/* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; -*- */

/* 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 nsBaseAppShell_h__

#define nsBaseAppShell_h__

#include "mozilla/Atomics.h"

#include "nsIAppShell.h"

#include "nsIThreadInternal.h"

#include "nsIObserver.h"

#include "nsIRunnable.h"

#include "nsCOMPtr.h"

#include "nsTArray.h"

#include "prinrval.h"

/**

 * A singleton that manages the UI thread's event queue.  Subclass this class

 * to enable platform-specific event queue support.

 */

class nsBaseAppShell : public nsIAppShell,

                       public nsIThreadObserver,

                       public nsIObserver {

 public:

  NS_DECL_THREADSAFE_ISUPPORTS

  NS_DECL_NSIAPPSHELL

  NS_DECL_NSITHREADOBSERVER

  NS_DECL_NSIOBSERVER

  nsBaseAppShell();

 protected:

  virtual ~nsBaseAppShell();

  /**

   * This method is called by subclasses when the app shell singleton is

   * instantiated.

   */

  nsresult Init();

  /**

   * Called by subclasses from a native event. See ScheduleNativeEventCallback.

   */

  void NativeEventCallback();

  /**

   * Make a decision as to whether or not NativeEventCallback will

   * trigger gecko event processing when there are pending gecko

   * events.

   */

  virtual void DoProcessMoreGeckoEvents();

  /**

   * Implemented by subclasses.  Invoke NativeEventCallback from a native

   * event.  This method may be called on any thread.

   */

  virtual void ScheduleNativeEventCallback() = 0;

  /**

   * Implemented by subclasses.  Process the next native event.  Only wait for

   * the next native event if mayWait is true.  This method is only called on

   * the main application thread.

   *

   * @param mayWait

   *   If "true", then this method may wait if necessary for the next available

   *   native event.  DispatchNativeEvent may be called to unblock a call to

   *   ProcessNextNativeEvent that is waiting.

   * @return

   *   This method returns "true" if a native event was processed.

   */

  virtual bool ProcessNextNativeEvent(bool mayWait) = 0;

  int32_t mSuspendNativeCount;

  uint32_t mEventloopNestingLevel;

 private:

  bool DoProcessNextNativeEvent(bool mayWait);

  bool DispatchDummyEvent(nsIThread* target);

  void IncrementEventloopNestingLevel();

  void DecrementEventloopNestingLevel();

  nsCOMPtr<nsIRunnable> mDummyEvent;

  /**

   * mBlockedWait points back to a slot that controls the wait loop in

   * an outer OnProcessNextEvent invocation.  Nested calls always set

   * it to false to unblock an outer loop, since all events may

   * have been consumed by the inner event loop(s).

   */

  bool* mBlockedWait;

  int32_t mFavorPerf;

  mozilla::Atomic<bool> mNativeEventPending;

  PRIntervalTime mStarvationDelay;

  PRIntervalTime mSwitchTime;

  PRIntervalTime mLastNativeEventTime;

  enum EventloopNestingState {

    eEventloopNone,   // top level thread execution

    eEventloopXPCOM,  // innermost native event loop is ProcessNextNativeEvent

    eEventloopOther   // innermost native event loop is a native library/plugin

                      // etc

  };

  EventloopNestingState mEventloopNestingState;

  bool mRunning;

  bool mExiting;

  /**

   * mBlockNativeEvent blocks the appshell from processing native events.

   * It is set to true while a nested native event loop (eEventloopOther)

   * is processing gecko events in NativeEventCallback(), thus queuing up

   * native events until we return to that loop (bug 420148).

   * We force mBlockNativeEvent to false in case handling one of the gecko

   * events spins up a nested XPCOM event loop (eg. modal window) which would

   * otherwise lead to a "deadlock" where native events aren't processed at all.

   */

  bool mBlockNativeEvent;

  /**

   * Tracks whether we have processed any gecko events in NativeEventCallback so

   * that we can avoid erroneously entering a blocking loop waiting for gecko

   * events to show up during OnProcessNextEvent.  This is required because on

   * OS X ProcessGeckoEvents may be invoked inside the context of

   * ProcessNextNativeEvent and may result in NativeEventCallback being invoked

   * and in turn invoking NS_ProcessPendingEvents.  Because

   * ProcessNextNativeEvent may be invoked prior to the NS_HasPendingEvents

   * waiting loop, this is the only way to make the loop aware that events may

   * have been processed.

   *

   * This variable is set to false in OnProcessNextEvent prior to the first

   * call to DoProcessNextNativeEvent.  It is set to true by

   * NativeEventCallback after calling NS_ProcessPendingEvents.

   */

  bool mProcessedGeckoEvents;

};

#endif  // nsBaseAppShell_h__