--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/org.eclipse.jface.examples.databinding/src/org/eclipse/jface/examples/databinding/snippets/Snippet008ComputedValue.d	Sun Apr 19 11:33:55 2009 +0200
@@ -0,0 +1,169 @@
+/*******************************************************************************
+ * Copyright (c) 2006 Brad Reynolds and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Brad Reynolds - initial API and implementation
+ *     Matthew Hall - bug 260329
+ ******************************************************************************/
+
+package org.eclipse.jface.examples.databinding.snippets;
+
+import org.eclipse.core.databinding.DataBindingContext;
+import org.eclipse.core.databinding.UpdateValueStrategy;
+import org.eclipse.core.databinding.observable.ObservableTracker;
+import org.eclipse.core.databinding.observable.Realm;
+import org.eclipse.core.databinding.observable.value.ComputedValue;
+import org.eclipse.core.databinding.observable.value.IObservableValue;
+import org.eclipse.core.databinding.observable.value.WritableValue;
+import org.eclipse.jface.databinding.swt.SWTObservables;
+import org.eclipse.jface.layout.GridDataFactory;
+import org.eclipse.jface.layout.GridLayoutFactory;
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.layout.FillLayout;
+import org.eclipse.swt.widgets.Composite;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Label;
+import org.eclipse.swt.widgets.Shell;
+import org.eclipse.swt.widgets.Text;
+
+/**
+ * Snippet that demostrates a simple use case using ComputedValue to format a
+ * name as the user enters first and last name.
+ * 
+ * @since 3.2
+ */
+public class Snippet008ComputedValue {
+	/**
+	 * @param args
+	 */
+	public static void main(String[] args) {
+		final Display display = new Display();
+		Realm.runWithDefault(SWTObservables.getRealm(display), new Runnable() {
+			public void run() {
+				Shell shell = new Shell(display);
+				shell.setLayout(new FillLayout());
+
+				final UI ui = new UI(shell);
+				final Data data = new Data();
+
+				// Bind the UI to the Data.
+				DataBindingContext dbc = new DataBindingContext();
+				dbc.bindValue(SWTObservables.observeText(ui.firstName,
+						SWT.Modify), data.firstName);
+				dbc.bindValue(SWTObservables.observeText(ui.lastName,
+						SWT.Modify), data.lastName);
+
+				// Construct the formatted name observable.
+				FormattedName formattedName = new FormattedName(data.firstName,
+						data.lastName);
+
+				// Bind the formatted name Text to the formatted name
+				// observable.
+				dbc.bindValue(SWTObservables.observeText(ui.formattedName,
+						SWT.None), formattedName, new UpdateValueStrategy(false, UpdateValueStrategy.POLICY_NEVER), null);
+
+				shell.pack();
+				shell.open();
+				while (!shell.isDisposed()) {
+					if (!display.readAndDispatch())
+						display.sleep();
+				}
+			}
+		});
+		display.dispose();
+	}
+
+	/**
+	 * Creates the formatted name on change of the first or last name
+	 * observables.
+	 * <p>
+	 * The key to understanding ComputedValue is understanding that it knows of
+	 * the observables that are queried without being told. This is done with
+	 * {@link ObservableTracker} voodoo. When calculate() is invoked
+	 * <code>ObservableTracker</code> records the observables that are
+	 * queried. It then exposes those observables and <code>ComputedValue</code>
+	 * can listen to changes in those objects and react accordingly.
+	 * </p>
+	 * 
+	 * @since 3.2
+	 */
+	static class FormattedName extends ComputedValue {
+		private IObservableValue firstName;
+
+		private IObservableValue lastName;
+
+		FormattedName(IObservableValue firstName, IObservableValue lastName) {
+			this.firstName = firstName;
+			this.lastName = lastName;
+		}
+
+		protected Object calculate() {
+			String lastName = (String) this.lastName.getValue();
+			String firstName = (String) this.firstName.getValue();
+			lastName = (lastName != null && lastName.length() > 0) ? lastName
+					: "[Last Name]";
+			firstName = (firstName != null && firstName.length() > 0) ? firstName
+					: "[First Name]";
+
+			StringBuffer buffer = new StringBuffer();
+			buffer.append(lastName).append(", ").append(firstName);
+
+			return buffer.toString();
+		}
+	}
+
+	static class Data {
+		final WritableValue firstName;
+
+		final WritableValue lastName;
+
+		Data() {
+			firstName = new WritableValue("", String.class);
+			lastName = new WritableValue("", String.class);
+		}
+	}
+
+	/**
+	 * Composite that creates the UI.
+	 * 
+	 * @since 3.2
+	 */
+	static class UI extends Composite {
+		final Text firstName;
+
+		final Text lastName;
+
+		final Text formattedName;
+
+		UI(Composite parent) {
+			super(parent, SWT.NONE);
+
+			GridLayoutFactory.swtDefaults().numColumns(2).applyTo(this);
+
+			new Label(this, SWT.NONE).setText("First Name:");
+			new Label(this, SWT.NONE).setText("Last Name");
+
+			GridDataFactory gdf = GridDataFactory.swtDefaults().align(SWT.FILL,
+					SWT.FILL).grab(true, false);
+			firstName = new Text(this, SWT.BORDER);
+			gdf.applyTo(firstName);
+
+			lastName = new Text(this, SWT.BORDER);
+			gdf.applyTo(lastName);
+
+			gdf = GridDataFactory.swtDefaults().span(2, 1).grab(true, false)
+					.align(SWT.FILL, SWT.BEGINNING);
+			Label label = new Label(this, SWT.NONE);
+			label.setText("Formatted Name:");
+			gdf.applyTo(label);
+
+			formattedName = new Text(this, SWT.BORDER);
+			formattedName.setEditable(false);
+			gdf.applyTo(formattedName);
+		}
+	}
+}