+ Stream_event *ev = unsmob<Stream_event> (sev);
+ SCM sym = ev->get_property ("symbol");
+ Grob_property_info gpi (context (), sym);
+
+ if (to_boolean (ev->get_property ("once")))
+ {
+ SCM token = gpi.temporary_revert (ev->get_property ("property-path"));
+ if (scm_is_pair (token))
+ if (Global_context *g = context ()->get_global_context ())
+ {
+ g->add_finalization (scm_list_4 (ly_context_matched_pop_property_proc,
+ context ()->self_scm (),
+ sym,
+ token));
+ }
+ }
+ else
+ gpi.pop (ev->get_property ("property-path"));
+}
+
+void
+Engraver_group::connect_to_context (Context *c)
+{
+ Translator_group::connect_to_context (c);
+ c->event_source ()->add_listener (GET_LISTENER (Engraver_group, override), ly_symbol2scm ("Override"));
+ c->event_source ()->add_listener (GET_LISTENER (Engraver_group, revert), ly_symbol2scm ("Revert"));
+}
+
+void
+Engraver_group::disconnect_from_context ()
+{
+ context ()->event_source ()->remove_listener (GET_LISTENER (Engraver_group, override), ly_symbol2scm ("Override"));
+ context ()->event_source ()->remove_listener (GET_LISTENER (Engraver_group, revert), ly_symbol2scm ("Revert"));
+ Translator_group::disconnect_from_context ();
+}
+
+void
+Engraver_group::announce_grob (Grob_info info, Direction dir,
+ Context *reroute_context)
+{
+ announce_infos_.push_back (Announce_grob_info (info, dir));
+
+ Context *dad_con = reroute_context ? reroute_context
+ : context_->get_parent_context ();