You can dereference a smartpointer with the -> operator, to call the methods of the underlying instance, just like a normal pointer.

Glib::RefPtr<Gdk::Pixbuf> refPixbuf = Gdk::Pixbuf::create_from_file(filename);
int width = refPixbuf->get_width();

But unlike most smartpointers, you can't use the * operator to access the underlying instance.

Glib::RefPtr<Gdk::Pixbuf> refPixbuf = Gdk::Pixbuf::create_from_file(filename);
Gdk::Pixbuf& underlying = *refPixbuf; //Syntax error - will not compile.