+
+ Simple_music_iterator::process (mom);
+}
+
+MAKE_SCHEME_CALLBACK (Property_iterator, once_finalization, 3);
+SCM
+Property_iterator::once_finalization (SCM ctx, SCM music, SCM previous_value)
+{
+ Music *m = Music::unsmob (music);
+ Context *c = Context::unsmob (ctx);
+
+ // Do not use UnsetProperty, which sets the default, but rather
+ // cache the value before the \once \set command and restore it now
+ send_stream_event (c, "SetProperty", m->origin (),
+ ly_symbol2scm ("symbol"), m->get_property ("symbol"),
+ ly_symbol2scm ("value"), previous_value);
+
+ return SCM_UNSPECIFIED;
+}
+
+void
+Property_iterator::do_quit ()
+{
+}
+
+bool
+check_grob (Music *mus, SCM sym)
+{
+ bool g = to_boolean (scm_object_property (sym, ly_symbol2scm ("is-grob?")));
+
+ if (!g)
+ mus->origin ()->warning (_f ("not a grob name, `%s'",
+ ly_symbol2string (sym)));
+
+ return g;