Implement crop rect for SkImageFilter

include/core/SkImageFilter.h

Index: include/core/SkImageFilter.h
diff --git a/include/core/SkImageFilter.h b/include/core/SkImageFilter.h
index fe383ae9e316d632ce04eb15efdd0b40efeeb46c..e467761a1f0607e2ce244003be132c295c4f9874 100644
--- a/include/core/SkImageFilter.h
+++ b/include/core/SkImageFilter.h
@@ -9,13 +9,13 @@
 #define SkImageFilter_DEFINED
 
 #include "SkFlattenable.h"
+#include "SkRect.h"
 
 class SkBitmap;
 class SkColorFilter;
 class SkDevice;
 class SkMatrix;
 struct SkIPoint;
-struct SkIRect;
 class SkShader;
 class GrEffectRef;
 class GrTexture;
@@ -139,14 +139,25 @@ public:
         return fInputs[i];
     }
 
+    /**
+     *  Returns the crop rectangle of this filter. This is set at construction
+     *  time, and determines which pixels from the input image will
+     *  be processed. The size of this rectangle should be used as the size
+     *  of the destination image. The origin of this rect should be used to
+     *  offset access to the input images, and should also be added to the
+     *  "offset" parameter in onFilterImage and filterImageGPU(). (The latter
+     *  ensures that the resulting buffer is drawn in the correct location.)
+     */
+    const SkIRect& cropRect() const { return fCropRect; }
+
 protected:
-    SkImageFilter(int inputCount, SkImageFilter** inputs);
+    SkImageFilter(int inputCount, SkImageFilter** inputs, const SkIRect* cropRect = NULL);
 
     // Convenience constructor for 1-input filters.
-    explicit SkImageFilter(SkImageFilter* input);
+    explicit SkImageFilter(SkImageFilter* input, const SkIRect* cropRect = NULL);
 
     // Convenience constructor for 2-input filters.
-    SkImageFilter(SkImageFilter* input1, SkImageFilter* input2);
+    SkImageFilter(SkImageFilter* input1, SkImageFilter* input2, const SkIRect* cropRect = NULL);
 
     virtual ~SkImageFilter();
 
@@ -160,10 +171,15 @@ protected:
     // Default impl copies src into dst and returns true
     virtual bool onFilterBounds(const SkIRect&, const SkMatrix&, SkIRect*);
 
+    // Sets rect to the intersection of rect and the crop rect. If there
+    // is no overlap, returns false and leaves rect unchanged.
+    bool applyCropRect(SkIRect* rect) const;
+
 private:
     typedef SkFlattenable INHERITED;
     int fInputCount;
     SkImageFilter** fInputs;
+    SkIRect fCropRect;
 };
 
 #endif