Doc: NR - changing-defaults.itely - various improvements

[lilypond.git] / lily / context.cc

diff --git a/lily/context.cc b/lily/context.cc
index ccbb455a01a2cec22bad189f4cd5953901b7b438..a6b1da6a3609787625c7546905cf61a2935d6bf2 100644 (file)
--- a/lily/context.cc
+++ b/lily/context.cc
@@ -32,9 +32,6 @@
 #include "warn.hh"
 #include "lily-imports.hh"
 
-using std::string;
-using std::vector;
-
 bool
 Context::is_removable () const
 {
@@ -93,8 +90,7 @@ Context::Context ()
 
   smobify_self ();
 
-  Scheme_hash_table *tab = new Scheme_hash_table;
-  properties_scm_ = tab->unprotect ();
+  properties_scm_ = Scheme_hash_table::make_smob ();
   event_source_ = new Dispatcher ();
   event_source_->unprotect ();
   events_below_ = new Dispatcher ();
@@ -255,7 +251,25 @@ Context::set_property_from_event (SCM sev)
       ok = type_check_assignment (sym, val, ly_symbol2scm ("translation-type?"));
 
       if (ok)
-        set_property (sym, val);
+        {
+          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));
+                }
+            }
+          set_property (sym, val);
+        }
     }
 }
 
@@ -265,8 +279,28 @@ Context::unset_property_from_event (SCM sev)
   Stream_event *ev = unsmob<Stream_event> (sev);
 
   SCM sym = ev->get_property ("symbol");
-  type_check_assignment (sym, SCM_EOL, ly_symbol2scm ("translation-type?"));
-  unset_property (sym);
+  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);
+    }
 }
 
 /*