Allow Windows to return a monitor out of the first quadrant

webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.h

Index: webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.h
diff --git a/webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.h b/webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.h
index 364690bcb933ed667038993210cb4943e6ad4cc7..c28eeb4bd39df8ed1b51d3939e63a528f6530484 100644
--- a/webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.h
+++ b/webrtc/modules/desktop_capture/win/dxgi_duplicator_controller.h
@@ -158,9 +158,7 @@ class DxgiDuplicatorController {
   // The minimum GetNumFramesCaptured() returned by |duplicators_|.
   int64_t GetNumFramesCaptured() const;
 
-  // Returns a DesktopSize to cover entire desktop_rect. This may be different
-  // than desktop_rect().size(), since top-left of the screen does not need to
-  // be started from (0, 0).
+  // Returns a DesktopSize to cover entire |desktop_rect_|.
   DesktopSize desktop_size() const;
 
   // Returns the size of one screen. |id| should be >= 0. If system does not
@@ -181,6 +179,16 @@ class DxgiDuplicatorController {
   // during first several capture attempts.
   bool EnsureFrameCaptured(Context* context, SharedDesktopFrame* target);
 
+  // Moves |desktop_rect_| and all underlying |duplicators_| to (0, 0).
+  // DXGI_OUTPUT_DESC may return negative values in DesktopCoordinate, which is
+  // not consistent with the requirement of DesktopFrame. But we cannot get the
+  // size of desktop without initializing all the DxgiAdapterDuplicator and
+  // DxgiOutputDuplicator instances. So this is a helper function to "move" the
+  // entire screen from any quadrant to (0, 0). This function is expected to be
+  // executed in DoInitialize() only.

[Sergey Ulanov, 2017/04/28 01:15:02]

Suggest rewording it a bit to simplify:

  // Moves |desktop_rect_| and all underlying |duplicators_|, putting top
  // left corner of the desktop at (0, 0). This is necessary because
  // DXGI_OUTPUT_DESC may return negative desktop coordinates.
  // Called from DoInitialize() after all DxgiAdapterDuplicator and 
  // DxgiOutputDuplicator instances are initialized.

[Hzj_jie, 2017/04/28 01:58:32]

Done.

+  // This comment makes this piece of logic deserve a standalone function.

[Sergey Ulanov, 2017/04/28 01:15:02]

I don't think you need this sentence.

[Hzj_jie, 2017/04/28 01:58:32]

Done.

+  void Translate();

[Sergey Ulanov, 2017/04/28 01:15:02]

TranslateDesktopRect()?

[Hzj_jie, 2017/04/28 01:58:32]

Done.

+
   // This lock must be locked whenever accessing any of the following objects.
   rtc::CriticalSection lock_;