+ static xbt::signal<void(ActivityImpl const&)> on_suspended;
+ static xbt::signal<void(ActivityImpl const&)> on_resumed;
+};
+
+/* This class exists to allow chained setters as in exec->set_name()->set_priority()->set_blah()
+ * The difficulty is that set_name() must return a qualified child class, not the generic ancestor
+ * But the getter is still in the ancestor to be usable on generic activities with no downcast */
+template <class AnyActivityImpl> class ActivityImpl_T : public ActivityImpl {