Gtkmm with C++11

i am using the gtkmm library and now i am trying to look for how to change this line of code for the C++ 11 :

button.signal_enter_notify_event().connect(sigc::bind<std::string>(sigc::mem_fun(*this, &Windows::showText), "Quit"));

For instance with this line :

button.signal_clicked().connect(sigc::mem_fun(*this, &Windows::unfullscreen));

In C++ 11 the line becomes :

button.signal_clicked().connect([this]() { unfullscreen(); });

I tried to do the same for the first line but it does not work unfortunately. If you have some ideas i will be very thankful to you :)