objective-c - iOS CoreText : CTFrameSetter is making wider lines than the CGPath allows

Question

我正在使用 CoreText 在 CGPath 中呈现我的文本这通常是一个矩形。路径的宽度为 230 像素。但是当我渲染我的文本时，CTLineGetTypographicBounds返回 292 像素的宽度，而不是最大值 230。

一切正常，直到我开始使用 CTRunDelegateCallbacks代表。我使用它是因为我就地渲染图像。回调只返回消息的正确宽度和高度。我看不出有什么问题。只有当我在 NSAttributedString 中添加很多笑脸时才会发生这种情况。 .我希望它能在多行中正确设置它，但事实并非如此。

static void _deallocCallback (void* ref)
{
    [(id)ref release];
}

static CGFloat _ascentCallback (void *ref)
{
    UIImage* smiley = [(NSDictionary*)ref objectForKey:@"smiley"];
    return smiley.size.height; // returns 16
}

static CGFloat _widthCallback (void* ref)
{
    UIImage* smiley = [(NSDictionary*)ref objectForKey:@"smiley"];
    return smiley.size.width; // returns 16
}

- (void)renderText:(NSString*)text inRect:(CGRect)rect
{
    CGMutablePathRef path = createMyPath();
    NSAttributedString* attrString = [self _createAttributedString:text];
    // Create the frame setter and it's frame
    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attrString);
    CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, attrString.length), path, NULL);

    // Get the height of the lines
    CFArrayRef lines = CTFrameGetLines(frame);
    CFIndex lineCount = CFArrayGetCount(lines);

    CGFloat ascent, descent, leading;

    // Get the origins of each line
    CGPoint origins[lineCount];
    CTFrameGetLineOrigins(frame, CFRangeMake(0, 0), origins);

    // Loop through every line
    for (CFIndex i = 0; i < lineCount; i++)
    {
        // Get the typographic bounds of this line
        CTLineRef line = (CTLineRef)CFArrayGetValueAtIndex(lines, i);
        textWidth = CTLineGetTypographicBounds(line, &ascent, &descent, &leading);
        // __this returns values wider than rect in path__
    }
}

- (NSAttributedString*)_createAttributedString:(NSString*)inString
{
    // Create our default font attribute
    NSDictionary* fontAttribute = [NSDictionary dictionaryWithObject:(id)_font forKey:(NSString*)kCTFontAttributeName];

    // Create the attributed string
    NSMutableAttributedString* attributedString = [[NSMutableAttributedString alloc] init];

    CTRunDelegateCallbacks callbacks;
    callbacks.version = kCTRunDelegateVersion1;
    callbacks.getAscent = _ascentCallback;
    callbacks.getDescent = NULL;
    callbacks.getWidth = _widthCallback;
    callbacks.dealloc = _deallocCallback;

    UIImage* smiley = getSmiley(@"sad.png");

    // Do this multiple times to add a long list of smileys   
    NSDictionary* attributes = [NSDictionary dictionaryWithObjectsAndKeys:                  smiley, @"smiley", nil];
    CTRunDelegateRef delegate = CTRunDelegateCreate(&callbacks, attributes);
    NSDictionary* attributeDelegate = [NSDictionary dictionaryWithObjectsAndKeys:(id)delegate, (NSString *)kCTRunDelegateAttributeName, smiley, @"smiley", nil];

    [attributedString appendAttributedString:[[[NSAttributedString alloc] initWithString:@" " attributes:attributeDelegate] autorelease]];

    [attributedString appendAttributedString:[[[NSAttributedString alloc] initWithString:@" blablabla " attributes:fontAttribute] autorelease]];

    return attributedString;
}

谢谢，
尼古拉斯

Answer 1

我不认为这是一个漂亮的解决方案，但它似乎可以解决您的问题。代码中的以下行负责文本未正确呈现/换行:

[attributedString appendAttributedString:[[[NSAttributedString alloc] initWithString:@" " attributes:attributeDelegate] autorelease]];

CoreText 似乎忽略了添加到 attributedString 中的这些空格。 .
您可以通过简单地添加一个“虚拟”字符来解决此问题，该字符实际上已渲染但与图像重叠，因此不可见。这个字符将被 Coretext 视为一个新的“单词”，应该可以很好地渲染/换行。

例如:

[attributedString appendAttributedString:[[[NSAttributedString alloc] initWithString:@"•" attributes:attributeDelegate] autorelease]];