CTLineGetTypographicBounds crash

[Koen van der Drift]

I'm looking to add some highlighting to my Core Text View, and implemented the 
following which comes straight from Apple's SimpleTextInput code example 
(https://developer.apple.com/library/iOs/#samplecode/SimpleTextInput/Introduction/Intro.html):

// Helper method for drawing the current selection range (as a simple filled 
rect)
- (void)drawRangeAsSelection:(NSRange)selectionRange
{
        // If not in editing mode, we do not draw selection rects
    if (!self.editing)
        return;

    // If selection range empty, do not draw
    if (selectionRange.length == 0 || selectionRange.location == NSNotFound)
        return;
    
        // set the fill color to the selection color
    [[SimpleCoreTextView selectionColor] setFill];
    
        // Iterate over the lines in our CTFrame, looking for lines that 
intersect
        // with the given selection range, and draw a selection rect for each 
intersection
    NSArray *lines = (NSArray *) CTFrameGetLines(_frame);
    for (int i = 0; i < [lines count]; i++) {
        CTLineRef line = (CTLineRef) [lines objectAtIndex:i];
        CFRange lineRange = CTLineGetStringRange(line);
        NSRange range = NSMakeRange(lineRange.location, lineRange.length);
        NSRange intersection = [self RangeIntersection:range 
withSecond:selectionRange];
        if (intersection.location != NSNotFound && intersection.length > 0) {
                        // The text range for this line intersects our 
selection range
            CGFloat xStart = CTLineGetOffsetForStringIndex(line, 
intersection.location, NULL);
            CGFloat xEnd = CTLineGetOffsetForStringIndex(line, 
intersection.location + intersection.length, NULL);
            CGPoint origin;
                        // Get coordinate and bounds information for the 
intersection text range
            CTFrameGetLineOrigins(_frame, CFRangeMake(i, 0), &origin);    
            CGFloat ascent, descent;
            CTLineGetTypographicBounds(line, &ascent, &descent, NULL);          
        <<<<<<<<<===========================  BOOM!
                        // Create a rect for the intersection and draw it with 
selection color
            CGRect selectionRect = CGRectMake(xStart, origin.y - descent, xEnd 
- xStart, ascent + descent);
            UIRectFill(selectionRect);
        }
    }    
}



But every time, I get an EXC_BAD_ACCESS error for the 
CTLineGetTypographicBounds() call.  I triple checked that _frame and line are 
valid at this point, and the debugger output shows what it is supposed to be 
(correct string, attributes, etc).

Here's the output from bt:

(lldb) bt
* thread #1: tid = 0x1c03, 0x0027bbd0 CoreText`CTLineGetTypographicBounds + 29, 
stop reason = EXC_BAD_ACCESS (code=2, address=0x60)
    frame #0: 0x0027bbd0 CoreText`CTLineGetTypographicBounds + 29
    frame #1: 0x000469a4 MyApp`-[MyView drawRangeAsSelection:](self=0x4576f000, 
_cmd=0x00000000, selectionRange=(null)) + 628 at MyView.m:461


Any suggestions why this could be happening?

Thanks,

- Koen.




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