iOS 基础排版引擎 - CoreText

CoreText

1. 创建AttributedString，定义样式

2. 通过 CFAttributedStringRef 生成 CTFramesetter

3. 通过CTFramesetter得到CTFrame

4. 绘制 (CTFrameDraw)

5. 如果有图片存在，先在AttributedString 对应位置添加占位符

6. 通过回调函数确定图片的宽高（CTRunDelegateCallbacks）

7. 遍历到对应CTRun上、获取对应CGRect、绘制图片（CGContextDrawImage）

单行文本 - layingOut

- (void)drawRect:(CGRect)rect {
    // Drawing code
    // Initialize a graphics context in iOS.
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    // Flip the context coordinates, in iOS only.
    CGContextTranslateCTM(context, 0, self.bounds.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);
    
    // Set the text matrix.
    CGContextSetTextMatrix(context, CGAffineTransformIdentity);
    
    // Create a path which bounds the area where you will be drawing text.
    // The path need not be rectangular.
    CGMutablePathRef path = CGPathCreateMutable();
    
    // In this simple example, initialize a rectangular path.
    CGRect bounds = CGRectMake(10.0,rect.size.height - 300.0, 200.0, 200.0);
    CGPathAddRect(path, NULL, bounds );
    
    // Initialize a string.
    CFStringRef textString = CFSTR("Hello, World! I know nothing in the world that has as much power as a word. Sometimes I write one, and I look at it, until it begins to shine.");
    
    // Create a mutable attributed string with a max length of 0.
    // The max length is a hint as to how much internal storage to reserve.
    // 0 means no hint.
    CFMutableAttributedStringRef attrString =
    CFAttributedStringCreateMutable(kCFAllocatorDefault, 0);
    
    // Copy the textString into the newly created attrString
    CFAttributedStringReplaceString (attrString, CFRangeMake(0, 0),
                                     textString);
    
    // Create a color that will be added as an attribute to the attrString.
    // 字体颜色设置.
    CFAttributedStringSetAttribute(attrString, CFRangeMake(0, 12), kCTForegroundColorAttributeName, [UIColor redColor].CGColor);
    // 大小设置
    CFAttributedStringSetAttribute(attrString, CFRangeMake(0, 12), kCTFontAttributeName, (__bridge CFTypeRef)([UIFont boldSystemFontOfSize:18]));
    
    //  下划线设置
    /***
     kCTUnderlineStyleNone           = 0x00,
     kCTUnderlineStyleSingle          = 0x01,
     kCTUnderlineStyleThick            = 0x02,
     kCTUnderlineStyleDouble         = 0x09
     ****/
    CFAttributedStringSetAttribute(attrString, CFRangeMake(12, 24), kCTUnderlineColorAttributeName, [UIColor greenColor].CGColor);
    CFAttributedStringSetAttribute(attrString, CFRangeMake(12, 24), kCTUnderlineStyleAttributeName, (__bridge CFTypeRef)[NSNumber numberWithInt:kCTUnderlineStyleSingle]);    
    // 字与字水平垂直间距调整
    CFAttributedStringSetAttribute(attrString, CFRangeMake(0, 12), kCTKernAttributeName, (__bridge CFTypeRef)[NSNumber numberWithInt:5]);
    CFAttributedStringSetAttribute(attrString, CFRangeMake(0, 12), kCTSuperscriptAttributeName, (__bridge CFTypeRef)[NSNumber numberWithInt:5]);
    // 背景颜色设置
    CFAttributedStringSetAttribute(attrString, CFRangeMake(0, 12), kCTBackgroundColorAttributeName, [UIColor grayColor].CGColor);
    
    // Create the framesetter with the attributed string.
    CTFramesetterRef framesetter =
    CTFramesetterCreateWithAttributedString(attrString);
    CFRelease(attrString);
    
    // Create a frame.
    CTFrameRef frame = CTFramesetterCreateFrame(framesetter,
                                                CFRangeMake(0, 0), path, NULL);
    
    // Draw the specified frame in the given context.
    CTFrameDraw(frame, context);
    
    // Release the objects we used.
    CFRelease(frame);
    CFRelease(path);
    CFRelease(framesetter);

}

竖版文本绘制 - ColumnsText

- (void)drawRect:(CGRect)rect {
    // Drawing code
    // Initialize a graphics context in iOS.
    CGContextRef context = UIGraphicsGetCurrentContext();
    
    // Flip the context coordinates in iOS only.
    CGContextTranslateCTM(context, 0, self.bounds.size.height);
    CGContextScaleCTM(context, 1.0, -1.0);
    
    // Set the text matrix.
    CGContextSetTextMatrix(context, CGAffineTransformIdentity);
    
    NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc]initWithString:@"Hello, World! I know nothing in the world that has as much power as a word. Sometimes I write one, and I look at it, until it begins to shine."];
    
    // Create the framesetter with the attributed string.
    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attributedString);
    
    // Call createColumnsWithColumnCount function to create an array of
    // three paths (columns).
    CFArrayRef columnPaths = [self createColumnsWithColumnCount:3];
    
    CFIndex pathCount = CFArrayGetCount(columnPaths);
    CFIndex startIndex = 0;
    int column;
    
    // Create a frame for each column (path).
    for (column = 0; column < pathCount; column++) {
        // Get the path for this column.
        CGPathRef path = (CGPathRef)CFArrayGetValueAtIndex(columnPaths, column);
        
        // Create a frame for this column and draw it.
        CTFrameRef frame = CTFramesetterCreateFrame(
                                                    framesetter, CFRangeMake(startIndex, 0), path, NULL);
        CTFrameDraw(frame, context);
        
        // Start the next frame at the first character not visible in this frame.
        CFRange frameRange = CTFrameGetVisibleStringRange(frame);
        startIndex += frameRange.length;
        CFRelease(frame);
        
    }
    CFRelease(columnPaths);
    CFRelease(framesetter);
}

- (CFArrayRef)createColumnsWithColumnCount:(int)columnCount
{
    int column;
    
    CGRect* columnRects = (CGRect*)calloc(columnCount, sizeof(*columnRects));
    // Set the first column to cover the entire view.
    columnRects[0] = self.bounds;
    
    // Divide the columns equally across the frame's width.
    CGFloat columnWidth = CGRectGetWidth(self.bounds) / columnCount;
    for (column = 0; column < columnCount - 1; column++) {
        CGRectDivide(columnRects[column], &columnRects[column],
                     &columnRects[column + 1], columnWidth, CGRectMinXEdge);
    }
    
    // Inset all columns by a few pixels of margin.
    for (column = 0; column < columnCount; column++) {
        columnRects[column] = CGRectInset(columnRects[column], 8.0, 15.0);
    }
    
    // Create an array of layout paths, one for each column.
    CFMutableArrayRef array =
    CFArrayCreateMutable(kCFAllocatorDefault,
                         columnCount, &kCFTypeArrayCallBacks);
    
    for (column = 0; column < columnCount; column++) {
        CGMutablePathRef path = CGPathCreateMutable();
        CGPathAddRect(path, NULL, columnRects[column]);
        CFArrayInsertValueAtIndex(array, column, path);
        CFRelease(path);
    }
    free(columnRects);
    return array;
}