fix slowness of getImageData() for CanvasRenderingContext2D in linux due to un-optimized format for…

src/gpu/GrGpu.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 GrGpu_DEFINED
@@ skipping 134 matching lines @@
     void resolveRenderTarget(GrRenderTarget* target);
 
     /**
      * Ensures that the current render target is actually set in the
      * underlying 3D API. Used when client wants to use 3D API to directly
      * render to the RT.
      */
     void forceRenderTargetFlush();
 
     /**
-     * Gets a preferred 8888 config to use for writing / reading pixel data. The returned config
-     * must have at least as many bits per channel as the config param.
+     * Gets a preferred 8888 config to use for writing/reading pixel data to/from a surface with
+     * config surfaceConfig. The returned config must have at least as many bits per channel as the
+     * readConfig or writeConfig param.
      */
-    virtual GrPixelConfig preferredReadPixelsConfig(GrPixelConfig config) const { return config; }
-    virtual GrPixelConfig preferredWritePixelsConfig(GrPixelConfig config) const { return config; }
+    virtual GrPixelConfig preferredReadPixelsConfig(GrPixelConfig readConfig,
+                                                    GrPixelConfig surfaceConfig) const {
+        return readConfig;
+    }
+    virtual GrPixelConfig preferredWritePixelsConfig(GrPixelConfig writeConfig,
+                                                     GrPixelConfig surfaceConfig) const {
+        return writeConfig;
+    }
 
     /**
      * Called before uploading writing pixels to a GrTexture when the src pixel config doesn't
      * match the texture's config.
      */
     virtual bool canWriteTexturePixels(const GrTexture*, GrPixelConfig srcConfig) const = 0;
 
     /**
      * OpenGL's readPixels returns the result bottom-to-top while the skia
      * API is top-to-bottom. Thus we have to do a y-axis flip. The obvious
@@ skipping 354 matching lines @@
     mutable GrIndexBuffer*                                              fQuadIndexBuffer;
     bool                                                                fContextIsDirty;
     // Used to abandon/release all resources created by this GrGpu. TODO: Move this
     // functionality to GrResourceCache.
     ResourceList                                                        fResourceList;
 
     typedef GrDrawTarget INHERITED;
 };
 
 #endif