Why no target(user_data) in atk_add_global_event_listener ()?

[Tal Hadad <tal_hd hotmail com>]

I wonder, why there is no user_data in method atk_add_global_event_listener?
Usually, GSignalEmissionHook methods have target(user_data).
Is there a specific reason why ATK doesn't have it?
It also very buggy in Vala language(since it assume this delegate has target).

Tal