///设置为我们的数据
@override
void setupParentData(RenderBox child) {
  if (child.parentData is! RenderCloudParentData)
    child.parentData = RenderCloudParentData();
}

@override
  void performLayout() {
    ///默认不需要裁剪
    _needClip = false;

    ///没有 childCount 不玩
    if (childCount == 0) {
      size = constraints.smallest;
      return;
    }

    ///初始化区域
    var recordRect = Rect.zero;
    var previousChildRect = Rect.zero;

    RenderBox child = firstChild;

    while (child != null) {
      var curIndex = -1;

      ///提出数据
      final RenderCloudParentData childParentData = child.parentData;

      child.layout(constraints, parentUsesSize: true);

      var childSize = child.size;

      ///记录大小
      childParentData.width = childSize.width;
      childParentData.height = childSize.height;

      do {
        ///设置 xy 轴的比例
        var rX = ratio >= 1 ? ratio : 1.0;
        var rY = ratio <= 1 ? ratio : 1.0;

        ///调整位置
        var step = 0.02 * _mathPi;
        var rotation = 0.0;
        var angle = curIndex * step;
        var angleRadius = 5 + 5 * angle;
        var x = rX * angleRadius * math.cos(angle + rotation);
        var y = rY * angleRadius * math.sin(angle + rotation);
        var position = Offset(x, y);

        ///计算得到绝对偏移
        var childOffset = position - Alignment.center.alongSize(childSize);

        ++curIndex;

        ///设置为遏制
        childParentData.offset = childOffset;

        ///判处是否交叠
      } while (overlaps(childParentData));

      ///记录区域
      previousChildRect = childParentData.content;
      recordRect = recordRect.expandToInclude(previousChildRect);

      ///下一个
      child = childParentData.nextSibling;
    }

    ///调整布局大小
    size = constraints
        .tighten(
          height: recordRect.height,
          width: recordRect.width,
        )
        .smallest;

    ///居中
    var contentCenter = size.center(Offset.zero);
    var recordRectCenter = recordRect.center;
    var transCenter = contentCenter - recordRectCenter;
    child = firstChild;
    while (child != null) {
      final RenderCloudParentData childParentData = child.parentData;
      childParentData.offset += transCenter;
      child = childParentData.nextSibling;
    }

    ///超过了嘛？
    _needClip =
        size.width < recordRect.width || size.height < recordRect.height;
  }