gecko-dev/gfx/thebes/VsyncSource.cpp

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "VsyncSource.h"
#include "nsThreadUtils.h"
#include "nsXULAppAPI.h"
#include "mozilla/VsyncDispatcher.h"
#include "MainThreadUtils.h"

namespace mozilla {
namespace gfx {

void VsyncSource::AddCompositorVsyncDispatcher(
    CompositorVsyncDispatcher* aCompositorVsyncDispatcher) {
  MOZ_ASSERT(XRE_IsParentProcess());
  MOZ_ASSERT(NS_IsMainThread());
  // Just use the global display until we have enough information to get the
  // corresponding display for compositor.
  GetGlobalDisplay().AddCompositorVsyncDispatcher(aCompositorVsyncDispatcher);
}

void VsyncSource::RemoveCompositorVsyncDispatcher(
    CompositorVsyncDispatcher* aCompositorVsyncDispatcher) {
  MOZ_ASSERT(XRE_IsParentProcess());
  MOZ_ASSERT(NS_IsMainThread());
  // See also AddCompositorVsyncDispatcher().
  GetGlobalDisplay().RemoveCompositorVsyncDispatcher(
      aCompositorVsyncDispatcher);
}

void VsyncSource::MoveListenersToNewSource(VsyncSource* aNewSource) {
  GetGlobalDisplay().MoveListenersToNewSource(aNewSource->GetGlobalDisplay());
}

RefPtr<RefreshTimerVsyncDispatcher>
VsyncSource::GetRefreshTimerVsyncDispatcher() {
  MOZ_ASSERT(XRE_IsParentProcess());
  // See also AddCompositorVsyncDispatcher().
  return GetGlobalDisplay().GetRefreshTimerVsyncDispatcher();
}

VsyncSource::Display::Display()
    : mDispatcherLock("display dispatcher lock"),
      mRefreshTimerNeedsVsync(false) {
  MOZ_ASSERT(NS_IsMainThread());
  mRefreshTimerVsyncDispatcher = new RefreshTimerVsyncDispatcher();
}

VsyncSource::Display::~Display() {
  MOZ_ASSERT(NS_IsMainThread());
  MutexAutoLock lock(mDispatcherLock);
  mRefreshTimerVsyncDispatcher = nullptr;
  mCompositorVsyncDispatchers.Clear();
}

void VsyncSource::Display::NotifyVsync(TimeStamp aVsyncTimestamp) {
  // Called on the vsync thread
  MutexAutoLock lock(mDispatcherLock);

  // mRefreshTimerVsyncDispatcher might be null here if MoveListenersToNewSource
  // was called concurrently with this function and won the race to acquire
  // mDispatcherLock. In this case the new VsyncSource that is replacing this
  // one will handle notifications from now on, so we can abort.
  if (!mRefreshTimerVsyncDispatcher) {
    return;
  }

  mVsyncId = mVsyncId.Next();
  VsyncEvent event(mVsyncId, aVsyncTimestamp);

  for (size_t i = 0; i < mCompositorVsyncDispatchers.Length(); i++) {
    mCompositorVsyncDispatchers[i]->NotifyVsync(event);
  }

  mRefreshTimerVsyncDispatcher->NotifyVsync(event);
}

TimeDuration VsyncSource::Display::GetVsyncRate() {
  // If hardware queries fail / are unsupported, we have to just guess.
  return TimeDuration::FromMilliseconds(1000.0 / 60.0);
}

void VsyncSource::Display::AddCompositorVsyncDispatcher(
    CompositorVsyncDispatcher* aCompositorVsyncDispatcher) {
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(aCompositorVsyncDispatcher);
  {  // scope lock
    MutexAutoLock lock(mDispatcherLock);
    if (!mCompositorVsyncDispatchers.Contains(aCompositorVsyncDispatcher)) {
      mCompositorVsyncDispatchers.AppendElement(aCompositorVsyncDispatcher);
    }
  }
  UpdateVsyncStatus();
}

void VsyncSource::Display::RemoveCompositorVsyncDispatcher(
    CompositorVsyncDispatcher* aCompositorVsyncDispatcher) {
  MOZ_ASSERT(NS_IsMainThread());
  MOZ_ASSERT(aCompositorVsyncDispatcher);
  {  // Scope lock
    MutexAutoLock lock(mDispatcherLock);
    if (mCompositorVsyncDispatchers.Contains(aCompositorVsyncDispatcher)) {
      mCompositorVsyncDispatchers.RemoveElement(aCompositorVsyncDispatcher);
    }
  }
  UpdateVsyncStatus();
}

void VsyncSource::Display::MoveListenersToNewSource(
    VsyncSource::Display& aNewDisplay) {
  MOZ_ASSERT(NS_IsMainThread());
  MutexAutoLock lock(mDispatcherLock);
  MutexAutoLock newLock(aNewDisplay.mDispatcherLock);
  aNewDisplay.mCompositorVsyncDispatchers.AppendElements(
      std::move(mCompositorVsyncDispatchers));

  aNewDisplay.mRefreshTimerVsyncDispatcher = mRefreshTimerVsyncDispatcher;
  mRefreshTimerVsyncDispatcher = nullptr;
}

void VsyncSource::Display::NotifyRefreshTimerVsyncStatus(bool aEnable) {
  MOZ_ASSERT(NS_IsMainThread());
  mRefreshTimerNeedsVsync = aEnable;
  UpdateVsyncStatus();
}

void VsyncSource::Display::UpdateVsyncStatus() {
  MOZ_ASSERT(NS_IsMainThread());
  // WARNING: This function SHOULD NOT BE CALLED WHILE HOLDING LOCKS
  // NotifyVsync grabs a lock to dispatch vsync events
  // When disabling vsync, we wait for the underlying thread to stop on some
  // platforms We can deadlock if we wait for the underlying vsync thread to
  // stop while the vsync thread is in NotifyVsync.
  bool enableVsync = false;
  {  // scope lock
    MutexAutoLock lock(mDispatcherLock);
    enableVsync =
        !mCompositorVsyncDispatchers.IsEmpty() || mRefreshTimerNeedsVsync;
  }

  if (enableVsync) {
    EnableVsync();
  } else {
    DisableVsync();
  }

  if (IsVsyncEnabled() != enableVsync) {
    NS_WARNING("Vsync status did not change.");
  }
}

RefPtr<RefreshTimerVsyncDispatcher>
VsyncSource::Display::GetRefreshTimerVsyncDispatcher() {
  return mRefreshTimerVsyncDispatcher;
}

void VsyncSource::Shutdown() { GetGlobalDisplay().Shutdown(); }

}  // namespace gfx
}  // namespace mozilla