Source/core/animation/AnimationClock.cpp

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#include "config.h"
#include "core/animation/AnimationClock.h"

#include "wtf/CurrentTime.h"
#include <math.h>

namespace {

// FIXME: This is an approximation of time between frames, used when
// ticking the animation clock outside of animation frame callbacks.
// Ideally this would be generated by the compositor.
const double approximateFrameTime = 1 / 60.0;

}

namespace blink {

unsigned AnimationClock::s_currentTask = 0;

void AnimationClock::updateTime(double time)
{
    if (time > m_time)
        m_time = time;
    m_currentTask = s_currentTask;
}

double AnimationClock::currentTime()
{
    if (m_currentTask != s_currentTask) {
        const double currentTime = m_monotonicallyIncreasingTime();
        if (m_time < currentTime) {
            // Advance to the first estimated frame after the current time.
            const double frameShift = fmod(currentTime - m_time, approximateFrameTime);
            const double newTime = currentTime + (approximateFrameTime - frameShift);
            ASSERT(newTime >= currentTime);
            ASSERT(newTime <= currentTime + approximateFrameTime);
            updateTime(newTime);
        } else {
            m_currentTask = s_currentTask;
        }
    }
    return m_time;
}

void AnimationClock::resetTimeForTesting(double time)
{
    m_time = time;
    m_currentTask = 0;
    s_currentTask = 0;
}

}