class Prawn::Table::Cell

def min_width
  return min_width_ignoring_span if @colspan == 1
  # Sum up the largest min-width from each column, including myself.
  min_widths = Hash.new(0)
  dummy_cells.each do |cell|
    min_widths[cell.column] =
      [min_widths[cell.column], cell.min_width].max
  end
  min_widths[column] = [min_widths[column], min_width_ignoring_span].max
  min_widths.values.inject(0, &:+)
end