Remove the need for asCoeff in SkXfermode.

src/core/SkPaintPriv.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 "SkPaintPriv.h"
 
 #include "SkBitmap.h"
 #include "SkColorFilter.h"
 #include "SkPaint.h"
 #include "SkShader.h"
 
 bool isPaintOpaque(const SkPaint* paint, SkPaintBitmapOpacity contentType) {
-    // TODO: SkXfermode should have a virtual isOpaque method, which would
-    // make it possible to test modes that do not have a Coeff representation.
-
     if (!paint) {
         return contentType != kUnknown_SkPaintBitmapOpacity;
     }
+    SkXfermode::SrcColorOpacity opacityType = SkXfermode::kUnknown_SrcColorOpacity;
 
-    SkXfermode::Coeff srcCoeff, dstCoeff;
-    if (SkXfermode::AsCoeff(paint->getXfermode(), &srcCoeff, &dstCoeff)){
-        if (SkXfermode::kDA_Coeff == srcCoeff || SkXfermode::kDC_Coeff == srcCoeff ||
-            SkXfermode::kIDA_Coeff == srcCoeff || SkXfermode::kIDC_Coeff == srcCoeff) {
-            return false;
-        }
-        switch (dstCoeff) {
-        case SkXfermode::kZero_Coeff:
-            return true;
-        case SkXfermode::kISA_Coeff:
-            if (paint->getAlpha() != 255) {
-                break;
-            }
-            if (contentType == kUnknown_SkPaintBitmapOpacity) {
-                break;
-            } else if (paint->getShader() && !paint->getShader()->isOpaque()) {
-                break;
-            }
-            if (paint->getColorFilter() &&
-                ((paint->getColorFilter()->getFlags() &
-                SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
-                break;
-            }
-            return true;
-        case SkXfermode::kSA_Coeff:
-            if (paint->getAlpha() != 0) {
-                break;
-            }
-            if (paint->getColorFilter() &&
-                ((paint->getColorFilter()->getFlags() &
-                SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
-                break;
-            }
-            return true;
-        case SkXfermode::kSC_Coeff:
-            if (paint->getColor() != 0) { // all components must be 0
-                break;
-            }
-            if (contentType != kNoBitmap_SkPaintBitmapOpacity || paint->getShader()) {
-                break;
-            }
-            if (paint->getColorFilter() && (
-                (paint->getColorFilter()->getFlags() &
-                SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
-                break;
-            }
-            return true;
-        default:
-            break;
+    if (!paint->getColorFilter() ||
+        ((paint->getColorFilter()->getFlags() &
+          SkColorFilter::kAlphaUnchanged_Flag) != 0)) {
+        if (0xff == paint->getAlpha() &&
+            contentType != kUnknown_SkPaintBitmapOpacity &&
+            (!paint->getShader() || paint->getShader()->isOpaque())) {
+            opacityType = SkXfermode::kOpaque_SrcColorOpacity;
+        } else if (0 == paint->getColor() &&
+                   contentType == kNoBitmap_SkPaintBitmapOpacity &&
+                   !paint->getShader()) {
+            opacityType = SkXfermode::kTransparentBlack_SrcColorOpacity;
+        } else if (0 == paint->getAlpha()) {
+            opacityType = SkXfermode::kTransparentAlpha_SrcColorOpacity;
         }
     }
-    return false;
+
+    return SkXfermode::IsOpaque(paint->getXfermode(), opacityType);
 }
 
 bool isPaintOpaque(const SkPaint* paint, const SkBitmap* bmpReplacesShader) {
     SkPaintBitmapOpacity contentType;
 
     if(!bmpReplacesShader)
         contentType = kNoBitmap_SkPaintBitmapOpacity;
     else if(bmpReplacesShader->isOpaque())
         contentType = kOpaque_SkPaintBitmapOpacity;
     else
         contentType = kUnknown_SkPaintBitmapOpacity;
 
     return isPaintOpaque(paint, contentType);
 }