add peekPixels to canvas

include/core/SkDevice.h

 
 /*
  * Copyright 2010 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkDevice_DEFINED
@@ skipping 351 matching lines @@
     virtual bool filterImage(const SkImageFilter*, const SkBitmap&, const SkMatrix&,
                              SkBitmap* result, SkIPoint* offset) = 0;
 
     // This is equal kBGRA_Premul_Config8888 or kRGBA_Premul_Config8888 if
     // either is identical to kNative_Premul_Config8888. Otherwise, -1.
     static const SkCanvas::Config8888 kPMColorAlias;
 
 protected:
     // default impl returns NULL
     virtual SkSurface* newSurface(const SkImageInfo&);
-
+    
+    // default impl returns NULL
+    virtual const void* peekPixels(SkImageInfo*, size_t* rowBytes);
+    
     /**
      *  Leaky properties are those which the device should be applying but it isn't.
      *  These properties will be applied by the draw, when and as it can.
      *  If the device does handle a property, that property should be set to the identity value
      *  for that property, effectively making it non-leaky.
      */
     SkDeviceProperties fLeakyProperties;
 
 private:
     friend class SkCanvas;
@@ skipping 35 matching lines @@
     SkMetaData* fMetaData;
 
 #ifdef SK_DEBUG
     bool        fAttachedToCanvas;
 #endif
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif