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comparison org.eclipse.jface.databinding/src/org/eclipse/jface/internal/databinding/provisional/swt/ControlUpdater.d @ 78:0a55d2d5a946

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Added file for databinding
author Frank Benoit <benoit@tionex.de>
date Tue, 14 Apr 2009 11:35:29 +0200
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76:f05e6e8b2f2d 78:0a55d2d5a946
1 /*******************************************************************************
2 * Copyright (c) 2005, 2007 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 *******************************************************************************/
11 module org.eclipse.jface.internal.databinding.provisional.swt.ControlUpdater;
12
13 import java.lang.all;
14
15 import org.eclipse.core.databinding.observable.ChangeEvent;
16 import org.eclipse.core.databinding.observable.IChangeListener;
17 import org.eclipse.core.databinding.observable.IObservable;
18 import org.eclipse.core.databinding.observable.ObservableTracker;
19 import org.eclipse.swt.events.DisposeEvent;
20 import org.eclipse.swt.events.DisposeListener;
21 import org.eclipse.swt.events.PaintEvent;
22 import org.eclipse.swt.events.PaintListener;
23 import org.eclipse.swt.widgets.Control;
24
25 /**
26 * NON-API - A ControlUpdater updates an SWT control in response to changes in the model.
27 * By wrapping a block of code in a ControlUpdater, clients can rely on the fact
28 * that the block of code will be re-executed whenever anything changes in the
29 * model that might affect its behavior.
30 *
31 * <p>
32 * ControlUpdaters only execute when their controls are visible. If something changes
33 * in the model while the control is invisible, the updator is flagged as dirty and
34 * the updator stops listening to the model until the next time the control repaints.
35 * This saves CPU cycles by deferring UI updates to widgets that are currently invisible.
36 * </p>
37 *
38 * <p>
39 * Clients should subclass this when copying information from the model to
40 * a control. Typical usage:
41 * </p>
42 *
43 * <ul>
44 * <li>Override updateControl. It should do whatever is necessary to display
45 * the contents of the model in the control.</li>
46 * <li>In the constructor, attach listeners to the model. The listeners should
47 * call markDirty whenever anything changes in the model that affects
48 * updateControl. Note: this step can be omitted when calling any method
49 * tagged with "@TrackedGetter" since ControlUpdater will automatically attach
50 * a listener to any object if a "@TrackedGetter" method is called in
51 * updateControl.</li>
52 * <li>(optional)Extend dispose() to remove any listeners attached in the constructor</li>
53 * </ul>
54 *
55 * <p>
56 * Example:
57 * </p>
58 *
59 * <code>
60 * // Displays an observable value in a label and keeps the label in synch with changes
61 * // in the value.
62 * IReadableValue someValue = ...
63 * final Label myLabel = new Label(parent, SWT.NONE);
64 * new ControlUpdater(myLabel) {
65 * protected void updateControl() {
66 * myLabel.setText(someValue.getValue().toString);
67 * }
68 * }
69 * // myLabel will display the value of someValue the next time it repaints, and will automatically
70 * // be updated whenever someValue changes and the label is visible
71 * </code>
72 *
73 * @since 1.1
74 */
75 public abstract class ControlUpdater {
76
77 private class PrivateInterface : PaintListener,
78 DisposeListener, Runnable, IChangeListener {
79
80 // PaintListener implementation
81 public void paintControl(PaintEvent e) {
82 updateIfNecessary();
83 }
84
85 // DisposeListener implementation
86 public void widgetDisposed(DisposeEvent e) {
87 this.outer.dispose();
88 }
89
90 // Runnable implementation. This method runs at most once per repaint whenever the
91 // value gets marked as dirty.
92 public void run() {
93 if (theControl !is null && !theControl.isDisposed() && theControl.isVisible()) {
94 updateIfNecessary();
95 }
96 }
97
98 // IChangeListener implementation (listening to the ComputedValue)
99 public void handleChange(ChangeEvent event) {
100 // Whenever this updator becomes dirty, schedule the run() method
101 makeDirty();
102 }
103
104 }
105
106 private Runnable updateRunnable = new class() Runnable {
107 public void run() {
108 updateControl();
109 }
110 };
111
112 private PrivateInterface privateInterface = new PrivateInterface();
113 private Control theControl;
114 private IObservable[] dependencies = new IObservable[0];
115 private bool dirty = false;
116
117 /**
118 * Creates an updater for the given control.
119 *
120 * @param toUpdate control to update
121 */
122 public this(Control toUpdate) {
123 theControl = toUpdate;
124
125 theControl.addDisposeListener(privateInterface);
126 theControl.addPaintListener(privateInterface);
127 makeDirty();
128 }
129
130 private void updateIfNecessary() {
131 if (dirty) {
132 dependencies = ObservableTracker.runAndMonitor(updateRunnable, privateInterface, null);
133 dirty = false;
134 }
135 }
136
137 /**
138 * This is called automatically when the control is disposed. It may also
139 * be called explicitly to remove this updator from the control. Subclasses
140 * will normally extend this method to detach any listeners they attached
141 * in their constructor.
142 */
143 public void dispose() {
144 theControl.removeDisposeListener(privateInterface);
145 theControl.removePaintListener(privateInterface);
146
147 stopListening();
148 }
149
150 private void stopListening() {
151 // Stop listening for dependency changes
152 for (int i = 0; i < dependencies.length; i++) {
153 IObservable observable = dependencies[i];
154
155 observable.removeChangeListener(privateInterface);
156 }
157 }
158
159 /**
160 * Updates the control. This method will be invoked once after the
161 * updator is created, and once before any repaint during which the
162 * control is visible and dirty.
163 *
164 * <p>
165 * Subclasses should overload this method to provide any code that
166 * changes the appearance of the widget.
167 * </p>
168 */
169 protected abstract void updateControl();
170
171 /**
172 * Marks this updator as dirty. Causes the updateControl method to
173 * be invoked before the next time the control is repainted.
174 */
175 protected final void makeDirty() {
176 if (!dirty) {
177 dirty = true;
178 stopListening();
179 SWTUtil.runOnce(theControl.getDisplay(), privateInterface);
180 }
181 }
182
183 }