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99 lines
3.1 KiB
C++
99 lines
3.1 KiB
C++
/* -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 2; -*- */
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/* vim: set sw=4 ts=8 et tw=80 : */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_dom_TaskThrottler_h
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#define mozilla_dom_TaskThrottler_h
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#include <stdint.h> // for uint32_t
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#include "base/task.h" // for CancelableTask
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#include "mozilla/TimeStamp.h" // for TimeDuration, TimeStamp
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#include "mozilla/mozalloc.h" // for operator delete
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#include "nsAutoPtr.h" // for nsAutoPtr
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#include "nsTArray.h" // for nsTArray
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namespace tracked_objects {
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class Location;
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}
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namespace mozilla {
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namespace layers {
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/** The TaskThrottler prevents update event overruns. It is used in cases where
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* you're sending an async message and waiting for a reply. You need to call
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* PostTask to queue a task and TaskComplete when you get a response.
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*
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* The call to TaskComplete will run the recent task posted since the last
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* request was sent, if any. This means that at any time there can be at most 1
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* outstanding request being processed and at most 1 queued behind it.
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*
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* This is used in the context of repainting a scrollable region. While another
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* process is painting you might get several updates from the UI thread but when
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* the paint is complete you want to send the most recent.
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*/
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class TaskThrottler {
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public:
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TaskThrottler(const TimeStamp& aTimeStamp);
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/** Post a task to be run as soon as there are no outstanding tasks.
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*
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* @param aLocation Use the macro FROM_HERE
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* @param aTask Ownership of this object is transferred to TaskThrottler
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* which will delete it when it is either run or becomes
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* obsolete or the TaskThrottler is destructed.
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*/
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void PostTask(const tracked_objects::Location& aLocation,
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CancelableTask* aTask, const TimeStamp& aTimeStamp);
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/**
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* Mark the task as complete and process the next queued task.
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*/
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void TaskComplete(const TimeStamp& aTimeStamp);
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/**
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* Calculate the average time between processing the posted task and getting
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* the TaskComplete() call back.
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*/
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TimeDuration AverageDuration();
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/**
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* return true if Throttler has an outstanding task
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*/
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bool IsOutstanding() { return mOutstanding; }
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/**
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* Return the time elapsed since the last request was processed
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*/
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TimeDuration TimeSinceLastRequest(const TimeStamp& aTimeStamp);
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/**
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* Clear average history.
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*/
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void ClearHistory() { mDurations.Clear(); }
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/**
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* @param aMaxDurations The maximum number of durations to measure.
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*/
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void SetMaxDurations(uint32_t aMaxDurations)
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{
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mMaxDurations = aMaxDurations;
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}
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private:
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bool mOutstanding;
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nsAutoPtr<CancelableTask> mQueuedTask;
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TimeStamp mStartTime;
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// How long it took in the past to paint after a series of previous requests.
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nsTArray<TimeDuration> mDurations;
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uint32_t mMaxDurations;
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};
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}
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}
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#endif // mozilla_dom_TaskThrottler_h
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