Function fixed_update 

pub fn fixed_update(
    saved: &mut [u8],
    rgba: &[u8],
    labels: &[u8],
    width: usize,
    height: usize,
    x0: i64,
    y0: i64,
    rw: usize,
    rh: usize,
    code: u8,
) -> bool

Refreshes the saved pixels of a fixed (screen-anchored) region from rgba and reports whether any pixel the region owns changed. saved is rw × rh RGBA laid out from the region’s floored origin (x0, y0); pixels outside the frame or not labelled code are neither compared nor written. Rows are split across the pool.