b=731974, requestAnimationFrame generates too short/long frames; r=bz,smaug,roc

layout/base/nsRefreshDriver.cpp

@@ -7,11 +7,27 @@
 /*
  * Code to notify things that animate before a refresh, at an appropriate
  * refresh rate.  (Perhaps temporary, until replaced by compositor.)
+ *
+ * Chrome and each tab have their own RefreshDriver, which in turn
+ * hooks into one of a few global timer based on RefreshDriverTimer,
+ * defined below.  There are two main global timers -- one for active
+ * animations, and one for inactive ones.  These are implemented as
+ * subclasses of RefreshDriverTimer; see below for a description of
+ * their implementations.  In the future, additional timer types may
+ * implement things like blocking on vsync.
  */
 
+#ifdef XP_WIN
+#include <windows.h>
+// mmsystem isn't part of WIN32_LEAN_AND_MEAN, so we have
+// to manually include it
+#include <mmsystem.h>
+#endif
+
 #include "mozilla/Util.h"
 
 #include "nsRefreshDriver.h"
+#include "nsITimer.h"
 #include "nsPresContext.h"
 #include "nsComponentManagerUtils.h"
 #include "prlog.h"
@@ -31,17 +47,386 @@ using mozilla::TimeDuration;
 
 using namespace mozilla;
 
+#ifdef PR_LOGGING
+static PRLogModuleInfo *gLog = nullptr;
+#define LOG(...) PR_LOG(gLog, PR_LOG_NOTICE, (__VA_ARGS__))
+#else
+#define LOG(...) do { } while(0)
+#endif
+
 #define DEFAULT_FRAME_RATE 60
 #define DEFAULT_THROTTLED_FRAME_RATE 1
+// after 10 minutes, stop firing off inactive timers
+#define DEFAULT_INACTIVE_TIMER_DISABLE_SECONDS 600
 
