s
    chebyshev_context.beginPath();
    for(var i = 0; i < chebyshev_n; ++i){
        chebyshev_context.moveTo(chebyshev_x_to_client(chebyshev_xs[i])-5.5, chebyshev_y_to_client(chebyshev_ys[i])+5.5);
        chebyshev_context.lineTo(chebyshev_x_to_client(chebyshev_xs[i])+5.5, chebyshev_y_to_client(chebyshev_ys[i])-5.5);
        chebyshev_context.moveTo(chebyshev_x_to_client(chebyshev_xs[i])+5.5, chebyshev_y_to_client(chebyshev_ys[i])+5.5);
        chebyshev_context.lineTo(chebyshev_x_to_client(chebyshev_xs