Ignore unmoved moved_rects in DxgiOutputDuplicator

webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc

Index: webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
diff --git a/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc b/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
index 13087cc9285daa71fcdc992c714144f36f0d4e0d..ba8d6257413dd6555c92be56ddb7a9b5cdde47cd 100644
--- a/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
+++ b/webrtc/modules/desktop_capture/win/dxgi_output_duplicator.cc
@@ -288,20 +288,23 @@ bool DxgiOutputDuplicator::DoDetectUpdatedRegion(
   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--;
   }