[cc] Rename all cc/ filenames to Chromium style

cc/CCDelayBasedTimeSource.cpp

-// Copyright 2011 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "config.h"
-
-#include "CCDelayBasedTimeSource.h"
-
-#include "TraceEvent.h"
-#include <algorithm>
-#include <wtf/CurrentTime.h>
-#include <wtf/MathExtras.h>
-
-namespace cc {
-
-namespace {
-
-// doubleTickThreshold prevents ticks from running within the specified fraction of an interval.
-// This helps account for jitter in the timebase as well as quick timer reactivation.
-const double doubleTickThreshold = 0.25;
-
-// intervalChangeThreshold is the fraction of the interval that will trigger an immediate interval change.
-// phaseChangeThreshold is the fraction of the interval that will trigger an immediate phase change.
-// If the changes are within the thresholds, the change will take place on the next tick.
-// If either change is outside the thresholds, the next tick will be canceled and reissued immediately.
-const double intervalChangeThreshold = 0.25;
-const double phaseChangeThreshold = 0.25;
-
-}
-
-
-PassRefPtr<CCDelayBasedTimeSource> CCDelayBasedTimeSource::create(base::TimeDelta interval, CCThread* thread)
-{
-    return adoptRef(new CCDelayBasedTimeSource(interval, thread));
-}
-
-CCDelayBasedTimeSource::CCDelayBasedTimeSource(base::TimeDelta interval, CCThread* thread)
-    : m_client(0)
-    , m_hasTickTarget(false)
-    , m_currentParameters(interval, base::TimeTicks())
-    , m_nextParameters(interval, base::TimeTicks())
-    , m_state(STATE_INACTIVE)
-    , m_timer(thread, this)
-{
-    turnOffVerifier();
-}
-
-CCDelayBasedTimeSource::~CCDelayBasedTimeSource()
-{
-}
-
-void CCDelayBasedTimeSource::setActive(bool active)
-{
-    TRACE_EVENT1("cc", "CCDelayBasedTimeSource::setActive", "active", active);
-    if (!active) {
-        m_state = STATE_INACTIVE;
-        m_timer.stop();
-        return;
-    }
-
-    if (m_state == STATE_STARTING || m_state == STATE_ACTIVE)
-        return;
-
-    if (!m_hasTickTarget) {
-        // Becoming active the first time is deferred: we post a 0-delay task. When
-        // it runs, we use that to establish the timebase, become truly active, and
-        // fire the first tick.
-        m_state = STATE_STARTING;
-        m_timer.startOneShot(0);
-        return;
-    }
-
-    m_state = STATE_ACTIVE;
-
-    postNextTickTask(now());
-}
-
-bool CCDelayBasedTimeSource::active() const
-{
-    return m_state != STATE_INACTIVE;
-}
-
-base::TimeTicks CCDelayBasedTimeSource::lastTickTime()
-{
-    return m_lastTickTime;
-}
-
-base::TimeTicks CCDelayBasedTimeSource::nextTickTime()
-{
-    return active() ? m_currentParameters.tickTarget : base::TimeTicks();
-}
-
-void CCDelayBasedTimeSource::onTimerFired()
-{
-    ASSERT(m_state != STATE_INACTIVE);
-
-    base::TimeTicks now = this->now();
-    m_lastTickTime = now;
-
-    if (m_state == STATE_STARTING) {
-        setTimebaseAndInterval(now, m_currentParameters.interval);
-        m_state = STATE_ACTIVE;
-    }
-
-    postNextTickTask(now);
-
-    // Fire the tick
-    if (m_client)
-        m_client->onTimerTick();
-}
-
-void CCDelayBasedTimeSource::setClient(CCTimeSourceClient* client)
-{
-    m_client = client;
-}
-
-void CCDelayBasedTimeSource::setTimebaseAndInterval(base::TimeTicks timebase, base::TimeDelta interval)
-{
-    m_nextParameters.interval = interval;
-    m_nextParameters.tickTarget = timebase;
-    m_hasTickTarget = true;
-
-    if (m_state != STATE_ACTIVE) {
-        // If we aren't active, there's no need to reset the timer.
-        return;
-    }
-
-    // If the change in interval is larger than the change threshold,
-    // request an immediate reset.
-    double intervalDelta = std::abs((interval - m_currentParameters.interval).InSecondsF());
-    double intervalChange = intervalDelta / interval.InSecondsF();
-    if (intervalChange > intervalChangeThreshold) {
-        setActive(false);
-        setActive(true);
-        return;
-    }
-
-    // If the change in phase is greater than the change threshold in either
-    // direction, request an immediate reset. This logic might result in a false
-    // negative if there is a simultaneous small change in the interval and the
-    // fmod just happens to return something near zero. Assuming the timebase
-    // is very recent though, which it should be, we'll still be ok because the
-    // old clock and new clock just happen to line up.
