Ignore unmoved moved_rects in DxgiOutputDuplicator

webrtc/modules/desktop_capture/win/dxgi_output_duplicator.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.
  */
 
@@ skipping 270 matching lines @@
       static_cast<UINT>(metadata_.capacity()) - buff_size, dirty_rects,
       &buff_size);
   if (error.Error() != S_OK) {
     LOG(LS_ERROR) << "Failed to get dirty rectangles, error "
                   << error.ErrorMessage() << ", code " << error.Error();
     return false;
   }
   dirty_rects_count = buff_size / sizeof(RECT);
 
   while (move_rects_count > 0) {
-    updated_region->AddRect(
-        RotateRect(DesktopRect::MakeXYWH(move_rects->SourcePoint.x,
-                                         move_rects->SourcePoint.y,
-                                         move_rects->DestinationRect.right -
-                                             move_rects->DestinationRect.left,
-                                         move_rects->DestinationRect.bottom -
-                                             move_rects->DestinationRect.top),
-                   unrotated_size_, rotation_));
-    updated_region->AddRect(
-        RotateRect(DesktopRect::MakeLTRB(move_rects->DestinationRect.left,
-                                         move_rects->DestinationRect.top,
-                                         move_rects->DestinationRect.right,
-                                         move_rects->DestinationRect.bottom),
-                   unrotated_size_, rotation_));
+    if (move_rects->SourcePoint.x != move_rects->DestinationRect.left ||

[Sergey Ulanov, 2017/03/14 19:47:27]

Do you know why the API returns unmoved rects? Do you know what they correspond
to (maybe there is a specific application that triggers that behavior, e.g. by
generating noop move events)? I think just logging these rects would provide
more information. 
In any case, please add a comment to explain why we need this.

[Hzj_jie, 2017/03/14 23:22:49]

No idea about this. I just randomly tried this idea, and found the impact. I
doubt this information is also from the video adapter or its driver, which may
be because of the noop move operations from applications or Windows (window
manager) itself.
I have logged the unmoved move_rect for further investigation, though it's may
not worthy. (0.015 ms is not so attractive.)
I also copy the description in this change into to source code to explain the
reason and impact.

+        move_rects->SourcePoint.y != move_rects->DestinationRect.top) {
+      updated_region->AddRect(
+          RotateRect(DesktopRect::MakeXYWH(move_rects->SourcePoint.x,
+                                           move_rects->SourcePoint.y,
+                                           move_rects->DestinationRect.right -
+                                               move_rects->DestinationRect.left,
+                                           move_rects->DestinationRect.bottom -
+                                               move_rects->DestinationRect.top),
+                     unrotated_size_, rotation_));
+      updated_region->AddRect(
+          RotateRect(DesktopRect::MakeLTRB(move_rects->DestinationRect.left,
+                                           move_rects->DestinationRect.top,
+                                           move_rects->DestinationRect.right,
+                                           move_rects->DestinationRect.bottom),
+                     unrotated_size_, rotation_));
+    }
     move_rects++;
     move_rects_count--;
   }
 
   while (dirty_rects_count > 0) {
     updated_region->AddRect(RotateRect(
         DesktopRect::MakeLTRB(dirty_rects->left, dirty_rects->top,
                               dirty_rects->right, dirty_rects->bottom),
         unrotated_size_, rotation_));
     dirty_rects++;
@@ skipping 28 matching lines @@
 }
 
 int64_t DxgiOutputDuplicator::num_frames_captured() const {
 #if !defined(NDEBUG)
   RTC_DCHECK_EQ(!!last_frame_, num_frames_captured_ > 0);
 #endif
   return num_frames_captured_;
 }
 
 }  // namespace webrtc