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

src/gpu/GrDrawTarget.h

 
 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef GrDrawTarget_DEFINED
@@ skipping 637 matching lines @@
         void adjustStartVertex(int vertexOffset);
         // shifts the start index
         void adjustStartIndex(int indexOffset);
 
         void setDevBounds(const SkRect& bounds) {
             fDevBoundsStorage = bounds;
             fDevBounds = &fDevBoundsStorage;
         }
         const SkRect* getDevBounds() const { return fDevBounds; }
 
+        // NULL if no copy of the dst is needed for the draw.
+        const GrDeviceCoordTexture* getDstCopy() const {
+            if (NULL != fDstCopy.texture()) {
+                return &fDstCopy;
+            } else {
+                return NULL;
+            }
+        }
+
     private:
         DrawInfo() { fDevBounds = NULL; }
 
         friend class GrDrawTarget;
 
-        GrPrimitiveType fPrimitiveType;
+        GrPrimitiveType         fPrimitiveType;
 
-        int             fStartVertex;
-        int             fStartIndex;
-        int             fVertexCount;
-        int             fIndexCount;
+        int                     fStartVertex;
+        int                     fStartIndex;
+        int                     fVertexCount;
+        int                     fIndexCount;
 
-        int             fInstanceCount;
-        int             fVerticesPerInstance;
-        int             fIndicesPerInstance;
+        int                     fInstanceCount;
+        int                     fVerticesPerInstance;
+        int                     fIndicesPerInstance;
 
-        SkRect          fDevBoundsStorage;
-        SkRect*         fDevBounds;
+        SkRect                  fDevBoundsStorage;
+        SkRect*                 fDevBounds;
+
+        GrDeviceCoordTexture    fDstCopy;
     };
 
 private:
     // A subclass can optionally overload this function to be notified before
     // vertex and index space is reserved.
     virtual void willReserveVertexAndIndexSpace(int vertexCount, int indexCount) {}
 
     // implemented by subclass to allocate space for reserved geom
     virtual bool onReserveVertexSpace(size_t vertexSize, int vertexCount, void** vertices) = 0;
     virtual bool onReserveIndexSpace(int indexCount, void** indices) = 0;
@@ skipping 21 matching lines @@
 
     // called by drawIndexed and drawNonIndexed. Use a negative indexCount to
     // indicate non-indexed drawing.
     bool checkDraw(GrPrimitiveType type, int startVertex,
                    int startIndex, int vertexCount,
                    int indexCount) const;
     // called when setting a new vert/idx source to unref prev vb/ib
     void releasePreviousVertexSource();
     void releasePreviousIndexSource();
 
+    // Makes a copy of the dst if it is necessary for the draw. Returns false if a copy is required
+    // but couldn't be made. Otherwise, returns true.
+    bool setupDstReadIfNecessary(DrawInfo* info);
+
     enum {
         kPreallocGeoSrcStateStackCnt = 4,
     };
     SkSTArray<kPreallocGeoSrcStateStackCnt, GeometrySrcState, true> fGeoSrcStateStack;
     const GrClipData*                                               fClip;
     GrDrawState*                                                    fDrawState;
     GrDrawState                                                     fDefaultDrawState;
     // The context owns us, not vice-versa, so this ptr is not ref'ed by DrawTarget.
     GrContext*                                                      fContext;
 
     typedef GrRefCnt INHERITED;
 };
 
 #endif