let x = if comp > 0 { dx/2 } else { dx };
let y = if comp > 0 { dy/2 } else { dy };
let sx_ = ((if comp > 0 { sx >> 1 } else { sx }) - pre) as usize;
let x = if comp > 0 { dx/2 } else { dx };
let y = if comp > 0 { dy/2 } else { dy };
let sx_ = ((if comp > 0 { sx >> 1 } else { sx }) - pre) as usize;