/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* 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 mozilla_SynchronizedEventQueue_h

#define mozilla_SynchronizedEventQueue_h

#include "mozilla/AlreadyAddRefed.h"

#include "mozilla/AbstractEventQueue.h"

#include "mozilla/MemoryReporting.h"

#include "mozilla/Mutex.h"

#include "nsTObserverArray.h"

class nsIThreadObserver;

namespace mozilla {

// A SynchronizedEventQueue is an abstract class for event queues that can be

// used across threads. A SynchronizedEventQueue implementation will typically

// use locks and condition variables to guarantee consistency. The methods of

// SynchronizedEventQueue are split between ThreadTargetSink (which contains

// methods for posting events) and SynchronizedEventQueue (which contains

// methods for getting events). This split allows event targets (specifically

// ThreadEventTarget) to use a narrow interface, since they only need to post

// events.

//

// ThreadEventQueue is the canonical implementation of

// SynchronizedEventQueue. When Quantum DOM is implemented, we will use a

// different synchronized queue on the main thread, SchedulerEventQueue, which

// will handle the cooperative threading model.

class ThreadTargetSink

{

public:

  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ThreadTargetSink)

  virtual bool PutEvent(already_AddRefed<nsIRunnable>&& aEvent,

                        EventPriority aPriority) = 0;

  // After this method is called, no more events can be posted.

  virtual void Disconnect(const MutexAutoLock& aProofOfLock) = 0;

  size_t SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf) const

  {

    return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);

  }

  virtual size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const = 0;

protected:

  virtual ~ThreadTargetSink() {}

};

class SynchronizedEventQueue : public ThreadTargetSink

{

public:

  virtual already_AddRefed<nsIRunnable> GetEvent(bool aMayWait,

                                                 EventPriority* aPriority) = 0;

  virtual bool HasPendingEvent() = 0;

  // This method atomically checks if there are pending events and, if there are

  // none, forbids future events from being posted. It returns true if there

  // were no pending events.

  virtual bool ShutdownIfNoPendingEvents() = 0;

  // These methods provide access to an nsIThreadObserver, whose methods are

  // called when posting and processing events. SetObserver should only be

  // called on the thread that processes events. GetObserver can be called from

  // any thread. GetObserverOnThread must be used from the thread that processes

  // events; it does not acquire a lock.

  virtual already_AddRefed<nsIThreadObserver> GetObserver() = 0;

  virtual already_AddRefed<nsIThreadObserver> GetObserverOnThread() = 0;

  virtual void SetObserver(nsIThreadObserver* aObserver) = 0;

  void AddObserver(nsIThreadObserver* aObserver);

  void RemoveObserver(nsIThreadObserver* aObserver);

  const nsTObserverArray<nsCOMPtr<nsIThreadObserver>>& EventObservers();

  virtual void EnableInputEventPrioritization() = 0;

  virtual void FlushInputEventPrioritization() = 0;

  virtual void SuspendInputEventPrioritization() = 0;

  virtual void ResumeInputEventPrioritization() = 0;

  size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const override

  {

    return mEventObservers.ShallowSizeOfExcludingThis(aMallocSizeOf);

  }

protected:

  virtual ~SynchronizedEventQueue() {}

private:

  nsTObserverArray<nsCOMPtr<nsIThreadObserver>> mEventObservers;

};

} // namespace mozilla

#endif // mozilla_SynchronizedEventQueue_h