Linux desktopCapture: fix the cursor position issue in Window sharing

webrtc/modules/desktop_capture/mouse_cursor_monitor_x11.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.
  */
 
@@ skipping 167 matching lines @@
     if (!result || error_trap.GetLastErrorAndDisable() != 0) {
       state = OUTSIDE;
     } else {
       // In screen mode (window_ == root_window) the mouse is always inside.
       // XQueryPointer() sets |child_window| to None if the cursor is outside
       // |window_|.
       state =
           (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));
   }
 }
 
 bool MouseCursorMonitorX11::HandleXEvent(const XEvent& event) {
   if (have_xfixes_ && event.type == xfixes_event_base_ + XFixesCursorNotify) {
     const XFixesCursorNotifyEvent* cursor_event =
         reinterpret_cast<const XFixesCursorNotifyEvent*>(&event);
     if (cursor_event->subtype == XFixesDisplayCursorNotify) {
@@ skipping 49 matching lines @@
 MouseCursorMonitor* MouseCursorMonitor::CreateForScreen(
     const DesktopCaptureOptions& options,
     ScreenId screen) {
   if (!options.x_display())
     return NULL;
   return new MouseCursorMonitorX11(
       options, DefaultRootWindow(options.x_display()->display()));
 }
 
 }  // namespace webrtc