-static bool sPrecisePref;
+namespace mozilla {
+
+/*
+ * The base class for all global refresh driver timers.  It takes care
+ * of managing the list of refresh drivers attached to them and
+ * provides interfaces for querying/setting the rate and actually
+ * running a timer 'Tick'.  Subclasses must implement StartTimer(),
+ * StopTimer(), and ScheduleNextTick() -- the first two just
+ * start/stop whatever timer mechanism is in use, and ScheduleNextTick
+ * is called at the start of the Tick() implementation to set a time
+ * for the next tick.
+ */
+class RefreshDriverTimer {
+public:
+  /*
+   * aRate -- the delay, in milliseconds, requested between timer firings
+   */
+  RefreshDriverTimer(double aRate)
+  {
+    SetRate(aRate);
+  }
+
+  virtual ~RefreshDriverTimer()
+  {
+    NS_ASSERTION(mRefreshDrivers.Length() == 0, "Should have removed all refresh drivers from here by now!");
+  }
+
+  virtual void AddRefreshDriver(nsRefreshDriver* aDriver)
+  {
+    NS_ASSERTION(!mRefreshDrivers.Contains(aDriver), "AddRefreshDriver for a refresh driver that's already in the list!");
+    mRefreshDrivers.AppendElement(aDriver);
+
+    if (mRefreshDrivers.Length() == 1) {
+      StartTimer();
+    }
+  }
+
+  virtual void RemoveRefreshDriver(nsRefreshDriver* aDriver)
+  {
+    NS_ASSERTION(mRefreshDrivers.Contains(aDriver), "RemoveRefreshDriver for a refresh driver that's not in the list!");
+    mRefreshDrivers.RemoveElement(aDriver);
+
+    if (mRefreshDrivers.Length() == 0) {
+      StopTimer();
+    }
+  }
+
+  double GetRate() const
+  {
+    return mRateMilliseconds;
+  }
+
+  // will take effect at next timer tick
+  virtual void SetRate(double aNewRate)
+  {
+    mRateMilliseconds = aNewRate;
+    mRateDuration = TimeDuration::FromMilliseconds(mRateMilliseconds);
+  }
+
+  TimeStamp MostRecentRefresh() const { return mLastFireTime; }
+  int64_t MostRecentRefreshEpochTime() const { return mLastFireEpoch; }
+
+protected:
+  virtual void StartTimer() = 0;
+  virtual void StopTimer() = 0;
+  virtual void ScheduleNextTick(TimeStamp aNowTime) = 0;
+
+  /*
+   * Actually runs a tick, poking all the attached RefreshDrivers.
+   * Grabs the "now" time via JS_Now and TimeStamp::Now().
+   */
+  void Tick()
+  {
+    int64_t jsnow = JS_Now();
+    TimeStamp now = TimeStamp::Now();
+
+    ScheduleNextTick(now);
+
+    mLastFireEpoch = jsnow;
+    mLastFireTime = now;
+
+    nsTArray<nsRefPtr<nsRefreshDriver> > drivers(mRefreshDrivers);
+    for (size_t i = 0; i < drivers.Length(); ++i) {
+      // don't poke this driver if it's in test mode
+      if (drivers[i]->IsTestControllingRefreshesEnabled()) {
+        continue;
+      }
+
+      TickDriver(drivers[i], jsnow, now);
+    }
+  }
+
+  static void TickDriver(nsRefreshDriver* driver, int64_t jsnow, TimeStamp now)
+  {
+    driver->Tick(jsnow, now);
+  }
+
+  double mRateMilliseconds;
+  TimeDuration mRateDuration;
+
+  int64_t mLastFireEpoch;
+  TimeStamp mLastFireTime;
+  TimeStamp mTargetTime;
+
+  nsTArray<nsRefPtr<nsRefreshDriver> > mRefreshDrivers;
+
+  // useful callback for nsITimer-based derived classes, here
+  // bacause of c++ protected shenanigans
+  static void TimerTick(nsITimer* aTimer, void* aClosure)
+  {
+    RefreshDriverTimer *timer = static_cast<RefreshDriverTimer*>(aClosure);
+    timer->Tick();
+  }
+};
+
+/*
+ * A RefreshDriverTimer that uses a nsITimer as the underlying timer.  Note that
+ * this is a ONE_SHOT timer, not a repeating one!  Subclasses are expected to
+ * implement ScheduleNextTick and intelligently calculate the next time to tick,
+ * and to reset mTimer.  Using a repeating nsITimer gets us into a lot of pain
+ * with its attempt at intelligent slack removal and such, so we don't do it.
+ */
+class SimpleTimerBasedRefreshDriverTimer :
+    public RefreshDriverTimer
+{
+public:
+  SimpleTimerBasedRefreshDriverTimer(double aRate)
+    : RefreshDriverTimer(aRate)
+  {
+    mTimer = do_CreateInstance(NS_TIMER_CONTRACTID);
+  }
+
+  virtual ~SimpleTimerBasedRefreshDriverTimer()
+  {
+    StopTimer();
+  }
+
+protected:
+
+  virtual void StartTimer()
+  {
+    mLastFireTime = TimeStamp::Now();
+    mTargetTime = mLastFireTime;
+
+    mTimer->InitWithFuncCallback(TimerTick, this, 0, nsITimer::TYPE_ONE_SHOT);
+  }
+
+  virtual void StopTimer()
+  {
+    mTimer->Cancel();
+  }
+
+  nsRefPtr<nsITimer> mTimer;
+};
+
+/*
+ * PreciseRefreshDriverTimer schedules ticks based on the current time
+ * and when the next tick -should- be sent if we were hitting our
+ * rate.  It always schedules ticks on multiples of aRate -- meaning that
+ * if some execution takes longer than an alloted slot, the next tick
+ * will be delayed instead of triggering instantly.  This might not be
+ * desired -- there's an #if 0'd block below that we could put behind
+ * a pref to control this behaviour.
+ */
+class PreciseRefreshDriverTimer :
+    public SimpleTimerBasedRefreshDriverTimer
+{
+public:
+  PreciseRefreshDriverTimer(double aRate)
+    : SimpleTimerBasedRefreshDriverTimer(aRate)
+  {
+  }
+
+protected:
+  virtual void ScheduleNextTick(TimeStamp aNowTime)
+  {
+    // The number of (whole) elapsed intervals between the last target
+    // time and the actual time.  We want to truncate the double down
+    // to an int number of intervals.
+    int numElapsedIntervals = static_cast<int>((aNowTime - mTargetTime) / mRateDuration);
+
+    // the last "tick" that may or may not have been actually sent was
