play_selection_button.unset_active_state ();
roll_button.unset_active_state ();
stop_button.set_active_state (Gtkmm2ext::ExplicitActive);
play_selection_button.unset_active_state ();
roll_button.unset_active_state ();
stop_button.set_active_state (Gtkmm2ext::ExplicitActive);