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_ACCELERATOR_KEY_HOLD_DETECTOR_H_
6#define ASH_ACCELERATOR_KEY_HOLD_DETECTOR_H_
7
8#include "ash/ash_export.h"
9#include "base/memory/scoped_ptr.h"
10#include "ui/events/event_handler.h"
11
12namespace ui {
13class KeyEvent;
14}
15
16namespace ash {
17
18// This class is used to implement action when a user press and hold the key.
19// When a user just pressed and released a key, normal pressed event gets
20// generated upon release.
21class ASH_EXPORT KeyHoldDetector : public ui::EventHandler {
22 public:
23  class Delegate {
24   public:
25    virtual ~Delegate() {}
26
27    // If this return false, the event handler does not process
28    // the event at all.
29    virtual bool ShouldProcessEvent(const ui::KeyEvent* event) const = 0;
30
31    // This should return true if the event should start the state transition.
32    virtual bool IsStartEvent(const ui::KeyEvent* event) const = 0;
33
34    // Called when the key is held.
35    virtual void OnKeyHold(const ui::KeyEvent* event) = 0;
36
37    // Called when the key is release after hold.
38    virtual void OnKeyUnhold(const ui::KeyEvent* event) = 0;
39  };
40
41  explicit KeyHoldDetector(scoped_ptr<Delegate> delegate);
42  virtual ~KeyHoldDetector();
43
44  // ui::EventHandler overrides:
45  virtual void OnKeyEvent(ui::KeyEvent* key_event) OVERRIDE;
46
47 private:
48  // A state to keep track of one click and click and hold operation.
49  //
50  // One click:
51  // INITIAL --(first press)--> PRESSED --(release)--> INITIAL[SEND PRESS]
52  //
53  // Click and hold:
54  // INITIAL --(first press)--> PRESSED --(press)-->
55  //   HOLD[OnKeyHold] --(press)--> HOLD[OnKeyHold] --(release)-->
56  //   INITIAL[OnKeyUnhold]
57  enum State {
58    INITIAL,
59    PRESSED,
60    HOLD
61  };
62
63  State state_;
64  scoped_ptr<Delegate> delegate_;
65
66  DISALLOW_COPY_AND_ASSIGN(KeyHoldDetector);
67};
68
69}  // namespace ash
70
71#endif  // ASH_ACCELERATOR_KEY_HOLD_DETECTOR_H_
72