+    // at this time.  For example, if the rate is 15ms, the target
+    // time is 200ms, and it's now 225ms, the last effective tick
+    // would have been at 215ms.  The next one should then be
+    // scheduled for 5 ms from now.
+    //
+    // We then add another mRateDuration to find the next tick target.
+    TimeStamp newTarget = mTargetTime + mRateDuration * (numElapsedIntervals + 1);
+
+    // the amount of (integer) ms until the next time we should tick
+    uint32_t delay = static_cast<uint32_t>((newTarget - aNowTime).ToMilliseconds());
+
+    // Without this block, we'll always schedule on interval ticks;
+    // with it, we'll schedule immediately if we missed our tick target
+    // last time.
+#if 0
+    if (numElapsedIntervals > 0) {
+      // we're late, so reset
+      newTarget = aNowTime;
+      delay = 0;
+    }
+#endif
+
+    // log info & lateness
+    LOG("[%p] precise timer last tick late by %f ms, next tick in %d ms",
+        this,
+        (aNowTime - mTargetTime).ToMilliseconds(),
+        delay);
+
+    // then schedule the timer
+    mTimer->InitWithFuncCallback(TimerTick, this, delay, nsITimer::TYPE_ONE_SHOT);
+
+    mTargetTime = newTarget;
+  }
+};
+
+/*
+ * A RefreshDriverTimer for inactive documents.  When a new refresh driver is
+ * added, the rate is reset to the base (normally 1s/1fps).  Every time
+ * it ticks, a single refresh driver is poked.  Once they have all been poked,
+ * the duration between ticks doubles, up to mDisableAfterMilliseconds.  At that point,
+ * the timer is quiet and doesn't tick (until something is added to it again).
+ *
+ * When a timer is removed, there is a possibility of another timer
+ * being skipped for one cycle.  We could avoid this by adjusting
+ * mNextDriverIndex in RemoveRefreshDriver, but there's little need to
+ * add that complexity.  All we want is for inactive drivers to tick
+ * at some point, but we don't care too much about how often.
+ */
+class InactiveRefreshDriverTimer :
+    public RefreshDriverTimer
+{
+public:
+  InactiveRefreshDriverTimer(double aRate)
+    : RefreshDriverTimer(aRate),
+      mNextTickDuration(aRate),
+      mDisableAfterMilliseconds(-1.0),
+      mNextDriverIndex(0)
+  {
+    mTimer = do_CreateInstance(NS_TIMER_CONTRACTID);
+  }
+
+  InactiveRefreshDriverTimer(double aRate, double aDisableAfterMilliseconds)
+    : RefreshDriverTimer(aRate),
+      mNextTickDuration(aRate),
+      mDisableAfterMilliseconds(aDisableAfterMilliseconds),
+      mNextDriverIndex(0)
+  {
+    mTimer = do_CreateInstance(NS_TIMER_CONTRACTID);
+  }
+
+  virtual void AddRefreshDriver(nsRefreshDriver* aDriver)
+  {
+    RefreshDriverTimer::AddRefreshDriver(aDriver);
+
+    LOG("[%p] inactive timer got new refresh driver %p, resetting rate",
+        this, aDriver);
+
+    // reset the timer, and start with the newly added one next time.
+    mNextTickDuration = mRateMilliseconds;
+
+    // we don't really have to start with the newly added one, but we may as well
+    // not tick the old ones at the fastest rate any more than we need to.
+    mNextDriverIndex = mRefreshDrivers.Length() - 1;
+
+    StopTimer();
+    StartTimer();
+  }
+
+protected:
+  virtual void StartTimer()
+  {
+    mLastFireTime = TimeStamp::Now();
+    mTargetTime = mLastFireTime;
+
+    mTimer->InitWithFuncCallback(TimerTickOne, this, 0, nsITimer::TYPE_ONE_SHOT);
+  }
+
+  virtual void StopTimer()
+  {
+    mTimer->Cancel();
+  }
+
+  virtual void ScheduleNextTick(TimeStamp aNowTime)
+  {
+    if (mDisableAfterMilliseconds > 0.0 &&
+        mNextTickDuration > mDisableAfterMilliseconds)
+    {
+      // We hit the time after which we should disable
+      // inactive window refreshes; don't schedule anything
+      // until we get kicked by an AddRefreshDriver call.
+      return;
+    }
+
+    // double the next tick time if we've already gone through all of them once
+    if (mNextDriverIndex >= mRefreshDrivers.Length()) {
+      mNextTickDuration *= 2.0;
+      mNextDriverIndex = 0;
+    }
+
+    // this doesn't need to be precise; do a simple schedule
+    uint32_t delay = static_cast<uint32_t>(mNextTickDuration);
+    mTimer->InitWithFuncCallback(TimerTickOne, this, delay, nsITimer::TYPE_ONE_SHOT);
+
+    LOG("[%p] inactive timer next tick in %f ms [index %d/%d]", this, mNextTickDuration,
+        mNextDriverIndex, mRefreshDrivers.Length());
+  }
+
+  /* Runs just one driver's tick. */
+  void TickOne()
+  {
+    int64_t jsnow = JS_Now();
+    TimeStamp now = TimeStamp::Now();
+
+    ScheduleNextTick(now);
+
+    mLastFireEpoch = jsnow;
+    mLastFireTime = now;
+
+    nsTArray<nsRefPtr<nsRefreshDriver> > drivers(mRefreshDrivers);
+    if (mNextDriverIndex < drivers.Length() &&
+        !drivers[mNextDriverIndex]->IsTestControllingRefreshesEnabled())
+    {
+      TickDriver(drivers[mNextDriverIndex], jsnow, now);
+    }
+
+    mNextDriverIndex++;
+  }
+
+  static void TimerTickOne(nsITimer* aTimer, void* aClosure)
+  {
+    InactiveRefreshDriverTimer *timer = static_cast<InactiveRefreshDriverTimer*>(aClosure);
+    timer->TickOne();
+  }
+
+  nsRefPtr<nsITimer> mTimer;
+  double mNextTickDuration;
+  double mDisableAfterMilliseconds;
+  uint32_t mNextDriverIndex;
+};
+
+} // namespace mozilla
+
+static PreciseRefreshDriverTimer *sRegularRateTimer = nullptr;
+static InactiveRefreshDriverTimer *sThrottledRateTimer = nullptr;
+
+static int32_t sHighPrecisionTimerRequests = 0;
 
