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diff --git a/widget/gtk/WaylandVsyncSource.h b/widget/gtk/WaylandVsyncSource.h
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+/* -*- 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/. */
+
+#ifndef _WaylandVsyncSource_h_
+#define _WaylandVsyncSource_h_
+
+#include "base/thread.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/Monitor.h"
+#include "mozilla/layers/NativeLayerWayland.h"
+#include "MozContainer.h"
+#include "nsWaylandDisplay.h"
+#include "VsyncSource.h"
+
+namespace mozilla {
+
+using layers::NativeLayerRootWayland;
+
+/*
+ * WaylandVsyncSource
+ *
+ * This class provides a per-widget VsyncSource under Wayland, emulated using
+ * frame callbacks on the widget surface with empty surface commits.
+ *
+ * Wayland does not expose vsync/vblank, as it considers that an implementation
+ * detail the clients should not concern themselves with. Instead, frame
+ * callbacks are provided whenever the compositor believes it is a good time to
+ * start drawing the next frame for a particular surface, giving us as much
+ * time as possible to do so.
+ *
+ * Note that the compositor sends frame callbacks only when it sees fit, and
+ * when that may be is entirely up to the compositor. One cannot expect a
+ * certain rate of callbacks, or any callbacks at all. Examples of common
+ * variations would be surfaces moved between outputs with different refresh
+ * rates, and surfaces that are hidden and therefore do not receieve any
+ * callbacks at all. Other hypothetical scenarios of variation could be
+ * throttling to conserve power, or because a user has requested it.
+ *
+ */
+class WaylandVsyncSource final : public gfx::VsyncSource {
+ public:
+  explicit WaylandVsyncSource(nsWindow* aWindow);
+  virtual ~WaylandVsyncSource();
+
+  static Maybe<TimeDuration> GetFastestVsyncRate();
+
+  void MaybeUpdateSource(MozContainer* aContainer);
+  void MaybeUpdateSource(
+      const RefPtr<NativeLayerRootWayland>& aNativeLayerRoot);
+
+  void EnableMonitor();
+  void DisableMonitor();
+
+  void FrameCallback(wl_callback* aCallback, uint32_t aTime);
+  // Returns whether we should keep firing.
+  bool IdleCallback();
+
+  TimeDuration GetVsyncRate() override;
+
+  void EnableVsync() override;
+
+  void DisableVsync() override;
+
+  bool IsVsyncEnabled() override;
+
+  void Shutdown() override;
+
+ private:
+  Maybe<TimeDuration> GetVsyncRateIfEnabled();
+
+  void Refresh(const MutexAutoLock& aProofOfLock);
+  void SetupFrameCallback(const MutexAutoLock& aProofOfLock);
+  void CalculateVsyncRate(const MutexAutoLock& aProofOfLock,
+                          TimeStamp aVsyncTimestamp);
+  void* GetWindowForLogging() { return mWindow; };
+
+  Mutex mMutex;
+  bool mIsShutdown MOZ_GUARDED_BY(mMutex) = false;
+  bool mVsyncEnabled MOZ_GUARDED_BY(mMutex) = false;
+  bool mMonitorEnabled MOZ_GUARDED_BY(mMutex) = false;
+  bool mCallbackRequested MOZ_GUARDED_BY(mMutex) = false;
+  MozContainer* mContainer MOZ_GUARDED_BY(mMutex) = nullptr;
+  RefPtr<NativeLayerRootWayland> mNativeLayerRoot MOZ_GUARDED_BY(mMutex);
+  TimeDuration mVsyncRate MOZ_GUARDED_BY(mMutex);
+  TimeStamp mLastVsyncTimeStamp MOZ_GUARDED_BY(mMutex);
+  wl_callback* mCallback MOZ_GUARDED_BY(mMutex) = nullptr;
+
+  guint mIdleTimerID = 0;   // Main thread only.
+  nsWindow* const mWindow;  // Main thread only, except for logging.
+  const guint mIdleTimeout;
+};
+
+}  // namespace mozilla
+
+#endif  // _WaylandVsyncSource_h_