/**
  * @param $rows
  * @param bool $pager
  */
 public function formatDisplay(&$rows, $pager = TRUE)
 {
     parent::formatDisplay($rows, $pager);
     // Format the nested rows.
     foreach ($this->_nestedRows as $month => &$mRows) {
         foreach ($mRows as $eventId => &$eRows) {
             $this->alterDisplay($eRows);
             CRM_Utils_Hook::alterReportVar('rows', $eRows, $this);
             $this->alterCustomDataDisplay($eRows);
         }
     }
     $this->assign('events', $this->_allEvents);
 }