# File lib/spreadsheet/excel/writer/n_worksheet.rb, line 508
  def write_guts
    # find the maximum outline_level in rows and columns
    row_outline_level = 0
    col_outline_level = 0
    if(row = @worksheet.rows.select{|x| x!=nil}.max{|a,b| a.outline_level <=> b.outline_level})
      row_outline_level = row.outline_level
    end
    if(col = @worksheet.columns.select{|x| x!=nil}.max{|a,b| a.outline_level <=> b.outline_level})
      col_outline_level = col.outline_level
    end
    # set data
    data = [
      0,  # Width of the area to display row outlines (left of the sheet), in pixel
      0,  # Height of the area to display column outlines (above the sheet), in pixel
      row_outline_level+1, # Number of visible row outline levels (used row levels+1; or 0,if not used)
      col_outline_level+1  # Number of visible column outline levels (used column levels+1; or 0,if not used)
    ]
    # write record
    write_op opcode(:guts), data.pack('v4')
  end