### Eclipse Workspace Patch 1.0
#P org.eclipse.compare
Index: compare/org/eclipse/compare/contentmergeviewer/TextMergeViewerResources.properties
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.compare/plugins/org.eclipse.compare/compare/org/eclipse/compare/contentmergeviewer/TextMergeViewerResources.properties,v
retrieving revision 1.31
diff -u -r1.31 TextMergeViewerResources.properties
--- compare/org/eclipse/compare/contentmergeviewer/TextMergeViewerResources.properties	20 Apr 2007 18:33:08 -0000	1.31
+++ compare/org/eclipse/compare/contentmergeviewer/TextMergeViewerResources.properties	14 Jan 2009 09:57:44 -0000
@@ -1,5 +1,5 @@
 ###############################################################################
-# Copyright (c) 2000, 2007 IBM Corporation and others.
+# Copyright (c) 2000, 2009 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
@@ -18,6 +18,9 @@
 saveDialog.title= Save Resource
 saveDialog.message= Resource has been modified. Save changes?
 
+redoDiffDialog.title=Resource Changed
+redoDiffDialog.message= Resource has been modified. Recalculate differences?
+
 compareProgressTask.title= Computing Differences...
 
 tooComplexError.title= Error
Index: compare/org/eclipse/compare/contentmergeviewer/TextMergeViewer.java
===================================================================
RCS file: /cvsroot/eclipse/org.eclipse.compare/plugins/org.eclipse.compare/compare/org/eclipse/compare/contentmergeviewer/TextMergeViewer.java,v
retrieving revision 1.241
diff -u -r1.241 TextMergeViewer.java
--- compare/org/eclipse/compare/contentmergeviewer/TextMergeViewer.java	12 Jan 2009 12:33:00 -0000	1.241
+++ compare/org/eclipse/compare/contentmergeviewer/TextMergeViewer.java	14 Jan 2009 09:57:44 -0000
@@ -79,6 +79,7 @@
 import org.eclipse.jface.action.Separator;
 import org.eclipse.jface.action.ToolBarManager;
 import org.eclipse.jface.dialogs.ErrorDialog;
+import org.eclipse.jface.dialogs.IDialogConstants;
 import org.eclipse.jface.dialogs.MessageDialog;
 import org.eclipse.jface.preference.IPreferenceStore;
 import org.eclipse.jface.preference.PreferenceConverter;
@@ -430,7 +431,7 @@
 	private List fSourceViewerDecorationSupport = new ArrayList(3);
 	// whether enhanced viewer configuration has been done
 	private boolean isConfigured = false;
-	// maps containing actions contributed by client
+	private boolean fRedoDiff = false;
 
 	private final class InternalOutlineViewerCreator extends OutlineViewerCreator implements ISelectionChangedListener {
 		public Viewer findStructureViewer(Viewer oldViewer,
@@ -1003,14 +1004,7 @@
 			IEditorInput input = getDocumentKey();
 			if (input != null && input.equals(element)) {
 				this.fViewer.updateDirtyState(input, getDocumentProvider(), fLeg);
-				
-				// recalculate diffs and update controls
-				new UIJob(CompareMessages.DocumentMerger_0) {
-					public IStatus runInUIThread(IProgressMonitor monitor) {
-						update(true);
-						return Status.OK_STATUS;
-					}
-				}.schedule();
+				updateInUIThread(true);
 			}
 		}
 		public void elementContentAboutToBeReplaced(Object element) {
@@ -2207,6 +2201,7 @@
 	 * @since 3.3
 	 */
 	protected boolean handleSetFocus() {
+		promptToRedoDiff();
 		if (fFocusPart == null) {
 			if (fLeft != null && fLeft.getEnabled()) {
 				fFocusPart= fLeft;
@@ -2224,6 +2219,25 @@
 		return false;	// could not set focus
 	}
 	
+	private void promptToRedoDiff() {
+		if (fRedoDiff) {
+			Shell shell = fComposite.getShell();
+			MessageDialog dialog = new MessageDialog(shell, Utilities
+					.getString(getResourceBundle(), "redoDiffDialog.title"), //$NON-NLS-1$
+					null, // accept the default window icon
+					Utilities.getString(getResourceBundle(),
+							"redoDiffDialog.message"), //$NON-NLS-1$
+					MessageDialog.QUESTION, new String[] {
+							IDialogConstants.YES_LABEL,
+							IDialogConstants.NO_LABEL, }, 0 /* default is "yes" */);
+			switch (dialog.open()) {
+			case 0:
+				updateInUIThread(true);
+			case 1:
+				fRedoDiff = false;
+			}
+		}
+	}
 	
 	class HoverResizer extends Resizer {
 		Canvas fCanvas;
@@ -2886,6 +2900,10 @@
 			setRightDirty(dirty);
 		}
 		
+		// the change has been undone
+		if (!isLeftDirty() && !isRightDirty())
+			fRedoDiff = false;
+
 		updateLines(doc);
 	}
 	
@@ -2964,10 +2982,27 @@
 	private void updateDirtyState(IEditorInput key,
 			IDocumentProvider documentProvider, char type) {
 		boolean dirty = documentProvider.canSaveDocument(key);
+		boolean oldLeftDirty = isLeftDirty();
+		boolean oldRightDirty = isRightDirty();
 		if (type == LEFT_CONTRIBUTOR)
 			setLeftDirty(dirty);
 		else if (type == RIGHT_CONTRIBUTOR)
 			setRightDirty(dirty);
+		if ((oldLeftDirty != isLeftDirty() && !isLeftDirty() && !isRightDirty())
+				|| (oldRightDirty != isRightDirty() && !isRightDirty() && !isLeftDirty())) {
+			/*
+			 * Dirty state has changed from true to false, combined dirty state
+			 * is false. _In most cases_ this means that save has taken place
+			 * outside compare editor. Ask to redo diff calculation when the
+			 * editor gets focus.
+			 * 
+			 * However, undoing all the changes made in another editor would
+			 * result in asking for redo diff as well. In this case, we set the
+			 * flag back to false, see
+			 * TextMergeViewer.documentChanged(DocumentEvent, boolean)
+			 */
+			fRedoDiff = true;
+		}
 	}
 
 	private Position getNewRange(char type, Object input) {
@@ -4876,6 +4911,16 @@
 		return Utilities.getBoolean(getCompareConfiguration(), ICompareUIConstants.PROP_IGNORE_ANCESTOR, false);
 	}
 	
+	private void updateInUIThread(final boolean includeControls) {
+		// recalculate diffs and update controls
+		new UIJob(CompareMessages.DocumentMerger_0) {
+			public IStatus runInUIThread(IProgressMonitor monitor) {
+				update(includeControls);
+				return Status.OK_STATUS;
+			}
+		}.schedule();
+	}
+
 	/* package */ void update(boolean includeControls) {
 		if (getControl().isDisposed())
 			return;