Function sc_content_sharing_picker_add_observer 

pub unsafe extern "C" fn sc_content_sharing_picker_add_observer(
    callback: extern "C" fn(i32, *const c_void, *const i8, *const c_void, *mut c_void),
    context_release: extern "C" fn(*mut c_void),
    user_data: *mut c_void,
) -> i64

Register a repeating observer. Returns a non-zero token, or 0 on failure.

callback receives (event, result_ptr, message, stream, user_data) where the event is 1 = updated (result_ptr non-null), 0 = cancelled, -1 = start failed (message non-null). stream is a non-owning identity pointer when the event targets an existing stream. context_release is invoked exactly once after detachment.