 /* static */ void
 nsRefreshDriver::InitializeStatics()
 {
-  Preferences::AddBoolVarCache(&sPrecisePref,
-                               "layout.frame_rate.precise",
-                               false);
+#ifdef PR_LOGGING
+  if (!gLog) {
+    gLog = PR_NewLogModule("nsRefreshDriver");
+  }
+#endif
+}
+
+/* static */ void
+nsRefreshDriver::Shutdown()
+{
+  // clean up our timers
+  delete sRegularRateTimer;
+  delete sThrottledRateTimer;
+
+  sRegularRateTimer = nullptr;
+  sThrottledRateTimer = nullptr;
 }
 
 /* static */ int32_t
@@ -52,46 +437,60 @@ nsRefreshDriver::DefaultInterval()
 
 // Compute the interval to use for the refresh driver timer, in
 // milliseconds
-int32_t
-nsRefreshDriver::GetRefreshTimerInterval() const
+double
+nsRefreshDriver::GetRegularTimerInterval() const
 {
-  const char* prefName =
-    mThrottled ? "layout.throttled_frame_rate" : "layout.frame_rate";
-  int32_t rate = Preferences::GetInt(prefName, -1);
+  int32_t rate = Preferences::GetInt("layout.frame_rate", -1);
   if (rate <= 0) {
     // TODO: get the rate from the platform
-    rate = mThrottled ? DEFAULT_THROTTLED_FRAME_RATE : DEFAULT_FRAME_RATE;
+    rate = DEFAULT_FRAME_RATE;
   }
-  NS_ASSERTION(rate > 0, "Must have positive rate here");
-  int32_t interval = NSToIntRound(1000.0/rate);
-  if (mThrottled) {
-    interval = NS_MAX(interval, mLastTimerInterval * 2);
-  }
-  mLastTimerInterval = interval;
-  return interval;
+  return 1000.0 / rate;
 }
 
-int32_t
-nsRefreshDriver::GetRefreshTimerType() const
+double
+nsRefreshDriver::GetThrottledTimerInterval() const
+{
+  int32_t rate = Preferences::GetInt("layout.throttled_frame_rate", -1);
+  if (rate <= 0) {
+    rate = DEFAULT_THROTTLED_FRAME_RATE;
+  }
+  return 1000.0 / rate;
+}
+
+double
+nsRefreshDriver::GetRefreshTimerInterval() const
+{
+  return mThrottled ? GetThrottledTimerInterval() : GetRegularTimerInterval();
+}
+
+RefreshDriverTimer*
+nsRefreshDriver::ChooseTimer() const
 {
   if (mThrottled) {
-    return nsITimer::TYPE_ONE_SHOT;
+    if (!sThrottledRateTimer) 
+      sThrottledRateTimer = new InactiveRefreshDriverTimer(GetThrottledTimerInterval(),
+                                                           DEFAULT_INACTIVE_TIMER_DISABLE_SECONDS * 1000.0);
+    return sThrottledRateTimer;
   }
-  if (HaveFrameRequestCallbacks() || sPrecisePref) {
-    return nsITimer::TYPE_REPEATING_PRECISE_CAN_SKIP;
-  }
-  return nsITimer::TYPE_REPEATING_SLACK;
+
+  if (!sRegularRateTimer)
+    sRegularRateTimer = new PreciseRefreshDriverTimer(GetRegularTimerInterval());
+  return sRegularRateTimer;
 }
 
-nsRefreshDriver::nsRefreshDriver(nsPresContext *aPresContext)
+nsRefreshDriver::nsRefreshDriver(nsPresContext* aPresContext)
   : mPresContext(aPresContext),
+    mActiveTimer(nullptr),
     mFrozen(false),
     mThrottled(false),
     mTestControllingRefreshes(false),
-    mTimerIsPrecise(false),
     mViewManagerFlushIsPending(false),
-    mLastTimerInterval(0)
+    mRequestedHighPrecision(false)
 {
+  mMostRecentRefreshEpochTime = JS_Now();
+  mMostRecentRefresh = TimeStamp::Now();
+
   mRequests.Init();
 }
 
