[External patch] Source-over support for SkLumaXfermode.

gm/lumamode.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 "gm.h"
 #include "SkCanvas.h"
 #include "SkGradientShader.h"
@@ skipping 58 matching lines @@
 
     canvas->restore();
     canvas->restore();
 }
 
 class LumaXfermodeGM : public skiagm::GM {
 public:
     LumaXfermodeGM() {
         fSrcInXfer.reset(SkLumaMaskXfermode::Create(SkXfermode::kSrcIn_Mode));
         fDstInXfer.reset(SkLumaMaskXfermode::Create(SkXfermode::kDstIn_Mode));
+        fSrcOverXfer.reset(SkLumaMaskXfermode::Create(SkXfermode::kSrcOver_Mode));
 
         SkColor  g1Colors[] = { kColor1, SkColorSetA(kColor1, 0x20) };
         SkColor  g2Colors[] = { kColor2, SkColorSetA(kColor2, 0x20) };
         SkPoint  g1Points[] = { { 0, 0 }, { 0,     100 } };
         SkPoint  g2Points[] = { { 0, 0 }, { kSize, 0   } };
         SkScalar pos[] = { 0.2f, 1.0f };
 
         fGr1.reset(SkGradientShader::CreateLinear(g1Points,
                                                   g1Colors,
                                                   pos,
                                                   SK_ARRAY_COUNT(g1Colors),
                                                   SkShader::kClamp_TileMode));
         fGr2.reset(SkGradientShader::CreateLinear(g2Points,
                                                   g2Colors,
                                                   pos,
                                                   SK_ARRAY_COUNT(g2Colors),
                                                   SkShader::kClamp_TileMode));
     }
 
 protected:
     virtual SkString onShortName() SK_OVERRIDE {
         return SkString("lumamode");
     }
 
     virtual SkISize onISize() SK_OVERRIDE {
         return SkISize::Make(600, 420);
     }
 
     virtual void onDraw(SkCanvas* canvas) SK_OVERRIDE {
-        SkXfermode* modes[] = { NULL, fSrcInXfer, fDstInXfer };
+        SkXfermode* modes[] = { NULL, fSrcInXfer, fDstInXfer, fSrcOverXfer };
         struct {
             SkShader*   fShader1;
             SkShader*   fShader2;
         } shaders[] = {
             { NULL, NULL },
             { NULL, fGr2 },
             { fGr1, NULL },
             { fGr1, fGr2 },
         };
 
         SkScalar gridStep = kSize + 2 * kInset;
         draw_label(canvas, "SrcOver", SkPoint::Make(gridStep, 20));
         draw_label(canvas, "SrcInLuma", SkPoint::Make(gridStep * 3, 20));
         draw_label(canvas, "DstInLuma", SkPoint::Make(gridStep * 5, 20));
+        draw_label(canvas, "SrcOverLuma", SkPoint::Make(gridStep * 7, 20));
         for (size_t i = 0; i < SK_ARRAY_COUNT(shaders); ++i) {
             canvas->save();
             canvas->translate(kInset, gridStep * i + 30);
             for (size_t m = 0; m < SK_ARRAY_COUNT(modes); ++m) {
                 draw_scene(canvas, modes[m], true, shaders[i].fShader1,
                            shaders[i].fShader2);
                 canvas->translate(gridStep, 0);
                 draw_scene(canvas, modes[m], false, shaders[i].fShader1,
                            shaders[i].fShader2);
                 canvas->translate(gridStep, 0);
             }
             canvas->restore();
         }
     }
 
 private:
     SkAutoTUnref<SkShader>   fGr1, fGr2;
-    SkAutoTUnref<SkXfermode> fSrcInXfer, fDstInXfer;
+    SkAutoTUnref<SkXfermode> fSrcInXfer, fDstInXfer, fSrcOverXfer;
 
     typedef skiagm::GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 DEF_GM( return SkNEW(LumaXfermodeGM); )