1 files changed, 143 insertions, 0 deletions
diff --git a/gfx/thebes/SoftwareVsyncSource.cpp b/gfx/thebes/SoftwareVsyncSource.cpp
new file mode 100644
index 0000000000..b8e12390e7
--- /dev/null
+++ b/gfx/thebes/SoftwareVsyncSource.cpp
@@ -0,0 +1,143 @@
+/* -*- 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 "SoftwareVsyncSource.h"
+#include "base/task.h"
+#include "gfxPlatform.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla::gfx {
+
+SoftwareVsyncSource::SoftwareVsyncSource(const TimeDuration& aInitialVsyncRate)
+    : mVsyncEnabled(false),
+      mVsyncRate(TimeDuration{aInitialVsyncRate},
+                 "SoftwareVsyncSource::mVsyncRate") {
+  MOZ_ASSERT(NS_IsMainThread());
+  mVsyncThread = new base::Thread("SoftwareVsyncThread");
+  MOZ_RELEASE_ASSERT(mVsyncThread->Start(),
+                     "GFX: Could not start software vsync thread");
+}
+
+SoftwareVsyncSource::~SoftwareVsyncSource() {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (mVsyncThread) {
+    mVsyncThread->Stop();
+    delete mVsyncThread;
+  }
+};
+
+void SoftwareVsyncSource::EnableVsync() {
+  MOZ_ASSERT(mVsyncThread->IsRunning());
+  if (NS_IsMainThread()) {
+    if (mVsyncEnabled) {
+      return;
+    }
+    mVsyncEnabled = true;
+
+    mVsyncThread->message_loop()->PostTask(
+        NewRunnableMethod("SoftwareVsyncSource::EnableVsync", this,
+                          &SoftwareVsyncSource::EnableVsync));
+    return;
+  }
+
+  MOZ_ASSERT(IsInSoftwareVsyncThread());
+  TimeStamp vsyncTime = TimeStamp::Now();
+  TimeStamp outputTime = vsyncTime + GetVsyncRate();
+  NotifyVsync(vsyncTime, outputTime);
+}
+
+void SoftwareVsyncSource::DisableVsync() {
+  MOZ_ASSERT(mVsyncThread->IsRunning());
+  if (NS_IsMainThread()) {
+    if (!mVsyncEnabled) {
+      return;
+    }
+    mVsyncEnabled = false;
+
+    mVsyncThread->message_loop()->PostTask(
+        NewRunnableMethod("SoftwareVsyncSource::DisableVsync", this,
+                          &SoftwareVsyncSource::DisableVsync));
+    return;
+  }
+
+  MOZ_ASSERT(IsInSoftwareVsyncThread());
+  if (mCurrentVsyncTask) {
+    mCurrentVsyncTask->Cancel();
+    mCurrentVsyncTask = nullptr;
+  }
+}
+
+bool SoftwareVsyncSource::IsVsyncEnabled() {
+  MOZ_ASSERT(NS_IsMainThread());
+  return mVsyncEnabled;
+}
+
+bool SoftwareVsyncSource::IsInSoftwareVsyncThread() {
+  return mVsyncThread->thread_id() == PlatformThread::CurrentId();
+}
+
+void SoftwareVsyncSource::NotifyVsync(const TimeStamp& aVsyncTimestamp,
+                                      const TimeStamp& aOutputTimestamp) {
+  MOZ_ASSERT(IsInSoftwareVsyncThread());
+
+  TimeStamp displayVsyncTime = aVsyncTimestamp;
+  TimeStamp now = 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;
+  }
+
+  VsyncSource::NotifyVsync(displayVsyncTime, aOutputTimestamp);
+
+  // Prevent skew by still scheduling based on the original
+  // vsync timestamp
+  ScheduleNextVsync(aVsyncTimestamp);
+}
+
+TimeDuration SoftwareVsyncSource::GetVsyncRate() {
+  auto rate = mVsyncRate.Lock();
+  return *rate;
+}
+
+void SoftwareVsyncSource::SetVsyncRate(const TimeDuration& aNewRate) {
+  auto rate = mVsyncRate.Lock();
+  *rate = aNewRate;
+}
+
+void SoftwareVsyncSource::ScheduleNextVsync(TimeStamp aVsyncTimestamp) {
+  MOZ_ASSERT(IsInSoftwareVsyncThread());
+  TimeDuration vsyncRate = GetVsyncRate();
+  TimeStamp nextVsync = aVsyncTimestamp + vsyncRate;
+  TimeDuration delay = nextVsync - TimeStamp::Now();
+  if (delay.ToMilliseconds() < 0) {
+    delay = TimeDuration::FromMilliseconds(0);
+    nextVsync = TimeStamp::Now();
+  }
+
+  TimeStamp outputTime = nextVsync + vsyncRate;
+
+  mCurrentVsyncTask = NewCancelableRunnableMethod<TimeStamp, TimeStamp>(
+      "SoftwareVsyncSource::NotifyVsync", this,
+      &SoftwareVsyncSource::NotifyVsync, nextVsync, outputTime);
+
+  RefPtr<Runnable> addrefedTask = mCurrentVsyncTask;
+  mVsyncThread->message_loop()->PostDelayedTask(addrefedTask.forget(),
+                                                delay.ToMilliseconds());
+}
+
+void SoftwareVsyncSource::Shutdown() {
+  MOZ_ASSERT(NS_IsMainThread());
+  DisableVsync();
+  mVsyncThread->Stop();
+  delete mVsyncThread;
+  mVsyncThread = nullptr;
+}
+
+}  // namespace mozilla::gfx