dom/base/nsStubMutationObserver.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   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 /*
   8  * nsStubMutationObserver is an implementation of the nsIMutationObserver
   9  * interface (except for the methods on nsISupports) that is intended to be
  10  * used as a base class within the content/layout library.  All methods do
  11  * nothing.
  12  */
  13
  14 #ifndef nsStubMutationObserver_h_
  15 #define nsStubMutationObserver_h_
  16
  17 #include "nsIMutationObserver.h"
  18
  19 /**
  20  * There are two advantages to inheriting from nsStubMutationObserver
  21  * rather than directly from nsIMutationObserver:
  22  *  1. smaller compiled code size (since there's no need for the code
  23  *     for the empty virtual function implementations for every
  24  *     nsIMutationObserver implementation)
  25  *  2. the performance of document's loop over observers benefits from
  26  *     the fact that more of the functions called are the same (which
  27  *     can reduce instruction cache misses and perhaps improve branch
  28  *     prediction)
  29  */
  30 class nsStubMutationObserver : public nsIMutationObserver {
  31  public:
  32   NS_DECL_NSIMUTATIONOBSERVER
  33 };
  34
  35 #endif /* !defined(nsStubMutationObserver_h_) */