rem: *data = gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON(checkbox));
add: gpointer *data;  data = gtk_object_get_data ( GTK_OBJECT ( checkbox ), "pointer"); if (data) *data = gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON(checkbox));  return FALSE;
context: set_boolean ( GtkWidget * checkbox,	      guint * data){  *data = gtk_toggle_button_get_active (GTK_TOGGLE_BUTTON(checkbox));}