]> allow-none NULL is ok, both for passing and for returning. closure This parameter is a 'user_data', for callbacks; many bindings can pass NULL here. transfer none Don't free data after the code is done. array Parameter points to an array of items. element-type Generics and defining elements of containers and arrays. in Parameter for input. Default is transfer none. transfer container Free data container after the code is done. transfer full Free data after the code is done. scope notified The callback is valid until the GDestroyNotify argument is called.