CTFramesetterSuggestFrameSizeWithConstraints sometimes returns incorrect size?

Question

In the code below, CTFramesetterSuggestFrameSizeWithConstraints sometimes returns a CGSize with a height that is not big enough to contain all the text that is being passed into it. I did look at this answer. But in my case the width of the text box needs to be constant. Is there any other/better way to figure out the correct height for my attributed string? Thanks!

CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(attributedString);
CGSize tmpSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetter, CFRangeMake(0,0), NULL, CGSizeMake(self.view.bounds.size.width, CGFLOAT_MAX), NULL); 
CGSize textBoxSize = CGSizeMake((int)tmpSize.width + 1, (int)tmpSize.height + 1);

Answer 1

CTFramesetterSuggestFrameSizeWithConstraints() is broken. I filed a bug on this a while back. Your alternative is to use CTFramesetterCreateFrame() with a path that is sufficiently high. Then you can measure the rect of the CTFrame that you get back. Note that you cannot use CGFLOAT_MAX for the height, as CoreText uses a flipped coordinate system from the iPhone and will locate its text at the "top" of the box. This means that if you use CGFLOAT_MAX, you won't have enough precision to actually tell the height of the box. I recommend using something like 10,000 as your height, as that's 10x taller than the screen itself and yet gives enough precision for the resulting rectangle. If you need to lay out even taller text, you can do this multiple times for each section of text (you can ask CTFrameRef for the range in the original string that it was able to lay out).