(define-gboxed-variant-cstruct event "GdkEvent"
  (type event-type)
  (window (g:object window))
  (send-event (:boolean :int8))
  (:variant type
            ...
            ((:visibility-notify) event-visibility
             (state visibility-state))
  ... ))  

type

The gdk:event-type type of the event.

window

The gdk:window object which received the event.

send-event

True if the event was sent explicitly.

state

The new gdk:visibility-state state, possible values are the :fully-obscured, :partial or :unobscured values.