calculate_bottom_margin (SVG::Graph::Graph)

    # File temp/Graph/Graph.rb, line 442
          def calculate_bottom_margin
            @border_bottom = 7
            if key and key_position == :bottom
              @border_bottom += @data.size * (font_size + 5)
              @border_bottom += 10
            end
            if show_x_labels
                      max_x_label_height_px = (not rotate_x_labels) ?
                x_label_font_size :
                get_x_labels.max{|a,b|
                  a.to_s.length<=>b.to_s.length
                }.to_s.length * x_label_font_size * 0.6
              @border_bottom += max_x_label_height_px
              @border_bottom += max_x_label_height_px + 10 if stagger_x_labels
            end
            @border_bottom += x_title_font_size + 5 if show_x_title
          end