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 59 matching lines @@
     */
     virtual int height() const = 0;
 
     /** Return the image properties of the device. */
     virtual const SkDeviceProperties& getDeviceProperties() const {
         //Currently, all the properties are leaky.
         return fLeakyProperties;
     }
 
     /**
+     *  Return ImageInfo for this device. If the canvas is not backed by pixels
+     *  (cpu or gpu), then the info's ColorType will be kUnknown_SkColorType.
+     */
+    virtual SkImageInfo imageInfo() const;
+    
+
+    /**
      *  Return the bounds of the device in the coordinate space of the root
      *  canvas. The root device will have its top-left at 0,0, but other devices
      *  such as those associated with saveLayer may have a non-zero origin.
      */
     void getGlobalBounds(SkIRect* bounds) const {
         SkASSERT(bounds);
         const SkIPoint& origin = this->getOrigin();
         bounds->setXYWH(origin.x(), origin.y(), this->width(), this->height());
     }
 
@@ skipping 272 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