Function lv_obj_bind_style 

pub unsafe extern "C" fn lv_obj_bind_style(
    obj: *mut lv_obj_t,
    style: *const lv_style_t,
    selector: lv_style_selector_t,
    subject: *mut lv_subject_t,
    ref_value: i32,
) -> *mut lv_observer_t

Disable a style if a subject’s value is not equal to a reference value @param obj pointer to Widget @param style pointer to a style @param selector pointer to a selector @param subject pointer to Subject @param ref_value reference value to compare Subject’s value with @return pointer to newly-created Observer