-    double targetDelta = std::abs((timebase - m_currentParameters.tickTarget).InSecondsF());
-    double phaseChange = fmod(targetDelta, interval.InSecondsF()) / interval.InSecondsF();
-    if (phaseChange > phaseChangeThreshold && phaseChange < (1.0 - phaseChangeThreshold)) {
-        setActive(false);
-        setActive(true);
-        return;
-    }
-}
-
-base::TimeTicks CCDelayBasedTimeSource::now() const
-{
-    return base::TimeTicks::Now();
-}
-
-// This code tries to achieve an average tick rate as close to m_interval as possible.
-// To do this, it has to deal with a few basic issues:
-//   1. postDelayedTask can delay only at a millisecond granularity. So, 16.666 has to
-//      posted as 16 or 17.
-//   2. A delayed task may come back a bit late (a few ms), or really late (frames later)
-//
-// The basic idea with this scheduler here is to keep track of where we *want* to run in
-// m_tickTarget. We update this with the exact interval.
-//
-// Then, when we post our task, we take the floor of (m_tickTarget and now()). If we
-// started at now=0, and 60FPs (all times in milliseconds):
-//      now=0    target=16.667   postDelayedTask(16)
-//
-// When our callback runs, we figure out how far off we were from that goal. Because of the flooring
-// operation, and assuming our timer runs exactly when it should, this yields:
-//      now=16   target=16.667
-//
-// Since we can't post a 0.667 ms task to get to now=16, we just treat this as a tick. Then,
-// we update target to be 33.333. We now post another task based on the difference between our target
-// and now:
-//      now=16   tickTarget=16.667  newTarget=33.333   --> postDelayedTask(floor(33.333 - 16)) --> postDelayedTask(17)
-//
-// Over time, with no late tasks, this leads to us posting tasks like this:
-//      now=0    tickTarget=0       newTarget=16.667   --> tick(), postDelayedTask(16)
-//      now=16   tickTarget=16.667  newTarget=33.333   --> tick(), postDelayedTask(17)
-//      now=33   tickTarget=33.333  newTarget=50.000   --> tick(), postDelayedTask(17)
-//      now=50   tickTarget=50.000  newTarget=66.667   --> tick(), postDelayedTask(16)
-//
-// We treat delays in tasks differently depending on the amount of delay we encounter. Suppose we
-// posted a task with a target=16.667:
-//   Case 1: late but not unrecoverably-so
-//      now=18 tickTarget=16.667
-//
-//   Case 2: so late we obviously missed the tick
-//      now=25.0 tickTarget=16.667
-//
-// We treat the first case as a tick anyway, and assume the delay was
-// unusual. Thus, we compute the newTarget based on the old timebase:
-//      now=18   tickTarget=16.667  newTarget=33.333   --> tick(), postDelayedTask(floor(33.333-18)) --> postDelayedTask(15)
-// This brings us back to 18+15 = 33, which was where we would have been if the task hadn't been late.
-//
-// For the really late delay, we we move to the next logical tick. The timebase is not reset.
-//      now=37   tickTarget=16.667  newTarget=50.000  --> tick(), postDelayedTask(floor(50.000-37)) --> postDelayedTask(13)
-base::TimeTicks CCDelayBasedTimeSource::nextTickTarget(base::TimeTicks now)
-{
-    base::TimeDelta newInterval = m_nextParameters.interval;
-    int intervalsElapsed = static_cast<int>(floor((now - m_nextParameters.tickTarget).InSecondsF() / newInterval.InSecondsF()));
-    base::TimeTicks lastEffectiveTick = m_nextParameters.tickTarget + newInterval * intervalsElapsed;
-    base::TimeTicks newTickTarget = lastEffectiveTick + newInterval;
-    ASSERT(newTickTarget > now);
-
-    // Avoid double ticks when:
-    // 1) Turning off the timer and turning it right back on.
-    // 2) Jittery data is passed to setTimebaseAndInterval().
-    if (newTickTarget - m_lastTickTime <= newInterval / static_cast<int>(1.0 / doubleTickThreshold))
-        newTickTarget += newInterval;
-
-    return newTickTarget;
-}
-
-void CCDelayBasedTimeSource::postNextTickTask(base::TimeTicks now)
-{
-    base::TimeTicks newTickTarget = nextTickTarget(now);
-
-    // Post another task *before* the tick and update state
-    base::TimeDelta delay = newTickTarget - now;
-    ASSERT(delay.InMillisecondsF() <=
-           m_nextParameters.interval.InMillisecondsF() * (1.0 + doubleTickThreshold));
-    m_timer.startOneShot(delay.InSecondsF());
-
-    m_nextParameters.tickTarget = newTickTarget;
-    m_currentParameters = m_nextParameters;
-}
-
-}