001 /* UndoableEditSupport.java --
002 Copyright (C) 2002, 2003, 2004, 2005, 2006, Free Software Foundation, Inc.
003
004 This file is part of GNU Classpath.
005
006 GNU Classpath is free software; you can redistribute it and/or modify
007 it under the terms of the GNU General Public License as published by
008 the Free Software Foundation; either version 2, or (at your option)
009 any later version.
010
011 GNU Classpath is distributed in the hope that it will be useful, but
012 WITHOUT ANY WARRANTY; without even the implied warranty of
013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014 General Public License for more details.
015
016 You should have received a copy of the GNU General Public License
017 along with GNU Classpath; see the file COPYING. If not, write to the
018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019 02110-1301 USA.
020
021 Linking this library statically or dynamically with other modules is
022 making a combined work based on this library. Thus, the terms and
023 conditions of the GNU General Public License cover the whole
024 combination.
025
026 As a special exception, the copyright holders of this library give you
027 permission to link this library with independent modules to produce an
028 executable, regardless of the license terms of these independent
029 modules, and to copy and distribute the resulting executable under
030 terms of your choice, provided that you also meet, for each linked
031 independent module, the terms and conditions of the license of that
032 module. An independent module is a module which is not derived from
033 or based on this library. If you modify this library, you may extend
034 this exception to your version of the library, but you are not
035 obligated to do so. If you do not wish to do so, delete this
036 exception statement from your version. */
037
038
039 package javax.swing.undo;
040
041 import java.util.Iterator;
042 import java.util.Vector;
043
044 import javax.swing.event.UndoableEditEvent;
045 import javax.swing.event.UndoableEditListener;
046
047 /**
048 * A helper class for supporting {@link
049 * javax.swing.event.UndoableEditListener}.
050 *
051 * @author Andrew Selkirk (aselkirk@sympatico.ca)
052 * @author Sascha Brawer (brawer@dandelis.ch)
053 */
054 public class UndoableEditSupport
055 {
056 /**
057 * The number of times that {@link #beginUpdate()} has been called
058 * without a matching call to {@link #endUpdate()}.
059 */
060 protected int updateLevel;
061
062
063 /**
064 * compoundEdit
065 */
066 protected CompoundEdit compoundEdit;
067
068
069 /**
070 * The currently registered listeners.
071 */
072 protected Vector<UndoableEditListener> listeners =
073 new Vector<UndoableEditListener>();
074
075
076 /**
077 * The source of the broadcast UndoableEditEvents.
078 */
079 protected Object realSource;
080
081
082 /**
083 * Constructs a new helper for broadcasting UndoableEditEvents. The
084 * events will indicate the newly constructed
085 * <code>UndoableEditSupport</code> instance as their source.
086 *
087 * @see #UndoableEditSupport(java.lang.Object)
088 */
089 public UndoableEditSupport()
090 {
091 realSource = this;
092 }
093
094
095 /**
096 * Constructs a new helper for broadcasting UndoableEditEvents.
097 *
098 * @param realSource the source of the UndoableEditEvents that will
099 * be broadcast by this helper. If <code>realSource</code> is
100 * <code>null</code>, the events will indicate the newly constructed
101 * <code>UndoableEditSupport</code> instance as their source.
102 */
103 public UndoableEditSupport(Object realSource)
104 {
105 if (realSource == null)
106 realSource = this;
107 this.realSource = realSource;
108 }
109
110
111 /**
112 * Returns a string representation of this object that may be useful
113 * for debugging.
114 */
115 public String toString()
116 {
117 // Note that often, this.realSource == this. Therefore, dumping
118 // realSource without additional checks may lead to infinite
119 // recursion. See Classpath bug #7119.
120 return super.toString() + " updateLevel: " + updateLevel
121 + " listeners: " + listeners + " compoundEdit: " + compoundEdit;
122 }
123
124
125 /**
126 * Registers a listener.
127 *
128 * @param val the listener to be added.
129 */
130 public synchronized void addUndoableEditListener(UndoableEditListener val)
131 {
132 listeners.add(val);
133 }
134
135
136 /**
137 * Unregisters a listener.
138 * @param val the listener to be removed.
