We may have fields that are updated by `on_change` calls for which we want to base the notification. Those fields should be checked with the changed fields. For example to implement #13750 which is based on the contact mechanism `value`, the `value` field is not always directly modified by the user but widget dedicated `Function` fields are. So without this behavior, we need to declare all the `Function` fields as depends of the `on_change_notify` which is not very modular.