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