Index: src/org/eclipse/ui/navigator/CommonViewer.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.ui.navigator/src/org/eclipse/ui/navigator/CommonViewer.java,v
retrieving revision 1.21
diff -u -r1.21 CommonViewer.java
--- src/org/eclipse/ui/navigator/CommonViewer.java	8 May 2006 20:54:43 -0000	1.21
+++ src/org/eclipse/ui/navigator/CommonViewer.java	29 May 2006 18:57:10 -0000
@@ -12,6 +12,7 @@
 
 import java.util.ArrayList;
 import java.util.Iterator;
+import java.util.List;
 
 import org.eclipse.jface.viewers.DecoratingLabelProvider;
 import org.eclipse.jface.viewers.IBaseLabelProvider;
@@ -23,6 +24,7 @@
 import org.eclipse.jface.viewers.ViewerSorter;
 import org.eclipse.swt.dnd.DND;
 import org.eclipse.swt.events.DisposeEvent;
+import org.eclipse.swt.events.SelectionEvent;
 import org.eclipse.swt.widgets.Composite;
 import org.eclipse.swt.widgets.Widget;
 import org.eclipse.ui.PlatformUI;
@@ -48,6 +50,8 @@
 public class CommonViewer extends TreeViewer {
 
 	private final NavigatorContentService contentService;
+    
+    private ISelection cachedSelection;
 
 	/**
 	 * <p>
@@ -329,6 +333,7 @@
 	public void setSelection(ISelection selection, boolean reveal) { 
 
 		if(selection instanceof IStructuredSelection) {
+            cachedSelection = null;
 			IStructuredSelection sSelection = (IStructuredSelection) selection;
 			
 			INavigatorPipelineService pipeDream = contentService
@@ -343,7 +348,8 @@
 				super.setSelection(new StructuredSelection(update.getRefreshTargets().toArray()) , reveal);
 			} else {
 				super.setSelection(selection, reveal);
-			}
+			}            
+            cachedSelection = super.getSelection();//update cachedSelection
 		}
 	}
 
@@ -408,6 +414,77 @@
 			return;
 		}
 		super.internalRefresh(element, updateLabels);
-	}
+	}  
+
+   
+
+    /* (non-Javadoc)
+     * @see org.eclipse.jface.viewers.TreeViewer#setSelection(java.util.List)
+     */
+    protected void setSelection(List items) {
+        cachedSelection = null;
+        super.setSelection(items);
+        cachedSelection = super.getSelection();
+    }    
+
+    /* (non-Javadoc)
+     * @see org.eclipse.jface.viewers.AbstractTreeViewer#getSelection()
+     */
+    public ISelection getSelection() {
+        if (cachedSelection == null) {
+            cachedSelection = super.getSelection();
+        }
+        return cachedSelection;
+    }   
+  
+    /* (non-Javadoc)
+     * @see org.eclipse.jface.viewers.AbstractTreeViewer#setSelectionToWidget(org.eclipse.jface.viewers.ISelection, boolean)
+     */
+    protected void setSelectionToWidget(ISelection selection, boolean reveal) {
+        cachedSelection = null;
+        super.setSelectionToWidget(selection, reveal);
+        cachedSelection = super.getSelection();
+    }   
+
+    /* (non-Javadoc)
+     * @see org.eclipse.jface.viewers.StructuredViewer#handlePostSelect(org.eclipse.swt.events.SelectionEvent)
+     */
+    protected void handlePostSelect(SelectionEvent e) {
+        cachedSelection = null;
+        super.handlePostSelect(e);
+    }
+
+    /* (non-Javadoc)
+     * @see org.eclipse.jface.viewers.StructuredViewer#handleSelect(org.eclipse.swt.events.SelectionEvent)
+     */
+    protected void handleSelect(SelectionEvent event) {
+        cachedSelection = null;
+        super.handleSelect(event);
+    }   
+
+    /* (non-Javadoc)
+     * @see org.eclipse.jface.viewers.StructuredViewer#preservingSelection(java.lang.Runnable)
+     */
+    protected void preservingSelection(Runnable updateCode) {
+        ISelection oldSelection = getSelection();        
+        super.preservingSelection(updateCode);
+        ISelection newSelection = getSelection();
+        if(newSelection.equals(oldSelection)){
+            //if they are equal, then we need to verify this. otherwise, handleInvalidSelection(...) had been called already 
+            cachedSelection = null;
+            newSelection = getSelection();
+            if (!newSelection.equals(oldSelection)) {
+                handleInvalidSelection(oldSelection, newSelection);
+            }
+        }        
+    }    
+
+    /* (non-Javadoc)
+     * @see org.eclipse.jface.viewers.StructuredViewer#updateSelection(org.eclipse.jface.viewers.ISelection)
+     */
+    protected void updateSelection(ISelection selection) {
+        cachedSelection = selection;//update cached selection
+        super.updateSelection(selection);
+    }   
 
 }