### Eclipse Workspace Patch 1.0
#P org.eclipse.core.databinding.property
Index: src/org/eclipse/core/databinding/property/list/IListProperty.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.core.databinding.property/src/org/eclipse/core/databinding/property/list/IListProperty.java,v
retrieving revision 1.5
diff -u -r1.5 IListProperty.java
--- src/org/eclipse/core/databinding/property/list/IListProperty.java	1 Jun 2010 19:22:39 -0000	1.5
+++ src/org/eclipse/core/databinding/property/list/IListProperty.java	20 Feb 2011 12:33:37 -0000
@@ -7,7 +7,7 @@
  *
  * Contributors:
  *     Matthew Hall - initial API and implementation (bug 194734)
- *     Matthew Hall - bug 195222
+ *     Matthew Hall - bug 195222, 300043
  ******************************************************************************/
 
 package org.eclipse.core.databinding.property.list;
@@ -161,4 +161,12 @@
 	 *         properties
 	 */
 	public IListProperty values(IValueProperty detailValue);
+
+	/**
+	 * @param reducer
+	 *            the strategy that reduces the list down to a value.
+	 * @return a read-only reduced value from this list property
+	 * @since 1.4
+	 */
+	public IValueProperty reduce(IListReducer reducer);
 }
Index: src/org/eclipse/core/databinding/property/list/IListReducer.java
===================================================================
RCS file: src/org/eclipse/core/databinding/property/list/IListReducer.java
diff -N src/org/eclipse/core/databinding/property/list/IListReducer.java
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ src/org/eclipse/core/databinding/property/list/IListReducer.java	1 Jan 1970 00:00:00 -0000
@@ -0,0 +1,49 @@
+/*******************************************************************************
+ * Copyright (c) 2010 Matthew Hall 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:
+ *     Matthew Hall - initial API and implementation (bug 300043)
+ ******************************************************************************/
+
+package org.eclipse.core.databinding.property.list;
+
+import java.util.List;
+
+import org.eclipse.core.databinding.observable.list.IObservableList;
+import org.eclipse.core.databinding.observable.value.IObservableValue;
+
+/**
+ * A list-to-value reducer. List reducers may be used to condense a list
+ * property down to a value property.
+ * 
+ * @since 1.4
+ * @noimplement This interface is not intended to be implemented by clients.
+ * @see ListReducer
+ */
+public interface IListReducer {
+
+	/**
+	 * @param list
+	 *            the list to reduce
+	 * @return the list reduction
+	 */
+	public Object reduce(List list);
+
+	/**
+	 * @return the value type of the reduction
+	 */
+	public Object getValueType();
+
+	/**
+	 * @param master
+	 *            the master list to reduce
+	 * @return an IObservableValue observing the reduction of the specified
+	 *         IObservableList
+	 */
+	public IObservableValue observeDetail(IObservableList master);
+
+}
Index: src/org/eclipse/core/databinding/property/list/ListProperty.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.core.databinding.property/src/org/eclipse/core/databinding/property/list/ListProperty.java,v
retrieving revision 1.8
diff -u -r1.8 ListProperty.java
--- src/org/eclipse/core/databinding/property/list/ListProperty.java	23 Dec 2010 21:43:31 -0000	1.8
+++ src/org/eclipse/core/databinding/property/list/ListProperty.java	20 Feb 2011 12:33:37 -0000
@@ -7,7 +7,7 @@
  *
  * Contributors:
  *     Matthew Hall - initial API and implementation (bug 194734)
- *     Matthew Hall - bug 195222
+ *     Matthew Hall - bug 195222, 300043
  *     Ovidio Mallo - bug 331348
  ******************************************************************************/
 
@@ -27,6 +27,7 @@
 import org.eclipse.core.databinding.observable.value.IObservableValue;
 import org.eclipse.core.databinding.property.value.IValueProperty;
 import org.eclipse.core.internal.databinding.property.ListPropertyDetailValuesList;
+import org.eclipse.core.internal.databinding.property.list.ReducedListValueProperty;
 
