xpcom/threads/nsIThreadInternal.idl

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim:set ts=2 sw=2 sts=2 et cindent: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "nsIThread.idl"
   8
   9 interface nsIRunnable;
  10 interface nsIThreadObserver;
  11
  12 /**
  13  * The XPCOM thread object implements this interface, which allows a consumer
  14  * to observe dispatch activity on the thread.
  15  */
  16 [builtinclass, scriptable, uuid(a3a72e5f-71d9-4add-8f30-59a78fb6d5eb)]
  17 interface nsIThreadInternal : nsIThread
  18 {
  19   /**
  20    * Get/set the current thread observer (may be null).  This attribute may be
  21    * read from any thread, but must only be set on the thread corresponding to
  22    * this thread object.  The observer will be released on the thread
  23    * corresponding to this thread object after all other events have been
  24    * processed during a call to Shutdown.
  25    */
  26   attribute nsIThreadObserver observer;
  27
  28   /**
  29    * Add an observer that will *only* receive onProcessNextEvent,
  30    * beforeProcessNextEvent. and afterProcessNextEvent callbacks. Always called
  31    * on the target thread, and the implementation does not have to be
  32    * threadsafe. Order of callbacks is not guaranteed (i.e.
  33    * afterProcessNextEvent may be called first depending on whether or not the
  34    * observer is added in a nested loop). Holds a strong ref.
  35    */
  36   void addObserver(in nsIThreadObserver observer);
  37
  38   /**
  39    * Remove an observer added via the addObserver call. Once removed the
  40    * observer will never be called again by the thread.
  41    */
  42   void removeObserver(in nsIThreadObserver observer);
  43 };
  44
  45 /**
  46  * This interface provides the observer with hooks to implement a layered
  47  * event queue.  For example, it is possible to overlay processing events
  48  * for a GUI toolkit on top of the events for a thread:
  49  *
  50  *   var NativeQueue;
  51  *   Observer = {
  52  *     onDispatchedEvent() {
  53  *       NativeQueue.signal();
  54  *     }
  55  *     onProcessNextEvent(thread, mayWait) {
  56  *       if (NativeQueue.hasNextEvent())
  57  *         NativeQueue.processNextEvent();
  58  *       while (mayWait && !thread.hasPendingEvent()) {
  59  *         NativeQueue.wait();
  60  *         NativeQueue.processNextEvent();
  61  *       }
  62  *     }
  63  *   };
  64  *
  65  * NOTE: The implementation of this interface must be threadsafe.
  66  *
  67  * NOTE: It is valid to change the thread's observer during a call to an
  68  *       observer method.
  69  *
  70  * NOTE: Will be split into two interfaces soon: one for onProcessNextEvent and
  71  *       afterProcessNextEvent, then another that inherits the first and adds
  72  *       onDispatchedEvent.
  73  */
  74 [uuid(cc8da053-1776-44c2-9199-b5a629d0a19d)]
  75 interface nsIThreadObserver : nsISupports
  76 {
  77   /**
  78    * This method is called after an event has been dispatched to the thread.
  79    * This method may be called from any thread.
  80    */
  81   void onDispatchedEvent();
  82
  83   /**
  84    * This method is called when nsIThread::ProcessNextEvent is called.  It does
  85    * not guarantee that an event is actually going to be processed.  This method
  86    * is only called on the target thread.
  87    *
  88    * @param thread
  89    *   The thread being asked to process another event.
  90    * @param mayWait
  91    *   Indicates whether or not the method is allowed to block the calling
  92    *   thread.  For example, this parameter is false during thread shutdown.
  93    */
  94   void onProcessNextEvent(in nsIThreadInternal thread, in boolean mayWait);
  95
  96   /**
  97    * This method is called (from nsIThread::ProcessNextEvent) after an event
  98    * is processed.  It does not guarantee that an event was actually processed
  99    * (depends on the value of |eventWasProcessed|.  This method is only called
 100    * on the target thread.  DO NOT EVER RUN SCRIPT FROM THIS CALLBACK!!!
 101    *
 102    * @param thread
 103    *   The thread that processed another event.
 104    * @param eventWasProcessed
 105    *   Indicates whether an event was actually processed. May be false if the
 106    *   |mayWait| flag was false when calling nsIThread::ProcessNextEvent().
 107    */
 108   void afterProcessNextEvent(in nsIThreadInternal thread,
 109                              in bool eventWasProcessed);
 110 };