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 aura {
  18 class Window;
  19 }  // namespace aura
  20
  21 namespace ash {
  22
  23 class WindowCycleList;
  24
  25 // Controls cycling through windows with the keyboard via alt-tab.
  26 // Windows are sorted primarily by most recently used, and then by screen order.
  27 // We activate windows as you cycle through them, so the order on the screen
  28 // may change during the gesture, but the most recently used list isn't updated
  29 // until the cycling ends.  Thus we maintain the state of the windows
  30 // at the beginning of the gesture so you can cycle through in a consistent
  31 // order.
  32 class ASH_EXPORT WindowCycleController {
  33  public:
  34   enum Direction {
  35     FORWARD,
  36     BACKWARD
  37   };
  38
  39   WindowCycleController();
  40   virtual ~WindowCycleController();
  41
  42   // Returns true if cycling through windows is enabled. This is false at
  43   // certain times, such as when the lock screen is visible.
  44   static bool CanCycle();
  45
  46   // Cycles between windows in the given |direction|.
  47   void HandleCycleWindow(Direction direction);
  48
  49   // Returns true if we are in the middle of a window cycling gesture.
  50   bool IsCycling() const { return window_cycle_list_.get() != NULL; }
  51
  52   // Call to start cycling windows. This funtion adds a pre-target handler to
  53   // listen to the alt key release.
  54   void StartCycling();
  55
  56   // Stops the current window cycle and removes the event filter.
  57   void StopCycling();
  58
  59   // Returns the WindowCycleList. Really only useful for testing.
  60   const WindowCycleList* window_cycle_list() const {
  61     return window_cycle_list_.get();
  62   }
  63
  64  private:
  65   // Cycles to the next or previous window based on |direction|.
  66   void Step(Direction direction);
  67
  68   scoped_ptr<WindowCycleList> window_cycle_list_;
  69
  70   // Tracks what Window was active when starting to cycle and used to determine
  71   // if the active Window changed in when ending cycling.
  72   aura::Window* active_window_before_window_cycle_ = nullptr;
  73
  74   // Event handler to watch for release of alt key.
  75   scoped_ptr<ui::EventHandler> event_handler_;
  76
  77   base::Time cycle_start_time_;
  78
  79   DISALLOW_COPY_AND_ASSIGN(WindowCycleController);
  80 };
  81
  82 }  // namespace ash
  83
  84 #endif  // ASH_WM_WINDOW_CYCLE_CONTROLLER_H_