|
78
|
1 /*******************************************************************************
|
|
|
2 * Copyright (c) 2005, 2008 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 * Brad Reynolds - bug 116920
|
|
|
11 * Brad Reynolds - bug 147515
|
|
|
12 *******************************************************************************/
|
|
|
13 module org.eclipse.core.databinding.observable.value.ComputedValue;
|
|
|
14
|
|
|
15 import java.lang.all;
|
|
|
16
|
|
|
17 import org.eclipse.core.databinding.observable.ChangeEvent;
|
|
|
18 import org.eclipse.core.databinding.observable.IChangeListener;
|
|
|
19 import org.eclipse.core.databinding.observable.IObservable;
|
|
|
20 import org.eclipse.core.databinding.observable.IStaleListener;
|
|
|
21 import org.eclipse.core.databinding.observable.ObservableTracker;
|
|
|
22 import org.eclipse.core.databinding.observable.Realm;
|
|
|
23 import org.eclipse.core.databinding.observable.StaleEvent;
|
|
|
24
|
|
|
25 /**
|
|
|
26 * A Lazily calculated value that automatically computes and registers listeners
|
|
|
27 * on its dependencies as long as all of its dependencies are IObservable
|
|
|
28 * objects
|
|
|
29 * <p>
|
|
|
30 * This class is thread safe. All state accessing methods must be invoked from
|
|
|
31 * the {@link Realm#isCurrent() current realm}. Methods for adding and removing
|
|
|
32 * listeners may be invoked from any thread.
|
|
|
33 * </p>
|
|
|
34 *
|
|
|
35 * @since 1.0
|
|
|
36 */
|
|
|
37 public abstract class ComputedValue : AbstractObservableValue {
|
|
|
38
|
|
|
39 private bool dirty = true;
|
|
|
40
|
|
|
41 private bool stale = false;
|
|
|
42
|
|
|
43 private Object cachedValue = null;
|
|
|
44
|
|
|
45 /**
|
|
|
46 * Array of observables this computed value depends on. This field has a
|
|
|
47 * value of <code>null</code> if we are not currently listening.
|
|
|
48 */
|
|
|
49 private IObservable[] dependencies = null;
|
|
|
50
|
|
|
51 /**
|
|
|
52 *
|
|
|
53 */
|
|
|
54 public this() {
|
|
|
55 this(Realm.getDefault(), null);
|
|
|
56 }
|
|
|
57
|
|
|
58 /**
|
|
|
59 * @param valueType
|
|
|
60 * can be <code>null</code>
|
|
|
61 */
|
|
|
62 public this(Object valueType) {
|
|
|
63 this(Realm.getDefault(), valueType);
|
|
|
64 }
|
|
|
65
|
|
|
66 /**
|
|
|
67 * @param realm
|
|
|
68 *
|
|
|
69 */
|
|
|
70 public this(Realm realm) {
|
|
|
71 this(realm, null);
|
|
|
72 }
|
|
|
73
|
|
|
74 /**
|
|
|
75 * @param realm
|
|
|
76 * @param valueType
|
|
|
77 */
|
|
|
78 public this(Realm realm, Object valueType) {
|
|
|
79 super(realm);
|
|
|
80 this.valueType = valueType;
|
|
|
81 }
|
|
|
82
|
|
|
83 /**
|
|
|
84 * Inner class that implements interfaces that we don't want to expose as
|
|
|
85 * public API. Each interface could have been implemented using a separate
|
|
|
86 * anonymous class, but we combine them here to reduce the memory overhead
|
|
|
87 * and number of classes.
|
|
|
88 *
|
|
|
89 * <p>
|
|
|
90 * The Runnable calls computeValue and stores the result in cachedValue.
|
|
|
91 * </p>
|
|
|
92 *
|
|
|
93 * <p>
|
|
|
94 * The IChangeListener stores each observable in the dependencies list. This
|
|
|
95 * is registered as the listener when calling ObservableTracker, to detect
|
|
|
96 * every observable that is used by computeValue.
|
|
|
97 * </p>
|
|
|
98 *
|
|
|
99 * <p>
|
|
|
100 * The IChangeListener is attached to every dependency.
|
|
|
101 * </p>
|
|
|
102 *
|
|
|
103 */
|
|
|
104 private class PrivateInterface : Runnable, IChangeListener,
|
|
|
105 IStaleListener {
|
|
|
106 public void run() {
|
|
|
107 cachedValue = calculate();
|
|
|
108 }
|
|
|
109
|
|
|
110 public void handleStale(StaleEvent event) {
|
|
|
111 if (!dirty && !stale) {
|
|
|
112 stale = true;
|
|
|
113 fireStale();
|
|
|
114 }
|
|
|
115 }
|
|
|
116
|
|
|
117 public void handleChange(ChangeEvent event) {
|
|
|
118 makeDirty();
|
|
|
119 }
|
|
|
120 }
|
|
|
121
|
|
|
122 private PrivateInterface privateInterface = new PrivateInterface();
|
|
|
123
|
|
|
124 private Object valueType;
|
|
|
125
|
|
|
126 protected final Object doGetValue() {
|
|
|
127 if (dirty) {
|
|
|
128 // This line will do the following:
|
|
|
129 // - Run the calculate method
|
|
|
130 // - While doing so, add any observable that is touched to the
|
|
|
131 // dependencies list
|
|
|
132 IObservable[] newDependencies = ObservableTracker.runAndMonitor(
|
|
|
133 privateInterface, privateInterface, null);
|
|
|
134
|
|
|
135 stale = false;
|
|
|
136 for (int i = 0; i < newDependencies.length; i++) {
|
|
|
137 IObservable observable = newDependencies[i];
|
|
|
138 // Add a change listener to the new dependency.
