@Override
 public boolean close() {
   if (showViewHandler != null) {
     IHandlerService service = PlatformUI.getWorkbench().getService(IHandlerService.class);
     service.deactivateHandler(showViewHandler);
     showViewHandler.getHandler().dispose();
     showViewHandler = null;
   }
   removeKeyScrolling();
   history.dispose();
   return super.close();
 }