def top_value(padding=nil) # :nodoc:
      topval = layers.inject(0) { |max, layer| (max = ((max < layer.top_value) ? layer.top_value : max)) unless layer.top_value.nil?; max }
      below_zero = (topval <= 0)
      topval = padding == :padded ? (topval + ((topval - bottom_value) * 0.15)) : topval
      (below_zero && topval > 0) ? 0 : topval
    end
def top_value(padding=nil) # :nodoc:
      topval = layers.inject(0) { |max, layer| (max = ((max < layer.top_value) ? layer.top_value : max)) unless layer.top_value.nil?; max }
      below_zero = (topval <= 0)
      topval = padding == :padded ? (topval + ((topval - bottom_value) * 0.15)) : topval
      (below_zero && topval > 0) ? 0 : topval
    end
Returns the highest value in any of this container's layers.

 If padding is set to :padded, a 15% padding is added to the highest value.