|
|
|
139 if (observable.isStale()) {
|
|
|
140 stale = true;
|
|
|
141 } else {
|
|
|
142 observable.addStaleListener(privateInterface);
|
|
|
143 }
|
|
|
144 }
|
|
|
145
|
|
|
146 dependencies = newDependencies;
|
|
|
147
|
|
|
148 dirty = false;
|
|
|
149 }
|
|
|
150
|
|
|
151 return cachedValue;
|
|
|
152 }
|
|
|
153
|
|
|
154 /**
|
|
|
155 * Subclasses must override this method to provide the object's value.
|
|
|
156 *
|
|
|
157 * @return the object's value
|
|
|
158 */
|
|
|
159 protected abstract Object calculate();
|
|
|
160
|
|
|
161 protected final void makeDirty() {
|
|
|
162 if (!dirty) {
|
|
|
163 dirty = true;
|
|
|
164
|
|
|
165 stopListening();
|
|
|
166
|
|
|
167 // copy the old value
|
|
|
168 final Object oldValue = cachedValue;
|
|
|
169 // Fire the "dirty" event. This implementation recomputes the new
|
|
|
170 // value lazily.
|
|
|
171 fireValueChange(new class() ValueDiff {
|
|
|
172
|
|
|
173 public Object getOldValue() {
|
|
|
174 return oldValue;
|
|
|
175 }
|
|
|
176
|
|
|
177 public Object getNewValue() {
|
|
|
178 return getValue();
|
|
|
179 }
|
|
|
180 });
|
|
|
181 }
|
|
|
182 }
|
|
|
183
|
|
|
184 /**
|
|
|
185 *
|
|
|
186 */
|
|
|
187 private void stopListening() {
|
|
|
188 // Stop listening for dependency changes.
|
|
|
189 if (dependencies !is null) {
|
|
|
190 for (int i = 0; i < dependencies.length; i++) {
|
|
|
191 IObservable observable = dependencies[i];
|
|
|
192
|
|
|
193 observable.removeChangeListener(privateInterface);
|
|
|
194 observable.removeStaleListener(privateInterface);
|
|
|
195 }
|
|
|
196 dependencies = null;
|
|
|
197 }
|
|
|
198 }
|
|
|
199
|
|
|
200 public bool isStale() {
|
|
|
201 // we need to recompute, otherwise staleness wouldn't mean anything
|
|
|
202 getValue();
|
|
|
203 return stale;
|
|
|
204 }
|
|
|
205
|
|
|
206 public Object getValueType() {
|
|
|
207 return valueType;
|
|
|
208 }
|
|
|
209
|
|
|
210 // this method exists here so that we can call it from the runnable below.
|
|
|
211 /**
|
|
|
212 * @since 1.1
|
|
|
213 */
|
|
|
214 protected bool hasListeners() {
|
|
|
215 return super.hasListeners();
|
|
|
216 }
|
|
|
217
|
|
|
218 public synchronized void addChangeListener(IChangeListener listener) {
|
|
|
219 super.addChangeListener(listener);
|
|
|
220 // If somebody is listening, we need to make sure we attach our own
|
|
|
221 // listeners
|
|
|
222 computeValueForListeners();
|
|
|
223 }
|
|
|
224
|
|
|
225 /**
|
|
|
226 * Some clients just add a listener and expect to get notified even if they
|
|
|
227 * never called getValue(), so we have to call getValue() ourselves here to
|
|
|
228 * be sure. Need to be careful about realms though, this method can be
|
|
|
229 * called outside of our realm. See also bug 198211. If a client calls this
|
|
|
230 * outside of our realm, they may receive change notifications before the
|
|
|
231 * runnable below has been executed. It is their job to figure out what to
|
|
|
232 * do with those notifications.
|
|
|
233 */
|
|
|
234 private void computeValueForListeners() {
|
|
|
235 getRealm().exec(new class() Runnable {
|
|
|
236 public void run() {
|
|
|
237 if (dependencies is null) {
|
|
|
238 // We are not currently listening.
|
|
|
239 if (hasListeners()) {
|
|
|
240 // But someone is listening for changes. Call getValue()
|
|
|
241 // to make sure we start listening to the observables we
|
|
|
242 // depend on.
|
|
|
243 getValue();
|
|
|
244 }
|
|
|
245 }
|
|
|
246 }
|
|
|
247 });
|
|
|
248 }
|
|
|
249
|
|
|
250 public synchronized void addValueChangeListener(
|
|
|
251 IValueChangeListener listener) {
|
|
|
252 super.addValueChangeListener(listener);
|
|
|
253 // If somebody is listening, we need to make sure we attach our own
|
|
|
254 // listeners
|
|
|
255 computeValueForListeners();
|
|
|
256 }
|
|
|
257
|
|
|
258 public synchronized void dispose() {
|
|
|
259 super.dispose();
|
|
|
260 stopListening();
|
|
|
261 }
|
|
|
262
|
|
|
263 }
|
