btn->set_tooltip("Extend straight track out of free endpoint (Shift+N)");
btn->signal_clicked.connect(sigc::mem_fun(&designer, &Designer::extend_track));
pnl_content->add(*(btn = new GLtk::Button("Conn")));
btn->set_tooltip("Extend straight track out of free endpoint (Shift+N)");
btn->signal_clicked.connect(sigc::mem_fun(&designer, &Designer::extend_track));
pnl_content->add(*(btn = new GLtk::Button("Conn")));