 /**
  * Abstract implementation of IListProperty.
@@ -152,4 +153,11 @@
 	public final IListProperty values(IValueProperty detailValue) {
 		return new ListPropertyDetailValuesList(this, detailValue);
 	}
+
+	/**
+	 * @since 1.4
+	 */
+	public final IValueProperty reduce(IListReducer reducer) {
+		return new ReducedListValueProperty(this, reducer);
+	}
 }
Index: src/org/eclipse/core/databinding/property/list/ListReducer.java
===================================================================
RCS file: src/org/eclipse/core/databinding/property/list/ListReducer.java
diff -N src/org/eclipse/core/databinding/property/list/ListReducer.java
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ src/org/eclipse/core/databinding/property/list/ListReducer.java	1 Jan 1970 00:00:00 -0000
@@ -0,0 +1,45 @@
+/*******************************************************************************
+ * Copyright (c) 2010 Matthew Hall 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:
+ *     Matthew Hall - initial API and implementation (bug 300043)
+ ******************************************************************************/
+
+package org.eclipse.core.databinding.property.list;
+
+import org.eclipse.core.databinding.observable.list.IObservableList;
+import org.eclipse.core.databinding.observable.value.IObservableValue;
+import org.eclipse.core.internal.databinding.property.value.ReducedListObservableValue;
+
+/**
+ * Abstract base implementation if {@link IListReducer}.
+ * 
+ * @since 1.4
+ */
+public abstract class ListReducer implements IListReducer {
+
+	private final Object valueType;
+
+	/**
+	 * Constructs a list reducer with the given value type
+	 * 
+	 * @param valueType
+	 *            the reduction value type
+	 */
+	protected ListReducer(Object valueType) {
+		this.valueType = valueType;
+	}
+
+	public Object getValueType() {
+		return valueType;
+	}
+
+	public IObservableValue observeDetail(IObservableList master) {
+		return new ReducedListObservableValue(master, this);
+	}
+
+}
Index: src/org/eclipse/core/databinding/property/list/ListReducers.java
===================================================================
RCS file: src/org/eclipse/core/databinding/property/list/ListReducers.java
diff -N src/org/eclipse/core/databinding/property/list/ListReducers.java
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ src/org/eclipse/core/databinding/property/list/ListReducers.java	1 Jan 1970 00:00:00 -0000
@@ -0,0 +1,44 @@
+/*******************************************************************************
+ * Copyright (c) 2010 Matthew Hall 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:
+ *     Matthew Hall - initial API and implementation (bug 300043)
+ ******************************************************************************/
+
+package org.eclipse.core.databinding.property.list;
+
+import java.util.Iterator;
+import java.util.List;
+
+/**
+ * Factory class for common list reducers
+ * 
+ * @since 1.4
+ */
+public class ListReducers {
+	/**
+	 * @param delimiter
+	 *            the delimiter between each list element
+	 * @return a String-valued list reducer which concatenates all elements in
+	 *         the list, with the specified delimiter between each element.
+	 */
+	public static IListReducer join(final String delimiter) {
+		return new ListReducer(String.class) {
+			public Object reduce(List list) {
+				StringBuffer buf = new StringBuffer();
+
+				for (Iterator it = list.iterator(); it.hasNext();) {
+					buf.append(it.next());
+					if (it.hasNext())
+						buf.append(delimiter);
+				}
+
+				return buf.toString();
+			}
+		};
+	}
+}
Index: src/org/eclipse/core/internal/databinding/property/list/ReducedListValueProperty.java
===================================================================
RCS file: src/org/eclipse/core/internal/databinding/property/list/ReducedListValueProperty.java
diff -N src/org/eclipse/core/internal/databinding/property/list/ReducedListValueProperty.java
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ src/org/eclipse/core/internal/databinding/property/list/ReducedListValueProperty.java	1 Jan 1970 00:00:00 -0000
@@ -0,0 +1,59 @@
+/*******************************************************************************
+ * Copyright (c) 2010 Matthew Hall 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:
+ *     Matthew Hall - initial API and implementation (bug 300043)
+ ******************************************************************************/
+
+package org.eclipse.core.internal.databinding.property.list;
+
+import org.eclipse.core.databinding.observable.ObservableTracker;
+import org.eclipse.core.databinding.observable.Realm;
+import org.eclipse.core.databinding.observable.list.IObservableList;
+import org.eclipse.core.databinding.observable.value.IObservableValue;
+import org.eclipse.core.databinding.property.list.IListReducer;
+import org.eclipse.core.databinding.property.list.ListProperty;
+import org.eclipse.core.databinding.property.value.ValueProperty;
+import org.eclipse.core.internal.databinding.property.PropertyObservableUtil;
+
+/**
+ * 
+ */
+public class ReducedListValueProperty extends ValueProperty {
+
+	private final ListProperty masterProperty;
+	private final IListReducer reducer;
+
+	/**
+	 * @param masterProperty
+	 * @param reducer
+	 */
+	public ReducedListValueProperty(ListProperty masterProperty,
+			IListReducer reducer) {
+		this.masterProperty = masterProperty;
+		this.reducer = reducer;
+	}
+
+	public Object getValueType() {
+		return reducer.getValueType();
+	}
+
+	public IObservableValue observe(Realm realm, Object source) {
+		IObservableList masterList;
+
+		ObservableTracker.setIgnore(true);
+		try {
+			masterList = masterProperty.observe(realm, source);
+		} finally {
+			ObservableTracker.setIgnore(false);
+		}
+
+		IObservableValue detailValue = reducer.observeDetail(masterList);
+		PropertyObservableUtil.cascadeDispose(detailValue, masterList);
+		return detailValue;
+	}
+}
Index: src/org/eclipse/core/internal/databinding/property/value/ReducedListObservableValue.java
===================================================================
RCS file: src/org/eclipse/core/internal/databinding/property/value/ReducedListObservableValue.java
diff -N src/org/eclipse/core/internal/databinding/property/value/ReducedListObservableValue.java
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ src/org/eclipse/core/internal/databinding/property/value/ReducedListObservableValue.java	1 Jan 1970 00:00:00 -0000
@@ -0,0 +1,41 @@
+/*******************************************************************************
+ * Copyright (c) 2010 Matthew Hall 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:
+ *     Matthew Hall - initial API and implementation (bug 300043)
+ ******************************************************************************/
+
+package org.eclipse.core.internal.databinding.property.value;
+
+import org.eclipse.core.databinding.observable.list.IObservableList;
+import org.eclipse.core.databinding.observable.value.ComputedValue;
+import org.eclipse.core.databinding.property.list.IListReducer;
+
+/**
+ * 
+ */
+public class ReducedListObservableValue extends ComputedValue {
+
+	private IObservableList masterList;
+	private IListReducer reducer;
+
+	/**
+	 * @param masterList
+	 * @param reducer
+	 */
+	public ReducedListObservableValue(IObservableList masterList,
+			IListReducer reducer) {
+		super(masterList.getRealm(), reducer.getValueType());
+		this.masterList = masterList;
+		this.reducer = reducer;
+	}
+
+	protected Object calculate() {
+		return reducer.reduce(masterList);
+	}
+
+}
#P org.eclipse.jface.examples.databinding
Index: src/org/eclipse/jface/examples/databinding/snippets/Snippet025TableViewerWithPropertyDerivedColumns.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.jface.examples.databinding/src/org/eclipse/jface/examples/databinding/snippets/Snippet025TableViewerWithPropertyDerivedColumns.java,v
retrieving revision 1.5
diff -u -r1.5 Snippet025TableViewerWithPropertyDerivedColumns.java
--- src/org/eclipse/jface/examples/databinding/snippets/Snippet025TableViewerWithPropertyDerivedColumns.java	25 May 2009 20:52:49 -0000	1.5
+++ src/org/eclipse/jface/examples/databinding/snippets/Snippet025TableViewerWithPropertyDerivedColumns.java	20 Feb 2011 12:33:38 -0000
@@ -14,6 +14,9 @@
 
