Use webrtc::DesktopCapturer for screen capturer implementation.

media/video/capture/screen/screen_capture_frame_queue.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 MEDIA_VIDEO_CAPTURE_SCREEN_SCREEN_CAPTURE_FRAME_QUEUE_H_
 #define MEDIA_VIDEO_CAPTURE_SCREEN_SCREEN_CAPTURE_FRAME_QUEUE_H_
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 
+namespace webrtc {
+class DesktopFrame;
+}  // namespace webrtc
+
 namespace media {
 
-class ScreenCaptureFrame;
-
 // Represents a queue of reusable video frames. Provides access to the 'current'
-// frame - the frame that the caller is working with at the moment, and to
-// the 'previous' frame - the predecessor of the current frame swapped by
-// DoneWithCurrentFrame() call, if any.
+// frame - the frame that the caller is working with at the moment, and to the
+// 'previous' frame - the predecessor of the current frame swapped by
+// MoveToNext() call, if any. Caller should use EmitCurrentFrame() to emit the

[alexeypa (please no reviews), 2013/05/08 22:24:59]

nit: MoveToNext() -> MoveToNextFrame()

[Sergey Ulanov, 2013/05/09 18:49:02]

Done.

+// current frame to the consumer.
 //
-// The caller is expected to (re)allocate frames if current_frame_needs_update()
-// is set. The caller can mark all frames in the queue for reallocation (when,
+// The caller is expected to (re)allocate frames if current_frame() returns
+// NULL. The caller can mark all frames in the queue for reallocation (when,
 // say, frame dimensions  change). The queue records which frames need updating

[alexeypa (please no reviews), 2013/05/08 22:24:59]

nit: "dimensions  change" -> "dimensions change"

[Sergey Ulanov, 2013/05/09 18:49:02]

Done.

 // which the caller can query.
+//
+// Frame consumer is expected to never holds more than kQueueLength frames
+// created by this function and it should release the earliest one before trying
+// to capture a new frame (i.e. before MoveToNextFrame() is called).
 class ScreenCaptureFrameQueue {
  public:
   ScreenCaptureFrameQueue();
   ~ScreenCaptureFrameQueue();
 
   // Moves to the next frame in the queue, moving the 'current' frame to become
   // the 'previous' one.
-  void DoneWithCurrentFrame();
+  void MoveToNextFrame();
+
+  // Emit the current frame to the consumer. Caller takes ownership of the
+  // result. The returned DesktopFrame object shares ownership of the underlying
+  // buffer with the queue.
+  webrtc::DesktopFrame* EmitCurrentFrame();
 
   // Replaces the current frame with a new one allocated by the caller.
   // The existing frame (if any) is destroyed.
-  void ReplaceCurrentFrame(scoped_ptr<ScreenCaptureFrame> frame);
+  void ReplaceCurrentFrame(scoped_ptr<webrtc::DesktopFrame> frame);
 
   // Marks all frames obsolete and resets the previous frame pointer. No
   // frames are freed though as the caller can still access them.
-  void SetAllFramesNeedUpdate();
+  void Reset();
 
-  ScreenCaptureFrame* current_frame() const {
-    return frames_[current_].get();
+  webrtc::DesktopFrame* current_frame() const {
+    return frames_[current_];
   }
 
-  bool current_frame_needs_update() const {
-    return !current_frame() || needs_update_[current_];
+  webrtc::DesktopFrame* previous_frame() const {
+    return frames_[(current_ + kQueueLength - 1) % kQueueLength];
   }
 
-  ScreenCaptureFrame* previous_frame() const { return previous_; }
+ private:
+  class EmittedFrame;
+  friend class EmittedFrame;
 
- private:
+  // Called by EmittedFrame when it's deleted.
+  void ReturnEmittedFrame(webrtc::DesktopFrame* frame, int index);
+
   // Index of the current frame.
   int current_;
 
   static const int kQueueLength = 2;
-  scoped_ptr<ScreenCaptureFrame> frames_[kQueueLength];
-
-  // True if the corresponding frame needs to be re-allocated.
-  bool needs_update_[kQueueLength];
-
-  // Points to the previous frame if any.
-  ScreenCaptureFrame* previous_;
+  webrtc::DesktopFrame* frames_[kQueueLength];
+  EmittedFrame* emitted_frames_[kQueueLength];
 
   DISALLOW_COPY_AND_ASSIGN(ScreenCaptureFrameQueue);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_VIDEO_CAPTURE_SCREEN_SCREEN_CAPTURE_FRAME_QUEUE_H_