draw_line_markers (Gruff::SideBar)

    # File lib/gruff/side_bar.rb, line 58
      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 = 5

        # TODO Round maximum marker value to a round number like 100, 0.1, 0.5, etc.
        increment = significant(@maximum_value.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

          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