* the kref and wf_unregister_control will decrement it, thus the
* object creating/disposing a given control shouldn't assume it
* still exists after wf_unregister_control has been called.
* the kref and wf_unregister_control will decrement it, thus the
* object creating/disposing a given control shouldn't assume it
* still exists after wf_unregister_control has been called.