Add support for color glyphs (Emoji) on Mac OS X and iOS

A new glyph type is added to the glyph caches for ARGB bitmap glyphs,
and the raster and OpenGL paint engines have been modified to support
this glyph type for drawCachedGlyphs().

The CoreText font engine implements support for these glyphs through
the CTFontDrawGlyphs API, since CGContextShowGlyphsWithAdvances does
not handle color glyphs.

Change-Id: Idad9ce75a911cae130d65aebe59142772a16fc12
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>

2 files changed, 44 insertions, 22 deletions

diff --git a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
index 70416bc2dd..078b639fa8 100644
--- a/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
+++ b/src/platformsupport/fontdatabases/mac/qfontengine_coretext.mm
@@ -158,7 +158,7 @@ void QCoreTextFontEngine::init()
     synthesisFlags = 0;
     CTFontSymbolicTraits traits = CTFontGetSymbolicTraits(ctfont);
 
-#if MAC_OS_X_VERSION_MAX_ALLOWED >= 1070
+#if defined(Q_OS_IOS) || MAC_OS_X_VERSION_MAX_ALLOWED >= 1070
     if (supportsColorGlyphs() && (traits & kCTFontColorGlyphsTrait))
         glyphFormat = QFontEngineGlyphCache::Raster_ARGB;
     else
@@ -457,7 +457,9 @@ QImage QCoreTextFontEngine::imageForGlyph(glyph_t glyph, QFixed subPixelPosition
         br.y      = QFixed::fromReal(br.y.toReal() * vscale);
     }
 
-    QImage im(qAbs(qRound(br.width))+2, qAbs(qRound(br.height))+2, QImage::Format_RGB32);
+    bool isColorGlyph = glyphFormat == QFontEngineGlyphCache::Raster_ARGB;
+    QImage::Format format = isColorGlyph ? QImage::Format_ARGB32_Premultiplied : QImage::Format_RGB32;
+    QImage im(qAbs(qRound(br.width)) + 2, qAbs(qRound(br.height)) + 2, format);
     im.fill(0);
 
 #ifndef Q_OS_IOS
@@ -465,7 +467,7 @@ QImage QCoreTextFontEngine::imageForGlyph(glyph_t glyph, QFixed subPixelPosition
 #else
     CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
 #endif
-    uint cgflags = kCGImageAlphaNoneSkipFirst;
+    uint cgflags = isColorGlyph ? kCGImageAlphaPremultipliedFirst : kCGImageAlphaNoneSkipFirst;
 #ifdef kCGBitmapByteOrder32Host //only needed because CGImage.h added symbols in the minor version
     cgflags |= kCGBitmapByteOrder32Host;
 #endif
@@ -476,38 +478,49 @@ QImage QCoreTextFontEngine::imageForGlyph(glyph_t glyph, QFixed subPixelPosition
     CGContextSetShouldAntialias(ctx, (aa || fontDef.pointSize > antialiasingThreshold)
                                  && !(fontDef.styleStrategy & QFont::NoAntialias));
     CGContextSetShouldSmoothFonts(ctx, aa);
-    CGAffineTransform oldTextMatrix = CGContextGetTextMatrix(ctx);
-    CGAffineTransform cgMatrix = CGAffineTransformIdentity;
 
-    CGAffineTransformConcat(cgMatrix, oldTextMatrix);
+    CGAffineTransform cgMatrix = CGAffineTransformIdentity;
 
     if (synthesisFlags & QFontEngine::SynthesizedItalic)
         cgMatrix = CGAffineTransformConcat(cgMatrix, CGAffineTransformMake(1, 0, SYNTHETIC_ITALIC_SKEW, 1, 0, 0));
 
-    cgMatrix = CGAffineTransformConcat(cgMatrix, transform);
+    if (!isColorGlyph) // CTFontDrawGlyphs incorporates the font's matrix already
+        cgMatrix = CGAffineTransformConcat(cgMatrix, transform);
+
     if (m.isScaling())
         cgMatrix = CGAffineTransformConcat(cgMatrix, CGAffineTransformMakeScale(m.m11(), m.m22()));
 
