nsStubMutationObserver.h (2947B)
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 #include "nsTHashMap.h" 19 20 /** 21 * There are two advantages to inheriting from nsStubMutationObserver 22 * rather than directly from nsIMutationObserver: 23 * 1. smaller compiled code size (since there's no need for the code 24 * for the empty virtual function implementations for every 25 * nsIMutationObserver implementation) 26 * 2. the performance of document's loop over observers benefits from 27 * the fact that more of the functions called are the same (which 28 * can reduce instruction cache misses and perhaps improve branch 29 * prediction) 30 */ 31 class nsStubMutationObserver : public nsIMutationObserver { 32 public: 33 NS_DECL_NSIMUTATIONOBSERVER 34 }; 35 36 class MutationObserverWrapper; 37 38 /** 39 * @brief Base class for MutationObservers that are used by multiple nodes. 40 * 41 * Mutation Observers are stored inside of a nsINode using a DoublyLinkedList, 42 * restricting the number of nodes a mutation observer can be inserted to one. 43 * 44 * To allow a mutation observer to be used by several nodes, this class 45 * provides a MutationObserverWrapper which implements the nsIMutationObserver 46 * interface and forwards all method calls to this class. For each node this 47 * mutation observer will be used for, a wrapper object is created. 48 */ 49 class nsMultiMutationObserver : public nsIMutationObserver { 50 public: 51 /** 52 * Adds the mutation observer to aNode by creating a MutationObserverWrapper 53 * and inserting it into aNode. 54 * Does nothing if there already is a mutation observer for aNode. 55 */ 56 void AddMutationObserverToNode(nsINode* aNode); 57 58 /** 59 * Removes the mutation observer from aNode. 60 * Does nothing if there is no mutation observer for aNode. 61 */ 62 void RemoveMutationObserverFromNode(nsINode* aNode); 63 64 /** 65 * Returns true if there is already a mutation observer for aNode. 66 */ 67 bool ContainsNode(const nsINode* aNode) const; 68 69 private: 70 friend class MutationObserverWrapper; 71 nsTHashMap<nsINode*, MutationObserverWrapper*> mWrapperForNode; 72 }; 73 74 /** 75 * Convenience class that provides support for multiple nodes and has 76 * default implementations for nsIMutationObserver. 77 */ 78 class nsStubMultiMutationObserver : public nsMultiMutationObserver { 79 public: 80 NS_DECL_NSIMUTATIONOBSERVER 81 }; 82 83 #endif /* !defined(nsStubMutationObserver_h_) */