private void hookContextMenu() {
   MenuManager menuMgr = new MenuManager("#PopupMenu");
   menuMgr.setRemoveAllWhenShown(true);
   menuMgr.addMenuListener(
       new IMenuListener() {
         public void menuAboutToShow(IMenuManager manager) {
           ResultModelTreeView.this.fillContextMenu(manager);
         }
       });
   Menu menu = menuMgr.createContextMenu(viewer.getControl());
   viewer.getControl().setMenu(menu);
   getSite().registerContextMenu(menuMgr, viewer);
 }
 @Override
 public void setFocus() {
   viewer.getControl().setFocus();
 }