[Chromoting] Improve DirectX capturer to support multiple outputs

webrtc/modules/desktop_capture/win/d3d_device.cc

+/*
+ *  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.
+ */
+
+#include "webrtc/modules/desktop_capture/win/d3d_device.h"
+
+#include "webrtc/system_wrappers/include/logging.h"
+
+namespace webrtc {
+
+using Microsoft::WRL::ComPtr;
+
+bool D3dDevice::Initialize(const ComPtr<IDXGIAdapter>& adapter) {
+  dxgi_adapter_ = adapter;
+  if (!dxgi_adapter_) {
+    LOG(LS_WARNING) << "An empty IDXGIAdapter instance has been received.";
+    return false;
+  }
+
+  D3D_FEATURE_LEVEL feature_level;
+  _com_error error = D3D11CreateDevice(
+      adapter.Get(), D3D_DRIVER_TYPE_UNKNOWN, nullptr,
+      D3D11_CREATE_DEVICE_BGRA_SUPPORT | D3D11_CREATE_DEVICE_SINGLETHREADED,
+      nullptr, 0, D3D11_SDK_VERSION, d3d_device_.GetAddressOf(), &feature_level,
+      context_.GetAddressOf());
+  if (error.Error() != S_OK || !d3d_device_ || !context_) {
+    LOG(LS_WARNING) << "D3D11CreateDeivce returns error "
+                    << error.ErrorMessage() << " with code " << error.Error();
+    return false;
+  }
+
+  if (feature_level < D3D_FEATURE_LEVEL_11_0) {
+    LOG(LS_WARNING) << "D3D11CreateDevice returns an instance without DirectX "
+                       "11 support, level "
+                    << feature_level;
+    return false;
+  }
+
+  error = _com_error(d3d_device_.As(&dxgi_device_));
+  if (error.Error() != S_OK || !dxgi_device_) {
+    LOG(LS_WARNING) << "ID3D11Device is not an implementation of IDXGIDevice, "
+                       "this usually means the system does not support DirectX "
+                       "11";
+    return false;
+  }
+
+  return true;
+}
+
+/* static */ std::vector<D3dDevice> D3dDevice::EnumDevices() {

[Sergey Ulanov, 2016/07/08 22:36:53]

Normally we use the following style for static comments like this:

// static
void foo() ..

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

Done.

+  ComPtr<IDXGIFactory1> factory;
+  _com_error error = _com_error(CreateDXGIFactory1(__uuidof(IDXGIFactory1),
+      reinterpret_cast<void**>(factory.GetAddressOf())));
+  if (error.Error() == S_OK && factory) {
+    std::vector<D3dDevice> result;
+    for (int i = 0;; i++) {
+      ComPtr<IDXGIAdapter> adapter;
+      error = _com_error(factory->EnumAdapters(i, adapter.GetAddressOf()));
+      if (error.Error() == S_OK) {
+        result.emplace_back();

[Sergey Ulanov, 2016/07/08 22:36:53]

emplace_back() is discouraged, see https://chromium-cpp.appspot.com/ .

Here it looks strange because you don't pass any parameters to the constructor.
I think it would be cleaner to initialize D3dDevice first, and then push_back()
it to the container.

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

Done.

+        if (!result.back().Initialize(adapter)) {
+          return std::vector<D3dDevice>();
+        }
+      } else if (error.Error() == DXGI_ERROR_NOT_FOUND) {
+        return result;

[Sergey Ulanov, 2016/07/08 22:36:53]

break; and then return result at the end. 

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

Done.

+      } else {
+        return std::vector<D3dDevice>();

[Sergey Ulanov, 2016/07/08 22:36:53]

log the error?

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

Done.

+      }
+    }
+  } else {
+    return std::vector<D3dDevice>();

[Sergey Ulanov, 2016/07/08 22:36:53]

move error handling to the beginning

if (error.Error() != S_OK || !factory) {
  return std::vector<D3dDevice>();
}

// enumerate devices here

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

Done.

+  }
+}
+
+}  // namespace webrtc