iOS文字排版(CoreText)

转自阿毛的蛋疼地

第一次比较深入接触iOS文字排版相关内容是在12年底，实现某IM项目聊天内容的图文混排，照着nimbus的AttributedLabel和Raywenderlish上的这篇文章《Core Text Tutorial for iOS: Making a Magazine App》改出了一个比较适用于聊天内容展现的图文混排(文字和表情)控件。

- (void)appendAttachment: (M80AttributedLabelAttachment *)attachment 
{ 
    attachment.fontAscent                   = _fontAscent; 
    attachment.fontDescent                  = _fontDescent; 
    unichar objectReplacementChar           = 0xFFFC; 
    NSString *objectReplacementString       = [NSString stringWithCharacters:&objectReplacementChar length:1]; 
    NSMutableAttributedString *attachText   = [[NSMutableAttributedString alloc]initWithString:objectReplacementString]; 
 
    CTRunDelegateCallbacks callbacks; 
    callbacks.version       = kCTRunDelegateVersion1; 
    callbacks.getAscent     = ascentCallback; 
    callbacks.getDescent    = descentCallback; 
    callbacks.getWidth      = widthCallback; 
    callbacks.dealloc       = deallocCallback; 
 
    CTRunDelegateRef delegate = CTRunDelegateCreate(&callbacks, (void *)attachment); 
    NSDictionary *attr = [NSDictionary dictionaryWithObjectsAndKeys:(__bridge id)delegate,kCTRunDelegateAttributeName, nil]; 
    [attachText setAttributes:attr range:NSMakeRange(0, 1)]; 
    CFRelease(delegate); 
 
    [_attachments addObject:attachment]; 
    [self appendAttributedText:attachText]; 
} 

CGFloat ascentCallback(void *ref) 
{ 
    M80AttributedLabelAttachment *image = (__bridge M80AttributedLabelAttachment *)ref; 
    CGFloat ascent = 0; 
    CGFloat height = [image boxSize].height; 
    switch (image.alignment) 
    { 
        case M80ImageAlignmentTop: 
            ascent = image.fontAscent; 
            break; 
        case M80ImageAlignmentCenter: 
        { 
            CGFloat fontAscent  = image.fontAscent; 
            CGFloat fontDescent = image.fontDescent; 
            CGFloat baseLine = (fontAscent + fontDescent) / 2 - fontDescent; 
            ascent = height / 2 + baseLine; 
        } 
            break; 
        case M80ImageAlignmentBottom: 
            ascent = height - image.fontDescent; 
            break; 
        default: 
            break; 
    } 
    return ascent; 
} 
 
CGFloat descentCallback(void *ref) 
{ 
    M80AttributedLabelAttachment *image = (__bridge M80AttributedLabelAttachment *)ref; 
    CGFloat descent = 0; 
    CGFloat height = [image boxSize].height; 
    switch (image.alignment) 
    { 
        case M80ImageAlignmentTop: 
        { 
            descent = height - image.fontAscent; 
            break; 
        } 
        case M80ImageAlignmentCenter: 
        { 
            CGFloat fontAscent  = image.fontAscent; 
            CGFloat fontDescent = image.fontDescent; 
            CGFloat baseLine = (fontAscent + fontDescent) / 2 - fontDescent; 
            descent = height / 2 - baseLine; 
        } 
            break; 
        case M80ImageAlignmentBottom: 
        { 
            descent = image.fontDescent; 
            break; 
        } 
        default: 
            break; 
    } 
 
    return descent; 
 
} 
 
CGFloat widthCallback(void* ref) 
{ 
    M80AttributedLabelAttachment *image  = (__bridge M80AttributedLabelAttachment *)ref; 
    return [image boxSize].width; 
} 

- (void)drawAttachments 
{ 
    if ([_attachments count] == 0) 
    { 
        return; 
    } 
    CGContextRef ctx = UIGraphicsGetCurrentContext(); 
    if (ctx == nil) 
    { 
        return; 
    } 
 
