docs: function toFontString(font) {
  	if (!font || helpers.isNullOrUndef(font.size) || helpers.isNullOrUndef(font.family)) {
  		return null;
  	}
  
  	return (font.style ? font.style + ' ' : '')
  		+ (font.weight ? font.weight + ' ' : '')
  		+ font.size + 'px '
  		+ font.family;
  }