Bug 291267 - Additional fixes for intermittent failures in restoring viewer state.

7 files changed, 202 insertions, 49 deletions

diff --git a/org.eclipse.debug.tests/src/org/eclipe/debug/tests/viewer/model/StateTests.java b/org.eclipse.debug.tests/src/org/eclipe/debug/tests/viewer/model/StateTests.java
index 70058c59a..04571b631 100644
--- a/org.eclipse.debug.tests/src/org/eclipe/debug/tests/viewer/model/StateTests.java
+++ b/org.eclipse.debug.tests/src/org/eclipe/debug/tests/viewer/model/StateTests.java
@@ -19,6 +19,7 @@ import org.eclipse.debug.internal.ui.viewers.model.ITreeModelViewer;
 import org.eclipse.debug.internal.ui.viewers.model.provisional.IModelDelta;
 import org.eclipse.debug.internal.ui.viewers.model.provisional.ModelDelta;
 import org.eclipse.jface.viewers.TreePath;
+import org.eclipse.jface.viewers.TreeSelection;
 import org.eclipse.swt.layout.FillLayout;
 import org.eclipse.swt.widgets.Display;
 import org.eclipse.swt.widgets.Shell;
@@ -224,7 +225,6 @@ abstract public class StateTests extends TestCase implements ITestModelUpdatesLi
         viewer.setExpandedState(path, true);
         while (!fListener.isFinished()) if (!fDisplay.readAndDispatch ()) fDisplay.sleep ();
         model.validateData(fViewer, TreePath.EMPTY, true);
-
     }
     
     public void testPreserveExpandedOnRemove() {
@@ -243,6 +243,10 @@ abstract public class StateTests extends TestCase implements ITestModelUpdatesLi
 
         expandAlternateElements(model);
         
+        // Set a selection in view
+        TreeSelection originalSelection = new TreeSelection(model.findElement("5.1.1"));
+        fViewer.setSelection(originalSelection);
+
         // Update the model
         ModelDelta delta = model.removeElementChild(TreePath.EMPTY, 0);
         
@@ -251,15 +255,17 @@ abstract public class StateTests extends TestCase implements ITestModelUpdatesLi
         model.postDelta(delta);
         while (!fListener.isFinished(MODEL_CHANGED_COMPLETE)) 
             if (!fDisplay.readAndDispatch ()) fDisplay.sleep ();
+        
+        // Validate data
         model.validateData(fViewer, TreePath.EMPTY, true);
-        ITreeModelContentProviderTarget viewer = (ITreeModelContentProviderTarget)fViewer; 
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("2")) == false);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("3")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("3.1")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("4")) == false);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("5")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("5.1")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("6")) == false);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("2")) == false);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("3")) == true);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("3.1")) == true);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("4")) == false);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("5")) == true);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("5.1")) == true);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("6")) == false);
+        Assert.assertEquals(originalSelection, fViewer.getSelection());
     }
 
     public void testPreserveExpandedOnInsert() {
@@ -278,6 +284,10 @@ abstract public class StateTests extends TestCase implements ITestModelUpdatesLi
 
         expandAlternateElements(model);
         
+        // Set a selection in view
+        TreeSelection originalSelection = new TreeSelection(model.findElement("5.1.1"));
+        fViewer.setSelection(originalSelection);
+        
         // Update the model
         ModelDelta delta = model.insertElementChild(TreePath.EMPTY, 0, new TestElement(model, "0 - new", new TestElement[0]));
         
@@ -289,21 +299,22 @@ abstract public class StateTests extends TestCase implements ITestModelUpdatesLi
         model.postDelta(delta);
         while (!fListener.isFinished(MODEL_CHANGED_COMPLETE | ALL_UPDATES_COMPLETE)) 
             if (!fDisplay.readAndDispatch ()) fDisplay.sleep ();
+        
+        // Validate data
         model.validateData(fViewer, TreePath.EMPTY, true);
-        ITreeModelContentProviderTarget viewer = (ITreeModelContentProviderTarget)fViewer; 
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("1")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("1.1")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("2")) == false);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("3")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("3.1")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("4")) == false);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("5")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("5.1")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("6")) == false);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("1")) == true);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("1.1")) == true);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("2")) == false);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("3")) == true);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("3.1")) == true);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("4")) == false);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("5")) == true);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("5.1")) == true);
+        Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("6")) == false);
+        Assert.assertEquals(originalSelection, fViewer.getSelection());
     }
 