    CFArrayRef lines = CTFrameGetLines(_textFrame); 
    CFIndex lineCount = CFArrayGetCount(lines); 
    CGPoint lineOrigins[lineCount]; 
    CTFrameGetLineOrigins(_textFrame, CFRangeMake(0, 0), lineOrigins); 
    NSInteger numberOfLines = [self numberOfDisplayedLines]; 
    for (CFIndex i = 0; i < numberOfLines; i++) 
    { 
        CTLineRef line = CFArrayGetValueAtIndex(lines, i); 
        CFArrayRef runs = CTLineGetGlyphRuns(line); 
        CFIndex runCount = CFArrayGetCount(runs); 
        CGPoint lineOrigin = lineOrigins[i]; 
        CGFloat lineAscent; 
        CGFloat lineDescent; 
        CTLineGetTypographicBounds(line, &lineAscent, &lineDescent, NULL); 
        CGFloat lineHeight = lineAscent + lineDescent; 
        CGFloat lineBottomY = lineOrigin.y - lineDescent; 
 
        // Iterate through each of the "runs" (i.e. a chunk of text) and find the runs that 
        // intersect with the range. 
        for (CFIndex k = 0; k < runCount; k++) 
        { 
            CTRunRef run = CFArrayGetValueAtIndex(runs, k); 
            NSDictionary *runAttributes = (NSDictionary *)CTRunGetAttributes(run); 
            CTRunDelegateRef delegate = (__bridge CTRunDelegateRef)[runAttributes valueForKey:(id)kCTRunDelegateAttributeName]; 
            if (nil == delegate) 
            { 
                continue; 
            } 
            M80AttributedLabelAttachment* attributedImage = (M80AttributedLabelAttachment *)CTRunDelegateGetRefCon(delegate); 
 
            CGFloat ascent = 0.0f; 
            CGFloat descent = 0.0f; 
            CGFloat width = (CGFloat)CTRunGetTypographicBounds(run, 
                                                               CFRangeMake(0, 0), 
                                                               &ascent, 
                                                               &descent, 
                                                               NULL); 
 
            CGFloat imageBoxHeight = [attributedImage boxSize].height; 
            CGFloat xOffset = CTLineGetOffsetForStringIndex(line, CTRunGetStringRange(run).location, nil); 
 
            CGFloat imageBoxOriginY = 0.0f; 
            switch (attributedImage.alignment) 
            { 
                case M80ImageAlignmentTop: 
                    imageBoxOriginY = lineBottomY + (lineHeight - imageBoxHeight); 
                    break; 
                case M80ImageAlignmentCenter: 
                    imageBoxOriginY = lineBottomY + (lineHeight - imageBoxHeight) / 2.0; 
                    break; 
                case M80ImageAlignmentBottom: 
                    imageBoxOriginY = lineBottomY; 
                    break; 
            } 
 
            CGRect rect = CGRectMake(lineOrigin.x + xOffset, imageBoxOriginY, width, imageBoxHeight); 
            UIEdgeInsets flippedMargins = attributedImage.margin; 
            CGFloat top = flippedMargins.top; 
            flippedMargins.top = flippedMargins.bottom; 
            flippedMargins.bottom = top; 
 
            CGRect attatchmentRect = UIEdgeInsetsInsetRect(rect, flippedMargins); 
 
            id content = attributedImage.content; 
            if ([content isKindOfClass:[UIImage class]]) 
            { 
                CGContextDrawImage(ctx, attatchmentRect, ((UIImage *)content).CGImage); 
            } 
            else if ([content isKindOfClass:[UIView class]]) 
            { 
                UIView *view = (UIView *)content; 
                if (view.superview == nil) 
                { 
                    [self addSubview:view]; 
                } 
                CGRect viewFrame = CGRectMake(attatchmentRect.origin.x, 
                                              self.bounds.size.height - attatchmentRect.origin.y - attatchmentRect.size.height, 
                                              attatchmentRect.size.width, 
                                              attatchmentRect.size.height); 
                [view setFrame:viewFrame]; 
            } 
            else 
            { 
                NSLog(@"Attachment Content Not Supported %@",content); 
            } 
 
        } 
    } 
}