--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/org.eclipse.core.databinding.observable/src/org/eclipse/core/internal/databinding/observable/StalenessObservableValue.d	Tue Apr 21 10:55:51 2009 +0200
@@ -0,0 +1,84 @@
+/*******************************************************************************
+ * Copyright (c) 2007, 2008 IBM Corporation 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:
+ *     Boris Bokowski, IBM Corporation - initial API and implementation
+ *     Matthew Hall - bug 212468
+ *******************************************************************************/
+package org.eclipse.core.internal.databinding.observable;
+
+import org.eclipse.core.databinding.observable.ChangeEvent;
+import org.eclipse.core.databinding.observable.Diffs;
+import org.eclipse.core.databinding.observable.IChangeListener;
+import org.eclipse.core.databinding.observable.IObservable;
+import org.eclipse.core.databinding.observable.IStaleListener;
+import org.eclipse.core.databinding.observable.StaleEvent;
+import org.eclipse.core.databinding.observable.value.AbstractObservableValue;
+
+/**
+ * An observable value that tracks the staleness of an {@link IObservable}.
+ * 
+ * @since 1.1
+ */
+public class StalenessObservableValue : AbstractObservableValue {
+
+    private class MyListener : IChangeListener, IStaleListener {
+        public void handleChange(ChangeEvent event) {
+            if (stale && !event.getObservable().isStale()) {
+                stale = false;
+                fireValueChange(Diffs.createValueDiff(Boolean.TRUE,
+                        Boolean.FALSE));
+            }
+        }
+
+        public void handleStale(StaleEvent staleEvent) {
+            if (!stale) {
+                stale = true;
+                fireValueChange(Diffs.createValueDiff(Boolean.FALSE,
+                        Boolean.TRUE));
+            }
+        }
+    }
+
+    private IObservable tracked;
+    private bool stale;
+    private MyListener listener = new MyListener();
+
+    /**
+     * Constructs a StalenessObservableValue that tracks the staleness of the
+     * given {@link IObservable}.
+     * 
+     * @param observable
+     *            the observable to track
+     */
+    public this(IObservable observable) {
+        super(observable.getRealm());
+        this.tracked = observable;
+        this.stale = observable.isStale();
+        tracked.addChangeListener(listener);
+        tracked.addStaleListener(listener);
+    }
+
+    protected Object doGetValue() {
+        return tracked.isStale() ? Boolean.TRUE : Boolean.FALSE;
+    }
+
+    public Object getValueType() {
+        return Boolean.TYPE;
+    }
+
+    public synchronized void dispose() {
+        if (tracked !is null) {
+            tracked.removeChangeListener(listener);
+            tracked.removeStaleListener(listener);
+            tracked = null;
+            listener = null;
+        }
+        super.dispose();
+    }
+
+}