1 /*

     2  * Copyright (c) 1997, 2008, 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      * @param e edit to be verified

   101      */

   102     protected void _postEdit(UndoableEdit e) {

   103         UndoableEditEvent ev = new UndoableEditEvent(realSource, e);

   104         @SuppressWarnings("unchecked")

   105         Enumeration<UndoableEditListener> cursor =

   106             ((Vector<UndoableEditListener>)listeners.clone()).elements();

   107         while (cursor.hasMoreElements()) {

   108             cursor.nextElement().undoableEditHappened(ev);

   109         }

   110     }

   111 

   112     /**

   113      * DEADLOCK WARNING: Calling this method may call

   114      * <code>undoableEditHappened</code> in all listeners.

   115      * It is unwise to call this method from one of its listeners.

   116      *

   117      * @param e edit to be posted

   118      */

   119     public synchronized void postEdit(UndoableEdit e) {

   120         if (updateLevel == 0) {

   121             _postEdit(e);

   122         } else {

   123             // PENDING(rjrjr) Throw an exception if this fails?

   124             compoundEdit.addEdit(e);

   125         }

   126     }

   127 

   128     /**

   129      * Returns the update level value.

   130      *

   131      * @return an integer representing the update level

   132      */

   133     public int getUpdateLevel() {

   134         return updateLevel;

   135     }

   136 

   137     /**

   138      *

   139      */

   140     public synchronized void beginUpdate() {

   141         if (updateLevel == 0) {

   142             compoundEdit = createCompoundEdit();

   143         }

   144         updateLevel++;

   145     }

   146 

   147     /**

   148      * Called only from <code>beginUpdate</code>.

   149      * Exposed here for subclasses' use.

   150      *

   151      * @return new created {@code CompoundEdit} object

   152      */

   153     protected CompoundEdit createCompoundEdit() {

   154         return new CompoundEdit();

   155     }

   156 

   157     /**

   158      * DEADLOCK WARNING: Calling this method may call

   159      * <code>undoableEditHappened</code> in all listeners.

   160      * It is unwise to call this method from one of its listeners.

   161      */

   162     public synchronized void endUpdate() {

   163         updateLevel--;

   164         if (updateLevel == 0) {

   165             compoundEdit.end();

   166             _postEdit(compoundEdit);

   167             compoundEdit = null;

   168         }

   169     }

   170 

   171     /**

   172      * Returns a string that displays and identifies this

   173      * object's properties.

   174      *

   175      * @return a <code>String</code> representation of this object

   176      */

   177     public String toString() {

   178         return super.toString() +

   179             " updateLevel: " + updateLevel +

   180             " listeners: " + listeners +

   181             " compoundEdit: " + compoundEdit;

   182     }

   183 }