public static function addDoubleAttributes(Tag &$Tag)
    {
        if (isset(TagInfo::$doubleAttrs[$Tag->name])) {
            $missing = array();
            $found = '';
            foreach (TagInfo::$doubleAttrs[$Tag->name] as $k => $name) {
                if ($k === '%callback') {
                    $callback = $name;
                    continue;
                }
                if (isset($Tag->attributes[$name])) {
                    $found = $Tag->attributes[$name];
                } else {
                    $missing[] = $name;
                }
            }
            if (empty($found) || empty($missing)) {
                return;
            }
            foreach ($missing as $k) {
                $Tag->attributes[$k] = $found;
            }

            if (count($missing) && isset($callback) && is_callable($callback)) {
                call_user_func_array($callback, array(&$Tag, $missing));
            }
        }
    }