avnd: name the port-callback storage condition

Author: jcelerier

src/plugins/score-plugin-avnd/Crousti/ProcessModel.hpp

@@ -40,6 +40,12 @@
 namespace oscr
 {
 
+// The condition under which a process needs the port-callback storage (a
+// model-side Info instance). The storage member and its init guard below must
+// both use it — keep them in sync.
+template <typename Info>
+concept needs_ports_callback_storage = has_dynamic_ports<Info>;
+
 template <typename Info>
 struct MessageBusWrapperToUi
 {
@@ -94,7 +100,8 @@ class ProcessModel final
   oscr::dynamic_ports_storage<Info> dynamic_ports;
 
   [[no_unique_address]]
-  ossia::type_if<Info, oscr::has_dynamic_ports<Info>> object_storage_for_ports_callbacks;
+  ossia::type_if<Info, oscr::needs_ports_callback_storage<Info>>
+      object_storage_for_ports_callbacks;
 
   ProcessModel(
       const TimeVal& duration, const Id<Process::ProcessModel>& id,
@@ -204,9 +211,7 @@ class ProcessModel final
 
   void init_controller_ports()
   {
-    if constexpr(
-        avnd::dynamic_ports_input_introspection<Info>::size > 0
-        || avnd::dynamic_ports_output_introspection<Info>::size > 0)
+    if constexpr(oscr::needs_ports_callback_storage<Info>)
     {
       avnd::control_input_introspection<Info>::for_all_n2(
           avnd::get_inputs<Info>((Info&)this->object_storage_for_ports_callbacks),