Seems to be an issue with CTLineGetTypographicBounds when calling it for a
single line.
Changing the code to below seems to fix the issue.
CGPoint origin[numberOfLines];
CTLineGetTypographicBounds(line, &ascent, &descent, NULL);
CTFrameGetLineOrigins(_frame, CFRangeMake(0, 0), origin);
I filed a bug report bug ID 9295523
Thanks
George
On Mon, Apr 11, 2011 at 11:22 PM, Malayil George <georg...@gmail.com> wrote:
> Hi,
> I'm trying to follow the SimpleTextInput example project at
> http://developer.apple.com/library/ios/#samplecode/SimpleTextInput/Introduction/Intro.html
>
> For the most part, it works fine, but, for some reason the following
> results in a wierd result drawing the caretRect.
> 1. Type in a few lines (about 7-8 lines in the Simulator (about
> 10 characters each line followed by a newline)
> 2. Click on some random point in the text in the last couple of
> lines. The caretRect is updated properly to the new location.
> 3. Click on some random point in the first or second line. The
> caret rect isn't drawn correctly and is way larger than usual - If there is
> a place I can post a screen shot that is acceptable to the thread, please
> let me know and I'd be happy to paste it :-)
>
>
> In an effort at debugging this, it looks like the ascent and descent
> values in caretRectForIndex function changes mid-call. I added a couple of
> NSLog statements to the relevant section ( I apologize for the lengthy code
> post here). The function is identical to Apple's except for the added NSLog
> statements.
> - (CGRect)caretRectForIndex:(int)index
> {
> NSArray *lines = (NSArray *) CTFrameGetLines(_frame);
>
> // Special case, no text
> if (_text.length == 0) {
> CGPoint origin = CGPointMake(CGRectGetMinX(self.bounds),
> CGRectGetMaxY(self.bounds) - self.font.leading);
> // Note: using fabs() for typically negative descender from fonts
> return CGRectMake(origin.x, origin.y - fabs(self.font.descender),
> 3, self.font.ascender + fabs(self.font.descender));
> }
>
> // Special case, insertion point at final position in text after
> newline
> if (index == _text.length && [_text characterAtIndex:(index - 1)] ==
> '\n') {
> CTLineRef line = (CTLineRef) [lines lastObject];
> CFRange range = CTLineGetStringRange(line);
> CGFloat xPos = CTLineGetOffsetForStringIndex(line, range.location,
> NULL);
> CGPoint origin;
> CGFloat ascent, descent;
> CTLineGetTypographicBounds(line, &ascent, &descent, NULL);
> NSLog(@"Ascent, Descent: %f, %f", ascent, descent);
> CTFrameGetLineOrigins(_frame, CFRangeMake(lines.count - 1, 0),
> &origin);
> // Place point after last line, including any font leading spacing
> if applicable
> origin.y -= self.font.leading;
> NSLog(@"Ascent, Descent: %f, %f", ascent, descent);
> return CGRectMake(xPos, origin.y - descent, 3, ascent +
> descent);
> }
>
> // Regular case, caret somewhere within our text content range
> for (int i = 0; i < [lines count]; i++) {
> CTLineRef line = (CTLineRef) [lines objectAtIndex:i];
> CFRange range = CTLineGetStringRange(line);
> NSInteger localIndex = index - range.location;
> if (localIndex >= 0 && localIndex <= range.length) {
> // index is in the range for this line
> CGFloat xPos = CTLineGetOffsetForStringIndex(line, index,
> NULL);
> CGPoint origin;
> CGFloat ascent, descent;
> CTLineGetTypographicBounds(line, &ascent, &descent, NULL);
> NSLog(@"Ascent, Descent: %f, %f", ascent, descent);
> CTFrameGetLineOrigins(_frame, CFRangeMake(i, 0), &origin);
> NSLog(@"Ascent, Descent: %f, %f", ascent, descent);
> // Make a small "caret" rect at the index position
> return CGRectMake(xPos, origin.y - descent, 3, ascent +
> descent);
> }
> }
>
> return CGRectNull;
> }
>
> The output from the above method when I click on the first couple of lines
> is something like
> 2011-04-11 23:09:02.670 SimpleTextInput[33460:207] Ascent, Descent:
> 13.860352, 4.139648
> 2011-04-11 23:09:02.670 SimpleTextInput[33460:207] Ascent, Descent:
> 237.339645, 0.000000
>
> The call to CTLineGetTypographicBounds seems to be working fine as
> evidenced by the low expected values of ascent and descent. But, for some
> reason, after CTFrameGetLineOrigins it is changing. I'm at a loss as to why
> these values are changing as there doesn't seem to be anything in the code
> modifying ascent and descent between the two NSLog statements.
> I've tried synchronizing the caretRect method body on self (but, it
> doesn't look like there are other threads that are modifying these values
> either).
>
> Any pointers on why ascent and descent is changing would be much
> appreciated :)
>
>
> Thanks
> George
>
>
>
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