-
-    public void testPreserveExpandedOnContent() {
+    public void testPreserveExpandedOnContentStress() {
         //TreeModelViewerAutopopulateAgent autopopulateAgent = new TreeModelViewerAutopopulateAgent(fViewer);
         TestModel model = alternatingSubsreesModel();
 
@@ -319,28 +330,59 @@ abstract public class StateTests extends TestCase implements ITestModelUpdatesLi
 
         expandAlternateElements(model);
         
-        // Update the model
-        model.removeElementChild(TreePath.EMPTY, 0);
-        
-        // Content delta should generate updates for the elements being re-expanded
-        ITreeModelContentProviderTarget viewer = (ITreeModelContentProviderTarget)fViewer;
-        // Note: Re-expanding nodes causes redundant updates.
-        fListener.reset(false, false);
-        fListener.addUpdates(viewer, TreePath.EMPTY, model.getRootElement(), -1, ALL_UPDATES_COMPLETE); 
-        model.postDelta(new ModelDelta(model.getRootElement(), IModelDelta.CONTENT));
-        while (!fListener.isFinished(ALL_UPDATES_COMPLETE)) 
-            if (!fDisplay.readAndDispatch ()) fDisplay.sleep ();
-        model.validateData(fViewer, TreePath.EMPTY, true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("2")) == false);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("3")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("3.1")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("4")) == false);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("5")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("5.1")) == true);
-        Assert.assertTrue(viewer.getExpandedState(model.findElement("6")) == false);
+        // Set a selection in view
+        TreeSelection originalSelection = new TreeSelection(model.findElement("5.1.1"));
+        fViewer.setSelection(originalSelection);
+        Assert.assertEquals(originalSelection, fViewer.getSelection());
+
+        // Run this test ten times as we've seen intermittent failures related 
+        // to timing in it.
+        for (int i = 0; i < 10; i++) {
+            // Update the model
+            model.removeElementChild(TreePath.EMPTY, 0);
+            
+            // Note: Re-expanding nodes causes redundant updates.
+            fListener.reset(false, false);
+            fListener.addUpdates(getCTargetViewer(), TreePath.EMPTY, model.getRootElement(), -1, ALL_UPDATES_COMPLETE); 
+            model.postDelta(new ModelDelta(model.getRootElement(), IModelDelta.CONTENT));
+            while (!fListener.isFinished(ALL_UPDATES_COMPLETE | STATE_RESTORE_COMPLETE)) 
+                if (!fDisplay.readAndDispatch ()) fDisplay.sleep ();
+
+            // Validate data
+            model.validateData(fViewer, TreePath.EMPTY, true);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("2")) == false);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("3")) == true);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("3.1")) == true);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("4")) == false);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("5")) == true);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("5.1")) == true);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("6")) == false);
+            Assert.assertEquals(originalSelection, fViewer.getSelection());
+            
+            // Update the model again
+            model.addElementChild(TreePath.EMPTY, 0, new TestElement(model, "1", new TestElement[0]));
+            
+            // Note: Re-expanding nodes causes redundant updates.
+            fListener.reset(false, false);
+            fListener.addUpdates(getCTargetViewer(), TreePath.EMPTY, model.getRootElement(), -1, ALL_UPDATES_COMPLETE); 
+            model.postDelta(new ModelDelta(model.getRootElement(), IModelDelta.CONTENT));
+            while (!fListener.isFinished(ALL_UPDATES_COMPLETE | STATE_RESTORE_COMPLETE)) 
+                if (!fDisplay.readAndDispatch ()) fDisplay.sleep ();
+
+            // Validate data
+            model.validateData(fViewer, TreePath.EMPTY, true);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("2")) == false);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("3")) == true);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("3.1")) == true);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("4")) == false);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("5")) == true);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("5.1")) == true);
+            Assert.assertTrue(getCTargetViewer().getExpandedState(model.findElement("6")) == false);
+            Assert.assertEquals(originalSelection, fViewer.getSelection());
+        }
     }
 
