Allow shaped-desktop hosts to send shape only when it changes.

remoting/client/frame_consumer.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 REMOTING_CLIENT_FRAME_CONSUMER_H_
 #define REMOTING_CLIENT_FRAME_CONSUMER_H_
 
 #include "base/basictypes.h"
 
 namespace webrtc {
 class DesktopFrame;
 class DesktopRect;
 class DesktopRegion;
 class DesktopSize;
 class DesktopVector;
 }  // namespace webrtc
 
 namespace remoting {
 
 class FrameConsumer {
  public:
 
   // List of supported pixel formats needed by various platforms.
   enum PixelFormat {
     FORMAT_BGRA,  // Used by the Pepper plugin.
     FORMAT_RGBA,  // Used for Android's Bitmap class.
   };
 
-  // Accepts a buffer to be painted to the screen. The buffer's dimensions and
-  // relative position within the frame are specified by |clip_area|. Only
-  // pixels falling within |region| and the current clipping area are painted.
-  // The function assumes that the passed buffer was scaled to fit a window
-  // having |view_size| dimensions.
+  // Paints the contents of |buffer| into the area of the view identified
+  // by |clip_area|. |view_size| specifies the full-frame dimensions to which
+  // the |buffer|/|clip_area| portion was scaled. Implementations may be
+  // optimized to only paint pixels within the intersection of |region| and
+  // |clip_area|. If |shape| is non-NULL then it specifies the complete shape
+  // of the frame, otherwise the frame is un-shaped.
   //
-  // N.B. Both |clip_area| and |region| are in output coordinates relative to
-  // the frame.
+  // N.B. |clip_area|, |region| and |shape| should be provided in output view
+  // coordinates.
   virtual void ApplyBuffer(const webrtc::DesktopSize& view_size,
                            const webrtc::DesktopRect& clip_area,
                            webrtc::DesktopFrame* buffer,
                            const webrtc::DesktopRegion& region,
-                           const webrtc::DesktopRegion& shape) = 0;
+                           const webrtc::DesktopRegion* shape) = 0;
 
   // Accepts a buffer that couldn't be used for drawing for any reason (shutdown
   // is in progress, the view area has changed, etc.). The accepted buffer can
   // be freed or reused for another drawing operation.
   virtual void ReturnBuffer(webrtc::DesktopFrame* buffer) = 0;
 
   // Set the dimension of the entire host screen.
   virtual void SetSourceSize(const webrtc::DesktopSize& source_size,
                              const webrtc::DesktopVector& dpi) = 0;
 
   // Returns the preferred pixel encoding for the platform.
   virtual PixelFormat GetPixelFormat() = 0;
 
  protected:
   FrameConsumer() {}
   virtual ~FrameConsumer() {}
 
  private:
   DISALLOW_COPY_AND_ASSIGN(FrameConsumer);
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_CLIENT_FRAME_CONSUMER_H_