+ virtual void inc_use_count ();
+ virtual void dec_use_count ();
+ int use_count() const { return g_atomic_int_get (const_cast<gint*>(&_use_count)); }
+ bool used() const { return use_count() > 0; }
+ uint32_t level() const { return _level; }
+
+ std::string ancestor_name() { return _ancestor_name.empty() ? name() : _ancestor_name; }
+ void set_ancestor_name(const std::string& name) { _ancestor_name = name; }
+