-    public void testSaveAndRstoreOnInputChange1() {
+    public void testSaveAndRstore1() {
         //TreeModelViewerAutopopulateAgent autopopulateAgent = new TreeModelViewerAutopopulateAgent(fViewer);
         TestModel model = alternatingSubsreesModel();
 
@@ -357,6 +399,9 @@ abstract public class StateTests extends TestCase implements ITestModelUpdatesLi
         // Expand some, but not all elements
         expandAlternateElements(model);
 
+        // Set a selection in view
+        fViewer.setSelection(new TreeSelection(model.findElement("5.1.1")));
+        
         // Extract the original state from viewer
         ModelDelta originalState = new ModelDelta(model.getRootElement(), IModelDelta.NO_CHANGE);
         fViewer.saveElementState(TreePath.EMPTY, originalState, IModelDelta.EXPAND | IModelDelta.SELECT);
@@ -382,4 +427,51 @@ abstract public class StateTests extends TestCase implements ITestModelUpdatesLi
         Assert.assertTrue( deltaMatches(originalState, restoredState) );
     }
 
+    public void testSaveAndRstore2() {
+        //TreeModelViewerAutopopulateAgent autopopulateAgent = new TreeModelViewerAutopopulateAgent(fViewer);
+        TestModel model = TestModel.simpleMultiLevel();
+
+        // expand all elements
+        fViewer.setAutoExpandLevel(-1);
+        
+        // Create the listener, only check the first level
+        fListener.reset(TreePath.EMPTY, model.getRootElement(), -1, true, false); 
+
+        // Set the input into the view and update the view.
+        fViewer.setInput(model.getRootElement());
+        while (!fListener.isFinished()) if (!fDisplay.readAndDispatch ()) fDisplay.sleep ();
+        model.validateData(fViewer, TreePath.EMPTY);
+
+        // Set a selection in view
+        fViewer.setSelection(new TreeSelection(model.findElement("3.2.3")));
+                
+        // Turn off the auto-expand now since we want to text the auto-expand logic
+        fViewer.setAutoExpandLevel(-1);
+
+        // Extract the original state from viewer
+        ModelDelta originalState = new ModelDelta(model.getRootElement(), IModelDelta.NO_CHANGE);
+        fViewer.saveElementState(TreePath.EMPTY, originalState, IModelDelta.EXPAND | IModelDelta.SELECT);
+
+        // Set the viewer input to null.  This will trigger the view to save the viewer state.
+        fListener.reset(true, false);
+        fListener.addStateUpdates(getCTargetViewer(), TreePath.EMPTY, model.getRootElement());
+
+        fViewer.setInput(null);
+        while (!fListener.isFinished(STATE_SAVE_COMPLETE)) if (!fDisplay.readAndDispatch ()) fDisplay.sleep ();
+
+        // Set the viewer input back to the model.  When view updates are complete
+        // the viewer 
+        // Note: disable redundant updates because the reveal delta triggers one.
+        fListener.reset(TreePath.EMPTY, model.getRootElement(), 1, false, false);
+        // TODO: add state updates somehow?
+        fViewer.setInput(model.getRootElement());
+        while (!fListener.isFinished()) if (!fDisplay.readAndDispatch ()) fDisplay.sleep ();
+
+        // Extract the restored state from viewer
+        ModelDelta restoredState = new ModelDelta(model.getRootElement(), IModelDelta.NO_CHANGE);
+        fViewer.saveElementState(TreePath.EMPTY, restoredState, IModelDelta.EXPAND | IModelDelta.SELECT);
+
+        Assert.assertTrue( deltaMatches(originalState, restoredState) );
+    }
+
 }
diff --git a/org.eclipse.debug.tests/src/org/eclipe/debug/tests/viewer/model/TestModelUpdatesListener.java b/org.eclipse.debug.tests/src/org/eclipe/debug/tests/viewer/model/TestModelUpdatesListener.java
index ea866c774..ea8e094c1 100644
--- a/org.eclipse.debug.tests/src/org/eclipe/debug/tests/viewer/model/TestModelUpdatesListener.java
+++ b/org.eclipse.debug.tests/src/org/eclipe/debug/tests/viewer/model/TestModelUpdatesListener.java
@@ -53,7 +53,10 @@ public class TestModelUpdatesListener
     private boolean fStateRestoreComplete;
 	private int fViewerUpdatesRunning;
 	private int fLabelUpdatesRunning;
-    
+	private int fTimeoutInterval = 60000;
+	private long fTimeoutTime;
+	
+	
     public TestModelUpdatesListener(boolean failOnRedundantUpdates, boolean failOnMultipleUpdateSequences) {
         setFailOnRedundantUpdates(failOnRedundantUpdates);
         setFailOnMultipleUpdateSequences(failOnMultipleUpdateSequences);
@@ -66,8 +69,15 @@ public class TestModelUpdatesListener
     public void setFailOnMultipleUpdateSequences(boolean failOnMultipleUpdateSequences) {
         fFailOnMultipleUpdateSequences = failOnMultipleUpdateSequences;
     }
-
-
+    
+    /**
+     * Sets the the maximum amount of time (in milliseconds) that the update listener 
+     * is going to wait. If set to -1, the listener will wait indefinitely. 
+     */
+    public void setTimeoutInterval(int milis) {
+        fTimeoutInterval = milis;
+    }
+    
     public void reset(TreePath path, TestElement element, int levels, boolean failOnRedundantUpdates, boolean failOnMultipleUpdateSequences) {
         reset();
         addUpdates(path, element, levels);
@@ -93,6 +103,7 @@ public class TestModelUpdatesListener
         fModelChangedComplete = false;
         fStateSaveComplete = false;
         fStateRestoreComplete = false;
+        fTimeoutTime = System.currentTimeMillis() + fTimeoutInterval;
     }
     
