code: public static double convertFontSize(double parent, CSSProperty.FontSize value)
      {
          double em = parent;
          double ret = em;
          if (value == CSSProperty.FontSize.MEDIUM)
              ret = medium_font;
          else if (value == CSSProperty.FontSize.SMALL)
              ret = medium_font / font_step;
          else if (value == CSSProperty.FontSize.X_SMALL)
              ret = medium_font / font_step / font_step;
          else if (value == CSSProperty.FontSize.XX_SMALL)
              ret = medium_font / font_step / font_step / font_step;
          else if (value == CSSProperty.FontSize.LARGE)
              ret = medium_font * font_step;
          else if (value == CSSProperty.FontSize.X_LARGE)
              ret = medium_font * font_step * font_step;
          else if (value == CSSProperty.FontSize.XX_LARGE)
              ret = medium_font * font_step * font_step * font_step;
          else if (value == CSSProperty.FontSize.SMALLER)
              ret = em / font_step;
          else if (value == CSSProperty.FontSize.LARGER)
              ret = em * font_step;
          return ret;
      }
docs: Converts the font size given by an identifier to absolute length in pixels.
  @param parent Parent font size (taken as 1em)
  @param value The size specification to be converted
  @return absolute font size in px