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1 /*
2 * Copyright (c) 2003 Scott Howlett & Paul Libbrecht.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 *
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in
14 * the documentation and/or other materials provided with the
15 * distribution.
16 *
17 * 3. The end-user documentation included with the redistribution,
18 * if any, must include the following acknowledgment:
19 * "This product includes software developed by the Xwing
20 * Project ( http://xwing.sourceforge.net/ )."
21 * Alternately, this acknowledgment may appear in the software itself,
22 * if and wherever such third-party acknowledgments normally appear.
23 *
24 * 4. The name "Xwing" must not be used to endorse or promote products
25 * derived from this software without prior written permission. For
26 * written permission, please contact the project authors via
27 * the Xwing project site, http://xwing.sourceforge.net/ .
28 *
29 * 5. Products derived from this software may not be called "Xwing",
30 * nor may "Xwing" appear in their name, without prior written
31 * permission of the Xwing project.
32 *
33 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
34 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
35 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
36 * DISCLAIMED. IN NO EVENT SHALL THE XWING AUTHORS OR THE PROJECT
37 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
38 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
39 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
40 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
41 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
42 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
43 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
44 * SUCH DAMAGE.
45 *
46 * For more information on Xwing, please see
47 * < http://xwing.sourceforge.net/ >.
48 */
49
50 package net.sourceforge.xwing;
51
52 import javax.swing.event.ChangeEvent;
53 import javax.swing.event.ChangeListener;
54
55
56 /***
57 * A SourceSink that channels a value from some other SourceSink.
58 * When the value of that SourceSink is null, a default value is
59 * retrieved from another SourceSink.
60 *
61 * @author Scott Howlett
62 * @version $Revision: 1.2 $
63 */
64
65 public class DefaultValueSourceSink extends AbstractSourceSink {
66
67 private SourceSink valueSrcSink;
68 private SourceSink defaultSrcSink;
69
70 private boolean usingDefault;
71
72 /***
73 * Create a new DefaultValueSourceSink.
74 * @param valueSS the SourceSink that values are read from and written to.
75 * @param defaultSS A SourceSink that values are read from if the value
76 * held by valueSS is null. defaultSS is never written to.
77 */
78
79 public DefaultValueSourceSink(SourceSink valueSS, SourceSink defaultSS) {
80 valueSrcSink = valueSS;
81 defaultSrcSink = defaultSS;
82
83 valueSrcSink.addChangeListener(new ChangeListener() {
84 public void stateChanged(ChangeEvent e) {
85 usingDefault = valueSrcSink.get() == null;
86 fireStateChanged();
87 }
88 });
89
90 defaultSrcSink.addChangeListener(new ChangeListener() {
91 public void stateChanged(ChangeEvent e) {
92 if (usingDefault) {
93 fireStateChanged();
94 }
95 }
96 });
97
98 usingDefault = valueSrcSink.get() == null;
99
100 }
101
102 public Object get() {
103 return usingDefault ? defaultSrcSink.get() : valueSrcSink.get();
104 }
105
106 public void set(Object newValue) {
107 valueSrcSink.set(newValue);
108 }
109
110 /***
111 * Is this SourceSink currently using its default value?
112 */
113 public boolean isUsingDefault() {
114 return usingDefault;
115 }
116
117 /***
118 * Cause this SourceSink to revert to its default value.
119 */
120 public void restoreDefault() {
121 valueSrcSink.set(null);
122 }
123 }
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