Javascript 如何在fabric.js中选择和拖动对象

我这里有一个例子，我在这里使用了fabric.js，当我们点击按钮时，它将创建行。。我的问题是如何在fabric.js中选择或移动画布中的对象

var canvas = new fabric.Canvas('c', { selection: false });

var line, isDown;

canvas.on('mouse:down', function(o){
  isDown = true;
  var pointer = canvas.getPointer(o.e);
  var points = [ pointer.x, pointer.y, pointer.x, pointer.y ];
  line = new fabric.Line(points, {
    strokeWidth: 5,
    fill: 'red',
    stroke: 'red',
    originX: 'center',
    originY: 'center'
  });
  canvas.add(line);
});

canvas.on('mouse:move', function(o){
  if (!isDown) return;
  var pointer = canvas.getPointer(o.e);
  line.set({ x2: pointer.x, y2: pointer.y });
  canvas.renderAll();
});

canvas.on('mouse:up', function(o){
  isDown = false;
});

如果我将第一行设置为

var canvas=newfabric.canvas（'c'，{selection:true}）我可以得到边界框，但无法拖动
我解决了这个问题

var canvas = new fabric.Canvas('c', { selection: false });

var line, isDown;

canvas.on('mouse:down', function(o){
    if(canvas.findTarget(o.e))return;
  isDown = true;
  var pointer = canvas.getPointer(o.e);
  var points = [ pointer.x, pointer.y, pointer.x, pointer.y ];
  line = new fabric.Line(points, {
    strokeWidth: 5,
    fill: 'red',
    stroke: 'red',
    originX: 'center',
    originY: 'center'
  });
  canvas.add(line);
});

canvas.on('mouse:move', function(o){
  if (!isDown) return;
  var pointer = canvas.getPointer(o.e);
  line.set({ x2: pointer.x, y2: pointer.y });
  line.setCoords();
  canvas.renderAll();
});

canvas.on('mouse:up', function(o){
  isDown = false;
});