Fix Apple Color Emoji support for OS X 10.7+

src/ports/SkFontHost_mac.cpp

Index: src/ports/SkFontHost_mac.cpp
diff --git a/src/ports/SkFontHost_mac.cpp b/src/ports/SkFontHost_mac.cpp
index c19df196b3a9a97b1ff4ad667ff550f44f27d56e..e6ece49af3080c8267b230df0588dfc1f3f4843e 100755
--- a/src/ports/SkFontHost_mac.cpp
+++ b/src/ports/SkFontHost_mac.cpp
@@ -115,6 +115,11 @@ public:
     const T* fData;
 };
 
+static bool CTFontIsAppleColorEmoji(CTFontRef font) {
+    AutoCFRelease<CFStringRef> name(CTFontCopyFamilyName(font));
+    return CFStringCompare(name.get(), CFSTR("Apple Color Emoji"), 0) == kCFCompareEqualTo;

[bungeman-skia, 2014/12/04 14:47:14]

No way we're doing this (testing by name).

+}
+
 // inline versions of these rect helpers
 
 static bool CGRectIsEmpty_inline(const CGRect& rect) {
@@ -680,6 +685,7 @@ private:
     bool fGeneratedFBoundingBoxes;
     const bool fDoSubPosition;
     const bool fVertical;
+    bool fIsColorEmoji;
 
     friend class Offscreen;
 
@@ -700,6 +706,7 @@ SkScalerContext_Mac::SkScalerContext_Mac(SkTypeface_Mac* typeface,
     CFIndex numGlyphs = CTFontGetGlyphCount(ctFont);
     SkASSERT(numGlyphs >= 1 && numGlyphs <= 0xFFFF);
     fGlyphCount = SkToU16(numGlyphs);
+    fIsColorEmoji = CTFontIsAppleColorEmoji(ctFont);
 
     SkMatrix skTransform;
     fRec.getSingleMatrixWithoutTextSize(&skTransform);
@@ -788,10 +795,12 @@ CGRGBPixel* Offscreen::getCG(const SkScalerContext_Mac& context, const SkGlyph&
         CGContextSetAllowsFontSubpixelQuantization(fCG, false);
         CGContextSetShouldSubpixelQuantizeFonts(fCG, false);
 
-        CGContextSetTextDrawingMode(fCG, kCGTextFill);
-        CGContextSetFont(fCG, context.fCGFont);
-        CGContextSetFontSize(fCG, CTFontGetSize(context.fCTFont));
-        CGContextSetTextMatrix(fCG, CTFontGetMatrix(context.fCTFont));
+        if (!context.fIsColorEmoji) {
+            CGContextSetTextDrawingMode(fCG, kCGTextFill);
+            CGContextSetFont(fCG, context.fCGFont);
+            CGContextSetFontSize(fCG, CTFontGetSize(context.fCTFont));
+            CGContextSetTextMatrix(fCG, CTFontGetMatrix(context.fCTFont));
+        }
 
         // Because CG always draws from the horizontal baseline,
         // if there is a non-integral translation from the horizontal origin to the vertical origin,
@@ -821,8 +830,8 @@ CGRGBPixel* Offscreen::getCG(const SkScalerContext_Mac& context, const SkGlyph&
     // skip rows based on the glyph's height
     image += (fSize.fHeight - glyph.fHeight) * fSize.fWidth;
 
-    // erase to black
-    sk_memset_rect32(image, 0, glyph.fWidth, glyph.fHeight, rowBytes);
+    // erase to black or white.
+    sk_memset_rect32(image, context.fIsColorEmoji ? 0xFFFFFFFF : 0, glyph.fWidth, glyph.fHeight, rowBytes);

[bungeman-skia, 2014/12/04 14:47:13]

We cannot make the background opaque.

 
     float subX = 0;
     float subY = 0;
@@ -839,9 +848,19 @@ CGRGBPixel* Offscreen::getCG(const SkScalerContext_Mac& context, const SkGlyph&
         subY += offset.fY;
     }
 
-    CGContextShowGlyphsAtPoint(fCG, -glyph.fLeft + subX,
-                               glyph.fTop + glyph.fHeight - subY,
-                               &glyphID, 1);
+    CGPoint pos = CGPointMake(-glyph.fLeft + subX, glyph.fTop + glyph.fHeight - subY);
+    if (context.fIsColorEmoji) {
+        CGContextSaveGState(fCG);
+        // CGContextSetTextMatrix does not work with color glyphs, so we use the

[bungeman-skia, 2014/12/04 14:47:13]

This isn't quite true, what happens is CoreText won't scale the bitmap up.
That's a whole 'nother issue.

