[Chromoting] Improve DirectX capturer to support multiple outputs

webrtc/modules/desktop_capture/win/dxgi_adapter_duplicator.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_ADAPTER_DUPLICATOR_H_
+#define MODULES_DESKTOP_CAPTURE_WIN_DXGI_ADAPTER_DUPLICATOR_H_
+
+#include <wrl/client.h>
+
+#include <vector>
+
+#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_duplicator.h"
+
+namespace webrtc {
+
+// A container of DxgiDuplicators to duplicate monitors attached to a single
+// video card.
+class DxgiAdapterDuplicator {
+ public:
+  // Initializes the DxgiAdapterDuplicator from a D3dDevice. Caller must
+  // maintain the lifetime of input device to make sure it outlives this
+  // instance.
+  bool Initialize(const D3dDevice& device);
+
+  // Sequential calls Duplicate function of all the DxgiDuplicators owned by
+  // this instance.
+  bool Duplicate(DesktopFrame* target,
+                 const DesktopFrame* last_frame);
+
+  // Captures one screen and writes into target. If id < 0 or greater than
+  // screen_count(), this function returns false.
+  bool Duplicate(int id,
+                 DesktopFrame* target,
+                 const DesktopFrame* last_frame);
+
+  // Returns desktop rect covered by this DxgiAdapterDuplicator.
+  DesktopRect desktop_rect() const {
+    return desktop_rect_;
+  }
+
+  // Returns the size of one screen owned by this DxgiAdapterDuplicator. If id
+  // is less than zero, or greater than screen_count(), this function returns
+  // an empty DesktopRect.
+  DesktopRect ScreenRect(int id) const;
+
+  // Returns the count of screens owned by this DxgiAdapterDuplicator. i.e. the
+  // size of duplicators_. These screens can be retrieved by an interger in the
+  // range of [0, screen_count()).

[Sergey Ulanov, 2016/07/08 22:36:54]

I don't think we want to use [0,N) indices as identifiers. Problem is that these
ID will break whenever displays are reconfigured (e.g. monitor is disconnected).
There is HMONITOR in DXGI_OUTPUT_DESC. Can use use it to identify monitors?

[Hzj_jie, 2016/07/11 00:54:59]

We can surely use HMONITOR to identify monitor, but there is no relationship
between HMONITOR and IDXGIOutputDuplication. In DirectX duplication APIs,
HMONITOR is not used anywhere. (They look like the APIs built by two companies.)
So we cannot select an IDXGIOutputDuplication from an HMONITOR, and won't be
able to capture a single monitor by using an HMONITOR parameter.

Each time the display reconfigured, this list will be updated through
DxgiDuplicatorContainer::Prepare function. So it won't make too much trouble.

+  int screen_count() const {
+    return static_cast<int>(duplicators_.size());
+  }
+
+ private:
+  bool DoInitialize(const D3dDevice& device);
+
+  std::vector<DxgiDuplicator> duplicators_;
+  DesktopRect desktop_rect_;
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_DESKTOP_CAPTURE_WIN_DXGI_ADAPTER_DUPLICATOR_H_