void updateContentDependantActions() {
   Iterator e = fActions.values().iterator();
   while (e.hasNext()) {
     Object next = e.next();
     if (next instanceof MergeViewerAction) {
       MergeViewerAction action = (MergeViewerAction) next;
       if (action.isContentDependent()) action.update();
     }
   }
 }
 public void selectionChanged(SelectionChangedEvent event) {
   Iterator e = fActions.values().iterator();
   while (e.hasNext()) {
     Object next = e.next();
     if (next instanceof MergeViewerAction) {
       MergeViewerAction action = (MergeViewerAction) next;
       if (action.isSelectionDependent()) action.update();
     }
   }
 }
 /** update all actions independent of their type */
 public void updateActions() {
   Iterator e = fActions.values().iterator();
   while (e.hasNext()) {
     Object next = e.next();
     if (next instanceof MergeViewerAction) {
       MergeViewerAction action = (MergeViewerAction) next;
       action.update();
     } else if (next instanceof FindReplaceAction) {
       FindReplaceAction action = (FindReplaceAction) next;
       action.update();
     } else if (next instanceof ChangeEncodingAction) {
       ChangeEncodingAction action = (ChangeEncodingAction) next;
       action.update();
     }
   }
 }