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CoreText: Prevent creation of CGContext for glyphs with empty bounding box

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If the alphaMapBoundingBox of a glyph is empty we don't want to create
a CGBitmapContext on it, as that will fail, and any further operations
on the invalid context will result in possibly fatal errors from CG.

This issue can be observed when drawing some glyphs of the Apple Color
Emoji font.

Change-Id: Ia45ba858b5fb6afa91e6d686a9c55e350d4095f3
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
This commit is contained in:
Tor Arne Vestbø 2014-04-30 15:26:57 +02:00 committed by The Qt Project
parent a669564597
commit 5a060a5ad3
1 changed files with 5 additions and 0 deletions
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5
src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
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@ -559,6 +559,9 @@ QImage QCoreTextFontEngine::imageForGlyph(glyph_t glyph, QFixed subPixelPosition
QImage im(br.width.ceil().toInt(), br.height.ceil().toInt(), imageFormat);
im.fill(0);
if (!im.width() || !im.height())
return im;
#ifndef Q_OS_IOS
CGColorSpaceRef colorspace = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
#else
@ -568,9 +571,11 @@ QImage QCoreTextFontEngine::imageForGlyph(glyph_t glyph, QFixed subPixelPosition
#ifdef kCGBitmapByteOrder32Host //only needed because CGImage.h added symbols in the minor version
cgflags |= kCGBitmapByteOrder32Host;
#endif
CGContextRef ctx = CGBitmapContextCreate(im.bits(), im.width(), im.height(),
8, im.bytesPerLine(), colorspace,
cgflags);
Q_ASSERT(ctx);
CGContextSetFontSize(ctx, fontDef.pixelSize);
CGContextSetShouldAntialias(ctx, (aa || fontDef.pointSize > antialiasingThreshold)
&& !(fontDef.styleStrategy & QFont::NoAntialias));