Convert CC scheduler logic to use base::TimeTicks/Delta instead of doubles

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>
@@ skipping 11 matching lines @@
 // 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(double interval, CCThread* thread)
+PassRefPtr<CCDelayBasedTimeSource> CCDelayBasedTimeSource::create(base::TimeDelta interval, CCThread* thread)
 {
     return adoptRef(new CCDelayBasedTimeSource(interval, thread));
 }
 
-CCDelayBasedTimeSource::CCDelayBasedTimeSource(double intervalSeconds, CCThread* thread)
+CCDelayBasedTimeSource::CCDelayBasedTimeSource(base::TimeDelta interval, CCThread* thread)
     : m_client(0)
     , m_hasTickTarget(false)
-    , m_lastTickTime(0)
-    , m_currentParameters(intervalSeconds, 0)
-    , m_nextParameters(intervalSeconds, 0)
+    , m_currentParameters(interval, base::TimeTicks())
+    , m_nextParameters(interval, base::TimeTicks())
     , m_state(STATE_INACTIVE)
     , m_timer(thread, this)
 {
     turnOffVerifier();
 }
 
 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;
 
-    double now = monotonicTimeNow();
-    postNextTickTask(now);
+    postNextTickTask(now());
 }
 
-double CCDelayBasedTimeSource::lastTickTime()
+base::TimeTicks CCDelayBasedTimeSource::lastTickTime()
 {
     return m_lastTickTime;
 }
 
-double CCDelayBasedTimeSource::nextTickTimeIfActivated()
+base::TimeTicks CCDelayBasedTimeSource::nextTickTimeIfActivated()
 {
-    return active() ? m_currentParameters.tickTarget : nextTickTarget(monotonicTimeNow());
+    return active() ? m_currentParameters.tickTarget : nextTickTarget(now());
 }
 
 void CCDelayBasedTimeSource::onTimerFired()
 {
     ASSERT(m_state != STATE_INACTIVE);
 
-    double now = monotonicTimeNow();
+    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::setTimebaseAndInterval(double timebase, double intervalSeconds)
+void CCDelayBasedTimeSource::setTimebaseAndInterval(base::TimeTicks timebase, base::TimeDelta interval)
 {
-    m_nextParameters.interval = intervalSeconds;
+    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(intervalSeconds - m_currentParameters.interval);
-    double intervalChange = intervalDelta / intervalSeconds;
+    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);
-    double phaseChange = fmod(targetDelta, intervalSeconds) / intervalSeconds;
+    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;
     }
 }
 
-double CCDelayBasedTimeSource::monotonicTimeNow() const
+base::TimeTicks CCDelayBasedTimeSource::now() const
 {
-    return monotonicallyIncreasingTime();
+    return base::TimeTicks::Now();
 }
 
-// This code tries to achieve an average tick rate as close to m_intervalMs as possible.
+// 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:
+// 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)
@@ skipping 12 matching lines @@
 //   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)
-//
-// Note, that in the above discussion, times are expressed in milliseconds, but in the code, seconds are used.
-double CCDelayBasedTimeSource::nextTickTarget(double now)
+base::TimeTicks CCDelayBasedTimeSource::nextTickTarget(base::TimeTicks now)
 {
-    double newInterval = m_nextParameters.interval;
-    double intervalsElapsed = floor((now - m_nextParameters.tickTarget) / newInterval);
-    double lastEffectiveTick = m_nextParameters.tickTarget + newInterval * intervalsElapsed;
-    double newTickTarget = lastEffectiveTick + newInterval;
+    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 * doubleTickThreshold)
+    if (newTickTarget - m_lastTickTime <= newInterval / static_cast<int>(1.0 / doubleTickThreshold))
         newTickTarget += newInterval;
 
     return newTickTarget;
 }
 
-void CCDelayBasedTimeSource::postNextTickTask(double now)
+void CCDelayBasedTimeSource::postNextTickTask(base::TimeTicks now)
 {
-    double newTickTarget = nextTickTarget(now);
+    base::TimeTicks newTickTarget = nextTickTarget(now);
 
     // Post another task *before* the tick and update state
-    double delay = newTickTarget - now;
-    ASSERT(delay <= m_nextParameters.interval * (1.0 + doubleTickThreshold));
-    m_timer.startOneShot(delay);
+    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;
 }
 
 }