     public void addHasChildrenUpdate(TreePath path) {
@@ -202,6 +213,10 @@ public class TestModelUpdatesListener
     }
     
     public boolean isFinished(int flags) {
+        if (fTimeoutInterval > 0 && fTimeoutTime < System.currentTimeMillis()) {
+            throw new RuntimeException("Test timed out");
+        }
+        
         if ( (flags & LABEL_UPDATES_COMPLETE) != 0) {
             if (!fLabelUpdatesComplete) return false;
         }
diff --git a/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ChildrenCountUpdate.java b/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ChildrenCountUpdate.java
index 19b0be07a..073ff0bcc 100644
--- a/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ChildrenCountUpdate.java
+++ b/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ChildrenCountUpdate.java
@@ -76,7 +76,7 @@ class ChildrenCountUpdate extends ViewerUpdateMonitor implements IChildrenCountU
 				return true;
 			} else if (getElementContentProvider().equals(request.getElementContentProvider())) {
 				if (fBatchedRequests == null) {
-					fBatchedRequests = new ArrayList();
+					fBatchedRequests = new ArrayList(4);
 					fBatchedRequests.add(this);
 				}
 				fBatchedRequests.add(request);
@@ -103,6 +103,19 @@ class ChildrenCountUpdate extends ViewerUpdateMonitor implements IChildrenCountU
 			getElementContentProvider().update(updates);
 		}
 	}
+	
+	boolean containsUpdate(TreePath path) {
+	    if (getElementPath().equals(path)) {
+	        return true;
+	    } else if (fBatchedRequests != null) {
+	        for (int i = 0; i < fBatchedRequests.size(); i++) {
+	            if (((ViewerUpdateMonitor)fBatchedRequests.get(i)).getElementPath().equals(path)) {
+	                return true;
+	            }
+	        }
+	    }
+	    return false;
+	}
 
 	/* (non-Javadoc)
 	 * @see org.eclipse.debug.internal.ui.viewers.model.ViewerUpdateMonitor#getPriority()
diff --git a/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ChildrenUpdate.java b/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ChildrenUpdate.java
index 21db89ddd..387403eae 100644
--- a/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ChildrenUpdate.java
+++ b/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ChildrenUpdate.java
@@ -126,7 +126,13 @@ public class ChildrenUpdate extends ViewerUpdateMonitor implements IChildrenUpda
 		}
 		return false;
 	}
+	
+	boolean containsUpdate(TreePath path) {
+        return getElementPath().equals(path);
+    }
+
 
