[Chromoting] Implement DualBufferFrameConsumer

remoting/client/dual_buffer_frame_consumer.h

+// Copyright 2016 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_DUAL_BUFFER_FRAME_CONSUMER_H_
+#define REMOTING_CLIENT_DUAL_BUFFER_FRAME_CONSUMER_H_
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/single_thread_task_runner.h"
+#include "base/threading/thread_checker.h"
+#include "remoting/protocol/frame_consumer.h"
+#include "third_party/webrtc/modules/desktop_capture/desktop_region.h"
+
+namespace webrtc {
+class SharedDesktopFrame;
+}  // namespace webrtc
+
+namespace remoting {
+
+// This class continuously uses two BasicDesktopFrame as buffer for decoding
+// updated regions until the resolution is changed.
+// This class should be used and destroyed on the same thread. If |task_runner|
+// is null |callback| will be run directly upon the stack of DrawFrame,
+// otherwise a task will be posted to feed the callback on the thread of
+// |task_runner|.
+// Only areas bound by updated_region() on the buffer are considered valid to
+// |callback|. Please use RequestFullDesktopFrame() if you want to get a full
+// desktop frame.
+class DualBufferFrameConsumer : public protocol::FrameConsumer {
+ public:
+  DualBufferFrameConsumer(
+      base::Callback<void(std::unique_ptr<webrtc::DesktopFrame>)> callback,
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner,
+      PixelFormat format);
+  ~DualBufferFrameConsumer() override;
+
+  // Feeds the callback on the right thread with a BasicDesktopFrame that merges
+  // updates from buffer_[0] and buffer_[1]. Do nothing if no updates have
+  // received yet.
+  void RequestFullDesktopFrame();
+
+  // FrameConsumer interface.
+  std::unique_ptr<webrtc::DesktopFrame> AllocateFrame(
+      const webrtc::DesktopSize& size) override;
+  void DrawFrame(std::unique_ptr<webrtc::DesktopFrame> frame,
+                 const base::Closure& done) override;
+  PixelFormat GetPixelFormat() override;
+
+  base::WeakPtr<DualBufferFrameConsumer> GetWeakPtr();
+
+ private:
+  void RunRenderCallback(std::unique_ptr<webrtc::DesktopFrame> frame,
+                 const base::Closure& done);
+  void OnFrameRendered(const base::Closure& done);
+
+  std::unique_ptr<webrtc::SharedDesktopFrame> buffers_[2];
+  webrtc::DesktopRegion buffer_1_mask_;

[Yuwei, 2016/07/21 19:00:32]

I'll add some comment here.

[Yuwei, 2016/07/22 03:38:22]

Done.

+  int current_buffer_ = 0;
+
+  base::Callback<void(std::unique_ptr<webrtc::DesktopFrame>)> callback_;
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  PixelFormat pixel_format_;
+  base::ThreadChecker thread_checker_;
+  base::WeakPtr<DualBufferFrameConsumer> weak_ptr_;
+  base::WeakPtrFactory<DualBufferFrameConsumer> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(DualBufferFrameConsumer);
+};
+
+}  // namespace remoting
+#endif  // REMOTING_CLIENT_DUAL_BUFFER_FRAME_CONSUMER_H_