@@ -99,7 +498,7 @@ nsRefreshDriver::~nsRefreshDriver()
 {
   NS_ABORT_IF_FALSE(ObserverCount() == 0,
                     "observers should have unregistered");
-  NS_ABORT_IF_FALSE(!mTimer, "timer should be gone");
+  NS_ABORT_IF_FALSE(!mActiveTimer, "timer should be gone");
   
   for (uint32_t i = 0; i < mPresShellsToInvalidateIfHidden.Length(); i++) {
     mPresShellsToInvalidateIfHidden[i]->InvalidatePresShellIfHidden();
@@ -112,12 +511,22 @@ nsRefreshDriver::~nsRefreshDriver()
 void
 nsRefreshDriver::AdvanceTimeAndRefresh(int64_t aMilliseconds)
 {
-  mTestControllingRefreshes = true;
+  // ensure that we're removed from our driver
+  StopTimer();
+
+  if (!mTestControllingRefreshes) {
+    mMostRecentRefreshEpochTime = JS_Now();
+    mMostRecentRefresh = TimeStamp::Now();
+
+    mTestControllingRefreshes = true;
+  }
+
   mMostRecentRefreshEpochTime += aMilliseconds * 1000;
-  mMostRecentRefresh += TimeDuration::FromMilliseconds(aMilliseconds);
+  mMostRecentRefresh += TimeDuration::FromMilliseconds((double) aMilliseconds);
+
   nsCxPusher pusher;
   if (pusher.PushNull()) {
-    Notify(nullptr);
+    DoTick();
     pusher.Pop();
   }
 }
@@ -126,31 +535,23 @@ void
 nsRefreshDriver::RestoreNormalRefresh()
 {
   mTestControllingRefreshes = false;
-  nsCxPusher pusher;
-  if (pusher.PushNull()) {
-    Notify(nullptr); // will call UpdateMostRecentRefresh()
-    pusher.Pop();
-  }
+  EnsureTimerStarted(false);
 }
 
 TimeStamp
 nsRefreshDriver::MostRecentRefresh() const
 {
-  const_cast<nsRefreshDriver*>(this)->EnsureTimerStarted(false);
-
   return mMostRecentRefresh;
 }
 
 int64_t
 nsRefreshDriver::MostRecentRefreshEpochTime() const
 {
-  const_cast<nsRefreshDriver*>(this)->EnsureTimerStarted(false);
-
   return mMostRecentRefreshEpochTime;
 }
 
 bool
-nsRefreshDriver::AddRefreshObserver(nsARefreshObserver *aObserver,
+nsRefreshDriver::AddRefreshObserver(nsARefreshObserver* aObserver,
                                     mozFlushType aFlushType)
 {
   ObserverArray& array = ArrayFor(aFlushType);
@@ -162,7 +563,7 @@ nsRefreshDriver::AddRefreshObserver(nsARefreshObserver *aObserver,
 }
 
 bool
-nsRefreshDriver::RemoveRefreshObserver(nsARefreshObserver *aObserver,
+nsRefreshDriver::RemoveRefreshObserver(nsARefreshObserver* aObserver,
                                        mozFlushType aFlushType)
 {
   ObserverArray& array = ArrayFor(aFlushType);
@@ -195,47 +596,67 @@ void nsRefreshDriver::ClearAllImageRequests()
 void
 nsRefreshDriver::EnsureTimerStarted(bool aAdjustingTimer)
 {
-  if (mTimer || mFrozen || !mPresContext) {
-    // It's already been started, or we don't want to start it now or
-    // we've been disconnected.
+  if (mTestControllingRefreshes)
+    return;
+
+  // if the only change that's needed is that we need high precision,
+  // then just set that
+  if (!mThrottled && !mRequestedHighPrecision && mFrameRequestCallbackDocs.Length() > 0) {
+    SetHighPrecisionTimersEnabled(true);
+  } else if (mRequestedHighPrecision) {
+    SetHighPrecisionTimersEnabled(false);
+  }
+
+  // will it already fire, and no other changes needed?
+  if (mActiveTimer && !aAdjustingTimer)
+    return;
+
+  if (mFrozen || !mPresContext) {
+    // If we don't want to start it now, or we've been disconnected.
+    StopTimer();
     return;
   }
 
-  if (!aAdjustingTimer) {
-    // If we didn't already have a timer and aAdjustingTimer is false,
-    // then we just got our first observer (or an explicit call to
-    // MostRecentRefresh by a caller who's likely to add an observer
-    // shortly).  This means we should fake a most-recent-refresh time
-    // of now so that said observer gets a reasonable refresh time, so
-    // things behave as though the timer had always been running.
-    UpdateMostRecentRefresh();
-  }
+  // we got here because we're either adjusting the time *or* we're
+  // starting it for the first time; make sure it's stopped.
+  StopTimer();
 
-  mTimer = do_CreateInstance(NS_TIMER_CONTRACTID);
-  if (!mTimer) {
-    return;
-  }
-
-  int32_t timerType = GetRefreshTimerType();
-  mTimerIsPrecise = (timerType == nsITimer::TYPE_REPEATING_PRECISE_CAN_SKIP);
-
-  nsresult rv = mTimer->InitWithCallback(this,
-                                         GetRefreshTimerInterval(),
-                                         timerType);
-  if (NS_FAILED(rv)) {
-    mTimer = nullptr;
-  }
+  mActiveTimer = ChooseTimer();
+  mActiveTimer->AddRefreshDriver(this);
 }
 
 void
 nsRefreshDriver::StopTimer()
 {
-  if (!mTimer) {
+  if (!mActiveTimer)
     return;
-  }
 
