michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim:set ts=2 sw=2 sts=2 et cindent: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "nsIThread.idl"
michael@0: 
michael@0: interface nsIRunnable;
michael@0: interface nsIThreadObserver;
michael@0: 
michael@0: /**
michael@0:  * The XPCOM thread object implements this interface, which allows a consumer
michael@0:  * to observe dispatch activity on the thread.
michael@0:  */
michael@0: [scriptable, uuid(b24c5af3-43c2-4d17-be14-94d6648a305f)]
michael@0: interface nsIThreadInternal : nsIThread
michael@0: {
michael@0:   /**
michael@0:    * Get/set the current thread observer (may be null).  This attribute may be
michael@0:    * read from any thread, but must only be set on the thread corresponding to
michael@0:    * this thread object.  The observer will be released on the thread
michael@0:    * corresponding to this thread object after all other events have been
michael@0:    * processed during a call to Shutdown.
michael@0:    */
michael@0:   attribute nsIThreadObserver observer;
michael@0: 
michael@0:   /**
michael@0:    * The current recursion depth, 0 when no events are running, 1 when a single
michael@0:    * event is running, and higher when nested events are running. Must only be
michael@0:    * called on the target thread.
michael@0:    */
michael@0:   readonly attribute unsigned long recursionDepth;
michael@0: 
michael@0:   /**
michael@0:    * Add an observer that will *only* receive onProcessNextEvent,
michael@0:    * beforeProcessNextEvent. and afterProcessNextEvent callbacks. Always called
michael@0:    * on the target thread, and the implementation does not have to be
michael@0:    * threadsafe. Order of callbacks is not guaranteed (i.e.
michael@0:    * afterProcessNextEvent may be called first depending on whether or not the
michael@0:    * observer is added in a nested loop). Holds a strong ref.
michael@0:    */
michael@0:   void addObserver(in nsIThreadObserver observer);
michael@0: 
michael@0:   /**
michael@0:    * Remove an observer added via the addObserver call. Once removed the
michael@0:    * observer will never be called again by the thread.
michael@0:    */
michael@0:   void removeObserver(in nsIThreadObserver observer);
michael@0: 
michael@0:   /**
michael@0:    * This method causes any events currently enqueued on the thread to be
michael@0:    * suppressed until PopEventQueue is called, and any event dispatched to this
michael@0:    * thread's nsIEventTarget will queue as well. Calls to PushEventQueue may be
michael@0:    * nested and must each be paired with a call to PopEventQueue in order to
michael@0:    * restore the original state of the thread. The returned nsIEventTarget may
michael@0:    * be used to push events onto the nested queue. Dispatching will be disabled
michael@0:    * once the event queue is popped. The thread will only ever process pending
michael@0:    * events for the innermost event queue. Must only be called on the target
michael@0:    * thread.
michael@0:    */
michael@0:   [noscript] nsIEventTarget pushEventQueue();
michael@0: 
michael@0:   /**
michael@0:    * Revert a call to PushEventQueue. When an event queue is popped, any events
michael@0:    * remaining in the queue are appended to the elder queue. This also causes
michael@0:    * the nsIEventTarget returned from PushEventQueue to stop dispatching events.
michael@0:    * Must only be called on the target thread, and with the innermost event
michael@0:    * queue.
michael@0:    */
michael@0:   [noscript] void popEventQueue(in nsIEventTarget aInnermostTarget);
michael@0: };
michael@0: 
michael@0: /**
michael@0:  * This interface provides the observer with hooks to implement a layered
michael@0:  * event queue.  For example, it is possible to overlay processing events
michael@0:  * for a GUI toolkit on top of the events for a thread:
michael@0:  *
michael@0:  *   var NativeQueue;
michael@0:  *   Observer = {
michael@0:  *     onDispatchedEvent(thread) {
michael@0:  *       NativeQueue.signal();
michael@0:  *     }
michael@0:  *     onProcessNextEvent(thread, mayWait, recursionDepth) {
michael@0:  *       if (NativeQueue.hasNextEvent())
michael@0:  *         NativeQueue.processNextEvent();
michael@0:  *       while (mayWait && !thread.hasPendingEvent()) {
michael@0:  *         NativeQueue.wait();
michael@0:  *         NativeQueue.processNextEvent();
michael@0:  *       }
michael@0:  *     }
michael@0:  *   };
michael@0:  *
michael@0:  * NOTE: The implementation of this interface must be threadsafe.
michael@0:  * 
michael@0:  * NOTE: It is valid to change the thread's observer during a call to an
michael@0:  *       observer method.
michael@0:  *
michael@0:  * NOTE: Will be split into two interfaces soon: one for onProcessNextEvent and
michael@0:  *       afterProcessNextEvent, then another that inherits the first and adds
michael@0:  *       onDispatchedEvent.
michael@0:  */
michael@0: [scriptable, uuid(09b424c3-26b0-4128-9039-d66f85b02c63)]
michael@0: interface nsIThreadObserver : nsISupports
michael@0: {
michael@0:   /**
michael@0:    * This method is called after an event has been dispatched to the thread.
michael@0:    * This method may be called from any thread. 
michael@0:    *
michael@0:    * @param thread
michael@0:    *   The thread where the event is being dispatched.
michael@0:    */
michael@0:   void onDispatchedEvent(in nsIThreadInternal thread);
michael@0: 
michael@0:   /**
michael@0:    * This method is called when nsIThread::ProcessNextEvent is called.  It does
michael@0:    * not guarantee that an event is actually going to be processed.  This method
michael@0:    * is only called on the target thread.
michael@0:    *
michael@0:    * @param thread
michael@0:    *   The thread being asked to process another event.
michael@0:    * @param mayWait
michael@0:    *   Indicates whether or not the method is allowed to block the calling
michael@0:    *   thread.  For example, this parameter is false during thread shutdown.
michael@0:    * @param recursionDepth
michael@0:    *   Indicates the number of calls to ProcessNextEvent on the call stack in
michael@0:    *   addition to the current call.
michael@0:    */
michael@0:   void onProcessNextEvent(in nsIThreadInternal thread, in boolean mayWait,
michael@0:                           in unsigned long recursionDepth);
michael@0: 
michael@0:   /**
michael@0:    * This method is called (from nsIThread::ProcessNextEvent) after an event
michael@0:    * is processed.  It does not guarantee that an event was actually processed
michael@0:    * (depends on the value of |eventWasProcessed|.  This method is only called
michael@0:    * on the target thread.
michael@0:    *
michael@0:    * @param thread
michael@0:    *   The thread that processed another event.
michael@0:    * @param recursionDepth
michael@0:    *   Indicates the number of calls to ProcessNextEvent on the call stack in
michael@0:    *   addition to the current call.
michael@0:    * @param eventWasProcessed
michael@0:    *   Indicates whether an event was actually processed. May be false if the
michael@0:    *   |mayWait| flag was false when calling nsIThread::ProcessNextEvent().
michael@0:    */
michael@0:   void afterProcessNextEvent(in nsIThreadInternal thread,
michael@0:                              in unsigned long recursionDepth,
michael@0:                              in bool eventWasProcessed);
michael@0: };