ent(x2), y_to_client(y2));
        }
    }
    spline_context.strokeStyle="#661100";
    spline_context.stroke();
    spline_context.closePath();

    // dots
    spline_context.beginPath();
    for(var i = 0; i < spline_n; ++i){
        spline_context.moveTo(x_to_client(spline_xs[i])-5.5, y_to_client(spline_ys[i])+5.5);
        spline_context.lineTo(x_to_client(spline_xs[i])+5.5, y_to_client(spline_ys[i])-5.5);
        spline_context.moveTo(x_to_client(spline_xs[i])+5.5, y_to_client(spline_ys[i])+5.5);
   