-  mTimer->Cancel();
-  mTimer = nullptr;
+  mActiveTimer->RemoveRefreshDriver(this);
+  mActiveTimer = nullptr;
+
+  if (mRequestedHighPrecision) {
+    SetHighPrecisionTimersEnabled(false);
+  }
+}
+
+void
+nsRefreshDriver::SetHighPrecisionTimersEnabled(bool aEnable)
+{
+  if (aEnable) {
+    NS_ASSERTION(!mRequestedHighPrecision, "SetHighPrecisionTimersEnabled(true) called when already requested!");
+#ifdef XP_WIN
+    if (++sHighPrecisionTimerRequests == 1)
+      timeBeginPeriod(1);
+#endif
+    mRequestedHighPrecision = true;
+  } else {
+    NS_ASSERTION(mRequestedHighPrecision, "SetHighPrecisionTimersEnabled(false) called when not requested!");
+#ifdef XP_WIN
+    if (--sHighPrecisionTimerRequests == 0)
+      timeEndPeriod(1);
+#endif
+    mRequestedHighPrecision = false;
+  }
 }
 
 uint32_t
@@ -263,18 +684,6 @@ nsRefreshDriver::ImageRequestCount() const
   return mRequests.Count();
 }
 
-void
-nsRefreshDriver::UpdateMostRecentRefresh()
-{
-  if (mTestControllingRefreshes) {
-    return;
-  }
-
-  // Call JS_Now first, since that can have nonzero latency in some rare cases.
-  mMostRecentRefreshEpochTime = JS_Now();
-  mMostRecentRefresh = TimeStamp::Now();
-}
-
 nsRefreshDriver::ObserverArray&
 nsRefreshDriver::ArrayFor(mozFlushType aFlushType)
 {
@@ -295,28 +704,34 @@ nsRefreshDriver::ArrayFor(mozFlushType aFlushType)
  * nsISupports implementation
  */
 
-NS_IMPL_ISUPPORTS1(nsRefreshDriver, nsITimerCallback)
+NS_IMPL_ISUPPORTS1(nsRefreshDriver, nsISupports)
 
 /*
  * nsITimerCallback implementation
  */
 
-NS_IMETHODIMP
-nsRefreshDriver::Notify(nsITimer *aTimer)
+void
+nsRefreshDriver::DoTick()
 {
-  SAMPLE_LABEL("nsRefreshDriver", "Notify");
-
   NS_PRECONDITION(!mFrozen, "Why are we notified while frozen?");
   NS_PRECONDITION(mPresContext, "Why are we notified after disconnection?");
   NS_PRECONDITION(!nsContentUtils::GetCurrentJSContext(),
                   "Shouldn't have a JSContext on the stack");
 
-  if (mTestControllingRefreshes && aTimer) {
-    // Ignore real refreshes from our timer (but honor the others).
-    return NS_OK;
+  if (mTestControllingRefreshes) {
+    Tick(mMostRecentRefreshEpochTime, mMostRecentRefresh);
+  } else {
+    Tick(JS_Now(), TimeStamp::Now());
   }
+}
 
-  UpdateMostRecentRefresh();
+void
+nsRefreshDriver::Tick(int64_t aNowEpoch, TimeStamp aNowTime)
+{
+  SAMPLE_LABEL("nsRefreshDriver", "Tick");
+
+  mMostRecentRefresh = aNowTime;
+  mMostRecentRefreshEpochTime = aNowEpoch;
 
   nsCOMPtr<nsIPresShell> presShell = mPresContext->GetPresShell();
   if (!presShell || (ObserverCount() == 0 && ImageRequestCount() == 0)) {
@@ -328,7 +743,7 @@ nsRefreshDriver::Notify(nsITimer *aTimer)
     // wait until we get a Notify() call when we have no observers
     // before stopping the timer.
     StopTimer();
-    return NS_OK;
+    return;
   }
 
   /*
@@ -341,11 +756,11 @@ nsRefreshDriver::Notify(nsITimer *aTimer)
     ObserverArray::EndLimitedIterator etor(mObservers[i]);
     while (etor.HasMore()) {
       nsRefPtr<nsARefreshObserver> obs = etor.GetNext();
-      obs->WillRefresh(mMostRecentRefresh);
+      obs->WillRefresh(aNowTime);
       
       if (!mPresContext || !mPresContext->GetPresShell()) {
         StopTimer();
-        return NS_OK;
+        return;
       }
     }
 
@@ -360,7 +775,7 @@ nsRefreshDriver::Notify(nsITimer *aTimer)
       // readded as needed.
       mFrameRequestCallbackDocs.Clear();
 