+	
 	/* (non-Javadoc)
 	 * @see org.eclipse.debug.internal.ui.viewers.model.provisional.IChildrenUpdate#getLength()
 	 */
diff --git a/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/HasChildrenUpdate.java b/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/HasChildrenUpdate.java
index 61bb05dc6..9572326cf 100644
--- a/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/HasChildrenUpdate.java
+++ b/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/HasChildrenUpdate.java
@@ -106,6 +106,20 @@ class HasChildrenUpdate extends ViewerUpdateMonitor implements IHasChildrenUpdat
 		}
 	}
 
+	boolean containsUpdate(TreePath path) {
+        if (getElementPath().equals(path)) {
+            return true;
+        } else if (fBatchedRequests != null) {
+            for (int i = 0; i < fBatchedRequests.size(); i++) {
+                if (((ViewerUpdateMonitor)fBatchedRequests.get(i)).getElementPath().equals(path)) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+
 	/* (non-Javadoc)
 	 * @see org.eclipse.debug.internal.ui.viewers.model.ViewerUpdateMonitor#getPriority()
 	 */
diff --git a/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ModelContentProvider.java b/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ModelContentProvider.java
index 1b793f53b..133df6b70 100644
--- a/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ModelContentProvider.java
+++ b/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ModelContentProvider.java
@@ -191,10 +191,16 @@ abstract class ModelContentProvider implements IContentProvider, IModelChangedLi
          * int)
          */
         public boolean visit(IModelDelta delta, int depth) {
-            if (delta.getFlags() != IModelDelta.NO_CHANGE) {
+            // Filster out the CONTENT flags from the delta flags, the content
+            // flag is only used as a marker indicating that all the sub-elements
+            // of a given delta have been retrieved.  
+            int flags = (delta.getFlags() & ~IModelDelta.CONTENT);
+            
+            if (flags != IModelDelta.NO_CHANGE) {
                 IModelDelta parentDelta = delta.getParentDelta();
                 // Remove the delta if :
-                // - The parent delta has no more flags on it.
+                // - The parent delta has no more flags on it (the content flag is removed as well), 
+                // which means that parent element's children have been completely exposed.
                 // - There are no more pending updates for the element.
                 // - If element is a memento, there are no state requests pending.
                 if (parentDelta != null && parentDelta.getFlags() == IModelDelta.NO_CHANGE) {
@@ -207,7 +213,7 @@ abstract class ModelContentProvider implements IContentProvider, IModelChangedLi
                     }
                 }
 
-                if (delta.getFlags() == IModelDelta.REVEAL && !(delta.getElement() instanceof IMemento)) {
+                if (flags == IModelDelta.REVEAL && !(delta.getElement() instanceof IMemento)) {
                     topDelta = delta;
                 } else {
                     complete = false;
@@ -241,7 +247,7 @@ abstract class ModelContentProvider implements IContentProvider, IModelChangedLi
                 if (requests != null) {
                     for (int i = 0; i < requests.size(); i++) {
                         ViewerUpdateMonitor update = (ViewerUpdateMonitor) requests.get(i);
-                        if (update.getElement().equals(path.getLastSegment())) {
+                        if (update.containsUpdate(path)) {
                             return true;
                         }
                     }
diff --git a/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ViewerUpdateMonitor.java b/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ViewerUpdateMonitor.java
index 9a137d227..9ba15c551 100644
--- a/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ViewerUpdateMonitor.java
+++ b/org.eclipse.debug.ui/ui/org/eclipse/debug/internal/ui/viewers/model/ViewerUpdateMonitor.java
@@ -201,6 +201,13 @@ public abstract class ViewerUpdateMonitor extends Request implements IViewerUpda
 	 * @return whether it worked
 	 */
 	abstract boolean coalesce(ViewerUpdateMonitor update);
+
+	/**
+	 * Returns whether this update or any coalesced updates is for an 
+	 * element at the given path.
+     * @since 3.6
+	 */
+	abstract boolean containsUpdate(TreePath path);
 	
 	/**
 	 * Starts this request. Subclasses must override startRequest().