code: func (f *Fpdf) GetFontDesc(familyStr, styleStr string) FontDescType {
  	if familyStr == "" {
  		return f.currentFont.Desc
  	}
  	return f.fonts[getFontKey(familyStr, styleStr)].Desc
  }
docs: // GetFontDesc returns the font descriptor, which can be used for
  // example to find the baseline of a font. If familyStr is empty
  // current font descriptor will be returned.
  // See FontDescType for documentation about the font descriptor.
  // See AddFont for details about familyStr and styleStr.