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      1 /*
      2  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
     14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
     17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
     21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     24  *
     25  */
     26 
     27 #include "config.h"
     28 #include "core/frame/DOMTimer.h"
     29 
     30 #include "core/dom/ExecutionContext.h"
     31 #include "core/inspector/InspectorInstrumentation.h"
     32 #include "core/inspector/InspectorTraceEvents.h"
     33 #include "platform/TraceEvent.h"
     34 #include "wtf/CurrentTime.h"
     35 
     36 namespace WebCore {
     37 
     38 static const int maxIntervalForUserGestureForwarding = 1000; // One second matches Gecko.
     39 static const int maxTimerNestingLevel = 5;
     40 static const double oneMillisecond = 0.001;
     41 // Chromium uses a minimum timer interval of 4ms. We'd like to go
     42 // lower; however, there are poorly coded websites out there which do
     43 // create CPU-spinning loops.  Using 4ms prevents the CPU from
     44 // spinning too busily and provides a balance between CPU spinning and
     45 // the smallest possible interval timer.
     46 static const double minimumInterval = 0.004;
     47 
     48 static int timerNestingLevel = 0;
     49 
     50 static inline bool shouldForwardUserGesture(int interval, int nestingLevel)
     51 {
     52     return UserGestureIndicator::processingUserGesture()
     53         && interval <= maxIntervalForUserGestureForwarding
     54         && nestingLevel == 1; // Gestures should not be forwarded to nested timers.
     55 }
     56 
     57 double DOMTimer::hiddenPageAlignmentInterval()
     58 {
     59     // Timers on hidden pages are aligned so that they fire once per
     60     // second at most.
     61     return 1.0;
     62 }
     63 
     64 double DOMTimer::visiblePageAlignmentInterval()
     65 {
     66     // Alignment does not apply to timers on visible pages.
     67     return 0;
     68 }
     69 
     70 int DOMTimer::install(ExecutionContext* context, PassOwnPtr<ScheduledAction> action, int timeout, bool singleShot)
     71 {
     72     int timeoutID = context->installNewTimeout(action, timeout, singleShot);
     73     TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "TimerInstall", "data", InspectorTimerInstallEvent::data(context, timeoutID, timeout, singleShot));
     74     TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline.stack"), "CallStack", "stack", InspectorCallStackEvent::currentCallStack());
     75     // FIXME(361045): remove InspectorInstrumentation calls once DevTools Timeline migrates to tracing.
     76     InspectorInstrumentation::didInstallTimer(context, timeoutID, timeout, singleShot);
     77     return timeoutID;
     78 }
     79 
     80 void DOMTimer::removeByID(ExecutionContext* context, int timeoutID)
     81 {
     82     context->removeTimeoutByID(timeoutID);
     83     TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "TimerRemove", "data", InspectorTimerRemoveEvent::data(context, timeoutID));
     84     TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline.stack"), "CallStack", "stack", InspectorCallStackEvent::currentCallStack());
     85     // FIXME(361045): remove InspectorInstrumentation calls once DevTools Timeline migrates to tracing.
     86     InspectorInstrumentation::didRemoveTimer(context, timeoutID);
     87 }
     88 
     89 DOMTimer::DOMTimer(ExecutionContext* context, PassOwnPtr<ScheduledAction> action, int interval, bool singleShot, int timeoutID)
     90     : SuspendableTimer(context)
     91     , m_timeoutID(timeoutID)
     92     , m_nestingLevel(timerNestingLevel + 1)
     93     , m_action(action)
     94 {
     95     ASSERT(timeoutID > 0);
     96     if (shouldForwardUserGesture(interval, m_nestingLevel))
     97         m_userGestureToken = UserGestureIndicator::currentToken();
     98 
     99     double intervalMilliseconds = std::max(oneMillisecond, interval * oneMillisecond);
    100     if (intervalMilliseconds < minimumInterval && m_nestingLevel >= maxTimerNestingLevel)
    101         intervalMilliseconds = minimumInterval;
    102     if (singleShot)
    103         startOneShot(intervalMilliseconds, FROM_HERE);
    104     else
    105         startRepeating(intervalMilliseconds, FROM_HERE);
    106 }
    107 
    108 DOMTimer::~DOMTimer()
    109 {
    110 }
    111 
    112 int DOMTimer::timeoutID() const
    113 {
    114     return m_timeoutID;
    115 }
    116 
    117 void DOMTimer::fired()
    118 {
    119     ExecutionContext* context = executionContext();
    120     timerNestingLevel = m_nestingLevel;
    121     ASSERT(!context->activeDOMObjectsAreSuspended());
    122     // Only the first execution of a multi-shot timer should get an affirmative user gesture indicator.
