Quelle nsStubMutationObserver.h Sprache: C

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
* nsStubMutationObserver is an implementation of the nsIMutationObserver
* interface (except for the methods on nsISupports) that is intended to be
* used as a base class within the content/layout library.  All methods do
* nothing.
*/

#ifndef nsStubMutationObserver_h_
#define nsStubMutationObserver_h_

#include "nsTHashMap.h"
#include "nsIMutationObserver.h"

/**
* There are two advantages to inheriting from nsStubMutationObserver
* rather than directly from nsIMutationObserver:
*  1. smaller compiled code size (since there's no need for the code
*     for the empty virtual function implementations for every
*     nsIMutationObserver implementation)
*  2. the performance of document's loop over observers benefits from
*     the fact that more of the functions called are the same (which
*     can reduce instruction cache misses and perhaps improve branch
*     prediction)
*/
class nsStubMutationObserver : public nsIMutationObserver {
public:
  NS_DECL_NSIMUTATIONOBSERVER
};

class MutationObserverWrapper;

/**
* @brief Base class for MutationObservers that are used by multiple nodes.
*
* Mutation Observers are stored inside of a nsINode using a DoublyLinkedList,
* restricting the number of nodes a mutation observer can be inserted to one.
*
* To allow a mutation observer to be used by several nodes, this class
* provides a MutationObserverWrapper which implements the nsIMutationObserver
* interface and forwards all method calls to this class. For each node this
* mutation observer will be used for, a wrapper object is created.
*/
class nsMultiMutationObserver : public nsIMutationObserver {
public:
  /**
   * Adds the mutation observer to aNode by creating a MutationObserverWrapper
   * and inserting it into aNode.
   * Does nothing if there already is a mutation observer for aNode.
   */
  void AddMutationObserverToNode(nsINode* aNode);

  /**
   * Removes the mutation observer from aNode.
   * Does nothing if there is no mutation observer for aNode.
   */
  void RemoveMutationObserverFromNode(nsINode* aNode);

  /**
   * Returns true if there is already a mutation observer for aNode.
   */
  bool ContainsNode(const nsINode* aNode) const;

private:
  friend class MutationObserverWrapper;
  nsTHashMap<nsINode*, MutationObserverWrapper*> mWrapperForNode;
};

/**
* Convenience class that provides support for multiple nodes and has
* default implementations for nsIMutationObserver.
*/
class nsStubMultiMutationObserver : public nsMultiMutationObserver {
public:
  NS_DECL_NSIMUTATIONOBSERVER
};

#endif /* !defined(nsStubMutationObserver_h_) */

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