CTFramesetterSuggestFrameSizeWithConstraints，剪切属性返回零高度

Question

ħ！ 我正在编写带有子视图剪辑功能的te​​xtview。我们的想法是让所有文字都围绕所有子视图绘制。问题是获得它的内容高度。

由于缺少文档，我认为CTFramesetterSuggestFrameSizeWithConstraints的属性字典与CTFramesetterCreateFrame的属性字典相同。

这是我的裁剪路径代码：

-(CFDictionaryRef)clippingPathsDictionary{
if(self.subviews.count==0)return NULL;

NSMutableArray *pathsArray = [[NSMutableArray alloc] init];

CGAffineTransform transform = CGAffineTransformIdentity;
transform = CGAffineTransformScale(transform, 1, -1);
transform = CGAffineTransformTranslate(transform, 0, -self.bounds.size.height);

for (int i=0; i<self.subviews.count; i++) {
    UIView *clippingView = self.subviews[i];
    CGPathRef clipPath = CGPathCreateWithRect(clippingView.frame, &transform);

    NSDictionary *clippingPathDictionary = [NSDictionary dictionaryWithObject:(__bridge id)(clipPath) forKey:(__bridge NSString *)kCTFramePathClippingPathAttributeName];
    [pathsArray addObject:clippingPathDictionary];
    CFRelease(clipPath);
}


int eFrameWidth=0;
CFNumberRef frameWidth = CFNumberCreate(NULL, kCFNumberNSIntegerType, &eFrameWidth);

int eFillRule = kCTFramePathFillEvenOdd;
CFNumberRef fillRule = CFNumberCreate(NULL, kCFNumberNSIntegerType, &eFillRule);

int eProgression = kCTFrameProgressionTopToBottom;
CFNumberRef progression = CFNumberCreate(NULL, kCFNumberNSIntegerType, &eProgression);


CFStringRef keys[] = { kCTFrameClippingPathsAttributeName, kCTFramePathFillRuleAttributeName, kCTFrameProgressionAttributeName, kCTFramePathWidthAttributeName};
CFTypeRef values[] = { (__bridge CFTypeRef)(pathsArray), fillRule, progression, frameWidth};




CFDictionaryRef clippingPathsDictionary = CFDictionaryCreate(NULL,
                                                             (const void **)&keys, (const void **)&values,
                                                             sizeof(keys) / sizeof(keys[0]),
                                                             &kCFTypeDictionaryKeyCallBacks,
                                                             &kCFTypeDictionaryValueCallBacks);
return clippingPathsDictionary;}

我用它来绘制文字，它运作正常。 这是我的绘图代码：

- (void)drawRect:(CGRect)rect{
CGAffineTransform transform = CGAffineTransformIdentity;
transform = CGAffineTransformScale(transform, 1, -1);
transform = CGAffineTransformTranslate(transform, 0, -rect.size.height);


CGContextRef context = UIGraphicsGetCurrentContext();
CGContextConcatCTM(context, transform);

CFAttributedStringRef attributedString = (__bridge CFAttributedStringRef)self.attributedString;
CTFramesetterRef frameSetter = CTFramesetterCreateWithAttributedString(attributedString);

CFDictionaryRef  attributesDictionary = [self clippingPathsDictionary];
CGPathRef path = CGPathCreateWithRect(rect, &transform);
CTFrameRef frame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, self.attributedString.length), path, attributesDictionary);
CFRelease(path);
CFRelease(attributesDictionary);

CTFrameDraw(frame, context);
CFRelease(frameSetter);
CFRelease(frame);

CGSize contentSize = [self contentSizeForWidth:self.bounds.size.width];

CGPathRef highlightPath = CGPathCreateWithRect((CGRect){CGPointZero, contentSize}, &transform);
CGContextSetFillColorWithColor(context, [UIColor colorWithRed:.0 green:1 blue:.0 alpha:.3].CGColor);
CGContextAddPath(context, highlightPath);
CGContextDrawPath(context, kCGPathFill);
CFRelease(highlightPath);

}

结果就是这样：

这正是我所期待的！

最后，这是检查高度的代码：

-(CGSize)contentSizeForWidth:(float)width{
CFAttributedStringRef attributedString = (__bridge CFAttributedStringRef)self.attributedString;
CTFramesetterRef frameSetter = CTFramesetterCreateWithAttributedString(attributedString);

