1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
3 /* This Source Code Form is subject to the terms of the Mozilla Public
4  * License, v. 2.0. If a copy of the MPL was not distributed with this
5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
6 
7 #include "InputEventStatistics.h"
8 
9 #include "mozilla/Preferences.h"
10 #include "nsRefreshDriver.h"
11 
12 namespace mozilla {
13 
Get()14 /*static*/ InputEventStatistics& InputEventStatistics::Get() {
15   static UniquePtr<InputEventStatistics> sInstance;
16   if (!sInstance) {
17     sInstance = MakeUnique<InputEventStatistics>(ConstructorCookie());
18     ClearOnShutdown(&sInstance);
19   }
20   return *sInstance;
21 }
22 
GetMean()23 TimeDuration InputEventStatistics::TimeDurationCircularBuffer::GetMean() {
24   return mTotal / (int64_t)mSize;
25 }
26 
InputEventStatistics(ConstructorCookie &&)27 InputEventStatistics::InputEventStatistics(ConstructorCookie&&)
28     : mEnable(false) {
29   MOZ_ASSERT(Preferences::IsServiceAvailable());
30   uint32_t inputDuration = Preferences::GetUint(
31       "input_event_queue.default_duration_per_event", sDefaultInputDuration);
32 
33   TimeDuration defaultDuration = TimeDuration::FromMilliseconds(inputDuration);
34 
35   uint32_t count = Preferences::GetUint(
36       "input_event_queue.count_for_prediction", sInputCountForPrediction);
37 
38   mLastInputDurations =
39       MakeUnique<TimeDurationCircularBuffer>(count, defaultDuration);
40 
41   uint32_t maxDuration = Preferences::GetUint("input_event_queue.duration.max",
42                                               sMaxReservedTimeForHandlingInput);
43 
44   uint32_t minDuration = Preferences::GetUint("input_event_queue.duration.min",
45                                               sMinReservedTimeForHandlingInput);
46 
47   mMaxInputDuration = TimeDuration::FromMilliseconds(maxDuration);
48   mMinInputDuration = TimeDuration::FromMilliseconds(minDuration);
49 }
50 
GetInputHandlingStartTime(uint32_t aInputCount)51 TimeStamp InputEventStatistics::GetInputHandlingStartTime(
52     uint32_t aInputCount) {
53   MOZ_ASSERT(mEnable);
54   Maybe<TimeStamp> nextTickHint = nsRefreshDriver::GetNextTickHint();
55 
56   if (nextTickHint.isNothing()) {
57     // Return a past time to process input events immediately.
58     return TimeStamp::Now() - TimeDuration::FromMilliseconds(1);
59   }
60   TimeDuration inputCost = mLastInputDurations->GetMean() * aInputCount;
61   inputCost = inputCost > mMaxInputDuration   ? mMaxInputDuration
62               : inputCost < mMinInputDuration ? mMinInputDuration
63                                               : inputCost;
64 
65   return nextTickHint.value() - inputCost;
66 }
67 
GetMaxInputHandlingDuration() const68 TimeDuration InputEventStatistics::GetMaxInputHandlingDuration() const {
69   MOZ_ASSERT(StaticPrefs::dom_input_events_strict_input_vsync_alignment());
70   return mMaxInputDuration;
71 }
72 }  // namespace mozilla
73