/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 *
 * ***** BEGIN LICENSE BLOCK *****
 * 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 the Mozilla browser.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1999
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Stuart Parmenter <pavlov@netscape.com>
 *
 * 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
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#include "nsISupports.idl"
#include "nsIRunnable.idl"

/**
 * Interface for the native event system layer.  This interface is designed
 * to be used on the main application thread only.
 */
[uuid(40bc6280-ad83-471e-b197-80ab90e2065e)]
interface nsIAppShell : nsISupports
{
  /**
   * Enter an event loop.  Don't leave until exit() is called.
   */
  void run();

  /**
   * Exit the handle event loop
   */
  void exit();

  /**
   * Give hint to native event queue notification mechanism. If the native
   * platform needs to tradeoff performance vs. native event starvation this
   * hint tells the native dispatch code which to favor.  The default is to
   * prevent native event starvation.
   *
   * Calls to this function may be nested. When the number of calls that pass
   * PR_TRUE is subtracted from the number of calls that pass PR_FALSE is
   * greater than 0, performance is given precedence over preventing event
   * starvation.
   *
   * The starvationDelay arg is only used when favorPerfOverStarvation is
   * PR_FALSE. It is the amount of time in milliseconds to wait before the
   * PR_FALSE actually takes effect.
   */
  void favorPerformanceHint(in boolean favorPerfOverStarvation,
                            in unsigned long starvationDelay);

  /**
   * Suspends the use of additional platform-specific methods (besides the
   * nsIAppShell->run() event loop) to run Gecko events on the main
   * application thread.  Under some circumstances these "additional methods"
   * can cause Gecko event handlers to be re-entered, sometimes leading to
   * hangs and crashes.  Calls to suspendNative() and resumeNative() may be
   * nested.  On some platforms (those that don't use any "additional
   * methods") this will be a no-op.  Does not (in itself) stop Gecko events
   * from being processed on the main application thread.  But if the
   * nsIAppShell->run() event loop is blocked when this call is made, Gecko
   * events will stop being processed until resumeNative() is called (even
   * if a plugin or library is temporarily processing events on a nested
   * event loop).
   */
  void suspendNative();

  /**
   * Resumes the use of additional platform-specific methods to run Gecko
   * events on the main application thread.  Calls to suspendNative() and
   * resumeNative() may be nested.  On some platforms this will be a no-op.
   */
  void resumeNative();

  /**
   * The current event loop nesting level.
   */
  readonly attribute unsigned long eventloopNestingLevel;
  
  /**
   * Allows running of a "synchronous section", in the form of an nsIRunnable
   * once the event loop has reached a "stable state". We've reached a stable
   * state when the currently executing task/event has finished, see:
   * http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#synchronous-section
   * In practice this runs aRunnable once the currently executing event
   * finishes. If called multiple times per task/event, all the runnables will
   * be executed, in the order in which runInStableState() was called.
   */
  void runInStableState(in nsIRunnable aRunnable);
};
