Dragging panels near screen edge

ash/wm/toplevel_window_event_handler.cc

Index: ash/wm/toplevel_window_event_handler.cc
diff --git a/ash/wm/toplevel_window_event_handler.cc b/ash/wm/toplevel_window_event_handler.cc
index ed4818f9b1fb282af396e2e4028c3c0b77fe0e79..9656aa75ed68c86bf306c4c8d75db05dc3b55fad 100644
--- a/ash/wm/toplevel_window_event_handler.cc
+++ b/ash/wm/toplevel_window_event_handler.cc
@@ -63,7 +63,7 @@ class ToplevelWindowEventHandler::ScopedWindowResizer
   WindowResizer* resizer() { return resizer_.get(); }
 
   // WindowObserver overrides:
-  virtual void OnWindowHierarchyChanging(
+  virtual void OnWindowHierarchyChanged(

[varkha, 2013/06/20 04:09:22]

PTAL. I think this is a cleaner solution. This avoids reentrant calls to
AddChild and mean that CompleteDrag only gets called after the window has been
reparented. In our case it will get reparented by SetBounds to a container with
the same id ("Panel") in second root window and then in FinishDragging will get
reparented to workspace (because it is not attached). So it will end up in
workspace as we want it to be. Interestingly this does not break any tests - at
least in ash_unittests. I will try some more but I doubt we consciously designed
with that AddChild reentrancy in mind.

[flackr, 2013/06/20 13:08:45]

I had assumed this wouldn't work. When the window is added to the panel
container on the second display, that PanelLayoutManager should be notified that
it was added, and not knowing that the panel is being dragged would proceed to
move it over the panel icon. This doesn't happen?

I don't think this is the right thing to do, given that the WindowResizer code
doesn't know that the dragged panel has been reparented out from under it and
the state at the time it was reparented may have been some temporary state just
for the purposes of dragging.

       const HierarchyChangeParams& params) OVERRIDE;
   virtual void OnWindowPropertyChanged(aura::Window* window,
                                        const void* key,
@@ -100,7 +100,7 @@ ToplevelWindowEventHandler::ScopedWindowResizer::~ScopedWindowResizer() {
     resizer_->GetTarget()->RemoveObserver(this);
 }
 
-void ToplevelWindowEventHandler::ScopedWindowResizer::OnWindowHierarchyChanging(
+void ToplevelWindowEventHandler::ScopedWindowResizer::OnWindowHierarchyChanged(
     const HierarchyChangeParams& params) {
   if (params.receiver != resizer_->GetTarget())
     return;