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1 /*******************************************************************************
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2 * Copyright (c) 2005, 2007 IBM Corporation and others.
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3 * All rights reserved. This program and the accompanying materials
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4 * are made available under the terms of the Eclipse Public License v1.0
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5 * which accompanies this distribution, and is available at
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6 * http://www.eclipse.org/legal/epl-v10.html
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7 *
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8 * Contributors:
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9 * IBM Corporation - initial API and implementation
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10 * Brad Reynolds - bug 164653
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11 *******************************************************************************/
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12 module org.eclipse.core.databinding.observable.value.AbstractVetoableValue;
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81
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13 import org.eclipse.core.databinding.observable.value.IVetoableValue;
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14 import org.eclipse.core.databinding.observable.value.ValueDiff;
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15 import org.eclipse.core.databinding.observable.value.AbstractObservableValue;
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16 import org.eclipse.core.databinding.observable.value.IValueChangingListener;
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17 import org.eclipse.core.databinding.observable.value.ChangeVetoException;
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18 import org.eclipse.core.databinding.observable.value.ValueChangingEvent;
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78
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19
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20 import java.lang.all;
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21
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22 import org.eclipse.core.databinding.observable.Diffs;
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23 import org.eclipse.core.databinding.observable.Realm;
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24 import org.eclipse.core.internal.databinding.Util;
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25
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26 /**
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27 *
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28 * <p>
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29 * This class is thread safe. All state accessing methods must be invoked from
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30 * the {@link Realm#isCurrent() current realm}. Methods for adding and removing
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31 * listeners may be invoked from any thread.
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32 * </p>
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33 * @since 1.0
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34 *
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35 */
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36 public abstract class AbstractVetoableValue : AbstractObservableValue
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37 , IVetoableValue {
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38
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39 /**
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40 * Creates a new vetoable value.
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41 */
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42 public this() {
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43 this(Realm.getDefault());
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44 }
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45
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46 /**
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47 * @param realm
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48 */
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49 public this(Realm realm) {
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50 super(realm);
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51 }
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52
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53 final protected void doSetValue(Object value) {
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54 Object currentValue = doGetValue();
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55 ValueDiff diff = Diffs.createValueDiff(currentValue, value);
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56 bool okToProceed = fireValueChanging(diff);
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57 if (!okToProceed) {
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58 throw new ChangeVetoException("Change not permitted"); //$NON-NLS-1$
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59 }
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60 doSetApprovedValue(value);
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61
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62 if (!Util.equals(diff.getOldValue(), diff.getNewValue())) {
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63 fireValueChange(diff);
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64 }
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65 }
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66
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67 /**
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68 * Sets the value. Invoked after performing veto checks. Should not fire change events.
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69 *
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70 * @param value
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71 */
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72 protected abstract void doSetApprovedValue(Object value);
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73
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74 public synchronized void addValueChangingListener(
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75 IValueChangingListener listener) {
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76 addListener(ValueChangingEvent.TYPE, listener);
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77 }
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78
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79 public synchronized void removeValueChangingListener(
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80 IValueChangingListener listener) {
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81 removeListener(ValueChangingEvent.TYPE, listener);
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82 }
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83
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84 /**
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85 * Notifies listeners about a pending change, and returns true if no
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86 * listener vetoed the change.
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87 *
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88 * @param diff
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89 * @return false if the change was vetoed, true otherwise
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90 */
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91 protected bool fireValueChanging(ValueDiff diff) {
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92 checkRealm();
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93
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94 ValueChangingEvent event = new ValueChangingEvent(this, diff);
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95 fireEvent(event);
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96 return !event.veto;
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97 }
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98
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99 public synchronized void dispose() {
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100 super.dispose();
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101 }
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102
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103 }
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