gir: Correct usage of the closure annotation (#704) Whenever you’re describing a function that takes a callback, you should always annotate the callback argument with the argument that contains the user data using the (closure argument) annotation You should not annotate the data argument with a unary (closure). The unary (closure) is meant to be used when annotating the callback type Ref: https://gitlab.gnome.org/GNOME/mutter/-/commit/077eb80a8d9bb2968c2bfac959c2f2ca966ca7e7 Co-authored-by: Fabio Fantoni <fantonifabio@tiscali.it>