class tgroup
{
public:
    tgroup(std::string id);

    void add_member(twidget* widget);

    const std::string& id() const { return id_; }

    std::vector<twidget*> get_members() { return members_; }

    virtual void operate_on_group() = 0;

private:
    std::string id_;

    std::vector<twidget*> members_;
};