The callback and associated user_data is only used until the callback is invoked, and the callback. is invoked always exactly once.
The callback and associated user_data is only used during the call to this function.
The callback and associated user_data is used until the process terminates
The argument is not of callback type.
The callback and associated user_data is used until the caller is notfied via the destroy_notify.
Scope type of a #GIArgInfo representing callback, determines how the callback is invoked and is used to decided when the invoke structs can be freed.