Function AEInstallSpecialHandler 

pub unsafe extern "C-unwind" fn AEInstallSpecialHandler(
    function_class: AEKeyword,
    handler: AEEventHandlerUPP,
    is_sys_handler: bool,
) -> i16

Available on crate features AEDataModel and AppleEvents only.

---

These calls are used to set up and modify special hooks into the AppleEvent manager.

---

Safety

handler must be implemented correctly.