ash/wm/window_cycle_controller.h

   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_