class Foo
{
public:
    /*
     * Modifies m_widget and the user
     * may modify the returned widget.
     */
    Widget *widget();

    /*
     * Does not modify m_widget but the
     * user may modify the returned widget.
     */
    Widget *widget() const;

    /*
     * Modifies m_widget, but the user
     * may not modify the returned widget.
     */
    const Widget *cWidget();

    /*
     * Does not modify m_widget and the user
     * may not modify the returned widget.
     */
    const Widget *cWidget() const;

private:
    Widget *m_widget;
}