anchor.diff:    BoxFit _fit;
     Alignment _alignment;
     bool _useIntrinsicSize = false;
  -
  -  @override
  -  Size computeDryLayout(BoxConstraints constraints) {
  -    return constraints
  -        .constrainSizeAndAttemptToPreserveAspectRatio(_intrinsicSize);
  -  }
   
     bool get useIntrinsicSize => _useIntrinsicSize;
     set useIntrinsicSize(bool value) {
  
positive.code:   @override
    void performLayout() {
      if (!sizedByParent) {
        size = constraints.constrain(_intrinsicSize);
      }
    }
  
  
negative.code: 
    @override
    void performResize() {
      size = constraints.biggest;
    }
  
  