Function lv_spinbox_bind_value 

pub unsafe extern "C" fn lv_spinbox_bind_value(
    obj: *mut lv_obj_t,
    subject: *mut lv_subject_t,
) -> *mut lv_observer_t

Bind an integer subject to a Spinbox’s value. @param obj pointer to Spinbox @param subject pointer to Subject @return pointer to newly-created Observer