-      int64_t eventTime = mMostRecentRefreshEpochTime / PR_USEC_PER_MSEC;
+      int64_t eventTime = aNowEpoch / PR_USEC_PER_MSEC;
       for (uint32_t i = 0; i < frameRequestCallbacks.Length(); ++i) {
         nsAutoMicroTask mt;
         frameRequestCallbacks[i]->Sample(eventTime);
@@ -412,10 +827,9 @@ nsRefreshDriver::Notify(nsITimer *aTimer)
    * for refresh events.
    */
 
-  ImageRequestParameters parms = {mMostRecentRefresh};
+  ImageRequestParameters parms = {aNowTime};
   if (mRequests.Count()) {
     mRequests.EnumerateEntries(nsRefreshDriver::ImageRequestEnumerator, &parms);
-    EnsureTimerStarted(false);
   }
     
   for (uint32_t i = 0; i < mPresShellsToInvalidateIfHidden.Length(); i++) {
@@ -433,25 +847,6 @@ nsRefreshDriver::Notify(nsITimer *aTimer)
     printf("Ending ProcessPendingUpdates\n");
 #endif
   }
-
-  if (mThrottled ||
-      (mTimerIsPrecise !=
-       (GetRefreshTimerType() == nsITimer::TYPE_REPEATING_PRECISE_CAN_SKIP))) {
-    // Stop the timer now and restart it here.  Stopping is in the mThrottled
-    // case ok because either it's already one-shot, and it just fired, and all
-    // we need to do is null it out, or it's repeating and we need to reset it
-    // to be one-shot.  Stopping and restarting in the case when we need to
-    // switch from precise to slack timers or vice versa is unfortunately
-    // required.
-
-    // Note that the EnsureTimerStarted() call here is ok because
-    // EnsureTimerStarted makes sure to not start the timer if it shouldn't be
-    // started.
-    StopTimer();
-    EnsureTimerStarted(true);
-  }
-
-  return NS_OK;
 }
 
 PLDHashOperator
@@ -500,10 +895,9 @@ nsRefreshDriver::SetThrottled(bool aThrottled)
 {
   if (aThrottled != mThrottled) {
     mThrottled = aThrottled;
-    if (mTimer) {
+    if (mActiveTimer) {
       // We want to switch our timer type here, so just stop and
       // restart the timer.
-      StopTimer();
       EnsureTimerStarted(true);
     }
   }
@@ -513,14 +907,14 @@ void
 nsRefreshDriver::DoRefresh()
 {
   // Don't do a refresh unless we're in a state where we should be refreshing.
-  if (!mFrozen && mPresContext && mTimer) {
-    Notify(nullptr);
+  if (!mFrozen && mPresContext && mActiveTimer) {
+    DoTick();
   }
 }
 
 #ifdef DEBUG
 bool
-nsRefreshDriver::IsRefreshObserver(nsARefreshObserver *aObserver,
+nsRefreshDriver::IsRefreshObserver(nsARefreshObserver* aObserver,
                                    mozFlushType aFlushType)
 {
   ObserverArray& array = ArrayFor(aFlushType);
@@ -544,8 +938,8 @@ nsRefreshDriver::ScheduleFrameRequestCallbacks(nsIDocument* aDocument)
                mFrameRequestCallbackDocs.NoIndex,
                "Don't schedule the same document multiple times");
   mFrameRequestCallbackDocs.AppendElement(aDocument);
-  // No need to worry about restarting our timer in precise mode if it's
-  // already running; that will happen automatically when it fires.
+
+  // make sure that the timer is running
   EnsureTimerStarted(false);
 }
 

layout/base/nsRefreshDriver.h

@@ -1,3 +1,4 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set shiftwidth=2 tabstop=8 autoindent cindent expandtab: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -13,7 +14,6 @@
 
 #include "mozilla/TimeStamp.h"
 #include "mozFlushType.h"
-#include "nsITimer.h"
 #include "nsCOMPtr.h"
 #include "nsTObserverArray.h"
 #include "nsTArray.h"
@@ -32,6 +32,10 @@ class imgIRequest;
  * notified at refresh times.  When nothing needs to be painted, callers
  * may not be notified.
  */
+namespace mozilla {
+    class RefreshDriverTimer;
+}
+
 class nsARefreshObserver {
 public:
   // AddRef and Release signatures that match nsISupports.  Implementors
@@ -46,25 +50,28 @@ public:
   virtual void WillRefresh(mozilla::TimeStamp aTime) = 0;
 };
 
-class nsRefreshDriver MOZ_FINAL : public nsITimerCallback {
+class nsRefreshDriver MOZ_FINAL : public nsISupports {
 public:
   nsRefreshDriver(nsPresContext *aPresContext);
   ~nsRefreshDriver();
 
   static void InitializeStatics();
+  static void Shutdown();
 
