[Chromoting] Improve DirectX capturer to support multiple outputs

webrtc/modules/desktop_capture/win/dxgi_duplicator_container.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 MODULES_DESKTOP_CAPTURE_WIN_DXGI_DUPLICATOR_CONTAINER_H_
+#define MODULES_DESKTOP_CAPTURE_WIN_DXGI_DUPLICATOR_CONTAINER_H_
+
+#include <vector>
+
+#include "webrtc/base/criticalsection.h"
+#include "webrtc/modules/desktop_capture/desktop_frame.h"
+#include "webrtc/modules/desktop_capture/desktop_geometry.h"
+#include "webrtc/modules/desktop_capture/desktop_region.h"
+#include "webrtc/modules/desktop_capture/win/d3d_device.h"
+#include "webrtc/modules/desktop_capture/win/dxgi_adapter_duplicator.h"
+#include "webrtc/modules/desktop_capture/win/dxgi_context.h"
+
+namespace webrtc {
+
+// A container for all the objects we need to call Windows DirectX based capture
+// APIs. Note, one application can only have one IDXGIOutputDuplication instance
+// per output, so this class should be singleton.
+//
+// Consumers should create a DxgiContext and keep it through their lifetime.
+// Calls Prepare() function with the DxgiContext before each Duplicate()
+// function calls. If a previous Prepare() function call returns true, but a
+// later one returns false, this usually means the display mode is changing.
+// Consumers should retry after a while. (Typically 50 milliseconds, but
+// according to hardware performance, this time may be various.)
+//
+// This implementation is typically for ScreenCapturer(s) with double buffering,
+// such as ScreenCapturerWinDirectx. And it should work with consumers with one
+// buffer, i.e. Consumers can always send nullptr for |last_frame|. Some minor
+// changes in DxgiOutputDuplicator class are nice to have to reduce size of data
+// to copy (Commented in dxgi_output_duplicator.cc). But this class won't work
+// with three or more buffers, the updated region merging logic will be broken
+// in such scenarios.
+class DxgiDuplicatorContainer {

[Sergey Ulanov, 2016/07/28 22:15:32]

Maybe call this DxgiDuplicatorController to make the purpose cleaner.

[Hzj_jie, 2016/07/29 02:12:23]

Done.

+ public:
+  // Creates or retrieves the singleton instance of DxgiDuplicatorContainer.
+  static DxgiDuplicatorContainer* Instance();
+
+  // Destructs current instance. We need to make sure COM components and their
+  // containers are destructed in correct order.
+  ~DxgiDuplicatorContainer();
+
+  // Initializes all the components and updates |context|. This function equals
+  // to call Prepare() and Setup(DxgiContext*) sequentially.
+  bool Prepare(DxgiContext* context);
+
+  // Initializes all the components. Returns false if system does not support
+  // DirectX based capture, or system resource is not enough to support to
+  // capture all monitors. By default, only four applications can capture the
+  // screen with DirectX based capture simultaneously. Returns true if this
+  // instance has been initialized already.
+  bool Prepare();
+
+  // Captures current screen and writes into target. Since we are using double
+  // buffering, |last_frame|.updated_region() is used to represent the not
+  // updated regions in current |target| frame, which should also be copied this
+  // time.
+  // TODO(zijiehe): Windows cannot guarantee the frames returned by each
+  // IDXGIOutputDuplication are synchronized. But we are using a totally
+  // different threading model than the way Windows suggested, it's hard to
+  // synchronize them manually. But we should find a way to do it.
+  bool Duplicate(DxgiContext* context,
+                 DesktopFrame* target,
+                 const DesktopFrame* last_frame);
+
+  // Captures one screen and writes into target. If id < 0 or greater than
+  // the total screen count of all the Duplicators, this function returns false.
+  bool Duplicate(DxgiContext* context,
+                 int id,
+                 DesktopFrame* target,
+                 const DesktopFrame* last_frame);
+
+  DesktopVector dpi() const { return dpi_; }
+
+  // Returns entire desktop size.
+  DesktopRect desktop_rect() const { return desktop_rect_; }
+
+  // Returns a DesktopSize to cover entire desktop_rect. This may be different
+  // than desktop_rect().size(), since top-left screen does not need to start
+  // from (0, 0).
+  DesktopSize desktop_size() const {
+    return DesktopSize(desktop_rect_.right(), desktop_rect_.bottom());
+  }
+
+  // Returns the size of one screen. If id < 0 or greater than the total screen
+  // count of all the Duplicators, this function returns an empty DesktopRect.
+  DesktopRect ScreenRect(int id) const;
+
+  // Returns the count of screens on the system. These screens can be retrieved
+  // by an integer in the range of [0, ScreenCount()).
+  int ScreenCount() const;
+
+ private:
+  // DxgiContext calls private Unregister(DxgiContext*) function during
+  // destructing.
+  friend class DxgiContext;
+
+  // A class to allow only one thread to enter. This class is used to make sure
+  // only one Initialize function call is being performed.
+  class SingleEntry {
+   public:
+    bool Enter();
+    void Exit();
+    bool Hold() const;
+
+   private:
+    rtc::CriticalSection lock_;
+    bool entered_ = false;
+  };
+
+  // A helper class to execute SingleEntry::Exit in its destructor.
+  class AutoExit;
+
+  // A private constructor to ensure consumers to use
+  // DxgiDuplicatorContainer::Instance().
+  DxgiDuplicatorContainer();
+
+  // A helper function to check whether a DxgiContext has been expired. This
+  // function should be called in lock_ locked scope.
+  bool DxgiContextExpired(const DxgiContext* const context) const;
+
+  // Updates DxgiContext if needed.
+  void Setup(DxgiContext* context);
+
+  // Unregisters DxgiContext from this instance and all DxgiAdapterDuplicator(s)
+  // it owns.
+  void Unregister(const DxgiContext* const context);
+
+  // Does the real initialization work.
+  bool DoInitialize();
+
+  // Clears all COM components referred by this instance. So next Prepare()
+  // call will eventually initialize this instance again.
+  void Deinitialize();
+
+  rtc::CriticalSection lock_;
+  SingleEntry initializing_;
+
+  // A self-incremented integer to compare with the one in DxgiContext, to
+  // ensure a DxgiContext has been initialized after DxgiDuplicatorContainer.
+  int identity_ = 0;
+  DesktopRect desktop_rect_;
+  DesktopVector dpi_;
+  std::vector<DxgiAdapterDuplicator> duplicators_;
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_DESKTOP_CAPTURE_WIN_DXGI_DUPLICATOR_CONTAINER_H_