139 */
140 public synchronized void removeUndoableEditListener(UndoableEditListener val)
141 {
142 listeners.removeElement(val);
143 }
144
145
146 /**
147 * Returns an array containing the currently registered listeners.
148 */
149 public synchronized UndoableEditListener[] getUndoableEditListeners()
150 {
151 UndoableEditListener[] result = new UndoableEditListener[listeners.size()];
152 return listeners.toArray(result);
153 }
154
155
156 /**
157 * Notifies all registered listeners that an {@link
158 * UndoableEditEvent} has occured.
159 *
160 * <p><b>Lack of Thread Safety:</b> It is <em>not</em> safe to call
161 * this method from concurrent threads, unless the call is protected
162 * by a synchronization on this <code>UndoableEditSupport</code>
163 * instance.
164 *
165 * @param edit the edit action to be posted.
166 */
167 protected void _postEdit(UndoableEdit edit)
168 {
169 UndoableEditEvent event;
170 Iterator<UndoableEditListener> iter;
171
172 // Do nothing if we have no listeners.
173 if (listeners.isEmpty())
174 return;
175
176 event = new UndoableEditEvent(realSource, edit);
177
178 // We clone the vector because this allows listeners to register
179 // or unregister listeners in their undoableEditHappened method.
180 // Otherwise, this would throw exceptions (in the case of
181 // Iterator, a java.util.ConcurrentModificationException; in the
182 // case of a direct loop over the Vector elements, some
183 // index-out-of-bounds exception).
184 iter = new Vector<UndoableEditListener>(listeners).iterator();
185 while (iter.hasNext())
186 iter.next().undoableEditHappened(event);
187 }
188
189
190 /**
191 * If {@link #beginUpdate} has been called (so that the current
192 * update level is greater than zero), adds the specified edit
193 * to {@link #compoundEdit}. Otherwise, notify listeners of the
194 * edit by calling {@link #_postEdit(UndoableEdit)}.
195 *
196 * <p><b>Thread Safety:</b> It is safe to call this method from any
197 * thread without external synchronization.
198 *
199 * @param edit the edit action to be posted.
200 */
201 public synchronized void postEdit(UndoableEdit edit)
202 {
203 if (compoundEdit != null)
204 compoundEdit.addEdit(edit);
205 else
206 _postEdit(edit);
207 }
208
209
210 /**
211 * Returns the current update level.
212 */
213 public int getUpdateLevel()
214 {
215 return updateLevel;
216 }
217
218
219 /**
220 * Starts a (possibly nested) update session. If the current update
221 * level is zero, {@link #compoundEdit} is set to the result of the
222 * {@link #createCompoundEdit} method. In any case, the update level
223 * is increased by one.
224 *
225 * <p><b>Thread Safety:</b> It is safe to call this method from any
226 * thread without external synchronization.
227 */
228 public synchronized void beginUpdate()
229 {
230 if (compoundEdit == null)
231 compoundEdit = createCompoundEdit();
232 ++updateLevel;
233 }
234
235
236 /**
237 * Creates a new instance of {@link CompoundEdit}. Called by {@link
238 * #beginUpdate}. If a subclass wants {@link #beginUpdate} to work
239 * on a specific {@link #compoundEdit}, it should override this
240 * method.
241 *
242 * @return a newly created instance of {@link CompoundEdit}.
243 */
244 protected CompoundEdit createCompoundEdit()
245 {
246 return new CompoundEdit();
247 }
248
249
250 /**
251 * Ends an update session. If the terminated session was the
252 * outermost session, {@link #compoundEdit} will receive an
253 * <code>end</code> message, and {@link #_postEdit} gets called in
254 * order to notify any listeners. Finally, the
255 * <code>compoundEdit</code> is discarded.
256 *
257 * <p><b>Thread Safety:</b> It is safe to call this method from any
258 * thread without external synchronization.
259 */
260 public synchronized void endUpdate()
261 {
262 if (updateLevel == 0)
263 throw new IllegalStateException();
264
265 if (--updateLevel > 0)
266 return;
267
268 compoundEdit.end();
269 _postEdit(compoundEdit);
270 compoundEdit = null;
271 }
272 }