1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/gfx/layers/apz/src/TaskThrottler.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,101 @@
1.4 +/* -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 2; -*- */
1.5 +/* vim: set sw=4 ts=8 et tw=80 : */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +#ifndef mozilla_dom_TaskThrottler_h
1.11 +#define mozilla_dom_TaskThrottler_h
1.12 +
1.13 +#include <stdint.h> // for uint32_t
1.14 +#include "base/task.h" // for CancelableTask
1.15 +#include "mozilla/TimeStamp.h" // for TimeDuration, TimeStamp
1.16 +#include "mozilla/RollingMean.h" // for RollingMean
1.17 +#include "mozilla/mozalloc.h" // for operator delete
1.18 +#include "nsAutoPtr.h" // for nsAutoPtr
1.19 +#include "nsTArray.h" // for nsTArray
1.20 +
1.21 +namespace tracked_objects {
1.22 +class Location;
1.23 +}
1.24 +
1.25 +namespace mozilla {
1.26 +namespace layers {
1.27 +
1.28 +/** The TaskThrottler prevents update event overruns. It is used in cases where
1.29 + * you're sending an async message and waiting for a reply. You need to call
1.30 + * PostTask to queue a task and TaskComplete when you get a response.
1.31 + *
1.32 + * The call to TaskComplete will run the recent task posted since the last
1.33 + * request was sent, if any. This means that at any time there can be at most 1
1.34 + * outstanding request being processed and at most 1 queued behind it.
1.35 + *
1.36 + * This is used in the context of repainting a scrollable region. While another
1.37 + * process is painting you might get several updates from the UI thread but when
1.38 + * the paint is complete you want to send the most recent.
1.39 + */
1.40 +
1.41 +class TaskThrottler {
1.42 +public:
1.43 + TaskThrottler(const TimeStamp& aTimeStamp);
1.44 +
1.45 + /** Post a task to be run as soon as there are no outstanding tasks.
1.46 + *
1.47 + * @param aLocation Use the macro FROM_HERE
1.48 + * @param aTask Ownership of this object is transferred to TaskThrottler
1.49 + * which will delete it when it is either run or becomes
1.50 + * obsolete or the TaskThrottler is destructed.
1.51 + */
1.52 + void PostTask(const tracked_objects::Location& aLocation,
1.53 + CancelableTask* aTask, const TimeStamp& aTimeStamp);
1.54 + /**
1.55 + * Mark the task as complete and process the next queued task.
1.56 + */
1.57 + void TaskComplete(const TimeStamp& aTimeStamp);
1.58 +
1.59 + /**
1.60 + * Calculate the average time between processing the posted task and getting
1.61 + * the TaskComplete() call back.
1.62 + */
1.63 + TimeDuration AverageDuration()
1.64 + {
1.65 + return mMean.empty() ? TimeDuration() : mMean.mean();
1.66 + }
1.67 +
1.68 + /**
1.69 + * return true if Throttler has an outstanding task
1.70 + */
1.71 + bool IsOutstanding() { return mOutstanding; }
1.72 +
1.73 + /**
1.74 + * Return the time elapsed since the last request was processed
1.75 + */
1.76 + TimeDuration TimeSinceLastRequest(const TimeStamp& aTimeStamp);
1.77 +
1.78 + /**
1.79 + * Clear average history.
1.80 + */
1.81 + void ClearHistory() { mMean.clear(); }
1.82 +
1.83 + /**
1.84 + * @param aMaxDurations The maximum number of durations to measure.
1.85 + */
1.86 +
1.87 + void SetMaxDurations(uint32_t aMaxDurations)
1.88 + {
1.89 + if (aMaxDurations != mMean.maxValues()) {
1.90 + mMean = RollingMean<TimeDuration, TimeDuration>(aMaxDurations);
1.91 + }
1.92 + }
1.93 +
1.94 +private:
1.95 + bool mOutstanding;
1.96 + nsAutoPtr<CancelableTask> mQueuedTask;
1.97 + TimeStamp mStartTime;
1.98 + RollingMean<TimeDuration, TimeDuration> mMean;
1.99 +};
1.100 +
1.101 +}
1.102 +}
1.103 +
1.104 +#endif // mozilla_dom_TaskThrottler_h
