在fabric js中缩放时如何保持矩形的圆角

var rect = new fabric.Rect({
  left: 100,
  top: 100,
  width: 200,
  height: 100,
  rx: 10, // 圆角的横向半径
  ry: 10, // 圆角的纵向半径
  fill: 'red'
});

canvas.on('object:scaling', function(e) {
  var obj = e.target;
  if (obj.type === 'rect') {
    var scaleX = obj.scaleX;
    var scaleY = obj.scaleY;
    var rx = obj.rx;
    var ry = obj.ry;
    obj.set({
      rx: rx / scaleX,
      ry: ry / scaleY
    });
  }
});