   // nsISupports implementation
   NS_DECL_ISUPPORTS
 
-  // nsITimerCallback implementation
-  NS_DECL_NSITIMERCALLBACK
-
   /**
    * Methods for testing, exposed via nsIDOMWindowUtils.  See
    * nsIDOMWindowUtils.advanceTimeAndRefresh for description.
    */
   void AdvanceTimeAndRefresh(int64_t aMilliseconds);
   void RestoreNormalRefresh();
+  void DoTick();
+  bool IsTestControllingRefreshesEnabled() const
+  {
+    return mTestControllingRefreshes;
+  }
 
   /**
    * Return the time of the most recent refresh.  This is intended to be
@@ -226,6 +233,8 @@ private:
   typedef nsTObserverArray<nsARefreshObserver*> ObserverArray;
   typedef nsTHashtable<nsISupportsHashKey> RequestTable;
 
+  void Tick(int64_t aNowEpoch, mozilla::TimeStamp aNowTime);
+
   void EnsureTimerStarted(bool aAdjustingTimer);
   void StopTimer();
 
@@ -233,22 +242,20 @@ private:
   uint32_t ImageRequestCount() const;
   static PLDHashOperator ImageRequestEnumerator(nsISupportsHashKey* aEntry,
                                           void* aUserArg);
-  void UpdateMostRecentRefresh();
   ObserverArray& ArrayFor(mozFlushType aFlushType);
   // Trigger a refresh immediately, if haven't been disconnected or frozen.
   void DoRefresh();
 
-  int32_t GetRefreshTimerInterval() const;
-  int32_t GetRefreshTimerType() const;
+  double GetRefreshTimerInterval() const;
+  double GetRegularTimerInterval() const;
+  double GetThrottledTimerInterval() const;
 
   bool HaveFrameRequestCallbacks() const {
     return mFrameRequestCallbackDocs.Length() != 0;
   }
 
-  nsCOMPtr<nsITimer> mTimer;
-  mozilla::TimeStamp mMostRecentRefresh; // only valid when mTimer non-null
-  int64_t mMostRecentRefreshEpochTime;   // same thing as mMostRecentRefresh,
-                                         // but in microseconds since the epoch.
+  mozilla::RefreshDriverTimer* ChooseTimer() const;
+  mozilla::RefreshDriverTimer *mActiveTimer;
 
   nsPresContext *mPresContext; // weak; pres context passed in constructor
                                // and unset in Disconnect
@@ -256,11 +263,11 @@ private:
   bool mFrozen;
   bool mThrottled;
   bool mTestControllingRefreshes;
-  /* If mTimer is non-null, this boolean indicates whether the timer is
-     a precise timer.  If mTimer is null, this boolean's value can be
-     anything.  */
-  bool mTimerIsPrecise;
   bool mViewManagerFlushIsPending;
+  bool mRequestedHighPrecision;
+
+  int64_t mMostRecentRefreshEpochTime;
+  mozilla::TimeStamp mMostRecentRefresh;
 
   // separate arrays for each flush type we support
   ObserverArray mObservers[3];
@@ -272,14 +279,14 @@ private:
   // nsTArray on purpose, because we want to be able to swap.
   nsTArray<nsIDocument*> mFrameRequestCallbackDocs;
 
-  // This is the last interval we used for our timer.  May be 0 if we
-  // haven't computed a timer interval yet.
-  mutable int32_t mLastTimerInterval;
-
   // Helper struct for processing image requests
   struct ImageRequestParameters {
       mozilla::TimeStamp ts;
   };
+
+  friend class mozilla::RefreshDriverTimer;
+
+  void SetHighPrecisionTimersEnabled(bool aEnable);
 };
 
 #endif /* !defined(nsRefreshDriver_h_) */

layout/build/nsLayoutStatics.cpp

@@ -359,4 +359,6 @@ nsLayoutStatics::Shutdown()
   nsDOMMutationObserver::Shutdown();
 
   ContentParent::ShutDown();
+
+  nsRefreshDriver::Shutdown();
 }

xpcom/ds/TimeStamp.h

@@ -83,6 +83,18 @@ public:
     mValue -= aOther.mValue;
     return *this;
   }
+  TimeDuration operator*(const double aMultiplier) const {
+    return TimeDuration::FromTicks(mValue * int64_t(aMultiplier));
+  }
+  TimeDuration operator*(const int32_t aMultiplier) const {
+    return TimeDuration::FromTicks(mValue * int64_t(aMultiplier));
+  }
+  TimeDuration operator*(const uint32_t aMultiplier) const {
+    return TimeDuration::FromTicks(mValue * int64_t(aMultiplier));
+  }
+  TimeDuration operator*(const int64_t aMultiplier) const {
+    return TimeDuration::FromTicks(mValue * int64_t(aMultiplier));
+  }
   double operator/(const TimeDuration& aOther) {
     return static_cast<double>(mValue) / aOther.mValue;
   }