BlankDetectorDesktopCapturerWrapper to detect a blank DesktopFrame

webrtc/modules/desktop_capture/screen_capturer_win.cc

 /*
  *  Copyright (c) 2013 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 <memory>
 #include <utility>
 
+#include "webrtc/modules/desktop_capture/blank_detector_desktop_capturer_wrapper.h"
 #include "webrtc/modules/desktop_capture/desktop_capturer.h"
 #include "webrtc/modules/desktop_capture/desktop_capture_options.h"
 #include "webrtc/modules/desktop_capture/fallback_desktop_capturer_wrapper.h"
+#include "webrtc/modules/desktop_capture/rgba_color.h"
 #include "webrtc/modules/desktop_capture/win/screen_capturer_win_directx.h"
 #include "webrtc/modules/desktop_capture/win/screen_capturer_win_gdi.h"
 #include "webrtc/modules/desktop_capture/win/screen_capturer_win_magnifier.h"
 
 namespace webrtc {
 
+namespace {
+
+std::unique_ptr<DesktopCapturer> CreateScreenCapturerWinDirectx(
+    const DesktopCaptureOptions& options) {
+  std::unique_ptr<DesktopCapturer> capturer(
+      new ScreenCapturerWinDirectx(options));
+  capturer.reset(new BlankDetectorDesktopCapturerWrapper(
+      std::move(capturer), RgbaColor(0, 0, 0, 0)));
+  return capturer;
+}
+
+}  // namespace
+
 // static
 std::unique_ptr<DesktopCapturer> DesktopCapturer::CreateRawScreenCapturer(
     const DesktopCaptureOptions& options) {
-  std::unique_ptr<DesktopCapturer> capturer;
+  std::unique_ptr<DesktopCapturer> capturer(new ScreenCapturerWinGdi(options));
   if (options.allow_directx_capturer() &&
       ScreenCapturerWinDirectx::IsSupported()) {
-    capturer.reset(new ScreenCapturerWinDirectx(options));
-  } else {
-    capturer.reset(new ScreenCapturerWinGdi(options));
+    capturer.reset(new FallbackDesktopCapturerWrapper(
+        CreateScreenCapturerWinDirectx(options), std::move(capturer)));
   }
 
   if (options.allow_use_magnification_api()) {
     // ScreenCapturerWinMagnifier cannot work on Windows XP or earlier, as well
     // as 64-bit only Windows, and it may randomly crash on multi-screen
     // systems. So we may need to fallback to use original capturer.
     capturer.reset(new FallbackDesktopCapturerWrapper(
         std::unique_ptr<DesktopCapturer>(new ScreenCapturerWinMagnifier()),
         std::move(capturer)));
   }
 
   return capturer;
 }
 
 }  // namespace webrtc