CFDictionaryRef attributesDictionary = [self clippingPathsDictionary];
CGSize size = CTFramesetterSuggestFrameSizeWithConstraints(frameSetter, CFRangeMake(0, self.attributedString.length),  attributesDictionary, CGSizeMake(width, CGFLOAT_MAX), NULL);
NSLog(@"%s: size = %@",__PRETTY_FUNCTION__, NSStringFromCGSize(size));
CFRelease(attributesDictionary);
CFRelease(frameSetter);
return size;

}

输出如下：

Core Text Demo[2222:a0b] -[DATextView contentSizeForWidth:]: size = {729.71484, 0}

有人有任何解决方案吗？感谢您的关注：）

Answer 1

在我看来，这似乎是一个iOS7错误。我一直在修补，在iOS6下，CTFramesetterSuggestFrameSizeWithConstraints返回高度大于0的大小。在iOS7下的相同代码返回高度为0。

CTFramesetterSuggestFrameSizeWithConstraints以其错误和无证件行为而闻名。例如，由于CTFramesetterSuggestFrameSizeWithConstraints执行了错误的计算，iOS6下的代码返回的高度不正确，计算中省略了最后一行。这是您在iOS6下运行的代码：

您应该在以下位置打开针对这些问题的错误报告以及请求文档增强功能：https://bugreport.apple.com

在iOS7下，使用TextKit，您可以更快更优雅地获得相同的结果：

@interface LeoView : UIView

@property (nonatomic, assign) UIEdgeInsets contentInset;
@property (nonatomic, retain) NSLayoutManager* layoutManager;
@property (nonatomic, retain) NSTextContainer* textContainer;
@property (nonatomic, retain) NSTextStorage* textStorage;

@end

@implementation LeoView

-(void)awakeFromNib
{
    //Leo: This should not be done here. Just for example. You should do this in the init.

    self.textStorage = [[NSTextStorage alloc] initWithString:@"Lorem ipsum dolor [...]"];

    self.layoutManager = [[NSLayoutManager alloc] init];
    [self.textStorage addLayoutManager:self.layoutManager];

    self.textContainer = [[NSTextContainer alloc] initWithSize:self.bounds.size];
    [self.layoutManager addTextContainer:self.textContainer];
}

- (void)layoutSubviews
{
    [super layoutSubviews];

    //Leo: At this point the user may have set content inset, so need to take into account.
    CGSize size = self.bounds.size;
    size.width -= (self.contentInset.left + self.contentInset.right);
    size.height -= (self.contentInset.top + self.contentInset.bottom);

    self.textContainer.size = size;

    NSMutableArray* exclussionPaths = [NSMutableArray new];
    for (UIView* subview in self.subviews)
    {
        if(subview.isHidden)
            continue;

        CGRect frame = subview.frame;
        //Leo: If there is content inset, need to compensate.
        frame.origin.y -= self.contentInset.top;
        frame.origin.x -= self.contentInset.left;

        [exclussionPaths addObject:[UIBezierPath bezierPathWithRect:frame]];
    }
    self.textContainer.exclusionPaths = exclussionPaths;

    [self setNeedsDisplay];
}

- (void)drawRect:(CGRect)rect
{
    [self.layoutManager drawGlyphsForGlyphRange:[self.layoutManager glyphRangeForTextContainer:self.textContainer] atPoint:CGPointMake(self.contentInset.left, self.contentInset.top)];

    //Leo: Move used rectangle according to content inset.
    CGRect usedRect = [self.layoutManager usedRectForTextContainer:self.textContainer];
    usedRect.origin.x += self.contentInset.left;
    usedRect.origin.y += self.contentInset.top;

    CGAffineTransform transform = CGAffineTransformIdentity;
    transform = CGAffineTransformScale(transform, 1, -1);
    transform = CGAffineTransformTranslate(transform, 0, -rect.size.height);

    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextConcatCTM(context, transform);
    CGPathRef highlightPath = CGPathCreateWithRect(usedRect, &transform);
    CGContextSetFillColorWithColor(context, [UIColor colorWithRed:.0 green:1 blue:.0 alpha:.3].CGColor);
    CGContextAddPath(context, highlightPath);
    CGContextDrawPath(context, kCGPathFill);
    CFRelease(highlightPath);
}

@end

以下是contentInset设置为UIEdgeInsetsMake(20, 200, 0, 35)的结果：

我使用你的代码在文本周围绘制绿色矩形。