Support copying a partial rectangle region from the compositing surface on Aura and GTK.

content/common/gpu/client/gl_helper.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_COMMON_GPU_CLIENT_GL_HELPER_H_
 #define CONTENT_COMMON_GPU_CLIENT_GL_HELPER_H_
 
 #include "base/atomicops.h"
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/platform/WebGraphicsContext3D.h"
 
 namespace gfx {
+class Rect;
 class Size;
 }
 
 namespace content {
 
 // Provides higher level operations on top of the WebKit::WebGraphicsContext3D
 // interfaces.
 class GLHelper {
  public:
   GLHelper(WebKit::WebGraphicsContext3D* context,
            WebKit::WebGraphicsContext3D* context_for_thread);
   virtual ~GLHelper();
 
   WebKit::WebGraphicsContext3D* context() const;
 
-  // Copies the contents of |src_texture| with the size of |src_size| into
-  // |out|. The contents is transformed so that it fits in |dst_size|.
-  // |callback| is invoked with the copy result when the copy operation has
-  //  completed.
+  // Copies the block of pixels specified with |src_subrect| from |src_texture|,
+  // scales it to |dst_size|, and writes it into |out|.
+  // |src_size| is the size of |src_texture|. |callback| is invoked with the
+  // copy result when the copy operation has completed.
   void CopyTextureTo(WebKit::WebGLId src_texture,
                      const gfx::Size& src_size,
+                     const gfx::Rect& src_subrect,
                      const gfx::Size& dst_size,
                      unsigned char* out,
                      const base::Callback<void(bool)>& callback);
 
   // Returns the shader compiled from the source.
   WebKit::WebGLId CompileShaderFromSource(const WebKit::WGC3Dchar* source,
                                           WebKit::WGC3Denum type);
 
  private:
   class CopyTextureToImpl;
 
   WebKit::WebGraphicsContext3D* context_;
   WebKit::WebGraphicsContext3D* context_for_thread_;
   scoped_ptr<CopyTextureToImpl> copy_texture_to_impl_;
 
   // The number of all GLHelper instances.
   static base::subtle::Atomic32 count_;
 
   DISALLOW_COPY_AND_ASSIGN(GLHelper);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_GPU_CLIENT_GL_HELPER_H_