Linux desktopCapture: fix the cursor position issue in Window sharing

webrtc/modules/desktop_capture/mouse_cursor_monitor_x11.cc

Index: webrtc/modules/desktop_capture/mouse_cursor_monitor_x11.cc
diff --git a/webrtc/modules/desktop_capture/mouse_cursor_monitor_x11.cc b/webrtc/modules/desktop_capture/mouse_cursor_monitor_x11.cc
index 4870bae7ff0baade0c476f670d074ee36f0b295b..22339d4221c9e48d9a55aec48a6ba8801a14e2f0 100644
--- a/webrtc/modules/desktop_capture/mouse_cursor_monitor_x11.cc
+++ b/webrtc/modules/desktop_capture/mouse_cursor_monitor_x11.cc
@@ -185,6 +185,21 @@ void MouseCursorMonitorX11::Capture() {
           (window_ == root_window || child_window != None) ? INSIDE : OUTSIDE;
     }
 
+    // As the comments to GetTopLevelWindow() above indicate, in window capture,
+    // the cursor position capture happens in |window_|, while the frame catpure
+    // happens in |child_window|. These two windows are not alwyas same, as
+    // window manager may add some decorations to the |window_|. So translate
+    // the coordinate in |window_| to the coordinate space of |child_window|.
+    if (window_ != root_window && state == INSIDE) {
+      int translated_x, translated_y;
+      Window unused;
+      if (XTranslateCoordinates(display(), window_, child_window, win_x, win_y,
+                                &translated_x, &translated_y, &unused)) {
+        win_x = translated_x;
+        win_y = translated_y;
+      }
+    }
+
     callback_->OnMouseCursorPosition(state,
                                      webrtc::DesktopVector(win_x, win_y));
   }