+ bool ok = type_check_assignment (sym, SCM_EOL, ly_symbol2scm ("translation-type?"));
+
+ if (ok)
+ {
+ if (to_boolean (ev->get_property ("once")))
+ {
+ if (Global_context *g = get_global_context ())
+ {
+ SCM old_val = SCM_UNDEFINED;
+ if (here_defined (sym, &old_val))
+ g->add_finalization (scm_list_4 (ly_context_set_property_x_proc,
+ self_scm (),
+ sym,
+ old_val));
+ else
+ g->add_finalization (scm_list_3 (ly_context_unset_property_proc,
+ self_scm (),
+ sym));
+ }
+ }
+ unset_property (sym);
+ }