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/*
* Copyright (C) 2014 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <wtf/RunLoop.h>
#include <wtf/Seconds.h>
namespace PAL {
static const Seconds defaultHysteresisDuration { 5_s };
enum class HysteresisState : bool { Started, Stopped };
class HysteresisActivity {
WTF_MAKE_FAST_ALLOCATED;
public:
explicit HysteresisActivity(Function<void(HysteresisState)>&& callback = [](HysteresisState) { }, Seconds hysteresisSeconds = defaultHysteresisDuration)
: m_callback(WTFMove(callback))
, m_hysteresisSeconds(hysteresisSeconds)
, m_timer(RunLoop::main(), this, &HysteresisActivity::hysteresisTimerFired)
{
}
void start()
{
if (m_active)
return;
m_active = true;
if (m_timer.isActive())
m_timer.stop();
else
m_callback(HysteresisState::Started);
}
void stop()
{
if (!m_active)
return;
m_active = false;
m_timer.startOneShot(m_hysteresisSeconds);
}
void impulse()
{
if (m_active)
return;
if (state() == HysteresisState::Stopped) {
m_active = true;
m_callback(HysteresisState::Started);
m_active = false;
}
m_timer.startOneShot(m_hysteresisSeconds);
}
HysteresisState state() const
{
return m_active || m_timer.isActive() ? HysteresisState::Started : HysteresisState::Stopped;
}
private:
void hysteresisTimerFired()
{
m_timer.stop();
m_callback(HysteresisState::Stopped);
}
Function<void(HysteresisState)> m_callback;
Seconds m_hysteresisSeconds;
RunLoop::Timer m_timer;
bool m_active { false };
};
} // namespace PAL
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