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/* ***** 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 Mozilla 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>
 *
 * 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 "nsIThread.idl"

interface nsIThreadObserver;
interface nsIThreadEventFilter;

/**
 * The XPCOM thread object implements this interface, which allows a consumer
 * to observe dispatch activity on the thread.
 */
[scriptable, uuid(e0d35c22-53d5-4b48-8627-93e05b94cf2c)]
interface nsIThreadInternal : nsIThread
{
  /**
   * Get/set the current thread observer (may be null).  This attribute may be
   * read from any thread, but must only be set on the thread corresponding to
   * this thread object.  The observer will be released on the thread
   * corresponding to this thread object after all other events have been
   * processed during a call to Shutdown.
   */
  attribute nsIThreadObserver observer;

  /**
   * This method causes any events currently enqueued on the thread to be
   * suppressed until PopEventQueue is called.  Additionally, any new events
   * dispatched to the thread will only be processed if they are accepted by
   * the given filter.  If the filter is null, then new events are accepted.
   * Calls to PushEventQueue may be nested and must each be paired with a call
   * to PopEventQueue in order to restore the original state of the thread.
   *
   * @param filter
   *   The thread event filter to apply to dispatched events, or null to accept
   *   all dispatched events.
   */
  void pushEventQueue(in nsIThreadEventFilter filter);

  /**
   * Revert a call to PushEventQueue.  When an event queue is popped, any
   * events remaining in the queue are appended to the elder queue.
   */
  void popEventQueue();

  /**
   * The current recursion depth, 0 when no events are running, 1 when a single
   * event is running, and higher when nested events are running. Must only be
   * called on the target thread.
   */
  readonly attribute unsigned long recursionDepth;

  /**
   * Add an observer that will *only* receive onProcessNextEvent and
   * afterProcessNextEvent callbacks. Always called on the target thread, and
   * the implementation does not have to be threadsafe. Order of callbacks is
   * not guaranteed (i.e. afterProcessNextEvent may be called first depending on
   * whether or not the observer is added in a nested loop). Holds a strong ref.
   */
  void addObserver(in nsIThreadObserver observer);

  /**
   * Remove an observer added via the addObserver call. Once removed the
   * observer will never be called again by the thread.
   */
  void removeObserver(in nsIThreadObserver observer);
};

/**
 * This interface provides the observer with hooks to implement a layered
 * event queue.  For example, it is possible to overlay processing events
 * for a GUI toolkit on top of the events for a thread:
 *
 *   var NativeQueue;
 *   Observer = {
 *     onDispatchedEvent(thread) {
 *       NativeQueue.signal();
 *     }
 *     onProcessNextEvent(thread, mayWait, recursionDepth) {
 *       if (NativeQueue.hasNextEvent())
 *         NativeQueue.processNextEvent();
 *       while (mayWait && !thread.hasPendingEvent()) {
 *         NativeQueue.wait();
 *         NativeQueue.processNextEvent();
 *       }
 *     }
 *   };
 *
 * NOTE: The implementation of this interface must be threadsafe.
 * 
 * NOTE: It is valid to change the thread's observer during a call to an
 *       observer method.
 *
 * NOTE: Will be split into two interfaces soon: one for onProcessNextEvent and
 *       afterProcessNextEvent, then another that inherits the first and adds
 *       onDispatchedEvent.
 */
[scriptable, uuid(81D0B509-F198-4417-8020-08EB4271491F)]
interface nsIThreadObserver : nsISupports
{
  /**
   * This method is called after an event has been dispatched to the thread.
   * This method may be called from any thread. 
   *
   * @param thread
   *   The thread where the event is being dispatched.
   */
  void onDispatchedEvent(in nsIThreadInternal thread);

  /**
   * This method is called (from nsIThread::ProcessNextEvent) before an event
   * is processed.  This method is only called on the target thread.
   *
   * @param thread
   *   The thread being asked to process another event.
   * @param mayWait
   *   Indicates whether or not the method is allowed to block the calling
   *   thread.  For example, this parameter is false during thread shutdown.
   * @param recursionDepth
   *   Indicates the number of calls to ProcessNextEvent on the call stack in
   *   addition to the current call.
   */
  void onProcessNextEvent(in nsIThreadInternal thread, in boolean mayWait,
                          in unsigned long recursionDepth);

  /**
   * This method is called (from nsIThread::ProcessNextEvent) after an event
   * is processed.  This method is only called on the target thread.
   *
   * @param thread
   *   The thread that processed another event.
   * @param recursionDepth
   *   Indicates the number of calls to ProcessNextEvent on the call stack in
   *   addition to the current call.
   */
  void afterProcessNextEvent(in nsIThreadInternal thread,
                             in unsigned long recursionDepth);
};

/**
 * Interface passed to the nsIThreadInternal::PushEventQueue method.
 */
[scriptable, uuid(a0605c0b-17f5-4681-b8cd-a1cd75d42559)]
interface nsIThreadEventFilter : nsISupports
{
  /**
   * This method is called to determine whether or not an event may be accepted
   * by a "nested" event queue (see nsIThreadInternal::PushEventQueue).
   *
   * @param event
   *   The event being dispatched.
   *
   * WARNING: This method must not make any calls on the thread object.
   */
  [notxpcom] boolean acceptEvent(in nsIRunnable event);
};
