1/*
2 * Copyright (C) 2014 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23 * THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#pragma once
27
28#include <wtf/RunLoop.h>
29#include <wtf/Seconds.h>
30
31namespace PAL {
32
33static const Seconds defaultHysteresisDuration { 5_s };
34
35enum class HysteresisState {
36 Started,
37 Stopped
38};
39
40class HysteresisActivity {
41public:
42 explicit HysteresisActivity(WTF::Function<void(HysteresisState)>&& callback = [](HysteresisState) { }, Seconds hysteresisSeconds = defaultHysteresisDuration)
43 : m_callback(WTFMove(callback))
44 , m_hysteresisSeconds(hysteresisSeconds)
45 , m_active(false)
46 , m_timer(RunLoop::main(), this, &HysteresisActivity::hysteresisTimerFired)
47 {
48 }
49
50 void start()
51 {
52 if (m_active)
53 return;
54 m_active = true;
55
56 if (m_timer.isActive())
57 m_timer.stop();
58 else
59 m_callback(HysteresisState::Started);
60 }
61
62 void stop()
63 {
64 if (!m_active)
65 return;
66 m_active = false;
67
68 m_timer.startOneShot(m_hysteresisSeconds);
69 }
70
71 void impulse()
72 {
73 if (!m_active) {
74 start();
75 stop();
76 }
77 }
78
79 HysteresisState state() const
80 {
81 return m_active || m_timer.isActive() ? HysteresisState::Started : HysteresisState::Stopped;
82 }
83
84private:
85 void hysteresisTimerFired()
86 {
87 m_timer.stop();
88 m_callback(HysteresisState::Stopped);
89 }
90
91 WTF::Function<void(HysteresisState)> m_callback;
92 Seconds m_hysteresisSeconds;
93 bool m_active;
94 RunLoop::Timer<HysteresisActivity> m_timer;
95};
96
97} // namespace PAL
98