/**
  * Adjust the query for RSS display.
  * Called from {@link display()}; calls {@link _prepare_sort()}.
  * @param QUERY $query
  * @access private
  */
 protected function _prepare_query($query)
 {
     $query->set_filter(Visible);
     $this->_prepare_sort($query);
     $class_name = $this->context->final_class_name('TIME_FRAME_SELECTOR', 'webcore/gui/time_frame_selector.php');
     $selector = new $class_name($this->context, Time_frame_recent);
     $selector->prepare_query($query);
 }