gfx/thebes/VsyncSource.cpp

   1 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  * This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "VsyncSource.h"
   7 #include "nsThreadUtils.h"
   8 #include "nsXULAppAPI.h"
   9 #include "mozilla/VsyncDispatcher.h"
  10 #include "MainThreadUtils.h"
  11 #include "gfxPlatform.h"
  12
  13 #ifdef MOZ_WAYLAND
  14 #  include "WaylandVsyncSource.h"
  15 #endif
  16
  17 namespace mozilla {
  18 namespace gfx {
  19
  20 VsyncSource::VsyncSource() : mState("VsyncSource::State") {
  21   MOZ_ASSERT(NS_IsMainThread());
  22 }
  23
  24 VsyncSource::~VsyncSource() { MOZ_ASSERT(NS_IsMainThread()); }
  25
  26 // Called on the vsync thread
  27 void VsyncSource::NotifyVsync(const TimeStamp& aVsyncTimestamp,
  28                               const TimeStamp& aOutputTimestamp) {
  29   VsyncId vsyncId;
  30   nsTArray<DispatcherRefWithCount> dispatchers;
  31
  32   {
  33     auto state = mState.Lock();
  34     vsyncId = state->mVsyncId.Next();
  35     dispatchers = state->mDispatchers.Clone();
  36     state->mVsyncId = vsyncId;
  37   }
  38
  39   // Notify our listeners, outside of the lock.
  40   const VsyncEvent event(vsyncId, aVsyncTimestamp, aOutputTimestamp);
  41   for (const auto& dispatcher : dispatchers) {
  42     dispatcher.mDispatcher->NotifyVsync(event);
  43   }
  44 }
  45
  46 void VsyncSource::AddVsyncDispatcher(VsyncDispatcher* aVsyncDispatcher) {
  47   MOZ_ASSERT(aVsyncDispatcher);
  48   {
  49     auto state = mState.Lock();
  50
  51     // Find the dispatcher in mDispatchers. If it is already present, increment
  52     // the count. If not, add it with a count of 1.
  53     bool found = false;
  54     for (auto& dispatcherRefWithCount : state->mDispatchers) {
  55       if (dispatcherRefWithCount.mDispatcher == aVsyncDispatcher) {
  56         dispatcherRefWithCount.mCount++;
  57         found = true;
  58         break;
  59       }
  60     }
  61     if (!found) {
  62       state->mDispatchers.AppendElement(
  63           DispatcherRefWithCount{aVsyncDispatcher, 1});
  64     }
  65   }
  66
  67   UpdateVsyncStatus();
  68 }
  69
  70 void VsyncSource::RemoveVsyncDispatcher(VsyncDispatcher* aVsyncDispatcher) {
  71   MOZ_ASSERT(aVsyncDispatcher);
  72   {
  73     auto state = mState.Lock();
  74
  75     // Find the dispatcher in mDispatchers. If found, decrement the count.
  76     // If the count becomes zero, remove it from mDispatchers.
  77     for (auto it = state->mDispatchers.begin(); it != state->mDispatchers.end();
  78          ++it) {
  79       if (it->mDispatcher == aVsyncDispatcher) {
  80         it->mCount--;
  81         if (it->mCount == 0) {
  82           state->mDispatchers.RemoveElementAt(it);
  83         }
  84         break;
  85       }
  86     }
  87
  88     // In the future we should probably MOZ_RELEASE_ASSERT here that we don't
  89     // try to remove a dispatcher which isn't in mDispatchers.
  90   }
  91
  92   UpdateVsyncStatus();
  93 }
  94
  95 // This is the base class implementation. Subclasses override this method.
  96 TimeDuration VsyncSource::GetVsyncRate() {
  97   // If hardware queries fail / are unsupported, we have to just guess.
  98   return TimeDuration::FromMilliseconds(1000.0 / 60.0);
  99 }
 100
 101 void VsyncSource::UpdateVsyncStatus() {
 102   if (!NS_IsMainThread()) {
 103     NS_DispatchToMainThread(NS_NewRunnableFunction(
 104         "VsyncSource::UpdateVsyncStatus",
 105         [self = RefPtr{this}] { self->UpdateVsyncStatus(); }));
 106     return;
 107   }
 108
 109   MOZ_ASSERT(NS_IsMainThread());
 110   // WARNING: This function SHOULD NOT BE CALLED WHILE HOLDING LOCKS
 111   // NotifyVsync grabs a lock to dispatch vsync events
 112   // When disabling vsync, we wait for the underlying thread to stop on some
 113   // platforms We can deadlock if we wait for the underlying vsync thread to
 114   // stop while the vsync thread is in NotifyVsync.
 115   bool enableVsync = false;
 116   {  // scope lock
 117     auto state = mState.Lock();
 118     enableVsync = !state->mDispatchers.IsEmpty();
 119   }
 120
 121   if (enableVsync) {
 122     EnableVsync();
 123   } else {
 124     DisableVsync();
 125   }
 126
 127   if (IsVsyncEnabled() != enableVsync) {
 128     NS_WARNING("Vsync status did not change.");
 129   }
 130 }
 131
 132 // static
 133 Maybe<TimeDuration> VsyncSource::GetFastestVsyncRate() {
 134   Maybe<TimeDuration> retVal;
 135   if (!gfxPlatform::Initialized()) {
 136     return retVal;
 137   }
 138
 139   RefPtr<VsyncDispatcher> vsyncDispatcher =
 140       gfxPlatform::GetPlatform()->GetGlobalVsyncDispatcher();
 141   RefPtr<VsyncSource> vsyncSource = vsyncDispatcher->GetCurrentVsyncSource();
 142   if (vsyncSource->IsVsyncEnabled()) {
 143     retVal.emplace(vsyncSource->GetVsyncRate());
 144 #ifdef MOZ_WAYLAND
 145     Maybe<TimeDuration> waylandRate = WaylandVsyncSource::GetFastestVsyncRate();
 146     if (waylandRate) {
 147       if (!retVal) {
 148         retVal.emplace(*waylandRate);
 149       } else if (*waylandRate < *retVal) {
 150         retVal = waylandRate;
 151       }
 152     }
 153 #endif
 154   }
 155
 156   return retVal;
 157 }
 158
 159 }  // namespace gfx
 160 }  // namespace mozilla