[Chromoting] Improve DirectX capturer to support multiple outputs

webrtc/modules/desktop_capture/win/dxgi_context.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_CONTEXT_H_
+#define MODULES_DESKTOP_CAPTURE_WIN_DXGI_CONTEXT_H_
+
+#include <vector>
+
+#include "webrtc/modules/desktop_capture/desktop_region.h"
+
+namespace webrtc {
+
+class DxgiOutputContext {
+ private:
+  friend class DxgiOutputDuplicator;
+
+  // The updated region DxgiOutputDuplicator::DetectUpdatedRegion() output
+  // during last Duplicate() function call. It's a DesktopRegion translated by
+  // offset of each DxgiOutputDuplicator instance.
+  DesktopRegion updated_region_;
+};
+
+class DxgiAdapterContext {
+ private:
+  friend class DxgiAdapterDuplicator;
+
+  // Child DxgiOutputContext belongs to this DxgiAdapterContext.
+  std::vector<DxgiOutputContext> contexts_;

[Sergey Ulanov, 2016/07/30 00:49:22]

DxgiOutputDuplicator holds pointer to list of registered DxgiOutputContext
instances. std::vector<> may move the values from one place to another (e.g.
when a new value is added). I'm not sure if it's the problem right now, because
this vector is resized only when the contexts are not registered (at least as
far as I can tell). Still this approach is error-prone. I suggest replacing this
with std::vector<std::unique_ptr<DxgiOutputContext>> and making
DxgiOutputContext not movable/copyable (by adding a constructor).

[Hzj_jie, 2016/07/31 22:04:42]

DxgiAdapterContext::contexts_ won't change during its lifetime. I use a vector
here, just for its convenient resize function.

+};
+
+// A context to store the status of a single consumer of
+// DxgiDuplicatorController. Consumers should create an instance of DxgiContext
+// and keep it through their lifetime, and send it as parameter to
+// DxgiDuplicatorController Duplicate() functions. For details, please refer to
+// comments of DxgiDuplicatorController.
+class DxgiContext {

[Sergey Ulanov, 2016/07/30 00:49:22]

If you move this class to dxgi_duplicator_controller.h/cc then it would be
acceptable to have it friend with DxgiDuplicatorController. DxgiOutputContext
and DxgiAdapterContext won't need to have anything private as the ScreenCapturer
won't have access to the instances anyway. And I think you can move these
classes to the corresponding headers and remove this dxgi_context.h

[Hzj_jie, 2016/07/31 22:04:42]

Done.

+ public:
+  // Unregister this DxgiContext instance from all Dxgi duplicators during
+  // destructing.
+  ~DxgiContext();
+
+ private:
+  friend class DxgiDuplicatorController;
+
+  // A DxgiContext will have an exactly same |identity_| as
+  // DxgiDuplicatorController, to ensure it has been correctly setted up after
+  // each DxgiDuplicatorController::Initialize().
+  int identity_ = 0;
+
+  // Child DxgiAdapterContext belongs to this DxgiContext.
+  std::vector<DxgiAdapterContext> contexts_;
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_DESKTOP_CAPTURE_WIN_DXGI_CONTEXT_H_