gecko-dev/widget/xpwidgets/nsBaseAppShell.h

/* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; -*- */
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 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Widget code.
 *
 * The Initial Developer of the Original Code is Google Inc.
 * Portions created by the Initial Developer are Copyright (C) 2006
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Darin Fisher <darin@meer.net> (original author)
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either the GNU General Public License Version 2 or later (the "GPL"), or
 * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
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#ifndef nsBaseAppShell_h__
#define nsBaseAppShell_h__

#include "nsIAppShell.h"
#include "nsIThreadInternal.h"
#include "nsIObserver.h"
#include "nsIRunnable.h"
#include "nsCOMArray.h"
#include "nsCOMPtr.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_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;

  PRInt32 mSuspendNativeCount;
  PRUint32 mEventloopNestingLevel;

private:
  bool DoProcessNextNativeEvent(bool mayWait);

  /**
   * Runs all synchronous sections which are queued up in mSyncSections.
   */
  void RunSyncSections();

  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;
  PRInt32 mFavorPerf;
  PRInt32 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;
  nsCOMArray<nsIRunnable> mSyncSections;
  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__