gecko-dev/gfx/thebes/SoftwareVsyncSource.cpp

141 lines
3.7 KiB
C++

/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* 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 "SoftwareVsyncSource.h"
#include "base/task.h"
#include "nsThreadUtils.h"
SoftwareVsyncSource::SoftwareVsyncSource()
{
mGlobalDisplay = new SoftwareDisplay();
}
SoftwareVsyncSource::~SoftwareVsyncSource()
{
MOZ_ASSERT(NS_IsMainThread());
// Ensure we disable vsync on the main thread here
mGlobalDisplay->DisableVsync();
mGlobalDisplay = nullptr;
}
SoftwareDisplay::SoftwareDisplay()
: mVsyncEnabled(false)
, mCurrentTaskMonitor("SoftwareVsyncCurrentTaskMonitor")
{
// Mimic 60 fps
MOZ_ASSERT(NS_IsMainThread());
const double rate = 1000 / 60.0;
mVsyncRate = mozilla::TimeDuration::FromMilliseconds(rate);
mVsyncThread = new base::Thread("SoftwareVsyncThread");
}
void
SoftwareDisplay::EnableVsync()
{
MOZ_ASSERT(NS_IsMainThread());
if (IsVsyncEnabled()) {
return;
}
{ // scope lock
mozilla::MonitorAutoLock lock(mCurrentTaskMonitor);
mVsyncEnabled = true;
MOZ_ASSERT(!mVsyncThread->IsRunning());
MOZ_RELEASE_ASSERT(mVsyncThread->Start(), "Could not start software vsync thread");
mCurrentVsyncTask = NewRunnableMethod(this,
&SoftwareDisplay::NotifyVsync,
mozilla::TimeStamp::Now());
mVsyncThread->message_loop()->PostTask(FROM_HERE, mCurrentVsyncTask);
}
}
void
SoftwareDisplay::DisableVsync()
{
MOZ_ASSERT(NS_IsMainThread());
if (!IsVsyncEnabled()) {
return;
}
MOZ_ASSERT(mVsyncThread->IsRunning());
{ // scope lock
mozilla::MonitorAutoLock lock(mCurrentTaskMonitor);
mVsyncEnabled = false;
if (mCurrentVsyncTask) {
mCurrentVsyncTask->Cancel();
mCurrentVsyncTask = nullptr;
}
}
mVsyncThread->Stop();
}
bool
SoftwareDisplay::IsVsyncEnabled()
{
MOZ_ASSERT(NS_IsMainThread());
mozilla::MonitorAutoLock lock(mCurrentTaskMonitor);
return mVsyncEnabled;
}
bool
SoftwareDisplay::IsInSoftwareVsyncThread()
{
return mVsyncThread->thread_id() == PlatformThread::CurrentId();
}
void
SoftwareDisplay::NotifyVsync(mozilla::TimeStamp aVsyncTimestamp)
{
MOZ_ASSERT(IsInSoftwareVsyncThread());
mozilla::TimeStamp displayVsyncTime = aVsyncTimestamp;
mozilla::TimeStamp now = mozilla::TimeStamp::Now();
// Posted tasks can only have integer millisecond delays
// whereas TimeDurations can have floating point delays.
// Thus the vsync timestamp can be in the future, which large parts
// of the system can't handle, including animations. Force the timestamp to be now.
if (aVsyncTimestamp > now) {
displayVsyncTime = now;
}
Display::NotifyVsync(displayVsyncTime);
// Prevent skew by still scheduling based on the original
// vsync timestamp
ScheduleNextVsync(aVsyncTimestamp);
}
void
SoftwareDisplay::ScheduleNextVsync(mozilla::TimeStamp aVsyncTimestamp)
{
MOZ_ASSERT(IsInSoftwareVsyncThread());
mozilla::TimeStamp nextVsync = aVsyncTimestamp + mVsyncRate;
mozilla::TimeDuration delay = nextVsync - mozilla::TimeStamp::Now();
if (delay.ToMilliseconds() < 0) {
delay = mozilla::TimeDuration::FromMilliseconds(0);
}
mozilla::MonitorAutoLock lock(mCurrentTaskMonitor);
// We could've disabled vsync between this posted task and when it actually
// executes
if (!mVsyncEnabled) {
return;
}
mCurrentVsyncTask = NewRunnableMethod(this,
&SoftwareDisplay::NotifyVsync,
nextVsync);
mVsyncThread->message_loop()->PostDelayedTask(FROM_HERE,
mCurrentVsyncTask,
delay.ToMilliseconds());
}
SoftwareDisplay::~SoftwareDisplay()
{
MOZ_ASSERT(NS_IsMainThread());
delete mVsyncThread;
}