+ # CHECKME:
+ # do we want to call the notifier
+ # - at all when adding it? (yes, though optional)
+ # - when the default is active? (yes)
+ # - when no value *yet* has been set,
+ # because no config has ever been read (currently yes)
+ # (though that's not so easy to detect.
+ # the entry could just be new.)
+ if initial_call:
+ notifier(self)
+