static void
device_added_cb (GdkDeviceManager *device_manager,
                 GdkDevice        *device,
		 gpointer          user_data)
{
  GtkWidget *widget = user_data;

  gdk_window_set_device_events (gtk_widget_get_window (widget),
                                device, gtk_widget_get_events (widget));
}

...

/* Folgendes aus dem Widget-Konstruktor aufrufen:
g_signal_connect (device_manager, "device-added",
                  G_CALLBACK (device_added_cb), NULL);