 import java.beans.PropertyChangeListener;
 import java.beans.PropertyChangeSupport;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
 
 import org.eclipse.core.databinding.DataBindingContext;
 import org.eclipse.core.databinding.beans.BeanProperties;
@@ -21,10 +24,12 @@
 import org.eclipse.core.databinding.observable.list.IObservableList;
 import org.eclipse.core.databinding.observable.list.WritableList;
 import org.eclipse.core.databinding.observable.value.IObservableValue;
+import org.eclipse.core.databinding.property.list.ListReducers;
+import org.eclipse.core.databinding.property.value.IValueProperty;
 import org.eclipse.jface.databinding.swt.SWTObservables;
 import org.eclipse.jface.databinding.swt.WidgetProperties;
-import org.eclipse.jface.databinding.viewers.ViewerSupport;
 import org.eclipse.jface.databinding.viewers.ViewerProperties;
+import org.eclipse.jface.databinding.viewers.ViewerSupport;
 import org.eclipse.jface.layout.GridDataFactory;
 import org.eclipse.jface.layout.GridLayoutFactory;
 import org.eclipse.jface.viewers.ComboViewer;
@@ -106,11 +111,28 @@
 		String name = "Donald Duck";
 		Person mother;
 		Person father;
+		List children = new ArrayList();
 
