Make SkImageFilter crop rects relative to the primitive origin, instead of relative to their parent

include/core/SkImageFilter.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 SkImageFilter_DEFINED
 #define SkImageFilter_DEFINED
 
@@ skipping 53 matching lines @@
     };
 
     /**
      *  Request a new (result) image to be created from the src image.
      *  If the src has no pixels (isNull()) then the request just wants to
      *  receive the config and width/height of the result.
      *
      *  The matrix is the current matrix on the canvas.
      *
      *  Offset is the amount to translate the resulting image relative to the
-     *  src when it is drawn.
+     *  src when it is drawn. This is an out-param.
      *
      *  If the result image cannot be created, return false, in which case both
      *  the result and offset parameters will be ignored by the caller.
      */
     bool filterImage(Proxy*, const SkBitmap& src, const SkMatrix& ctm,
                      SkBitmap* result, SkIPoint* offset);
 
     /**
      *  Given the src bounds of an image, this returns the bounds of the result
      *  image after the filter has been applied.
@@ skipping 75 matching lines @@
      *  Constructs a new SkImageFilter read from an SkFlattenableReadBuffer object.
      *
      *  @param inputCount    The exact number of inputs expected for this SkImageFilter object.
      *                       -1 can be used if the filter accepts any number of inputs.
      *  @param rb            SkFlattenableReadBuffer object from which the SkImageFilter is read.
      */
     explicit SkImageFilter(int inputCount, SkFlattenableReadBuffer& rb);
 
     virtual void flatten(SkFlattenableWriteBuffer& wb) const SK_OVERRIDE;
 
-    // Default impl returns false
+    /**
+     *  This is the virtual which should be overridden by the derived class
+     *  to perform image filtering.
+     *
+     *  src is the original primitive bitmap. If the filter has a connected
+     *  input, it should recurse on that input and use that in place of src.
+     *
+     *  The matrix is the current matrix on the canvas.
+     *
+     *  Offset is the amount to translate the resulting image relative to the
+     *  src when it is drawn. This is an out-param.
+     *
+     *  If the result image cannot be created, this should false, in which
+     *  case both the result and offset parameters will be ignored by the
+     *  caller.
+     */
     virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
                                SkBitmap* result, SkIPoint* offset);
     // Default impl copies src into dst and returns true
     virtual bool onFilterBounds(const SkIRect&, const SkMatrix&, SkIRect*);
 
     // Applies "matrix" to the crop rect, and sets "rect" to the intersection of
     // "rect" and the transformed crop rect. If there is no overlap, returns
     // false and leaves "rect" unchanged.
     bool applyCropRect(SkIRect* rect, const SkMatrix& matrix) const;
 
@@ skipping 18 matching lines @@
                              const SkIRect& bounds) const;
 
 private:
     typedef SkFlattenable INHERITED;
     int fInputCount;
     SkImageFilter** fInputs;
     CropRect fCropRect;
 };
 
 #endif