protected function getColumnWidths()
    {
        $column_widths = [];

        for ($i = 0; $i < $this->column_count; $i++) {
            if (!isset($this->data[$i])) {
                $column_widths[] = 0;
                continue;
            }
            $column_widths[] = $this->getColumnWidth($this->data[$i]);
        }

        return $column_widths;
    }