[Chromoting] Improve DirectX capturer to support multiple outputs

webrtc/modules/desktop_capture/win/dxgi_duplicator_container.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/dxgi_duplicator_container.h"
+
+#include <windows.h>
+
+#include <algorithm>
+
+#include "webrtc/base/checks.h"
+
+namespace webrtc {
+
+bool DxgiDuplicatorContainer::SingleEntry::Enter() {
+  rtc::CritScope lock(&lock_);
+  if (entered_) {
+    return false;
+  }
+  entered_ = true;
+  return true;
+}
+
+void DxgiDuplicatorContainer::SingleEntry::Exit() {
+  rtc::CritScope lock(&lock_);
+  RTC_DCHECK(entered_);
+  entered_ = false;
+}
+
+bool DxgiDuplicatorContainer::SingleEntry::Hold() const {
+  rtc::CritScope lock(&lock_);
+  return entered_;
+}
+
+class DxgiDuplicatorContainer::AutoExit {
+ public:
+  explicit AutoExit(DxgiDuplicatorContainer::SingleEntry* gate) : gate_(gate) {
+    RTC_DCHECK(gate_);
+  }
+
+  ~AutoExit() { gate_->Exit(); }
+
+ private:
+  DxgiDuplicatorContainer::SingleEntry* gate_;
+};
+
+// static
+DxgiDuplicatorContainer* DxgiDuplicatorContainer::Instance() {
+  // The static instance won't be deleted to ensure it can be used by other
+  // threads even during program exiting.
+  static DxgiDuplicatorContainer* instance = new DxgiDuplicatorContainer();
+  return instance;
+}
+
+DxgiDuplicatorContainer::DxgiDuplicatorContainer() = default;
+
+DxgiDuplicatorContainer::~DxgiDuplicatorContainer() {
+  rtc::CritScope lock(&lock_);
+  Deinitialize();
+}
+
+bool DxgiDuplicatorContainer::Prepare(DxgiContext* context) {
+  if (Prepare()) {
+    Setup(context);
+    return true;
+  }
+  return false;
+}
+
+bool DxgiDuplicatorContainer::Prepare() {
+  // If the instance has been initialized already, does nothing and returns
+  // true.
+  {
+    rtc::CritScope lock(&lock_);
+    if (!duplicators_.empty()) {
+      return true;
+    }
+  }
+
+  if (initializing_.Enter()) {

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

Looking at this again I'm still not sure you really need to add new
synchronization primitives, given that you have the global |lock_|. 
Can this function just acquire the lock and initialize with the lock held, e.g.:

rtc::CritScope lock(&lock_);
if (!duplicators_.empty())
  return true;  // already initialized.

if (!DoInitialize()) {
  // Failed.
  Deinitialize();
  return false; 
}

return true;

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

Yes, I was wrong, this logic is out-of-date. As we are always Deinitialize() if
last Duplicate() function failed.

+    AutoExit exit(&initializing_);
+    rtc::CritScope lock(&lock_);
+    if (!duplicators_.empty()) {
+      // Another thread has initialized this instance before this thread reaches
+      // line initializing_.Enter(), so does nothing and returns true.
+      return true;
+    }
+
+    if (DoInitialize()) {
+      return true;
+    }
+
+    Deinitialize();
+    return false;
+  } else {
+    // Some other thread is initializing, wait for its finish and check the
+    // result.
+    while (initializing_.Hold()) {
+      rtc::CritScope lock(&lock_);
+    }
+    rtc::CritScope lock(&lock_);
+    return !duplicators_.empty();
+  }
+}
+
+bool DxgiDuplicatorContainer::DxgiContextExpired(
+    const DxgiContext* const context) const {
+  return context->identity_ != identity_ ||
+         context->contexts_.size() != duplicators_.size();
+}
+
+void DxgiDuplicatorContainer::Setup(DxgiContext* context) {
+  rtc::CritScope lock(&lock_);
+  if (duplicators_.empty()) {
+    // The most recent initialization has failed. So we do not waste time to
+    // setup DxgiContext, it will be setup again later.
+    return;
+  }
+  if (DxgiContextExpired(context)) {
+    context->contexts_.clear();
+    context->contexts_.resize(duplicators_.size());
+    for (size_t i = 0; i < duplicators_.size(); i++) {
+      duplicators_[i].Setup(&context->contexts_[i]);
+    }
+    context->identity_ = identity_;
+  }
+}
+
+void DxgiDuplicatorContainer::Unregister(const DxgiContext* const context) {
+  rtc::CritScope lock(&lock_);
+  if (DxgiContextExpired(context)) {
+    // The DxgiContext has not been setup after a recent initialization, so it
+    // should not been registered in duplicators.
+    return;
+  }
+  for (size_t i = 0; i < duplicators_.size(); i++) {
+    duplicators_[i].Unregister(&context->contexts_[i]);
+  }
+}
+
+void DxgiDuplicatorContainer::Deinitialize() {
+  desktop_rect_ = DesktopRect();
+  duplicators_.clear();
+}
+
+bool DxgiDuplicatorContainer::DoInitialize() {
+  RTC_DCHECK(desktop_rect_.is_empty());
+  RTC_DCHECK(duplicators_.empty());
+
+  std::vector<D3dDevice> devices = D3dDevice::EnumDevices();
+  if (devices.empty()) {
+    return false;
+  }
+
+  for (size_t i = 0; i < devices.size(); i++) {
+    duplicators_.emplace_back(devices[i]);

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

Please don't use push_back() instead of emplace_back()

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

Oh, this emplace_back is expected, as devices[i] is the constructor parameter of
DxgiAdapterDuplicator.

