DirectX based screen capturer logic

webrtc/modules/desktop_capture/win/desktop_frame_win_dxgi.h

+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MODULES_DESKTOP_CAPTURE_WIN_DESKTOP_FRAME_WIN_DXGI_H_
+#define WEBRTC_MODULES_DESKTOP_CAPTURE_WIN_DESKTOP_FRAME_WIN_DXGI_H_
+
+#include <windows.h>
+
+#include <windef.h>
+#include <wrl/client.h>
+
+#include <memory>
+#include <vector>
+
+#include <D3D11.h>
+#include <DXGI.h>
+#include <DXGI1_2.h>
+
+#include "webrtc/modules/desktop_capture/desktop_frame.h"
+#include "webrtc/modules/desktop_capture/desktop_geometry.h"
+
+namespace webrtc {
+
+// DesktopFrame implementation used by screen captures on Windows.
+// Frame data is stored in the IDXGISurface instance and also the SharedMemory.
+// Since Windows does not allow to share memory between a file mapping and
+// IDXGIResource.
+// To avoid memory recreation in ID3D11Texture2D, we reuse DesktopFrameWinDxgi
+// instance. So a Capture function is added.
+// Capture function is thread unsafe.
+class DesktopFrameWinDxgi : public DesktopFrame {
+ public:
+  virtual ~DesktopFrameWinDxgi();
+
+  // Initialize device and context for further use. Thread unsafe.
+  static void Initialize(ID3D11Device* device, ID3D11DeviceContext* context);
+
+  // Creates a DesktopFrameWinDxgi instance, returns nullptr when memory
+  // allocation failed.
+  static std::unique_ptr<DesktopFrameWinDxgi> Create(
+      DesktopSize size,
+      SharedMemoryFactory* shared_memory_factory);
+
+  uint8_t* data() const override { return rect_.pBits; }

[Sergey Ulanov, 2016/04/08 21:22:26]

virtual methods should not be inlined, but I don't think you need to override it
here. Just initialize DesktopFrame with the correct pointer to the buffer.

[Hzj_jie, 2016/04/11 22:19:16]

Done.

+
+  // Captures a frame represented by frame_info and resource. Returns false if
+  // anything wrong.
+  // Before the first Capture is called, this instance is still workable, but
+  // the data in underlying buffer (SharedMemory) is undefined.
+  bool Capture(const DXGI_OUTDUPL_FRAME_INFO& frame_info,

[Sergey Ulanov, 2016/04/08 21:22:26]

DesktopFrame is supposed to be a dumb holder of the frame. I don't think that
the capture logic belongs here.

[Hzj_jie, 2016/04/11 22:19:16]

The reason to leave capture logic here is because DesktopFrameWinDxgi holds an
instance of ID3D11Texture2D, which contains a large memory buffer we do not want
to reallocate for each frame. As I have mentioned in ScreenCapturerWinDirectX.

+               IDXGIResource* resource);
+
+ private:
+  DesktopFrameWinDxgi(DesktopSize size,
+                      int stride,
+                      SharedMemory* shared_memory);
+
+  // Initializes stage_ from a CPU inaccessible IDXGIResource.
+  // Returns false if it fails to execute windows api.
+  bool CreateTexture(ID3D11Texture2D* texture);
+
+  // Update during Capture (CreateTexture).
+  Microsoft::WRL::ComPtr<ID3D11Texture2D> stage_;
+  Microsoft::WRL::ComPtr<IDXGISurface> surface_;
+  // Always be the mapped rectangle or empty.
+  DXGI_MAPPED_RECT rect_;
+
+  RTC_DISALLOW_COPY_AND_ASSIGN(DesktopFrameWinDxgi);
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_WIN_DESKTOP_FRAME_WIN_DXGI_H_