def print_header
      r,c = rowcol
      value = convert_value_to_text :columns, 0
      len = @width - @internal_width
      truncate value # else it can later suddenly exceed line
      @header_color_pair ||= get_color $promptcolor, @header_fgcolor, @header_bgcolor
      @header_attrib ||= @attr
      print_header_row r, c, len, value, @header_color_pair, @header_attrib
    end
def print_header
      r,c = rowcol
      value = convert_value_to_text :columns, 0
      len = @width - @internal_width
      truncate value # else it can later suddenly exceed line
      @header_color_pair ||= get_color $promptcolor, @header_fgcolor, @header_bgcolor
      @header_attrib ||= @attr
      print_header_row r, c, len, value, @header_color_pair, @header_attrib
    end
prints the column headers
 Uses +convert_value_to_text+ and +print_header_row+