+#include "warn.hh"
+
+IMPLEMENT_LISTENER (Engraver_group, override);
+void
+Engraver_group::override (SCM sev)
+{
+ Stream_event *ev = Stream_event::unsmob (sev);
+
+ Grob_property_info (context (), ev->get_property ("symbol"))
+ .push (ev->get_property ("property-path"),
+ ev->get_property ("value"));
+}
+
+IMPLEMENT_LISTENER (Engraver_group, revert);
+void
+Engraver_group::revert (SCM sev)
+{
+ Stream_event *ev = Stream_event::unsmob (sev);
+
+ Grob_property_info (context (), ev->get_property ("symbol"))
+ .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 (override), ly_symbol2scm ("Override"));
+ c->event_source ()->add_listener (GET_LISTENER (revert), ly_symbol2scm ("Revert"));
+}
+
+void
+Engraver_group::disconnect_from_context ()
+{
+ context ()->event_source ()->remove_listener (GET_LISTENER (override), ly_symbol2scm ("Override"));
+ context ()->event_source ()->remove_listener (GET_LISTENER (revert), ly_symbol2scm ("Revert"));
+ Translator_group::disconnect_from_context ();
+}