protected function drawConnectionLine($poid, $oid) {
    list($start, $end) = $this->calculateEndPoints($poid, $oid);
    if($this->lineType == self::LINETYPE_DIRECT) {
      $this->drawDirectLine($start, $end);
    }
    else if($this->lineType == self::LINETYPE_ROUTED) {
      $this->drawRoutedLine($start, $end);
    }
  }