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1 /*******************************************************************************
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2 * Copyright (c) 2006, 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.MenuUpdater;
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85
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12 import org.eclipse.jface.internal.databinding.provisional.swt.SWTUtil;
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78
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13
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14 import java.lang.all;
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15
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16 import org.eclipse.core.databinding.observable.ChangeEvent;
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17 import org.eclipse.core.databinding.observable.IChangeListener;
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18 import org.eclipse.core.databinding.observable.IObservable;
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19 import org.eclipse.core.databinding.observable.ObservableTracker;
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20 import org.eclipse.swt.events.DisposeEvent;
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21 import org.eclipse.swt.events.DisposeListener;
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22 import org.eclipse.swt.events.MenuEvent;
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23 import org.eclipse.swt.events.MenuListener;
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24 import org.eclipse.swt.widgets.Menu;
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25
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26 /**
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27 * NON-API - A MenuUpdater updates an SWT menu in response to changes in the model. By
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28 * wrapping a block of code in a MenuUpdater, clients can rely on the fact that
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29 * the block of code will be re-executed whenever anything changes in the model
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30 * that might affect its behavior.
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31 *
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32 * <p>
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33 * MenuUpdaters only execute once their menus are shown. If something changes in
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34 * the model, the updater is flagged as dirty and it stops listening to the
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35 * model until the next time the menu is shown. If the menu is visible while the
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36 * model changes, it will be updated right away.
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37 * </p>
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38 *
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39 * <p>
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40 * Clients should subclass this when copying information from the model to a
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41 * menu. Typical usage:
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42 * </p>
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43 *
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44 * <ul>
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45 * <li>Override updateMenu. It should do whatever is necessary to display the
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46 * contents of the model in the menu.</li>
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47 * <li>In the constructor, attach listeners to the model. The listeners should
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48 * call markDirty whenever anything changes in the model that affects
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49 * updateMenu. Note: this step can be omitted when calling any method tagged
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50 * with "@TrackedGetter" since MenuUpdater will automatically attach a listener
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51 * to any object if a "@TrackedGetter" method is called in updateMenu.</li>
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52 * <li>(optional)Extend dispose() to remove any listeners attached in the
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53 * constructor</li>
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54 * </ul>
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55 *
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56 * @since 1.1
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57 */
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58 public abstract class MenuUpdater {
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59
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60 private class PrivateInterface : MenuListener,
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61 DisposeListener, Runnable, IChangeListener {
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62
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63 // DisposeListener implementation
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64 public void widgetDisposed(DisposeEvent e) {
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65 this.outer.dispose();
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66 }
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67
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68 // Runnable implementation. This method runs at most once per repaint whenever the
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69 // value gets marked as dirty.
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70 public void run() {
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71 if (theMenu !is null && !theMenu.isDisposed() && theMenu.isVisible()) {
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72 updateIfNecessary();
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73 }
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74 }
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75
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76 // IChangeListener implementation (listening to the ComputedValue)
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77 public void handleChange(ChangeEvent event) {
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78 // Whenever this updator becomes dirty, schedule the run() method
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79 makeDirty();
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80 }
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81
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82 public void menuHidden(MenuEvent e) {
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83 // do nothing
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84 }
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85
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86 public void menuShown(MenuEvent e) {
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87 updateIfNecessary();
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88 }
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89
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90 }
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91
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92 private Runnable updateRunnable;
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93 class UpdateRunnable : Runnable {
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94 public void run() {
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95 updateMenu();
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96 }
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97 };
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98
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99 private PrivateInterface privateInterface;
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100 private Menu theMenu;
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101 private IObservable[] dependencies;
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102 private bool dirty = false;
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103
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104 /**
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105 * Creates an updator for the given menu.
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106 *
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107 * @param toUpdate menu to update
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108 */
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109 public this(Menu toUpdate) {
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110 updateRunnable = new UpdateRunnable();
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111 privateInterface = new PrivateInterface();
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112 theMenu = toUpdate;
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113
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114 theMenu.addDisposeListener(privateInterface);
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115 theMenu.addMenuListener(privateInterface);
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116 makeDirty();
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117 }
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118
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119 private void updateIfNecessary() {
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120 if (dirty) {
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121 dependencies = ObservableTracker.runAndMonitor(updateRunnable, privateInterface, null);
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122 dirty = false;
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123 }
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124 }
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125
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126 /**
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127 * This is called automatically when the menu is disposed. It may also
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128 * be called explicitly to remove this updator from the menu. Subclasses
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129 * will normally extend this method to detach any listeners they attached
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130 * in their constructor.
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131 */
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132 public void dispose() {
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133 theMenu.removeDisposeListener(privateInterface);
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134 theMenu.removeMenuListener(privateInterface);
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135
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136 stopListening();
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137 }
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138
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139 private void stopListening() {
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140 // Stop listening for dependency changes
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141 for (int i = 0; i < dependencies.length; i++) {
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142 IObservable observable = dependencies[i];
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143
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144 observable.removeChangeListener(privateInterface);
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145 }
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146 }
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147
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148 /**
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149 * Updates the menu. This method will be invoked once after the
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150 * updater is created, and once for any SWT.Show event if this
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151 * updater is marked as dirty at that time.
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152 *
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153 * <p>
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154 * Subclasses should overload this method to provide any code that
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155 * udates the menu.
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156 * </p>
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157 */
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158 protected abstract void updateMenu();
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159
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160 /**
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161 * Marks this updator as dirty. Causes the updateControl method to
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162 * be invoked before the next time the control is repainted.
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163 */
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164 protected final void makeDirty() {
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165 if (!dirty) {
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166 dirty = true;
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167 stopListening();
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168 SWTUtil.runOnce(theMenu.getDisplay(), privateInterface);
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169 }
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170 }
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171
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172 }
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