Re: Layout manager's -rectArrayForCharacterRange:::: returns zero rectangles??

FROM : John Stiles
DATE : Mon Feb 25 23:09:03 2008

I managed to reproduce this in a small test app so it's filed as:
rdar://5764057    NSLayoutManager cannot get bounding rect of glyph
when deleting at end of text 

For now I will use -performSelector:inMainThread:afterDelay: to kludge
around it. It's better than nothing.


John Stiles wrote:
> Hmm. I tried another approach and it's still no good. This produces
> NSZeroRect:
>
>        NSLayoutManager* layout = [myTextView layoutManager];
>
>        NSRange glyphRange = [layout glyphRangeForCharacterRange:selection
>                                            actualCharacterRange:NULL];
>              rect = [layout boundingRectForGlyphRange:glyphRange
>                                inTextContainer:[myTextView
> textContainer]];
>
> Interestingly, this only happens in the -textViewDidChangeSelection:
> delegate. If I defer the call until after -textViewDidChangeSelection:
> completes, then I can call the exact same function with the exact same
> inputs, and get a valid result.
>
> If no one else has any ideas, maybe that's what I'll end up doing…
>
>
> John Stiles wrote:

>> I'm trying to write some code which figures out where the insertion
>> point is located, every time the selection changes. (Imagine a text
>> editor which has a "current line number" indicator at the bottom of
>> the screen that stays updated as the user types.)
>>
>> To do this, in my text view's delegate, I have implemented the
>> delegate method -textViewDidChangeSelection:. From there I call
>> -selectedRange and then ask the layout manager for the rectangles via:
>>
>>    NSRectArray  rects = [[myTextView layoutManager]
>> rectArrayForCharacterRange:selection
>>                                                 
>> withinSelectedCharacterRange:NSMakeRange(NSNotFound, 0)
>>                                                               
>> inTextContainer:[myTextView textContainer]
>>                                                                     
>> rectCount:&rectCount];
>>
>> Normally, this works perfectly.
>>
>> However, if I go to the very end of the document and start making
>> insertions or deletions, I don't get a rectangle back—"rectCount" is
>> zero. I've checked [[[TextView() textStorage] string] length] and
>> compared it against the selection, so I'm pretty confident that I'm
>> not querying past the end of the text, which in the past is the only
>> time I've seen behavior like this up until now.
>>
>> Any ideas as to what's wrong? This seems pretty straightforward to me
>> so I'm not sure what I'm missing.
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