Cancel drag if display configuration changes.

ash/wm/toplevel_window_event_filter.cc

Index: ash/wm/toplevel_window_event_filter.cc
diff --git a/ash/wm/toplevel_window_event_filter.cc b/ash/wm/toplevel_window_event_filter.cc
index 146a9085eea5339547315c29b3d242820c99ede8..bb203a941652d44f62894ec1a1f677d2bee04cce 100644
--- a/ash/wm/toplevel_window_event_filter.cc
+++ b/ash/wm/toplevel_window_event_filter.cc
@@ -47,12 +47,15 @@ gfx::Point ConvertPointToParent(aura::Window* window,
 
 ToplevelWindowEventFilter::ToplevelWindowEventFilter(aura::Window* owner)
     : in_move_loop_(false),
+      move_cancelled_(false),
       in_gesture_resize_(false),
       grid_size_(0) {
   aura::client::SetWindowMoveClient(owner, this);
+  Shell::GetInstance()->display_controller()->AddObserver(this);
 }
 
 ToplevelWindowEventFilter::~ToplevelWindowEventFilter() {
+  Shell::GetInstance()->display_controller()->RemoveObserver(this);
 }
 
 bool ToplevelWindowEventFilter::PreHandleKeyEvent(aura::Window* target,
@@ -202,10 +205,12 @@ ui::EventResult ToplevelWindowEventFilter::PreHandleGestureEvent(
   return ui::ER_CONSUMED;
 }
 
-void ToplevelWindowEventFilter::RunMoveLoop(aura::Window* source,
-                                            const gfx::Point& drag_offset) {
+aura::client::WindowMoveResult ToplevelWindowEventFilter::RunMoveLoop(
+    aura::Window* source,
+    const gfx::Point& drag_offset) {
   DCHECK(!in_move_loop_);  // Can only handle one nested loop at a time.
   in_move_loop_ = true;
+  move_cancelled_ = false;
   aura::RootWindow* root_window = source->GetRootWindow();
   DCHECK(root_window);
   gfx::Point drag_location;
@@ -230,6 +235,8 @@ void ToplevelWindowEventFilter::RunMoveLoop(aura::Window* source,
   run_loop.Run();
 #endif  // !defined(OS_MACOSX)
   in_gesture_resize_ = in_move_loop_ = false;
+  return move_cancelled_ ? aura::client::MOVE_CANCELED :
+      aura::client::MOVE_SUCCESSFUL;
 }
 
 void ToplevelWindowEventFilter::EndMoveLoop() {
@@ -244,6 +251,16 @@ void ToplevelWindowEventFilter::EndMoveLoop() {
   quit_closure_.Run();
 }
 
+void ToplevelWindowEventFilter::OnDisplayConfigurationChanging() {
+  if (in_move_loop_) {
+    move_cancelled_ = true;
+    EndMoveLoop();
+  } else if (window_resizer_.get()) {
+    window_resizer_->RevertDrag();

[sky, 2012/09/05 22:45:37]

Does this do the right thing if you're dragging a window on a display that is
removed? Specifically does it make sure the window isn't moved back to the wrong
display?

+    window_resizer_.reset();
+  }
+}
+
 // static
 WindowResizer* ToplevelWindowEventFilter::CreateWindowResizer(
     aura::Window* window,