1 /*
2 * Copyright (c) 1997, 2004, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package javax.swing.undo;
27
28 import javax.swing.event.*;
29 import java.util.*;
30
31 /**
32 * A support class used for managing <code>UndoableEdit</code> listeners.
33 *
34 * @author Ray Ryan
35 */
36 public class UndoableEditSupport {
37 protected int updateLevel;
38 protected CompoundEdit compoundEdit;
39 protected Vector<UndoableEditListener> listeners;
40 protected Object realSource;
41
42 /**
43 * Constructs an <code>UndoableEditSupport</code> object.
44 */
45 public UndoableEditSupport() {
46 this(null);
47 }
48
49 /**
50 * Constructs an <code>UndoableEditSupport</code> object.
51 *
52 * @param r an <code>Object</code>
53 */
54 public UndoableEditSupport(Object r) {
55 realSource = r == null ? this : r;
56 updateLevel = 0;
57 compoundEdit = null;
58 listeners = new Vector<UndoableEditListener>();
59 }
60
61 /**
62 * Registers an <code>UndoableEditListener</code>.
63 * The listener is notified whenever an edit occurs which can be undone.
64 *
65 * @param l an <code>UndoableEditListener</code> object
66 * @see #removeUndoableEditListener
67 */
68 public synchronized void addUndoableEditListener(UndoableEditListener l) {
69 listeners.addElement(l);
70 }
71
72 /**
73 * Removes an <code>UndoableEditListener</code>.
74 *
75 * @param l the <code>UndoableEditListener</code> object to be removed
76 * @see #addUndoableEditListener
77 */
78 public synchronized void removeUndoableEditListener(UndoableEditListener l)
79 {
80 listeners.removeElement(l);
81 }
82
83 /**
84 * Returns an array of all the <code>UndoableEditListener</code>s added
85 * to this UndoableEditSupport with addUndoableEditListener().
86 *
87 * @return all of the <code>UndoableEditListener</code>s added or an empty
88 * array if no listeners have been added
89 * @since 1.4
90 */
91 public synchronized UndoableEditListener[] getUndoableEditListeners() {
92 return listeners.toArray(new UndoableEditListener[0]);
93 }
94
95 /**
96 * Called only from <code>postEdit</code> and <code>endUpdate</code>. Calls
97 * <code>undoableEditHappened</code> in all listeners. No synchronization
98 * is performed here, since the two calling methods are synchronized.
99 */
100 protected void _postEdit(UndoableEdit e) {
101 UndoableEditEvent ev = new UndoableEditEvent(realSource, e);
102 Enumeration cursor = ((Vector)listeners.clone()).elements();
103 while (cursor.hasMoreElements()) {
104 ((UndoableEditListener)cursor.nextElement()).
105 undoableEditHappened(ev);
106 }
107 }
108
109 /**
110 * DEADLOCK WARNING: Calling this method may call
111 * <code>undoableEditHappened</code> in all listeners.
112 * It is unwise to call this method from one of its listeners.
113 */
114 public synchronized void postEdit(UndoableEdit e) {
115 if (updateLevel == 0) {
116 _postEdit(e);
117 } else {
118 // PENDING(rjrjr) Throw an exception if this fails?
119 compoundEdit.addEdit(e);
120 }
121 }
122
123 /**
124 * Returns the update level value.
125 *
126 * @return an integer representing the update level
127 */
128 public int getUpdateLevel() {
129 return updateLevel;
130 }
131
132 /**
133 *
134 */
135 public synchronized void beginUpdate() {
136 if (updateLevel == 0) {
137 compoundEdit = createCompoundEdit();
138 }
139 updateLevel++;
140 }
141
142 /**
143 * Called only from <code>beginUpdate</code>.
144 * Exposed here for subclasses' use.
145 */
146 protected CompoundEdit createCompoundEdit() {
147 return new CompoundEdit();
148 }
149
150 /**
151 * DEADLOCK WARNING: Calling this method may call
152 * <code>undoableEditHappened</code> in all listeners.
153 * It is unwise to call this method from one of its listeners.
154 */
155 public synchronized void endUpdate() {
156 updateLevel--;
157 if (updateLevel == 0) {
158 compoundEdit.end();
159 _postEdit(compoundEdit);
160 compoundEdit = null;
161 }
162 }
163
164 /**
165 * Returns a string that displays and identifies this
166 * object's properties.
167 *
168 * @return a <code>String</code> representation of this object
169 */
170 public String toString() {
171 return super.toString() +
172 " updateLevel: " + updateLevel +
173 " listeners: " + listeners +
174 " compoundEdit: " + compoundEdit;
175 }
176 }