docs: @Pure
  	protected final boolean boundsContains(double x, double y, double delta) {
  		final Rectangle2d bounds = getBoundingBox();
  		assert bounds != null;
  		double dlt = delta;
  		if (dlt < 0) {
  			dlt = -dlt;
  		}
  		final Point2d p = new Point2d(x, y);
  		if (dlt == 0) {
  			return bounds.contains(p);
  		}
  		p.subX(dlt);
  		p.subY(dlt);
  		final Point2d p2 = new Point2d(p.getX() + dlt, p.getY() + dlt);
  		return bounds.contains(p) && bounds.contains(p2);
  	}