+        // CTM instead. This means we must translate the CTM as well, to set the
+        // glyph position, instead of using CGContextSetTextPosition.
+        CGContextConcatCTM(fCG, CTFontGetMatrix(context.fCTFont));
+        CGContextTranslateCTM(fCG, pos.x, pos.y);
+        CTFontDrawGlyphs(context.fCTFont, &glyphID, &CGPointZero, 1, fCG);
+        CGContextRestoreGState(fCG);
+    } else {
+        CGContextShowGlyphsAtPoint(fCG, pos.x, pos.y, &glyphID, 1);
+    }
 
     SkASSERT(rowBytesPtr);
     *rowBytesPtr = rowBytes;
@@ -1140,22 +1159,12 @@ static void rgb_to_lcd16(const CGRGBPixel* SK_RESTRICT cgPixels, size_t cgRowByt
     }
 }
 
-#ifdef HACK_COLORGLYPHS
-// hack to colorize the output for testing kARGB32_Format
-static SkPMColor cgpixels_to_pmcolor(CGRGBPixel rgb, const SkGlyph& glyph,
-                                     int x, int y) {
+static SkPMColor cgpixels_to_pmcolor(CGRGBPixel rgb) {
     U8CPU r = (rgb >> 16) & 0xFF;
     U8CPU g = (rgb >>  8) & 0xFF;
     U8CPU b = (rgb >>  0) & 0xFF;
-    unsigned a = SkComputeLuminance(r, g, b);
-
-    // compute gradient from x,y
-    r = x * 255 / glyph.fWidth;
-    g = 0;
-    b = (glyph.fHeight - y) * 255 / glyph.fHeight;
-    return SkPreMultiplyARGB(a, r, g, b);    // red
+    return SkPreMultiplyARGB(0xFF, r, g, b);    // red

[bungeman-skia, 2014/12/04 14:47:13]

We cannot make these opaque, transparency must be maintained.

 }
-#endif
 
 template <typename T> T* SkTAddByteOffset(T* ptr, size_t byteOffset) {
     return (T*)((char*)ptr + byteOffset);
@@ -1228,20 +1237,18 @@ void SkScalerContext_Mac::generateImage(const SkGlyph& glyph) {
                 dst += dstRB;
             }
         } break;
-#ifdef HACK_COLORGLYPHS
         case SkMask::kARGB32_Format: {
             const int width = glyph.fWidth;
             size_t dstRB = glyph.rowBytes();
             SkPMColor* dst = (SkPMColor*)glyph.fImage;
             for (int y = 0; y < glyph.fHeight; y++) {
                 for (int x = 0; x < width; ++x) {
-                    dst[x] = cgpixels_to_pmcolor(cgPixels[x], glyph, x, y);
+                    dst[x] = cgpixels_to_pmcolor(cgPixels[x]);
                 }
                 cgPixels = (CGRGBPixel*)((char*)cgPixels + cgRowBytes);
                 dst = (SkPMColor*)((char*)dst + dstRB);
             }
         } break;
-#endif
         default:
             SkDEBUGFAIL("unexpected mask format");
             break;
@@ -1828,6 +1835,9 @@ void SkTypeface_Mac::onFilterRec(SkScalerContextRec* rec) const {
         }
     }
 
+    if (CTFontIsAppleColorEmoji(fFontRef.get()))
+        rec->fMaskFormat = SkMask::kARGB32_Format;
+
     // Unhinted A8 masks (those not derived from LCD masks) must respect SK_GAMMA_APPLY_TO_A8.
     // All other masks can use regular gamma.
     if (SkMask::kA8_Format == rec->fMaskFormat && SkPaint::kNo_Hinting == hinting) {