Don't try to render color fonts using distance fields.

Adds detection of ARGB mask format, which is only used for color fonts.

BUG=skia:2173
R=bungeman@google.com, reed@google.com, bsalomon@google.com, robertphillips@google.com

Author: jvanverth@google.com

Review URL: https://codereview.chromium.org/224903012

git-svn-id: http://skia.googlecode.com/svn/trunk@14098 2bbb7eff-a529-9590-31e7-b0007b416f81

3 files changed, 31 insertions, 23 deletions

diff --git a/src/core/SkScalerContext.h b/src/core/SkScalerContext.h
index 63b1f186f1..f18d217f62 100644
--- a/src/core/SkScalerContext.h
+++ b/src/core/SkScalerContext.h
@@ -192,8 +192,8 @@ public:
     SkFontID findTypefaceIdForChar(SkUnichar uni);
 #endif
 
-    static inline void MakeRec(const SkPaint&, const SkDeviceProperties* deviceProperties,
-                               const SkMatrix*, Rec* rec);
+    static void MakeRec(const SkPaint&, const SkDeviceProperties* deviceProperties,
+                        const SkMatrix*, Rec* rec);
     static inline void PostMakeRec(const SkPaint&, Rec*);
 
     static SkMaskGamma::PreBlend GetMaskPreBlend(const Rec& rec);
diff --git a/src/gpu/GrDistanceFieldTextContext.cpp b/src/gpu/GrDistanceFieldTextContext.cpp
index 675c146d60..1739c530dc 100755
--- a/src/gpu/GrDistanceFieldTextContext.cpp
+++ b/src/gpu/GrDistanceFieldTextContext.cpp
@@ -55,11 +55,32 @@ GrDistanceFieldTextContext::~GrDistanceFieldTextContext() {
 }
 
 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) {
diff --git a/src/gpu/GrTextStrike.cpp b/src/gpu/GrTextStrike.cpp
index 8c2fa0bdd2..65ead0f0bb 100644
--- a/src/gpu/GrTextStrike.cpp
+++ b/src/gpu/GrTextStrike.cpp
@@ -332,22 +332,9 @@ bool GrTextStrike::addGlyphToAtlas(GrGlyph* glyph, GrFontScaler* scaler) {
                                                     (unsigned char*)storage.get(),
                                                     width, height, DISTANCE_FIELD_RANGE);
         } else {
-            // TODO: Fix color emoji
-            // for now, copy glyph into distance field storage
-            // this is not correct, but it won't crash
-            sk_bzero(dfStorage.get(), dfSize);
-            unsigned char* ptr = (unsigned char*) storage.get();
-            unsigned char* dfPtr = (unsigned char*) dfStorage.get();
-            size_t dfStride = dfWidth*bytesPerPixel;
-            dfPtr += DISTANCE_FIELD_RANGE*dfStride;
-            dfPtr += DISTANCE_FIELD_RANGE*bytesPerPixel;
-
-            for (int i = 0; i < height; ++i) {
-                memcpy(dfPtr, ptr, stride);
-
-                dfPtr += dfStride;
-                ptr += stride;
-            }
+            // distance fields should only be used to represent alpha masks
+            SkASSERT(false);
+            return false;
         }
 
         // copy to atlas