gecko-dev/gfx/thebes/VsyncSource.h

/* -*- 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 GFX_VSYNCSOURCE_H
#define GFX_VSYNCSOURCE_H

#include "nsTArray.h"
#include "mozilla/RefPtr.h"
#include "mozilla/Mutex.h"
#include "mozilla/TimeStamp.h"
#include "nsISupportsImpl.h"
#include "mozilla/layers/LayersTypes.h"

namespace mozilla {
class RefreshTimerVsyncDispatcher;
class CompositorVsyncDispatcher;
class VsyncObserver;
struct VsyncEvent;

class VsyncIdType {};
typedef layers::BaseTransactionId<VsyncIdType> VsyncId;

namespace gfx {

// Controls how and when to enable/disable vsync. Lives as long as the
// gfxPlatform does on the parent process
class VsyncSource {
  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(VsyncSource)

  typedef mozilla::RefreshTimerVsyncDispatcher RefreshTimerVsyncDispatcher;
  typedef mozilla::CompositorVsyncDispatcher CompositorVsyncDispatcher;

 public:
  // Controls vsync unique to each display and unique on each platform
  class Display {
    NS_INLINE_DECL_THREADSAFE_REFCOUNTING(Display)
   public:
    Display();

    // Notified when this display's vsync callback occurs, on the vsync thread
    // Different platforms give different aVsyncTimestamp values.
    // macOS: TimeStamp::Now() or the output time of the previous vsync
    //        callback, whichever is older.
    // Windows: It's messy, see gfxWindowsPlatform.
    // Android: TODO
    //
    // @param aVsyncTimestamp  The time of the Vsync that just occured. Needs to
    //     be at or before the time of the NotifyVsync call.
    // @param aOutputTimestamp  The estimated timestamp at which drawing will
    //     appear on the screen, if the drawing happens within a certain
    //     (unknown) budget. Useful for Audio/Video sync. On platforms where
    //     this timestamp is provided by the system (macOS), it is a much more
    //     stable and consistent timing source than the time at which the vsync
    //     callback is called.
    virtual void NotifyVsync(const TimeStamp& aVsyncTimestamp,
                             const TimeStamp& aOutputTimestamp);
    void NotifyGenericObservers(VsyncEvent aEvent);

    RefPtr<RefreshTimerVsyncDispatcher> GetRefreshTimerVsyncDispatcher();

    void RegisterCompositorVsyncDispatcher(
        CompositorVsyncDispatcher* aCompositorVsyncDispatcher);
    void DeregisterCompositorVsyncDispatcher(
        CompositorVsyncDispatcher* aCompositorVsyncDispatcher);
    void EnableCompositorVsyncDispatcher(
        CompositorVsyncDispatcher* aCompositorVsyncDispatcher);
    void DisableCompositorVsyncDispatcher(
        CompositorVsyncDispatcher* aCompositorVsyncDispatcher);
    void AddGenericObserver(VsyncObserver* aObserver);
    void RemoveGenericObserver(VsyncObserver* aObserver);

    void MoveListenersToNewSource(const RefPtr<VsyncSource>& aNewSource);
    void NotifyRefreshTimerVsyncStatus(bool aEnable);
    virtual TimeDuration GetVsyncRate();

    // These should all only be called on the main thread
    virtual void EnableVsync() = 0;
    virtual void DisableVsync() = 0;
    virtual bool IsVsyncEnabled() = 0;
    virtual void Shutdown() = 0;

   protected:
    virtual ~Display();

   private:
    void UpdateVsyncStatus();

    Mutex mDispatcherLock;
    bool mRefreshTimerNeedsVsync;
    nsTArray<RefPtr<CompositorVsyncDispatcher>>
        mEnabledCompositorVsyncDispatchers;
    nsTArray<RefPtr<CompositorVsyncDispatcher>>
        mRegisteredCompositorVsyncDispatchers;
    RefPtr<RefreshTimerVsyncDispatcher> mRefreshTimerVsyncDispatcher;
    nsTArray<RefPtr<VsyncObserver>>
        mGenericObservers;  // can only be touched from the main thread
    VsyncId mVsyncId;
    VsyncId mLastVsyncIdSentToMainThread;     // hold mDispatcherLock to touch
    VsyncId mLastMainThreadProcessedVsyncId;  // hold mDispatcherLock to touch
  };

  void EnableCompositorVsyncDispatcher(
      CompositorVsyncDispatcher* aCompositorVsyncDispatcher);
  void DisableCompositorVsyncDispatcher(
      CompositorVsyncDispatcher* aCompositorVsyncDispatcher);
  void RegisterCompositorVsyncDispatcher(
      CompositorVsyncDispatcher* aCompositorVsyncDispatcher);
  void DeregisterCompositorVsyncDispatcher(
      CompositorVsyncDispatcher* aCompositorVsyncDispatcher);

  // Add and remove a generic observer for vsync. Note that keeping an observer
  // registered means vsync will keep firing, which may impact power usage. So
  // this is intended only for "short term" vsync observers. These methods must
  // be called on the parent process main thread, and the observer will likewise
  // be notified on the parent process main thread.
  void AddGenericObserver(VsyncObserver* aObserver);
  void RemoveGenericObserver(VsyncObserver* aObserver);

  void MoveListenersToNewSource(const RefPtr<VsyncSource>& aNewSource);

  RefPtr<RefreshTimerVsyncDispatcher> GetRefreshTimerVsyncDispatcher();
  virtual Display& GetGlobalDisplay() = 0;  // Works across all displays
  void Shutdown();

 protected:
  virtual ~VsyncSource() = default;
};

}  // namespace gfx

struct VsyncEvent {
  VsyncId mId;
  TimeStamp mTime;
  TimeStamp mOutputTime;  // estimate

  VsyncEvent(const VsyncId& aId, const TimeStamp& aVsyncTime,
             const TimeStamp& aOutputTime)
      : mId(aId), mTime(aVsyncTime), mOutputTime(aOutputTime) {}
  VsyncEvent() = default;
};

}  // namespace mozilla

#endif /* GFX_VSYNCSOURCE_H */