draw_line_markers (Gruff::Base)

    # File lib/gruff/base.rb, line 637
        def draw_line_markers
          return if @hide_line_markers

          @d = @d.stroke_antialias false

          if @y_axis_increment.nil?
            # Try to use a number of horizontal lines that will come out even.
            #
            # TODO Do the same for larger numbers...100, 75, 50, 25
            if @marker_count.nil?
              (3..7).each do |lines|
                if @spread % lines == 0.0
                  @marker_count = lines
                  break
                end
              end
              @marker_count ||= 4
            end
            @increment = (@spread > 0) ? significant(@spread / @marker_count) : 1
          else
            # TODO Make this work for negative values
            @maximum_value = [@maximum_value.ceil, @y_axis_increment].max
            @minimum_value = @minimum_value.floor
            calculate_spread
            normalize(true)

            @marker_count = (@spread / @y_axis_increment).to_i
            @increment = @y_axis_increment
          end
          @increment_scaled = @graph_height.to_f / (@spread / @increment)

          # Draw horizontal line markers and annotate with numbers
          (0..@marker_count).each do |index|
            y = @graph_top + @graph_height - index.to_f * @increment_scaled

            @d = @d.stroke(@marker_color)
            @d = @d.stroke_width 1
            @d = @d.line(@graph_left, y, @graph_right, y)

            marker_label = index * @increment + @minimum_value.to_f

            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 = EastGravity

              # Vertically center with 1.0 for the height
              @d = @d.annotate_scaled( @base_image,
                                @graph_left - LABEL_MARGIN, 1.0,
                                0.0, y,
                                label(marker_label), @scale)
            end
          end

          # # Submitted by a contibutor...the utility escapes me
          # i = 0
          # @additional_line_values.each do |value|
          #   @increment_scaled = @graph_height.to_f / (@maximum_value.to_f / value)
          #
          #   y = @graph_top + @graph_height - @increment_scaled
          #
          #   @d = @d.stroke(@additional_line_colors[i])
          #   @d = @d.line(@graph_left, y, @graph_right, y)
          #
          #
          #   @d.fill = @additional_line_colors[i]
          #   @d.font = @font if @font
          #   @d.stroke('transparent')
          #   @d.pointsize = scale_fontsize(@marker_font_size)
          #   @d.gravity = EastGravity
          #   @d = @d.annotate_scaled( @base_image,
          #                     100, 20,
          #                     -10, y - (@marker_font_size/2.0),
          #                     "", @scale)
          #   i += 1
          # end

          @d = @d.stroke_antialias true
        end