anchor.diff:        fontWeight: fontWeight,
         fontStyle: fontStyle,
         fontFamily: fontFamily,
  -      fontSize: fontSize
  +      fontSize: fontSize,
  +      letterSpacing: letterSpacing
       );
     }
   
  
positive.code:       fontSize: other.fontSize,
        fontWeight: other.fontWeight,
        fontStyle: other.fontStyle,
        textAlign: other.textAlign,
        textBaseline: other.textBaseline,
        height: other.height,
  
negative.code:     this.fontSize,
      this.fontWeight,
      this.fontStyle,
      this.letterSpacing,
      this.textAlign,
      this.textBaseline,
      this.height,
  