Fabric js如何防止对象缩放到画布边界之外？

canvas.on('object:scaling', function(e) {
  var obj = e.target;
  var canvasWidth = canvas.getWidth();
  var canvasHeight = canvas.getHeight();

  // 获取对象的宽度和高度
  var objWidth = obj.getScaledWidth();
  var objHeight = obj.getScaledHeight();

  // 计算对象的边界
  var objLeft = obj.getLeft();
  var objTop = obj.getTop();
  var objRight = objLeft + objWidth;
  var objBottom = objTop + objHeight;

  // 检查对象是否超出画布边界
  if (objLeft < 0 || objTop < 0 || objRight > canvasWidth || objBottom > canvasHeight) {
    // 缩放对象到边界之内
    var scaleX = canvasWidth / objWidth;
    var scaleY = canvasHeight / objHeight;
    var scale = Math.min(scaleX, scaleY);
    obj.scale(scale);
  }
});