tgroup* twindow::add_group(const std::string& id)
{
    FOREACH(const AUTO & group, groups_)
    {
        if(group.id() == id) {
            // TODO: add error?
            return NULL;
        }
    }

    groups_.push_back(*(new tgroup(id)));

    return groups_.last();
}

void twindow::add_to_group(tgroup* group, twidget* widget)
{
    group.add_member(widget);
}

tgroup* twindow::add_to_group(const std::string& group_id, twidget* widget,
        const bool create_if_nonexistant)
{
    FOREACH(AUTO & group, groups_)
    {
        if(group.id() == group_id) {
            group.add_member(widget);

            return &group;
        }
    }

    if(create_if_nonexistant) {
        tgroup* new_group = add_group(group_id);
        assert(new_group);

        add_to_group(new_group, widget);

        return new_group;
    } else {
        // TODO: add error?
    }

    return NULL;
}