Don't try to render color fonts using distance fields

src/gpu/GrDistanceFieldTextContext.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrDistanceFieldTextContext.h"
 #include "GrAtlas.h"
 #include "GrDrawTarget.h"
@@ skipping 37 matching lines @@
 
     fVertices = NULL;
     fMaxVertices = 0;
 }
 
 GrDistanceFieldTextContext::~GrDistanceFieldTextContext() {
     this->flushGlyphs();
 }
 
 bool GrDistanceFieldTextContext::canDraw(const SkPaint& paint) {
-    return (kForceDistanceFieldFonts || paint.isDistanceFieldTextTEMP()) &&
-           !paint.getRasterizer() && !paint.getMaskFilter() &&
-           paint.getStyle() == SkPaint::kFill_Style &&
-           fContext->getTextTarget()->caps()->shaderDerivativeSupport() &&
-           !SkDraw::ShouldDrawTextAsPaths(paint, fContext->getMatrix());
+    if (!kForceDistanceFieldFonts && !paint.isDistanceFieldTextTEMP()) {
+        return false;
+    }
+
+    // rasterizers and mask filters modify alpha, which doesn't 
+    // translate well to distance
+    if (paint.getRasterizer() || paint.getMaskFilter() ||
+        !fContext->getTextTarget()->caps()->shaderDerivativeSupport()) {
+        return false;
+    }
+
+    // TODO: add some stroking support
+    if (paint.getStyle() != SkPaint::kFill_Style) {
+        return false;
+    }
+
+    // TODO: choose an appropriate maximum scale for distance fields and
+    //       enable perspective
+    if (SkDraw::ShouldDrawTextAsPaths(paint, fContext->getMatrix())) {
+        return false;
+    }
+
+    // distance fields cannot represent color fonts
+    SkScalerContext::Rec    rec;
+    SkScalerContext::MakeRec(paint, &fDeviceProperties, NULL, &rec);
+    return rec.getFormat() != SkMask::kARGB32_Format;
 }
 
 static inline GrColor skcolor_to_grcolor_nopremultiply(SkColor c) {
     unsigned r = SkColorGetR(c);
     unsigned g = SkColorGetG(c);
     unsigned b = SkColorGetB(c);
     return GrColorPackRGBA(r, g, b, 0xff);
 }
 
 void GrDistanceFieldTextContext::flushGlyphs() {
@@ skipping 399 matching lines @@
                                       SkScalarToFixed(y) - (glyph.fAdvanceY >> alignShift)
                                         + SK_FixedHalf, //d1g.fHalfSampleY,
                                       fontScaler);
             }
             pos += scalarsPerPosition;
         }
     }
 
     this->finish();
 }