Set a breakpoint on CTLogSuboptimalRequest to debug.
40. Specifying a non-PostScript name Font Names NSDictionary *attributes = @{ (id)kCTFontFamilyNameAttribute : @"Times New Roman" }; CTFontDescriptorRef descriptor = CTFontDescriptorCreateWithAttributes( (CFDictionaryRef)attributes); NSArray *matches = (NSArray *)CTFontDescriptorCreateMatchingFontDescriptors( descriptor, NULL); if ([matches count] != 0) { // at least one match found, first one would have been returned by // CTFontDescriptorCreateMatchingFontDescriptor() }
41. Fallback Fonts •Layout relies on fallback fonts •Augment system cascade using kCTFontCascadeListAttribute •Terminate fallback processing with font covering all characters ▪ “LastResort” •Composite (CFR) fonts on Mountain Lion ▪ /System/Library/DTDs/SplicedFont.dtd
42. Embedding Fonts •Fonts need not live in distinct files to be usable •On Mountain Lion or iOS CGDataProviderRef provider = CGDataProviderCreateWithCFData(data); CGFontRef cgFont = CGFontCreateWithDataProvider(provider); CFErrorRef error = NULL; if (CTFontManagerRegisterGraphicsFont(cgFont, &error)) { // access font via font names CTFontManagerUnregisterGraphicsFont(cgFont, NULL); } •On Lion or higher ▪ CTFontManagerCreateFontDescriptorFromData()
43. Emoji
44. Emoji
45. Emoji •Unification is a big problem I — Unicode I — Unicode ≠
46. Emoji •Unicode 6.1 solution—variation sequences <U+2665> ??? <U+2665 U+FE0E> — <U+2665 U+FE0F>
47. Drawing Color Glyphs •Automatic with CTFrameDraw(), CTLineDraw(), and CTRunDraw() •Or use CTFontDrawGlyphs() ▪ Analogous to CGContextShowGlyphsAtPositions()
48. Identifying Color Glyphs CTFontRef font; CGGlyph glyph; CTFontSymbolicTraits symTraits = CTFontGetSymbolicTraits(font); if ((symTraits & kCTFontTraitColorGlyphs) != 0) { // font has color glyphs CGPathRef path = CTFontCreatePathForGlyph(font, glyph, NULL); if (path == NULL) { // this is a color glyph } else { // not a color glyph CFRelease(path); } }
49. CGContext Drawing Parameters •CoreText only sets what it needs to •Most string attributes correspond to a particular parameter •Exception to the rule—kCTForegroundColorAttributeName ▪ Use kCTForegroundColorFromContextAttributeName
50. Synthesizing Styles •CoreText does not synthesize font styles (bold, italic) •Clients may choose to do something for compatibility reasons ▪ Italic: Skewed font matrix ▪ Bold: No best approach
51. More Information Jake Behrens UI Frameworks Evangelist behrens@apple.com Documentation Mac OS X Human Interface Guidelines http://developer.apple.com/ue Apple Developer Forums http://devforums.apple.com
52. Related Sessions Introduction to Attributed Strings for iOS Mission Wednesday 3:15PM Advanced Attributed Strings for iOS Mission Thursday 10:15AM
53. Labs Core Text Framework Lab Essentials Lab B Thursday 11:30AM
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