问在Fabric js中缩放或更改位置时，Fabric.Path对象的object.path不提供更新路径

EN

<script src="./js/fabric.js"></script>
<canvas
  id="c"
  width="500"
  height="500"
  style="border: 1px solid #ccc"
></canvas>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.12.1/jquery.min.js"></script>
<script id="main">
  var canvas = new fabric.Canvas("c");
  var circle = new fabric.Circle({
    radius: 30,
    fill: "#f55"
  });

  canvas.add(circle);

  var line = new fabric.Path(
    "M 0 0 L 200 100 L 170 200 z",
    {
      fill: "",
      stroke: "black",
      objectCaching : true
    }
  );
  line.set({ name: "dummy" });
  canvas.add(line);

  var points = getPathValues("M 0 0 L 200 100 L 170 200 z", 1000);
   function getPathValues(path_val, samples) {
    var path = document.createElementNS(
      "http://www.w3.org/2000/svg",
      "path"
    );
    path.setAttribute("d", path_val);
    var points = [];
    var len = path.getTotalLength();
    var step = (step = len / samples);
    for (var i = 0; i <= len; i += step) {
      var p = path.getPointAtLength(i);
      points.push(p.x);
      points.push(p.y);
    }
    return points;
  }

  var i = 0;

  var interval = setInterval(function animate() {
      i = i + 2;
      if (i > points.length) {
        // clearInterval(interval);
        i = 0;
      }

      circle.left = line.left + points[i] - circle.radius;
      circle.top = line.top + points[i + 1] - circle.radius;
      canvas.renderAll();
    }, 10);