widget/nsIAppShell.idl

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
   2  *
   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 "nsISupports.idl"
   8
   9 interface nsIRunnable;
  10
  11 /**
  12  * Interface for the native event system layer.  This interface is designed
  13  * to be used on the main application thread only.
  14  */
  15 [uuid(2d10ca53-f143-439a-bb2e-c1fbc71f6a05)]
  16 interface nsIAppShell : nsISupports
  17 {
  18   /**
  19    * Enter an event loop.  Don't leave until exit() is called.
  20    */
  21   void run();
  22
  23   /**
  24    * Exit the handle event loop
  25    */
  26   void exit();
  27
  28   /**
  29    * Give hint to native event queue notification mechanism. If the native
  30    * platform needs to tradeoff performance vs. native event starvation this
  31    * hint tells the native dispatch code which to favor.  The default is to
  32    * prevent native event starvation.
  33    *
  34    * Calls to this function may be nested. When the number of calls that pass
  35    * PR_TRUE is subtracted from the number of calls that pass PR_FALSE is
  36    * greater than 0, performance is given precedence over preventing event
  37    * starvation.
  38    *
  39    * The starvationDelay arg is only used when favorPerfOverStarvation is
  40    * PR_FALSE. It is the amount of time in milliseconds to wait before the
  41    * PR_FALSE actually takes effect.
  42    */
  43   void favorPerformanceHint(in boolean favorPerfOverStarvation,
  44                             in unsigned long starvationDelay);
  45
  46   /**
  47    * Suspends the use of additional platform-specific methods (besides the
  48    * nsIAppShell->run() event loop) to run Gecko events on the main
  49    * application thread.  Under some circumstances these "additional methods"
  50    * can cause Gecko event handlers to be re-entered, sometimes leading to
  51    * hangs and crashes.  Calls to suspendNative() and resumeNative() may be
  52    * nested.  On some platforms (those that don't use any "additional
  53    * methods") this will be a no-op.  Does not (in itself) stop Gecko events
  54    * from being processed on the main application thread.  But if the
  55    * nsIAppShell->run() event loop is blocked when this call is made, Gecko
  56    * events will stop being processed until resumeNative() is called (even
  57    * if a plugin or library is temporarily processing events on a nested
  58    * event loop).
  59    */
  60   void suspendNative();
  61
  62   /**
  63    * Resumes the use of additional platform-specific methods to run Gecko
  64    * events on the main application thread.  Calls to suspendNative() and
  65    * resumeNative() may be nested.  On some platforms this will be a no-op.
  66    */
  67   void resumeNative();
  68
  69   /**
  70    * The current event loop nesting level.
  71    */
  72   readonly attribute unsigned long eventloopNestingLevel;
  73
  74   /**
  75    * Allows running of a "synchronous section", in the form of an nsIRunnable
  76    * once the event loop has reached a "stable state". We've reached a stable
  77    * state when the currently executing task/event has finished, see:
  78    * http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#synchronous-section
  79    * In practice this runs aRunnable once the currently executing event
  80    * finishes. If called multiple times per task/event, all the runnables will
  81    * be executed, in the order in which runInStableState() was called.
  82    */
  83   void runInStableState(in nsIRunnable runnable);
  84
  85   /**
  86    * Run the given runnable before the next iteration of the event loop (this
  87    * includes native events too). If a nested loop is spawned within the current
  88    * event then the runnable will not be run until that loop has terminated.
  89    */
  90   void runBeforeNextEvent(in nsIRunnable runnable);
  91 };