MeasureSize.dart

MeasureSize.dart

class MeasureSizeRenderObject extends RenderProxyBox {
  Size? oldSize;
  final ValueChanged<Size> onChange;

  MeasureSizeRenderObject(this.onChange);

  @override
  void performLayout() {
    super.performLayout();

    Size newSize = child!.size;
    if (oldSize == newSize) return;

    oldSize = newSize;
    WidgetsBinding.instance!.addPostFrameCallback((_) {
      onChange(newSize);
    });
  }
}

class MeasureSize extends SingleChildRenderObjectWidget {
  final ValueChanged<Size> onChange;

  const MeasureSize({
    required this.onChange,
    required Widget child,
    Key? key,
  }) : super(key: key, child: child);

  @override
  RenderObject createRenderObject(BuildContext context) {
    return MeasureSizeRenderObject(onChange);
  }
}