NSLayoutManager / Justification incorrect when using drawGlyphsForGlyphRange
NSLayoutManager / Justification incorrect when using drawGlyphsForGlyphRange
- Subject: NSLayoutManager / Justification incorrect when using drawGlyphsForGlyphRange
- From: vade <email@hidden>
- Date: Tue, 19 Jul 2011 18:20:15 -0400
I am drawing an NSAttributedString into a bitmap image and uploading to OpenGL as a texture. The strings origin is animated to mimic a scroll view, so speed is of the essence. Considering my need for animation I have migrated to NSLayoutManager / NSTextContainer and NSTextStorage, as opposed simply drawing with NSAttributedString drawWithRect: options, which has been a *huge* performance gain, but now I have some layout inconsistencies.
I have noticed that I have lost paragraph justification in the process of my migration/optimization with NSLayoutManager. I am drawing using drawGlyphsForGlyphRange: atPoint. Is there another mechanism that I need to trigger/calculate to ensure justification is correct? I had assumed this was part of the layout process that drawGlyphsForGlyphRange states it handles, which is apparently incorrect.
My drawing code is as follows, with only the relevant bitmap and string drawing code left in:
[NSGraphicsContext saveGraphicsState];
// Must supply flipped context for NSLayoutManagers drawing.
NSGraphicsContext* flipped = [NSGraphicsContext graphicsContextWithBitmapImageRep:bitmapImage];
flipped = [NSGraphicsContext graphicsContextWithGraphicsPort:[flipped graphicsPort] flipped:YES];
[NSGraphicsContext setCurrentContext:flipped];
NSAffineTransform *transform = [NSAffineTransform transform];
[transform translateXBy:0 yBy:h];
[transform scaleXBy:1.0 yBy:-1.0];
[transform concat];
// This is slower. Layout Manager is the way to go.
// This nets us 80% CPU for our test text - however justification is correct.
//[self.drawString drawWithRect:rect options:NSStringDrawingUsesLineFragmentOrigin];
// This might be optimizable more? This gets us ~ 40% CPU for our test text
//NSRange glyphRange = [self.layoutManager glyphRangeForTextContainer:self.textContainer];
// Only give us the glyphs we need for our rect. ~15 - 30% CPU for our test text
NSRange glyphRange = [self.layoutManager glyphRangeForBoundingRect:rect inTextContainer:self.textContainer];
// Possibly even better?
//NSRange glyphRange = [self.layoutManager glyphRangeForBoundingRectWithoutAdditionalLayout:rect inTextContainer:self.textContainer];
[self.layoutManager drawBackgroundForGlyphRange:glyphRange atPoint:drawPoint];
[self.layoutManager drawGlyphsForGlyphRange: glyphRange atPoint:drawPoint];
[NSGraphicsContext restoreGraphicsState];
Thank you for any information.
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