Lines missing from tall UILabel when embedding NSTextAttachment

Question

I can create a multi-line NSAttributedString by using escaped new-line characters (@\"\\n\"). With iOS 7, I can now embed a UIImage in

Answer 1

Did you try to get the actually height of the text using the boundingRectWithSize method:

NSAttributedString *text;
CGFloat width = 200;
CGRect rect = [text boundingRectWithSize:CGSizeMake(width, CGFLOAT_MAX) options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading context:nil];
CGFloat height = rect.size.height;

Answer 2

I have found another workaround for this bug, which is sufficiently different from my previous answer that I'm providing it as another answer: let the label set its own height.

In this code, I'm removing the height constraint from a label with a fixed width constraint, and replacing it with a greater-than height constraint (and I'm sure there are other ways to achieve the same outcome):

[self.lab removeConstraint:self.labelHeight];
[self.lab addConstraint:
 [NSLayoutConstraint constraintWithItem:self.lab 
 attribute:NSLayoutAttributeHeight 
 relatedBy:NSLayoutRelationGreaterThanOrEqual 
 toItem:nil attribute:0 multiplier:1 constant:20]];

That label displays correctly every attributed string I throw at it! Of course, you lose the automatic vertical centering of the string, but that's the whole source of the bug, so losing it is not so terrible.

Answer 3

It seems to be a bug in UILabel. The same code works fine when UITextView is used instead of UILabel (UITextView's default font size is different, so I tested it on different heights).

Answer 4

It really has nothing to do with the NSTextAttachment. It's that in iOS 7 as released so far, UILabel is not very good at drawing attributed strings. A simple attributed string with some underlining and a centered paragraph style will show up blank, or partially blank, in a UILabel; the same attributed string draws fine in a UITextView.

So, one solution for now is: Use UITextView instead. This is actually a pretty good solution because, in iOS 7, UITextView is just a wrapper around the Text Kit stack. So it is drawing the attributed string in a straightforward way. It is not hampered by the under-the-hood relationship to Web Kit that it had in previous iOS versions.

On the other hand, I have also found a workaround for this UILabel bug; you have to fiddle with the number of lines of the label and the string in such a way as to jam the text up to the top of the label: see my answer here - https://stackoverflow.com/a/19409962/341994

Or you could just wait for Apple to fix the bug and keep your fingers crossed. EDIT: In iOS 7.1, it appears that the bug will be fixed and no workaround will be needed.