# File lib/gruff/side_bar.rb, line 80
  def draw_line_markers

    return if @hide_line_markers

    @d = @d.stroke_antialias false

    # Draw horizontal line markers and annotate with numbers
    @d = @d.stroke(@marker_color)
    @d = @d.stroke_width 1
    number_of_lines = @marker_count || 5
    number_of_lines = 1 if number_of_lines == 0

    # TODO Round maximum marker value to a round number like 100, 0.1, 0.5, etc.
    increment = significant(@spread.to_f / number_of_lines)
    (0..number_of_lines).each do |index|

      line_diff = (@graph_right - @graph_left) / number_of_lines
      x = @graph_right - (line_diff * index) - 1
      @d = @d.line(x, @graph_bottom, x, @graph_top)
      diff = index - number_of_lines
      marker_label = diff.abs * increment + @minimum_value

      unless @hide_line_numbers
        @d.fill = @font_color
        @d.font = @font if @font
        @d.stroke = 'transparent'
        @d.pointsize = scale_fontsize(@marker_font_size)
        @d.gravity = CenterGravity
        # TODO Center text over line
        @d = @d.annotate_scaled(@base_image,
                                0, 0, # Width of box to draw text in
                                x, @graph_bottom + (LABEL_MARGIN * 2.0), # Coordinates of text
                                marker_label.to_s, @scale)
      end # unless
      @d = @d.stroke_antialias true
    end
  end