ZoneBinaryCallback RegisterBinaryCallbackHandler(Zone self, ZoneDelegate parent, Zone zone, R f(T1 arg1, T2 arg2))

Source 

typedef ZoneBinaryCallback<R, T1, T2> RegisterBinaryCallbackHandler<R, T1, T2>(
    Zone self, ZoneDelegate parent, Zone zone, R f(T1 arg1, T2 arg2));