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

src/gpu/GrGpu.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 GrGpu_DEFINED
@@ skipping 348 matching lines @@
             case kLines_GrPrimitiveType:
             case kLineStrip_GrPrimitiveType:
                 return kDrawLines_DrawType;
             default:
                 GrCrash("Unexpected primitive type");
                 return kDrawTriangles_DrawType;
         }
     }
 
     // prepares clip flushes gpu state before a draw
-    bool setupClipAndFlushState(DrawType);
+    bool setupClipAndFlushState(DrawType, const GrDeviceCoordTexture* dstCopy);
 
     // Functions used to map clip-respecting stencil tests into normal
     // stencil funcs supported by GPUs.
     static GrStencilFunc ConvertStencilFunc(bool stencilInClip,
                                             GrStencilFunc func);
     static void ConvertStencilFuncAndMask(GrStencilFunc func,
                                           bool clipInStencil,
                                           unsigned int clipBit,
                                           unsigned int userBits,
                                           unsigned int* ref,
@@ skipping 95 matching lines @@
     // width and height may be larger than rt (if underlying API allows it).
     // Should attach the SB to the RT. Returns false if compatible sb could
     // not be created.
     virtual bool createStencilBufferForRenderTarget(GrRenderTarget*, int width, int height) = 0;
 
     // attaches an existing SB to an existing RT.
     virtual bool attachStencilBufferToRenderTarget(GrStencilBuffer*, GrRenderTarget*) = 0;
 
     // The GrGpu typically records the clients requested state and then flushes
     // deltas from previous state at draw time. This function does the
-    // backend-specific flush of the state
+    // backend-specific flush of the state.
     // returns false if current state is unsupported.
-    virtual bool flushGraphicsState(DrawType) = 0;
+    virtual bool flushGraphicsState(DrawType, const GrDeviceCoordTexture* dstCopy) = 0;
 
     // clears the entire stencil buffer to 0
     virtual void clearStencil() = 0;
 
     // Given a rt, find or create a stencil buffer and attach it
     bool attachStencilBufferToRenderTarget(GrRenderTarget* target);
 
     // GrDrawTarget overrides
     virtual void onDraw(const DrawInfo&) SK_OVERRIDE;
     virtual void onStencilPath(const GrPath* path, const SkStrokeRec& stroke,
@@ skipping 33 matching lines @@
     // these are mutable so they can be created on-demand
     mutable GrVertexBuffer*                                             fUnitSquareVertexBuffer;
     mutable GrIndexBuffer*                                              fQuadIndexBuffer;
     bool                                                                fContextIsDirty;
     ResourceList                                                        fResourceList;
 
     typedef GrDrawTarget INHERITED;
 };
 
 #endif