YYText 簡單介紹
YYText 是YYKit中的一個(gè)富文本顯示,編輯組件虾宇，擁有YYLabel凤类，YYTextView 兩個(gè)控件扛稽。其中YYLabel類似于UILabel柴灯，但功能更為強(qiáng)大物延，支持異步文本渲染宣旱，更豐富的效果顯示，支持UIImage叛薯，UIView, CALayer 文本附件浑吟，自定義強(qiáng)調(diào)文本范圍，支持垂直文本顯示等等耗溜。YYTextView 類似UITextView组力，除了兼容UITextView API，擴(kuò)展了更多的CoreText 效果屬性抖拴，支持高亮鏈接忿项，支持自定義內(nèi)部文本路徑形狀，支持圖片拷貝城舞，粘貼等等轩触。下面是YYText 與 TextKit 的比較圖：
YYLabel
YYLabel 的實(shí)現(xiàn)，是基于CoreText 框架 在 Context 上進(jìn)行繪制家夺，通過設(shè)置NSMutableAttributedString實(shí)現(xiàn)文本各種效果屬性的展現(xiàn)脱柱。下面是YYLabel 主要相關(guān)的部分：
- YYAsyncLayer: YYLabel的異步渲染，通過YYAsyncLayerDisplayTask 回調(diào)渲染
- YYTextLayout: YYLabel的布局管理類拉馋，也負(fù)責(zé)繪制
- YYTextContainer: YYLabel的布局類
- NSAttributedString+YYText: YYLabel 所有效果屬性設(shè)置
YYAsyncLayer 的異步實(shí)現(xiàn)
YYAsyncLayer 是 CALayer的子類榨为，通過設(shè)置 YYLabel 類方法 layerClass
返回自定義的 YYAsyncLayer ，重寫了父類的 setNeedsDisplay , display 實(shí)現(xiàn) contents 自定義刷新煌茴。YYAsyncLayerDelegate返回新的刷新任務(wù) newAsyncDisplayTask 用于更新過程回調(diào)随闺，返回到 YYLabel 進(jìn)行文本渲染。其中 YYSentinel是一個(gè)線程安全的原子遞增計(jì)數(shù)器蔓腐，用于判斷更新是否取消矩乐。
YYTextLayout
YYLabel 實(shí)現(xiàn)了 YYAsyncLayerDelegate 代理方法 newAsyncDisplayTask，回調(diào)處理3種文本渲染狀態(tài)willDisplay ，display散罕，didDisplay 分歇。在渲染之前，移除不需要的文本附件欧漱，渲染完成后职抡，添加需要的文本附件。渲染時(shí)误甚，首先獲取YYTextLayout, 一般包含了 YYTextContainer 和 NSAttributedString 兩部分缚甩， 分別負(fù)責(zé)文本展示的形狀和內(nèi)容。不管是渲染時(shí)和渲染完成后窑邦，最后都需要調(diào)用 YYTextLayout的
- (void) drawInContext:(CGContextRef)context
size:(CGSize)size
point:(CGPoint)point
view:(UIView *)view
layer:(CALayer *)layer
debug:(YYTextDebugOption *)debug
cancel:(BOOL (^)(void))cancel{
其中 context是圖形上下文蹄胰，文本的繪制在它上面進(jìn)行，size是 context 的大小奕翔，point 是繪制的起始點(diǎn),view,layer 是添加文本附件的視圖(層)裕寨，debug 調(diào)試選項(xiàng)，cancel 取消繪制派继，根據(jù)傳入的文本是否需要繪制YYText自定義屬性效果依次進(jìn)行相應(yīng)的繪制宾袜。有以下這些屬性：
///< Has highlight attribute
@property (nonatomic, readonly) BOOL containsHighlight;
///< Has block border attribute
@property (nonatomic, readonly) BOOL needDrawBlockBorder;
///< Has background border attribute
@property (nonatomic, readonly) BOOL needDrawBackgroundBorder;
///< Has shadow attribute
@property (nonatomic, readonly) BOOL needDrawShadow;
///< Has underline attribute
@property (nonatomic, readonly) BOOL needDrawUnderline;
///< Has visible text
@property (nonatomic, readonly) BOOL needDrawText;
///< Has attachment attribute
@property (nonatomic, readonly) BOOL needDrawAttachment;
///< Has inner shadow attribute
@property (nonatomic, readonly) BOOL needDrawInnerShadow;
///< Has strickthrough attribute
@property (nonatomic, readonly) BOOL needDrawStrikethrough;
///< Has border attribute
@property (nonatomic, readonly) BOOL needDrawBorder;
以其中的 needDrawShadow 為例，在Demo中YYTextAttributeExample.m, 為文本 Shadow自定義了 textShadow, 在NSAttributedString+YYText.m 中 調(diào)用 addAttribute:(NSString *)name value:(id)value range:(NSRange)range 添加了此文本屬性驾窟∏烀ǎ可以在 YYTextAttribute 查看所有屬性信息
