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      1 // Copyright 2014 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef ASH_WM_WINDOW_CYCLE_CONTROLLER_H_
      6 #define ASH_WM_WINDOW_CYCLE_CONTROLLER_H_
      7 
      8 #include "ash/ash_export.h"
      9 #include "base/basictypes.h"
     10 #include "base/memory/scoped_ptr.h"
     11 #include "base/time/time.h"
     12 
     13 namespace ui {
     14 class EventHandler;
     15 }
     16 
     17 namespace ash {
     18 
     19 class WindowCycleList;
     20 
     21 // Controls cycling through windows with the keyboard via alt-tab.
     22 // Windows are sorted primarily by most recently used, and then by screen order.
     23 // We activate windows as you cycle through them, so the order on the screen
     24 // may change during the gesture, but the most recently used list isn't updated
     25 // until the cycling ends.  Thus we maintain the state of the windows
     26 // at the beginning of the gesture so you can cycle through in a consistent
     27 // order.
     28 class ASH_EXPORT WindowCycleController {
     29  public:
     30   enum Direction {
     31     FORWARD,
     32     BACKWARD
     33   };
     34 
     35   WindowCycleController();
     36   virtual ~WindowCycleController();
     37 
     38   // Returns true if cycling through windows is enabled. This is false at
     39   // certain times, such as when the lock screen is visible.
     40   static bool CanCycle();
     41 
     42   // Cycles between windows in the given |direction|.
     43   void HandleCycleWindow(Direction direction);
     44 
     45   // Returns true if we are in the middle of a window cycling gesture.
     46   bool IsCycling() const { return window_cycle_list_.get() != NULL; }
     47 
     48   // Call to start cycling windows. This funtion adds a pre-target handler to
     49   // listen to the alt key release.
     50   void StartCycling();
     51 
     52   // Stops the current window cycle and removes the event filter.
     53   void StopCycling();
     54 
     55   // Returns the WindowCycleList. Really only useful for testing.
     56   const WindowCycleList* window_cycle_list() const {
     57     return window_cycle_list_.get();
     58   }
     59 
     60  private:
     61   // Cycles to the next or previous window based on |direction|.
     62   void Step(Direction direction);
     63 
     64   scoped_ptr<WindowCycleList> window_cycle_list_;
     65 
     66   // Event handler to watch for release of alt key.
     67   scoped_ptr<ui::EventHandler> event_handler_;
     68 
     69   base::Time cycle_start_time_;
     70 
     71   DISALLOW_COPY_AND_ASSIGN(WindowCycleController);
     72 };
     73 
     74 }  // namespace ash
     75 
     76 #endif  // ASH_WM_WINDOW_CYCLE_CONTROLLER_H_
     77