Add support for reading the dst pixel value in an effect. Use in a new effect for the kDarken xfer …

src/gpu/gl/GrGLProgram.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef GrGLProgram_DEFINED
 #define GrGLProgram_DEFINED
@@ skipping 84 matching lines @@
         }
     };
 
     /**
      * This function uploads uniforms and calls each GrGLEffect's setData. It is called before a
      * draw occurs using the program after the program has already been bound. It also uses the
      * GrGpuGL object to bind the textures required by the GrGLEffects.
      *
      * The color and coverage params override the GrDrawState's getColor() and getCoverage() values.
      */
-    void setData(GrGpuGL*, GrColor color, GrColor coverage, SharedGLState*);
+    void setData(GrGpuGL*,
+                 GrColor color,
+                 GrColor coverage,
+                 const GrDeviceCoordTexture* dstCopy, // can be NULL
+                 SharedGLState*);
 
 private:
     GrGLProgram(const GrGLContext& gl,
                 const GrGLProgramDesc& desc,
                 const GrEffectStage* stages[]);
 
     bool succeeded() const { return 0 != fProgramID; }
 
     /**
      *  This is the heavy initialization routine for building a GLProgram.
@@ skipping 31 matching lines @@
     // Helper for setData() that sets the view matrix and loads the render target height uniform
     void setMatrixAndRenderTargetHeight(const GrDrawState&);
 
     typedef SkSTArray<4, UniformHandle, true> SamplerUniSArray;
 
     struct UniformHandles {
         UniformHandle       fViewMatrixUni;
         UniformHandle       fColorUni;
         UniformHandle       fCoverageUni;
         UniformHandle       fColorFilterUni;
+
         // We use the render target height to provide a y-down frag coord when specifying
         // origin_upper_left is not supported.
         UniformHandle       fRTHeightUni;
+
+        // Uniforms for computing texture coords to do the dst-copy lookup
+        UniformHandle       fDstCopyTopLeftUni;
+        UniformHandle       fDstCopyScaleUni;
+        UniformHandle       fDstCopySamplerUni;
+
         // An array of sampler uniform handles for each effect.
-        SamplerUniSArray    fSamplerUnis[GrDrawState::kNumStages];
+        SamplerUniSArray    fEffectSamplerUnis[GrDrawState::kNumStages];
 
         UniformHandles() {
             fViewMatrixUni = GrGLUniformManager::kInvalidUniformHandle;
             fColorUni = GrGLUniformManager::kInvalidUniformHandle;
             fCoverageUni = GrGLUniformManager::kInvalidUniformHandle;
             fColorFilterUni = GrGLUniformManager::kInvalidUniformHandle;
             fRTHeightUni = GrGLUniformManager::kInvalidUniformHandle;
+            fDstCopyTopLeftUni = GrGLUniformManager::kInvalidUniformHandle;
+            fDstCopyScaleUni = GrGLUniformManager::kInvalidUniformHandle;
+            fDstCopySamplerUni = GrGLUniformManager::kInvalidUniformHandle;
         }
     };
 
     // GL IDs
     GrGLuint                    fVShaderID;
     GrGLuint                    fGShaderID;
     GrGLuint                    fFShaderID;
     GrGLuint                    fProgramID;
 
     // these reflect the current values of uniforms (GL uniform values travel with program)
     MatrixState                 fMatrixState;
     GrColor                     fColor;
     GrColor                     fCoverage;
     GrColor                     fColorFilterColor;
 
     GrGLEffect*                 fEffects[GrDrawState::kNumStages];
 
     GrGLProgramDesc             fDesc;
     const GrGLContext&          fContext;
 
     GrGLUniformManager          fUniformManager;
     UniformHandles              fUniformHandles;
 
     typedef GrRefCnt INHERITED;
 };
 
 #endif