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

[lilypond.git] / lily / context.cc

diff --git a/lily/context.cc b/lily/context.cc
index 192cdaa3ee8e1a7b6eaa7cb2f18ee59c97165236..a6b1da6a3609787625c7546905cf61a2935d6bf2 100644 (file)
--- a/lily/context.cc
+++ b/lily/context.cc
@@ -70,7 +70,7 @@ Context::add_context (Context *child)
                               scm_cons (child->self_scm (), SCM_EOL));
 
   child->daddy_context_ = this;
-  this->events_below_->register_as_listener (child->events_below_);
+  events_below_->register_as_listener (child->events_below_);
 }
 
 Context::Context ()
@@ -90,8 +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 ();
@@ -252,7 +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);
+        }
     }
 }
 
@@ -262,8 +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);
+    }
 }
 
 /*
@@ -315,7 +352,7 @@ Context::create_context_from_event (SCM sev)
                 ly_symbol2scm ("UnsetProperty"));
 
   new_context->events_below_->register_as_listener (new_context->event_source_);
-  this->add_context (new_context);
+  add_context (new_context);
 
   new_context->unprotect ();
 
@@ -414,7 +451,7 @@ Context::get_default_interpreter (const string &context_id)
       if (!t)
         {
           warning (_f ("cannot find or create: `%s'", name.c_str ()));
-          t = unsmob<Context_def> (this->definition_);
+          t = unsmob<Context_def> (definition_);
         }
       if (scm_is_symbol (t->get_default_child (SCM_EOL)))
         {
@@ -572,8 +609,8 @@ Context::remove_context (SCM)
 void
 Context::disconnect_from_parent ()
 {
-  daddy_context_->events_below_->unregister_as_listener (this->events_below_);
-  daddy_context_->context_list_ = scm_delq_x (this->self_scm (), daddy_context_->context_list_);
+  daddy_context_->events_below_->unregister_as_listener (events_below_);
+  daddy_context_->context_list_ = scm_delq_x (self_scm (), daddy_context_->context_list_);
   daddy_context_ = 0;
 }