+    if (!duplicators_.back().Initialize()) {
+      return false;
+    }
+    if (desktop_rect_.is_empty()) {
+      desktop_rect_ = duplicators_.back().desktop_rect();
+    } else {
+      const DesktopRect& left = desktop_rect_;
+      const DesktopRect& right = duplicators_.back().desktop_rect();
+      desktop_rect_ =
+          DesktopRect::MakeLTRB(std::min(left.left(), right.left()),
+                                std::min(left.top(), right.top()),
+                                std::max(left.right(), right.right()),
+                                std::max(left.bottom(), right.bottom()));
+    }
+  }
+
+  HDC hdc = GetDC(nullptr);
+  // Use old DPI value if failed.
+  if (hdc != nullptr) {

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

nit: s/ != nullptr//

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

Done.

+    dpi_.set(GetDeviceCaps(hdc, LOGPIXELSX), GetDeviceCaps(hdc, LOGPIXELSY));
+    ReleaseDC(nullptr, hdc);
+  }
+
+  identity_++;
+  return true;
+}
+
+DesktopRect DxgiDuplicatorContainer::ScreenRect(int id) const {
+  RTC_DCHECK(id >= 0);
+  rtc::CritScope lock(&lock_);
+  for (size_t i = 0; i < duplicators_.size(); i++) {
+    if (id >= duplicators_[i].screen_count()) {
+      id -= duplicators_[i].screen_count();
+    } else {
+      return duplicators_[i].ScreenRect(id);
+    }
+  }
+  return DesktopRect();
+}
+
+int DxgiDuplicatorContainer::ScreenCount() const {
+  rtc::CritScope lock(&lock_);
+  int result = 0;
+  for (auto& duplicator : duplicators_) {
+    result += duplicator.screen_count();
+  }
+  return result;
+}
+
+bool DxgiDuplicatorContainer::Duplicate(DxgiContext* context,
+                                        DesktopFrame* target,
+                                        const DesktopFrame* last_frame) {
+  RTC_DCHECK(target);
+  if (last_frame != nullptr && !target->size().equals(last_frame->size())) {

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

nit: s/last_frame != nullptr/last_frame/

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

Replace with a DCHECK()

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

Done.

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

Returns false here can help consumers to decide whether release all existing
frames are required. Considering on a single monitor system, switching from full
screen to an individual monitor does not really need to recreate all frames.

+    return false;
+  }
+  target->mutable_updated_region()->Clear();
+  rtc::CritScope lock(&lock_);
+  if (duplicators_.empty() || DxgiContextExpired(context)) {
+    // Next Prepare call will initialize duplicators_ or context.
+    return false;
+  }
+  for (size_t i = 0; i < duplicators_.size(); i++) {
+    if (!duplicators_[i].Duplicate(&context->contexts_[i], target,
+                                   last_frame)) {
+      Deinitialize();
+      return false;
+    }
+  }
+  target->set_dpi(dpi());
+  return true;
+}
+
+bool DxgiDuplicatorContainer::Duplicate(DxgiContext* context,

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

call this DuplicateScreen()?
https://google.github.io/styleguide/cppguide.html#Function_Overloading

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

To match the design doc, changed to DuplicateMonitor. (So we can have a
DuplicateAdapter if needed later.)

+                                        int id,

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

screen_id?

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

Done.

+                                        DesktopFrame* target,
+                                        const DesktopFrame* last_frame) {

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

swap the last two arguments, see
https://google.github.io/styleguide/cppguide.html#Function_Parameter_Ordering
Also make last_frame a reference instead of a pointer.

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

Order changed, but last_frame may be nullptr.

+  RTC_DCHECK(target);
+  RTC_DCHECK(id >= 0);
+  if (last_frame != nullptr && !target->size().equals(last_frame->size())) {

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

Replace this with a DCHECK.

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

Same as above.

+    return false;
+  }
+  target->mutable_updated_region()->Clear();
+  rtc::CritScope lock(&lock_);
+  if (duplicators_.empty() || DxgiContextExpired(context)) {
+    // Next Prepare call will initialize duplicators_ or context.
+    return false;
+  }
+  for (size_t i = 0; i < duplicators_.size() && i < context->contexts_.size();
+       i++) {
+    if (id >= duplicators_[i].screen_count()) {
+      id -= duplicators_[i].screen_count();
+    } else {
+      if (duplicators_[i].Duplicate(&context->contexts_[i], id, target,
+                                    last_frame)) {
+        target->set_dpi(dpi());
+        return true;
+      }
+      Deinitialize();
+      return false;
+    }
+  }
+  // id >= ScreenCount(). This is a user error, so we do not need to
+  // deinitialize.
+  return false;
+}
+
+}  // namespace webrtc