window.signal_button_press.connect(sigc::mem_fun(this, &Root::button_press_event));
window.signal_button_release.connect(sigc::mem_fun(this, &Root::button_release_event));
window.signal_pointer_motion.connect(sigc::mem_fun(this, &Root::pointer_motion_event));
window.signal_button_press.connect(sigc::mem_fun(this, &Root::button_press_event));
window.signal_button_release.connect(sigc::mem_fun(this, &Root::button_release_event));
window.signal_pointer_motion.connect(sigc::mem_fun(this, &Root::pointer_motion_event));