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comparison org.eclipse.core.commands/src/org/eclipse/core/commands/common/EventManager.d @ 12:bc29606a740c

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Added dwt-addons in original directory structure of eclipse.org
author Frank Benoit <benoit@tionex.de>
date Sat, 14 Mar 2009 18:23:29 +0100
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11:43904fec5dca 12:bc29606a740c
1 /*******************************************************************************
2 * Copyright (c) 2005, 2006 IBM Corporation and others.
3 * All rights reserved. This program and the accompanying materials
4 * are made available under the terms of the Eclipse Public License v1.0
5 * which accompanies this distribution, and is available at
6 * http://www.eclipse.org/legal/epl-v10.html
7 *
8 * Contributors:
9 * IBM Corporation - initial API and implementation
10 * Port to the D programming language:
11 * Frank Benoit <benoit@tionex.de>
12 *******************************************************************************/
13
14 module org.eclipse.core.commands.common.EventManager;
15
16 import org.eclipse.core.runtime.ListenerList;
17
18 /**
19 * <p>
20 * A manager to which listeners can be attached. This handles the management of
21 * a list of listeners -- optimizing memory and performance. All the methods on
22 * this class are guaranteed to be thread-safe.
23 * </p>
24 * <p>
25 * Clients may extend.
26 * </p>
27 *
28 * @since 3.2
29 */
30 public abstract class EventManager {
31
32 /**
33 * An empty array that can be returned from a call to
34 * {@link #getListeners()} when {@link #listenerList} is <code>null</code>.
35 */
36 private static const Object[] EMPTY_ARRAY = null;
37
38 /**
39 * A collection of objects listening to changes to this manager. This
40 * collection is <code>null</code> if there are no listeners.
41 */
42 private /+transient+/ ListenerList listenerList = null;
43
44 /**
45 * Adds a listener to this manager that will be notified when this manager's
46 * state changes.
47 *
48 * @param listener
49 * The listener to be added; must not be <code>null</code>.
50 */
51 protected synchronized final void addListenerObject(Object listener) {
52 if (listenerList is null) {
53 listenerList = new ListenerList(ListenerList.IDENTITY);
54 }
55
56 listenerList.add(listener);
57 }
58
59 /**
60 * Clears all of the listeners from the listener list.
61 */
62 protected synchronized final void clearListeners() {
63 if (listenerList !is null) {
64 listenerList.clear();
65 }
66 }
67
68 /**
69 * Returns the listeners attached to this event manager.
70 *
71 * @return The listeners currently attached; may be empty, but never
72 * <code>null</code>
73 */
74 protected final Object[] getListeners() {
75 ListenerList list = listenerList;
76 if (list is null) {
77 return EMPTY_ARRAY;
78 }
79
80 return list.getListeners();
81 }
82
83 /**
84 * Whether one or more listeners are attached to the manager.
85 *
86 * @return <code>true</code> if listeners are attached to the manager;
87 * <code>false</code> otherwise.
88 */
89 protected final bool isListenerAttached() {
90 return listenerList !is null;
91 }
92
93 /**
94 * Removes a listener from this manager.
95 *
96 * @param listener
97 * The listener to be removed; must not be <code>null</code>.
98 */
99 protected synchronized final void removeListenerObject(Object listener) {
100 if (listenerList !is null) {
101 listenerList.remove(listener);
102
103 if (listenerList.isEmpty()) {
104 listenerList = null;
105 }
106 }
107 }
108 }