- Ensure that selection of NavigatorViewPart is never empty in order to work around #1491

refs 1491

org.fortiss.tooling.kernel.ui/trunk/src/org/fortiss/tooling/kernel/ui/internal/views/NavigatorViewPart.java

@@ -37,6 +37,8 @@ import org.eclipse.jface.viewers.ISelection;
 import org.eclipse.jface.viewers.ISelectionChangedListener;
 import org.eclipse.jface.viewers.SelectionChangedEvent;
 import org.eclipse.jface.viewers.StructuredSelection;
+import org.eclipse.jface.viewers.TreePath;
+import org.eclipse.jface.viewers.TreeSelection;
 import org.eclipse.jface.viewers.TreeViewer;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.widgets.Composite;
@@ -104,6 +106,9 @@ public final class NavigatorViewPart extends ViewPart implements ISelectionListe
 	/** Dialog setting ID for the link with editor action flag. */
 	private static final String LINK_WITH_EDITOR_FLAG = "navigatorSettingLinkWithEditor";
 
+	/** Element used to ensure that the selection of the {@link NavigatorViewPart} is not empty. */
+	private EObject backupElementToBeSelected;
+
 	/** Stores the UI update job. */
 	private final UIJob updateUI = new UIJob("Update Model Navigator") {
 		@Override
@@ -114,6 +119,28 @@ public final class NavigatorViewPart extends ViewPart implements ISelectionListe
 			IActionService.INSTANCE.refresh();
 			viewer.refresh();
 
+			// Ensure that the selection of the {@link NavigatorViewPart} is not empty. Otherwise
+			// undo/redo (and also other global commands) is not enabled when model elements are
+			// added directly using the context menu of the model navigator.
+			ISelection selection = viewer.getSelection();
+			if(selection instanceof TreeSelection && !selection.isEmpty()) {
+				Object firstSelectedElement = ((TreeSelection)selection).getFirstElement();
+				if(firstSelectedElement instanceof EObject) {
+
+					// Preserve container of current element. This is required to determine a valid
+					// model element in case the next operation is to delete the currently selected
+					// element
+					backupElementToBeSelected = ((EObject)firstSelectedElement).eContainer();
+				}
+			} else if(backupElementToBeSelected != null) {
+
+				// Selection would be empty. Use backup element to force selection to the container
+				// of the element that has been selected last.
+				viewer.setSelection(new TreeSelection(new TreePath(
+						new Object[] {backupElementToBeSelected})));
+				backupElementToBeSelected = null;
+			}
+
 			firePropertyChange(IWorkbenchPartConstants.PROP_DIRTY);
 			return Status.OK_STATUS;
 		}