最后在 YYTextLayout 的初始化方法中獲取，代碼如下：
layout.needDrawText = YES;
void (^block)(NSDictionary *attrs, NSRange range, BOOL *stop) = ^(NSDictionary *attrs, NSRange range, BOOL *stop) {
if (attrs[YYTextHighlightAttributeName]) layout.containsHighlight = YES;
if (attrs[YYTextBlockBorderAttributeName]) layout.needDrawBlockBorder = YES;
if (attrs[YYTextBackgroundBorderAttributeName]) layout.needDrawBackgroundBorder = YES;
if (attrs[YYTextShadowAttributeName] || attrs[NSShadowAttributeName]) layout.needDrawShadow = YES;
if (attrs[YYTextUnderlineAttributeName]) layout.needDrawUnderline = YES;
if (attrs[YYTextAttachmentAttributeName]) layout.needDrawAttachment = YES;
if (attrs[YYTextInnerShadowAttributeName]) layout.needDrawInnerShadow = YES;
if (attrs[YYTextStrikethroughAttributeName]) layout.needDrawStrikethrough = YES;
if (attrs[YYTextBorderAttributeName]) layout.needDrawBorder = YES;
};
[layout.text enumerateAttributesInRange:visibleRange options:NSAttributedStringEnumerationLongestEffectiveRangeNotRequired usingBlock:block];
根據(jù)YYTextContainer 和 NSAttributedString生成 YYTextLayout绅络，接下來就是渲染了月培， 具體的渲染由 CoreText來實(shí)現(xiàn)。
CoreText
CoreText是iOS/OSX里的文字渲染引擎恩急，在iOS/OSX上看到的所有文字在底層都是由CoreText去渲染杉畜。
一個(gè)
NSAttributeString通過CoreText的CTFramesetterCreateWithAttributedString生成CTFramesetter,它是創(chuàng)建 CTFrame的工廠，為 CTFramesetter 提供一個(gè) CGPath衷恭，它就會(huì)通過它持有的 CTTypesetter生成 CTFrame此叠，CTFrame里面包含了 CTLine CTLine 中包含了此行所有的 CTRun，然后就可以繪制到畫布上随珠。CTFrame,CTLine,CTRun都提供了渲染接口灭袁，但前兩者是封裝，最后實(shí)際都是調(diào)用到 CTRun的渲染接口去繪制窗看。
在YYTextlayout 中的代碼體現(xiàn)
// create CoreText objects
ctSetter = CTFramesetterCreateWithAttributedString((CFTypeRef)text);
if (!ctSetter) goto fail;
ctFrame = CTFramesetterCreateFrame(ctSetter, YYCFRangeFromNSRange(range), cgPath, (CFTypeRef)frameAttrs);
if (!ctFrame) goto fail;
lines = [NSMutableArray new];
ctLines = CTFrameGetLines(ctFrame);
lineCount = CFArrayGetCount(ctLines);
if (lineCount > 0) {
lineOrigins = malloc(lineCount * sizeof(CGPoint));
if (lineOrigins == NULL) goto fail;
CTFrameGetLineOrigins(ctFrame, CFRangeMake(0, lineCount), lineOrigins);
}
CGRect textBoundingRect = CGRectZero;
CGSize textBoundingSize = CGSizeZero;
NSInteger rowIdx = -1;
NSUInteger rowCount = 0;
CGRect lastRect = CGRectMake(0, -FLT_MAX, 0, 0);
CGPoint lastPosition = CGPointMake(0, -FLT_MAX);
if (isVerticalForm) {
lastRect = CGRectMake(FLT_MAX, 0, 0, 0);
lastPosition = CGPointMake(FLT_MAX, 0);
}
在這之前茸歧，需要生成 CGPath 根據(jù) YYTextContainer 生成
// set cgPath and cgPathBox
if (container.path == nil && container.exclusionPaths.count == 0) {
if (container.size.width <= 0 || container.size.height <= 0) goto fail;
