Adding a gray semi transparent backdrop behind the topmost window within the default container

ash/wm/workspace/workspace_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_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_H_
 #define ASH_WM_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_H_
 
 #include <set>
 
 #include "ash/ash_export.h"
 #include "ash/shell_observer.h"
 #include "ash/wm/window_state_observer.h"
 #include "ash/wm/wm_types.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
 #include "ui/aura/client/activation_change_observer.h"
 #include "ui/aura/layout_manager.h"
 #include "ui/aura/window_observer.h"
 #include "ui/gfx/rect.h"
 
 namespace aura {
 class RootWindow;
 class Window;
 }
 
 namespace ui {
 class Layer;
 }
 
 namespace ash {
 namespace wm {
 class WindowState;
 }
 
 namespace internal {
 
 class ShelfLayoutManager;
+class WorkspaceLayoutManagerBackdrop;
 
 // LayoutManager used on the window created for a workspace.
 class ASH_EXPORT WorkspaceLayoutManager
     : public aura::LayoutManager,
       public aura::WindowObserver,
       public aura::client::ActivationChangeObserver,
       public ShellObserver,
       public wm::WindowStateObserver {
  public:
   explicit WorkspaceLayoutManager(aura::Window* window);
   virtual ~WorkspaceLayoutManager();
 
   void SetShelf(internal::ShelfLayoutManager* shelf);
 
+  // If enabled, the topmost window in the container will have a backdrop which
+  // covers the rest of the container.
+  void AddBackdropBehindTopWindow(bool enable);
+
   // Overridden from aura::LayoutManager:
   virtual void OnWindowResized() OVERRIDE {}
   virtual void OnWindowAddedToLayout(aura::Window* child) OVERRIDE;
   virtual void OnWillRemoveWindowFromLayout(aura::Window* child) OVERRIDE;
   virtual void OnWindowRemovedFromLayout(aura::Window* child) OVERRIDE;
   virtual void OnChildWindowVisibilityChanged(aura::Window* child,
                                               bool visibile) OVERRIDE;
   virtual void SetChildBounds(aura::Window* child,
                               const gfx::Rect& requested_bounds) OVERRIDE;
 
@@ skipping 26 matching lines @@
   // If this is called for a display size change (i.e. |event|
   // is DISPLAY_RESIZED), the non-maximized/non-fullscreen
   // windows are readjusted to make sure the window is completely within the
   // display region. Otherwise, it makes sure at least some parts of the window
   // is on display.
   void AdjustAllWindowsBoundsForWorkAreaChange(wm::WMEvent event);
 
   // Updates the visibility state of the shelf.
   void UpdateShelfVisibility();
 
+  // Updates the visibility of the backdrop.
+  void UpdateStackingAndVisibilityOfBackdrop();
+
   // Updates the fullscreen state of the workspace and notifies Shell if it
   // has changed.
   void UpdateFullscreenState();
 
   // Updates the bounds of the window for a show type change from
   // |old_show_type|.
   void UpdateBoundsFromShowType(wm::WindowState* window_state,
                                 wm::WindowShowType old_show_type);
 
   // If |window_state| is maximized or fullscreen the bounds of the
   // window are set and true is returned. Does nothing otherwise.
   bool SetMaximizedOrFullscreenBounds(wm::WindowState* window_state);
 
   // Animates the window bounds to |bounds|.
   void SetChildBoundsAnimated(aura::Window* child, const gfx::Rect& bounds);
 
   internal::ShelfLayoutManager* shelf_;
   aura::Window* window_;
   aura::Window* root_window_;
 
   // Set of windows we're listening to.
   WindowSet windows_;
 
   // The work area in the coordinates of |window_|.
   gfx::Rect work_area_in_parent_;
 
   // True if this workspace is currently in fullscreen mode.
   bool is_fullscreen_;
 
+  // A window which covers the full container and which gets inserted behind the
+  // topmost visible window.
+  scoped_ptr<WorkspaceLayoutManagerBackdrop> backdrop_;
+
   DISALLOW_COPY_AND_ASSIGN(WorkspaceLayoutManager);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_WM_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_H_