# File lib/rbreadline.rb, line 2579
  def init_line_structures(minsize)
    if @invisible_line.nil? # initialize it
      if (@line_size < minsize)
        @line_size = minsize
      end
      @visible_line = 0.chr * @line_size
      @invisible_line = 0.chr * @line_size # 1.chr
    elsif (@line_size < minsize)  # ensure it can hold MINSIZE chars
      @line_size *= 2
      if (@line_size < minsize)
        @line_size = minsize
      end
      @visible_line << 0.chr * (@line_size - @visible_line.length)
      @invisible_line << 1.chr * (@line_size - @invisible_line.length)
    end
    @visible_line[minsize,@line_size-minsize] = 0.chr * (@line_size-minsize)
    @invisible_line[minsize,@line_size-minsize] = 1.chr * (@line_size-minsize)

    if @vis_lbreaks.nil?
      @inv_lbreaks = []
      @vis_lbreaks = []
      @_rl_wrapped_line = []
      @inv_lbreaks[0] = @vis_lbreaks[0] = 0
    end
  end