def ligature_attribute(styles={})
      return nil if styles.nil?
      value = styles[:ligature]
      return 0 if [0, :off, :none].include?(value)
      return 1 if [1, :on, :default].include?(value)
      nil
    end
def ligature_attribute(styles={})
      return nil if styles.nil?
      value = styles[:ligature]
      return 0 if [0, :off, :none].include?(value)
      return 1 if [1, :on, :default].include?(value)
      nil
    end
NSLigatureAttributeName

 :ligature
   = 0, :off, :none
   = 1, :on, :default