--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/org.eclipse.jface.databinding/src/org/eclipse/jface/internal/databinding/viewers/ObservableViewerElementSet.d	Tue Apr 14 11:35:29 2009 +0200
@@ -0,0 +1,203 @@
+/*******************************************************************************
+ * Copyright (c) 2008 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 215531)
+ *     Matthew Hall - bug 230267
+ ******************************************************************************/
+
+module org.eclipse.jface.internal.databinding.viewers.ObservableViewerElementSet;
+
+import java.lang.all;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.Set;
+
+import org.eclipse.core.databinding.observable.Diffs;
+import org.eclipse.core.databinding.observable.Realm;
+import org.eclipse.core.databinding.observable.set.AbstractObservableSet;
+import org.eclipse.core.databinding.observable.set.IObservableSet;
+import org.eclipse.core.databinding.observable.set.WritableSet;
+import org.eclipse.core.runtime.Assert;
+import org.eclipse.jface.viewers.IElementComparer;
+import org.eclipse.jface.viewers.StructuredViewer;
+
+/**
+ * An {@link IObservableSet} of elements in a {@link StructuredViewer}.
+ * Elements of the set are compared using an {@link IElementComparer} instead of
+ * {@link #equals(Object)}.
+ * <p>
+ * This class is <i>not</i> a strict implementation the {@link IObservableSet}
+ * interface. It intentionally violates the {@link Set} contract, which requires
+ * the use of {@link #equals(Object)} when comparing elements. This class is
+ * designed for use with {@link StructuredViewer} which uses
+ * {@link IElementComparer} for element comparisons.
+ * 
+ * 
+ * @since 1.2
+ */
+public class ObservableViewerElementSet : AbstractObservableSet {
+    private Set wrappedSet;
+    private Object elementType;
+    private IElementComparer comparer;
+
+    /**
+     * Constructs an ObservableViewerElementSet on the given {@link Realm} which
+     * uses the given {@link IElementComparer} to compare elements.
+     * 
+     * @param realm
+     *            the realm of the constructed set.
+     * @param elementType
+     *            the element type of the constructed set.
+     * @param comparer
+     *            the {@link IElementComparer} used to compare elements.
+     */
+    public this(Realm realm, Object elementType,
+            IElementComparer comparer) {
+        super(realm);
+
+        Assert.isNotNull(comparer);
+        this.wrappedSet = new ViewerElementSet(comparer);
+        this.elementType = elementType;
+        this.comparer = comparer;
+    }
+
+    protected Set getWrappedSet() {
+        return wrappedSet;
+    }
+
+    public Object getElementType() {
+        return elementType;
+    }
+
+    public Iterator iterator() {
+        getterCalled();
+        final Iterator wrappedIterator = wrappedSet.iterator();
+        return new class() Iterator {
+            Object last;
+
+            public bool hasNext() {
+                getterCalled();
+                return wrappedIterator.hasNext();
+            }
+
+            public Object next() {
+                getterCalled();
+                return last = wrappedIterator.next();
+            }
+
+            public void remove() {
+                getterCalled();
+                wrappedIterator.remove();
+                fireSetChange(Diffs.createSetDiff(Collections.EMPTY_SET,
+                        Collections.singleton(last)));
+            }
+        };
+    }
+
+    public bool add(Object o) {
+        getterCalled();
+        bool changed = wrappedSet.add(o);
+        if (changed)
+            fireSetChange(Diffs.createSetDiff(Collections.singleton(o),
+                    Collections.EMPTY_SET));
+        return changed;
+    }
+
+    public bool addAll(Collection c) {
+        getterCalled();
+        Set additions = new ViewerElementSet(comparer);
+        for (Iterator iterator = c.iterator(); iterator.hasNext();) {
+            Object element = iterator.next();
+            if (wrappedSet.add(element))
+                additions.add(element);
+        }
+        bool changed = !additions.isEmpty();
+        if (changed)
+            fireSetChange(Diffs.createSetDiff(additions, Collections.EMPTY_SET));
+        return changed;
+    }
+
+    public bool remove(Object o) {
+        getterCalled();
+        bool changed = wrappedSet.remove(o);
+        if (changed)
+            fireSetChange(Diffs.createSetDiff(Collections.EMPTY_SET,
+                    Collections.singleton(o)));
+        return changed;
+    }
+
+    public bool removeAll(Collection c) {
+        getterCalled();
+        Set removals = new ViewerElementSet(comparer);
+        for (Iterator iterator = c.iterator(); iterator.hasNext();) {
+            Object element = iterator.next();
+            if (wrappedSet.remove(element))
+                removals.add(element);
+        }
+        bool changed = !removals.isEmpty();
+        if (changed)
+            fireSetChange(Diffs.createSetDiff(Collections.EMPTY_SET, removals));
+        return changed;
+    }
+
+    public bool retainAll(Collection c) {
+        getterCalled();
+        Set removals = new ViewerElementSet(comparer);
+        Object[] toRetain = c.toArray();
+        outer: for (Iterator iterator = wrappedSet.iterator(); iterator
+                .hasNext();) {
+            Object element = iterator.next();
+            // Cannot rely on c.contains(element) because we must compare
+            // elements using IElementComparer.
+            for (int i = 0; i < toRetain.length; i++) {
+                if (comparer.equals(element, toRetain[i]))
+                    continue outer;
+            }
+            iterator.remove();
+            removals.add(element);
+        }
+        bool changed = !removals.isEmpty();
+        if (changed)
+            fireSetChange(Diffs.createSetDiff(Collections.EMPTY_SET, removals));
+        return changed;
+    }
+
+    public void clear() {
+        getterCalled();
+        if (!wrappedSet.isEmpty()) {
+            Set removals = wrappedSet;
+            wrappedSet = new ViewerElementSet(comparer);
+            fireSetChange(Diffs.createSetDiff(Collections.EMPTY_SET, removals));
+        }
+    }
+
+    /**
+     * Returns an {@link IObservableSet} for holding viewer elements, using the
+     * given {@link IElementComparer} for comparisons.
+     * 
+     * @param realm
+     *            the realm of the returned observable
+     * @param elementType
+     *            the element type of the returned set
+     * @param comparer
+     *            the element comparer to use in element comparisons (may be
+     *            null). If null, the returned set will compare elements
+     *            according to the standard contract for {@link Set} interface
+     *            contract.
+     * @return a Set for holding viewer elements, using the given
+     *         {@link IElementComparer} for comparisons.
+     */
+    public static IObservableSet withComparer(Realm realm, Object elementType,
+            IElementComparer comparer) {
+        if (comparer is null)
+            return new WritableSet(realm, Collections.EMPTY_SET, elementType);
+        return new ObservableViewerElementSet(realm, elementType, comparer);
+    }
+}