    123     UserGestureIndicator gestureIndicator(m_userGestureToken.release());
    124 
    125     TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "TimerFire", "data", InspectorTimerFireEvent::data(context, m_timeoutID));
    126     // FIXME(361045): remove InspectorInstrumentation calls once DevTools Timeline migrates to tracing.
    127     InspectorInstrumentationCookie cookie = InspectorInstrumentation::willFireTimer(context, m_timeoutID);
    128 
    129     // Simple case for non-one-shot timers.
    130     if (isActive()) {
    131         if (repeatInterval() && repeatInterval() < minimumInterval) {
    132             m_nestingLevel++;
    133             if (m_nestingLevel >= maxTimerNestingLevel)
    134                 augmentRepeatInterval(minimumInterval - repeatInterval());
    135         }
    136 
    137         // No access to member variables after this point, it can delete the timer.
    138         m_action->execute(context);
    139 
    140         InspectorInstrumentation::didFireTimer(cookie);
    141 
    142         return;
    143     }
    144 
    145     // Delete timer before executing the action for one-shot timers.
    146     OwnPtr<ScheduledAction> action = m_action.release();
    147 
    148     // This timer is being deleted; no access to member variables allowed after this point.
    149     context->removeTimeoutByID(m_timeoutID);
    150 
    151     action->execute(context);
    152 
    153     InspectorInstrumentation::didFireTimer(cookie);
    154     TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "UpdateCounters", "data", InspectorUpdateCountersEvent::data());
    155 
    156     timerNestingLevel = 0;
    157 }
    158 
    159 void DOMTimer::contextDestroyed()
    160 {
    161     SuspendableTimer::contextDestroyed();
    162 }
    163 
    164 void DOMTimer::stop()
    165 {
    166     SuspendableTimer::stop();
    167     // Need to release JS objects potentially protected by ScheduledAction
    168     // because they can form circular references back to the ExecutionContext
    169     // which will cause a memory leak.
    170     m_action.clear();
    171 }
    172 
    173 double DOMTimer::alignedFireTime(double fireTime) const
    174 {
    175     double alignmentInterval = executionContext()->timerAlignmentInterval();
    176     if (alignmentInterval) {
    177         double currentTime = monotonicallyIncreasingTime();
    178         if (fireTime <= currentTime)
    179             return fireTime;
    180 
    181         // When a repeating timer is scheduled for exactly the
    182         // background page alignment interval, because it's impossible
    183         // for the timer to be rescheduled instantaneously, it misses
    184         // every other fire time. Avoid this by looking at the next
    185         // fire time rounded both down and up.
    186 
    187         double alignedTimeRoundedDown = floor(fireTime / alignmentInterval) * alignmentInterval;
    188         double alignedTimeRoundedUp = ceil(fireTime / alignmentInterval) * alignmentInterval;
    189 
    190         // If the version rounded down is in the past, discard it
    191         // immediately.
    192 
    193         if (alignedTimeRoundedDown <= currentTime)
    194             return alignedTimeRoundedUp;
    195 
    196         // Only use the rounded-down time if it's within a certain
    197         // tolerance of the fire time. This avoids speeding up timers
    198         // on background pages in the common case.
    199 
    200         if (fireTime - alignedTimeRoundedDown < minimumInterval)
    201             return alignedTimeRoundedDown;
    202 
    203         return alignedTimeRoundedUp;
    204     }
    205 
    206     return fireTime;
    207 }
    208 
    209 } // namespace WebCore
    210