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 #ifndef HysteresisActivity_h
27 #define HysteresisActivity_h
28
29 #include <wtf/RunLoop.h>
30 #include <wtf/Seconds.h>
31
32 namespace WebCore {
33
34 static const Seconds defaultHysteresisDuration { 5_s };
35
36 enum class HysteresisState {
37 Started,
38 Stopped
39 };
40
41 class HysteresisActivity {
42 public:
43 explicit HysteresisActivity(WTF::Function<void(HysteresisState)>&& callback = [](HysteresisState) { }, Seconds hysteresisSeconds = defaultHysteresisDuration)
44 : m_callback(WTFMove(callback))
45 , m_hysteresisSeconds(hysteresisSeconds)
46 , m_active(false)
47 , m_timer(RunLoop::main(), this, &HysteresisActivity::hysteresisTimerFired)
48 {
49 }
50
51 void start()
52 {
53 if (m_active)
54 return;
55 m_active = true;
56
57 if (m_timer.isActive())
58 m_timer.stop();
59 else
60 m_callback(HysteresisState::Started);
61 }
62
63 void stop()
64 {
65 if (!m_active)
66 return;
67 m_active = false;
68
69 m_timer.startOneShot(m_hysteresisSeconds);
70 }
71
72 void impulse()
73 {
74 if (!m_active) {
75 start();
76 stop();
77 }
78 }
79
80 HysteresisState state() const
81 {
82 return m_active || m_timer.isActive() ? HysteresisState::Started : HysteresisState::Stopped;
83 }
84
85 private:
86 void hysteresisTimerFired()
87 {
88 m_timer.stop();
89 m_callback(HysteresisState::Stopped);
90 }
91
92 WTF::Function<void(HysteresisState)> m_callback;
93 Seconds m_hysteresisSeconds;
94 bool m_active;
95 RunLoop::Timer<HysteresisActivity> m_timer;
96 };
97
98 } // namespace WebCore
99
100 #endif // HysteresisActivity_h