static int drawAddComponentMenu(IEntityExt entity)
        {
            var componentInfos = getComponentInfos(entity)
                                 .Where(info => !entity.HasComponent(info.index))
                                 .ToArray();
            var componentNames = componentInfos
                                 .Select(info => info.name)
                                 .ToArray();
            var index = EditorGUILayout.Popup("Add Component", -1, componentNames);

            if (index >= 0)
            {
                return(componentInfos[index].index);
            }

            return(-1);
        }