Function due_cleanup 

fn due_cleanup(
    st: &StripeState,
    trigger: u32,
    start: u32,
    keys: bool,
    still: u32,
    unclean: u32,
    motion: f32,
) -> Cleanup

The cleanup a region is due with still frames held still, unclean frames since it first changed after its last cleanup, and motion the share of its recent frames in motion.