-    CGContextSetTextMatrix(ctx, cgMatrix);
-    CGContextSetRGBFillColor(ctx, 1, 1, 1, 1);
-    CGContextSetTextDrawingMode(ctx, kCGTextFill);
-
-    CGContextSetFont(ctx, cgFont);
-
+    CGGlyph cgGlyph = glyph;
     qreal pos_x = -br.x.truncate() + subPixelPosition.toReal();
     qreal pos_y = im.height() + br.y.toReal();
-    CGContextSetTextPosition(ctx, pos_x, pos_y);
 
-    CGSize advance;
-    advance.width = 0;
-    advance.height = 0;
-    CGGlyph cgGlyph = glyph;
-    CGContextShowGlyphsWithAdvances(ctx, &cgGlyph, &advance, 1);
+    if (!isColorGlyph) {
+        CGContextSetTextMatrix(ctx, cgMatrix);
+        CGContextSetRGBFillColor(ctx, 1, 1, 1, 1);
+        CGContextSetTextDrawingMode(ctx, kCGTextFill);
+        CGContextSetFont(ctx, cgFont);
+        CGContextSetTextPosition(ctx, pos_x, pos_y);
 
-    if (synthesisFlags & QFontEngine::SynthesizedBold) {
-        CGContextSetTextPosition(ctx, pos_x + 0.5 * lineThickness().toReal(), pos_y);
-        CGContextShowGlyphsWithAdvances(ctx, &cgGlyph, &advance, 1);
+        CGContextShowGlyphsWithAdvances(ctx, &cgGlyph, &CGSizeZero, 1);
+
+        if (synthesisFlags & QFontEngine::SynthesizedBold) {
+            CGContextSetTextPosition(ctx, pos_x + 0.5 * lineThickness().toReal(), pos_y);
+            CGContextShowGlyphsWithAdvances(ctx, &cgGlyph, &CGSizeZero, 1);
+        }
+    }
+#if defined(Q_OS_IOS) || MAC_OS_X_VERSION_MAX_ALLOWED >= 1070
+    else if (supportsColorGlyphs()) {
+        // CGContextSetTextMatrix does not work with color glyphs, so we use
+        // the CTM instead. This means we must translate the CTM as well, to
+        // set the glyph position, instead of using CGContextSetTextPosition.
+        CGContextTranslateCTM(ctx, pos_x, pos_y);
+        CGContextConcatCTM(ctx, cgMatrix);
+
+        // CGContextShowGlyphsWithAdvances does not support the 'sbix' color-bitmap
+        // glyphs in the Apple Color Emoji font, so we use CTFontDrawGlyphs instead.
+        CTFontDrawGlyphs(ctfont, &cgGlyph, &CGPointZero, 1, ctx);
     }
+#endif
 
     CGContextRelease(ctx);
     CGColorSpaceRelease(colorspace);
@@ -556,6 +569,14 @@ QImage QCoreTextFontEngine::alphaRGBMapForGlyph(glyph_t glyph, QFixed subPixelPo
     return im;
 }
 
+QImage QCoreTextFontEngine::bitmapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t)
+{
+    if (t.type() > QTransform::TxScale)
+        return QFontEngine::bitmapForGlyph(glyph, subPixelPosition, t);
+
+    return imageForGlyph(glyph, subPixelPosition, true, t);
+}
+
 void QCoreTextFontEngine::recalcAdvances(QGlyphLayout *glyphs, QFontEngine::ShaperFlags flags) const
 {
     int i, numGlyphs = glyphs->numGlyphs;
diff --git a/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h b/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h
index e7fec4be14..7c8f28aabd 100644
--- a/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h
+++ b/src/platformsupport/fontdatabases/mac/qfontengine_coretext_p.h
@@ -98,6 +98,7 @@ public:
     virtual QImage alphaMapForGlyph(glyph_t, QFixed subPixelPosition);
     virtual QImage alphaMapForGlyph(glyph_t glyph, QFixed subPixelPosition, const QTransform &t);
     virtual QImage alphaRGBMapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t);
+    virtual QImage bitmapForGlyph(glyph_t, QFixed subPixelPosition, const QTransform &t);
     virtual qreal minRightBearing() const;
     virtual qreal minLeftBearing() const;
     virtual QFixed emSquareSize() const;