class Prawn::Table

def row_heights
  @natural_row_heights ||=
    begin
      heights_by_row = Hash.new(0)
      cells.each do |cell|
        next if cell.is_a?(Cell::SpanDummy)
        # Split the height of row-spanned cells evenly by rows
        height_per_row = cell.height.to_f / cell.rowspan
        cell.rowspan.times do |i|
          heights_by_row[cell.row + i] =
            [heights_by_row[cell.row + i], height_per_row].max
        end
      end
      heights_by_row.sort_by { |row, _| row }.map { |_, h| h }
    end
end