CGRect rect = (CGRect) {CGPointZero, container.size };
if (needFixLayoutSizeBug) {
constraintSizeIsExtended = YES;
constraintRectBeforeExtended = UIEdgeInsetsInsetRect(rect, container.insets);
constraintRectBeforeExtended = CGRectStandardize(constraintRectBeforeExtended);
if (container.isVerticalForm) {
rect.size.width = YYTextContainerMaxSize.width;
} else {
rect.size.height = YYTextContainerMaxSize.height;
}
}
rect = UIEdgeInsetsInsetRect(rect, container.insets);
rect = CGRectStandardize(rect);
cgPathBox = rect;
rect = CGRectApplyAffineTransform(rect, CGAffineTransformMakeScale(1, -1));
cgPath = CGPathCreateWithRect(rect, NULL); // let CGPathIsRect() returns true
} else if (container.path && CGPathIsRect(container.path.CGPath, &cgPathBox) && container.exclusionPaths.count == 0) {
CGRect rect = CGRectApplyAffineTransform(cgPathBox, CGAffineTransformMakeScale(1, -1));
cgPath = CGPathCreateWithRect(rect, NULL); // let CGPathIsRect() returns true
} else {
rowMaySeparated = YES;
CGMutablePathRef path = NULL;
if (container.path) {
path = CGPathCreateMutableCopy(container.path.CGPath);
} else {
CGRect rect = (CGRect) {CGPointZero, container.size };
rect = UIEdgeInsetsInsetRect(rect, container.insets);
CGPathRef rectPath = CGPathCreateWithRect(rect, NULL);
if (rectPath) {
path = CGPathCreateMutableCopy(rectPath);
CGPathRelease(rectPath);
}
}
if (path) {
[layout.container.exclusionPaths enumerateObjectsUsingBlock: ^(UIBezierPath *onePath, NSUInteger idx, BOOL *stop) {
CGPathAddPath(path, NULL, onePath.CGPath);
}];
cgPathBox = CGPathGetPathBoundingBox(path);
CGAffineTransform trans = CGAffineTransformMakeScale(1, -1);
CGMutablePathRef transPath = CGPathCreateMutableCopyByTransformingPath(path, &trans);
CGPathRelease(path);
path = transPath;
}
cgPath = path;
}
YYTextContainer有下面兩個(gè)屬性，可以用來自定義path
/// Custom constrained path. Set this property to ignore `size` and `insets`. Default is nil.
@property (nullable, copy) UIBezierPath *path;
/// An array of `UIBezierPath` for path exclusion. Default is nil.
@property (nullable, copy) NSArray<UIBezierPath *> *exclusionPaths;
復(fù)雜的就是每行的frame的計(jì)算显沈， calculate line frame 部分软瞎，看的有點(diǎn)暈～～～
需要進(jìn)行坐標(biāo)系的轉(zhuǎn)化，YYTextLine是對(duì) CTLine的進(jìn)一步封裝。
最終文字的繪制都會(huì)調(diào)用
YYTextDrawText(YYTextLayout *layout, CGContextRef context, CGSize size, CGPoint point, BOOL (^cancel)(void))
//坐標(biāo)系變化
CGContextTranslateCTM(context, point.x, point.y);
CGContextTranslateCTM(context, 0, size.height);
CGContextScaleCTM(context, 1, -1);
CGContextSaveGState(context); {
// 所有的渲染有關(guān)代碼
} CGContextRestoreGState(context);
最后都需要調(diào)用 YYTextDrawRun 進(jìn)行繪制 CTRunDraw(run, context, CFRangeMake(0, 0));
YYTextView
其繪制原理同 YYLabel铜涉，其中 YYTextContainerView 是文本顯示的視圖，其layout 屬性用來繪制文本遂唧。
