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
13namespace ui {
14class EventHandler;
15}
16
17namespace ash {
18
19class 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.
28class 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