# File lib/gruff/scatter.rb, line 197
  def draw_line_markers
    # do all of the stuff for the horizontal lines on the y-axis
    super
    return if @hide_line_markers
    
    @d = @d.stroke_antialias false

    if @x_axis_increment.nil?
      # TODO Do the same for larger numbers...100, 75, 50, 25
      if @marker_x_count.nil?
        (3..7).each do |lines|
          if @x_spread % lines == 0.0
            @marker_x_count = lines
            break
          end
        end
        @marker_x_count ||= 4
      end
      @x_increment = (@x_spread > 0) ? significant(@x_spread / @marker_x_count) : 1
    else
      # TODO Make this work for negative values
      @maximum_x_value = [@maximum_value.ceil, @x_axis_increment].max
      @minimum_x_value = @minimum_x_value.floor
      calculate_spread
      normalize(true)
      
      @marker_count = (@x_spread / @x_axis_increment).to_i
      @x_increment = @x_axis_increment
    end
    @increment_x_scaled = @graph_width.to_f / (@x_spread / @x_increment)

    # Draw vertical line markers and annotate with numbers
    (0..@marker_x_count).each do |index|

      # TODO Fix the vertical lines.  Not pretty when they don't match up with top y-axis line
      # x = @graph_left + @graph_width - index.to_f * @increment_x_scaled
      # @d = @d.stroke(@marker_color)
      # @d = @d.stroke_width 1
      # @d = @d.line(x, @graph_top, x, @graph_bottom)

      unless @hide_line_numbers
        marker_label = index * @x_increment + @minimum_x_value.to_f
        y_offset = @graph_bottom + LABEL_MARGIN 
        x_offset = get_x_coord(index.to_f, @increment_x_scaled, @graph_left)

        @d.fill = @font_color
        @d.font = @font if @font
        @d.stroke('transparent')
        @d.pointsize = scale_fontsize(@marker_font_size)
        @d.gravity = NorthGravity
        
        @d = @d.annotate_scaled(@base_image, 
                          1.0, 1.0, 
                          x_offset, y_offset, 
                          label(marker_label, @x_increment), @scale)
      end
    end
    
    @d = @d.stroke_antialias true
  end