 		public Person(String name, Person mother, Person father) {
 			this.name = name;
 			this.mother = mother;
 			this.father = father;
+			if (mother != null) {
+				mother.addChild(this);
+			}
+			if (father != null) {
+				father.addChild(this);
+			}
+		}
+
+		private void addChild(Person person) {
+			children.add(person);
+			firePropertyChange("children", null, children);
+		}
+
+		private void removeChild(Person person) {
+			children.remove(person);
+			firePropertyChange("children", null, children);
 		}
 
 		public String getName() {
@@ -125,8 +147,18 @@
 			return mother;
 		}
 
+		public Person[] getChildren() {
+			return (Person[]) children.toArray(new Person[children.size()]);
+		}
+
 		public void setMother(Person mother) {
+			if (this.mother != null) {
+				this.mother.removeChild(this);
+			}
 			firePropertyChange("mother", this.mother, this.mother = mother);
+			if (this.mother != null) {
+				this.mother.addChild(this);
+			}
 		}
 
 		public Person getFather() {
@@ -134,7 +166,13 @@
 		}
 
 		public void setFather(Person father) {
+			if (this.father != null) {
+				this.father.removeChild(this);
+			}
 			firePropertyChange("father", this.father, this.father = father);
+			if (this.father != null) {
+				this.father.addChild(this);
+			}
 		}
 	}
 
@@ -145,6 +183,7 @@
 	// data access tier. Since this snippet doesn't have any persistent objects
 	// ro retrieve, this ViewModel just instantiates a model object to edit.
 	static class ViewModel {
+
 		// The model to bind
 		private IObservableList people = new WritableList();
 		{
@@ -197,6 +236,7 @@
 			createColumn("Maternal Grandfather");
 			createColumn("Paternal Grandmother");
 			createColumn("Paternal Grandfather");
+			createColumn("Children").setWidth(200);
 
 			duckFamily.setLinesVisible(true);
 
@@ -216,17 +256,18 @@
 
 			GridLayoutFactory.swtDefaults().numColumns(2).applyTo(shell);
 			// Open and return the Shell
-			shell.setSize(800, 300);
+			shell.setSize(1000, 300);
 			shell.open();
 			return shell;
 		}
 
-		private void createColumn(String string) {
+		private TableColumn createColumn(String string) {
 			final TableColumn column = new TableColumn(duckFamily, SWT.NONE);
 			column.setText(string);
 			column.pack();
 			if (column.getWidth() < 100)
 				column.setWidth(100);
+			return column;
 		}
 
 		protected void bindGUI(DataBindingContext dbc) {
@@ -240,10 +281,7 @@
 			});
 
 			ViewerSupport.bind(peopleViewer, viewModel.getPeople(),
-					BeanProperties.values(Person.class, new String[] { "name",
-							"mother.name", "father.name", "mother.mother.name",
-							"mother.father.name", "father.mother.name",
-							"father.father.name" }));
+					getProperties());
 
 			IObservableValue masterSelection = ViewerProperties
 					.singleSelection().observe(peopleViewer);
@@ -269,4 +307,20 @@
 					"father").observeDetail(masterSelection));
 		}
 	}
+
+	private static IValueProperty[] getProperties() {
+		List<IValueProperty> properties = new ArrayList<IValueProperty>();
+
+		// Add the "simple" properties.
+		properties.addAll(Arrays.asList(BeanProperties.values(Person.class,
+				new String[] { "name", "mother.name", "father.name",
+						"mother.mother.name", "mother.father.name",
+						"father.mother.name", "father.father.name" })));
+
+		// Add the "complex" property.
+		properties.add(BeanProperties.list("children").values("name").reduce(
+				ListReducers.join(", ")));
+
+		return properties.toArray(new IValueProperty[properties.size()]);
+	}
 }