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[chromium-blink-merge.git] / ash / accelerators / key_hold_detector.h
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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.
5 #ifndef ASH_ACCELERATOR_KEY_HOLD_DETECTOR_H_
6 #define ASH_ACCELERATOR_KEY_HOLD_DETECTOR_H_
8 #include "ash/ash_export.h"
9 #include "base/memory/scoped_ptr.h"
10 #include "ui/events/event_handler.h"
12 namespace ui {
13 class KeyEvent;
16 namespace ash {
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.
21 class ASH_EXPORT KeyHoldDetector : public ui::EventHandler {
22 public:
23 class Delegate {
24 public:
25 virtual ~Delegate() {}
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;
31 // This should return true if the event should start the state transition.
32 virtual bool IsStartEvent(const ui::KeyEvent* event) const = 0;
34 // Called when the key is held.
35 virtual void OnKeyHold(const ui::KeyEvent* event) = 0;
37 // Called when the key is release after hold.
38 virtual void OnKeyUnhold(const ui::KeyEvent* event) = 0;
41 explicit KeyHoldDetector(scoped_ptr<Delegate> delegate);
42 ~KeyHoldDetector() override;
44 // ui::EventHandler overrides:
45 void OnKeyEvent(ui::KeyEvent* key_event) override;
47 private:
48 // A state to keep track of one click and click and hold operation.
50 // One click:
51 // INITIAL --(first press)--> PRESSED --(release)--> INITIAL[SEND PRESS]
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
63 State state_;
64 scoped_ptr<Delegate> delegate_;
66 DISALLOW_COPY_AND_ASSIGN(KeyHoldDetector);
69 } // namespace ash
71 #endif // ASH_ACCELERATOR_KEY_HOLD_DETECTOR_H_