Implement a callout widget for the active panel.

ash/wm/panel_layout_manager.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_WM_PANEL_LAYOUT_MANAGER_H_
 #define ASH_WM_PANEL_LAYOUT_MANAGER_H_
 #pragma once
 
 #include <list>
 
 #include "ash/ash_export.h"
 #include "ash/launcher/launcher_icon_observer.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
 #include "ui/aura/layout_manager.h"
 #include "ui/aura/window_observer.h"
 
 namespace aura {
 class Window;
 }
 
 namespace gfx {
 class Rect;
 }
 
+namespace views {
+class Widget;
+}
+
 namespace ash {
 class Launcher;
 
 namespace internal {
 
 // PanelLayoutManager is responsible for organizing panels within the
 // workspace. It is associated with a specific container window (i.e.
 // kShellWindowId_PanelContainer) and controls the layout of any windows
 // added to that container.
 //
@@ skipping 35 matching lines @@
  private:
   typedef std::list<aura::Window*> PanelList;
 
   // Called whenever the panel layout might change.
   void Relayout();
 
   // Called whenever the panel stacking order needs to be updated (e.g. focus
   // changes or a panel is moved).
   void UpdateStacking(aura::Window* active_panel);
 
+  // Trigger a delayed task to update the callout. We use this because
+  // otherwise, ShadowController::OnWindowPropertyChanged may be invoked after
+  // we've already updated the callout, causing the drop shadow to be stacked on
+  // top of the callout rather than the other way around.
+  // TODO(dcheng): Possibly a bug in the shadow controller. If a window is
+  // focused but not stacked at the top, I don't think its shadow should be
+  // drawn on top of "higher" windows.
+  void UpdateCallout(aura::Window* active_window);
+  // Don't call this directly. Only UpdateCallout() should call this method.

[sky, 2012/04/27 15:42:42]

nit: newline between 94/95. In fact typical style is newline between all members
below too.

+  void ShowCalloutHelper(aura::Window* active_panel);
+
   // Parent window associated with this layout manager.
   aura::Window* panel_container_;
   // Protect against recursive calls to Relayout().
   bool in_layout_;
   // Ordered list of unowned pointers to panel windows.
   PanelList panel_windows_;
   // The panel being dragged.
   aura::Window* dragged_panel_;
   // The launcher we are observing for launcher icon changes.
   Launcher* launcher_;
   // The last active panel. Used to maintain stacking even if no panels are
   // currently focused.
   aura::Window* last_active_panel_;
+  // Manage the callout for the focused panel, if any.
+  scoped_ptr<views::Widget> callout_widget_;
+  base::WeakPtrFactory<PanelLayoutManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PanelLayoutManager);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_WM_PANEL_LAYOUT_MANAGER_H_