class SliverClipRect extends SingleChildRenderObjectWidget {
  const SliverClipRect({
    super.key,
    super.child,
    this.clipper,
    this.clipBehavior = Clip.hardEdge,
    this.clipOverlap = true,
  });

  /// If non-null, determines which clip rectangle to use.
  final CustomClipper<Rect>? clipper;

  /// {@macro flutter.rendering.ClipRectLayer.clipBehavior}
  final Clip clipBehavior;

  /// Whether to automatically clip the portion of the child that is overlapped
  /// by preceding pinned slivers.
  ///
  /// If true, the clip rect will be adjusted to exclude the area defined by
  /// [SliverConstraints.overlap].
  final bool clipOverlap;
}

class SliverClipRRect extends SingleChildRenderObjectWidget {
  /// Creates a sliver that clips its child using a rounded rectangle.
  const SliverClipRRect({
    super.key,
    required Widget sliver,
    this.borderRadius = BorderRadius.zero,
    this.clipper,
    this.clipBehavior = Clip.antiAlias,
    this.clipOverlap = true,
  }) : super(child: sliver);

  /// The border radius of the rounded corners.
  ///
  /// Values are clamped so that horizontal and vertical radii sums do not
  /// exceed width/height.
  ///
  /// This value is ignored if [clipper] is non-null.
  final BorderRadiusGeometry borderRadius;

  /// If non-null, determines which clip to use.
  final CustomClipper<RRect>? clipper;

  /// {@macro flutter.rendering.ClipRectLayer.clipBehavior}
  final Clip clipBehavior;

  /// Whether to automatically clip the portion of the child that is overlapped
  /// by preceding pinned slivers.
  ///
  /// If true, the clip rect will be adjusted to exclude the area defined by
  /// [SliverConstraints.overlap].
  final bool clipOverlap;
}

Scaffold(
  body: DecoratedBox(
    decoration: BoxDecoration(
      gradient: LinearGradient(
        begin: Alignment.topCenter,
        end: Alignment.bottomCenter,
        colors: <Color>[Colors.blue.shade200, Colors.blue.shade800],
      ),
    ),
    child: CustomScrollView(
      slivers: <Widget>[
        const SliverAppBar(
          pinned: true,
          title: Text('Group Clipping'),
          backgroundColor: Colors.transparent,
        ),
        SliverSafeArea(
          top: false,
          sliver: SliverPadding(
            padding: const EdgeInsets.all(16),
            sliver: SliverClipRRect(
              borderRadius: BorderRadius.circular(12),
              sliver: DecoratedSliver(
                decoration: const BoxDecoration(
                  gradient: LinearGradient(
                    begin: Alignment.topCenter,
                    end: Alignment.bottomCenter,
                    colors: <Color>[Colors.blue, Colors.purple],
                ),
                sliver: SliverMainAxisGroup(
                  slivers: <Widget>[
                    const PinnedHeaderSliver(
                      child: ListTile(
                        title: Text('Pinned Header', style: TextStyle(color: Colors.white)),
                      ),
                    ),
                    SliverClipRect(
                      sliver: SliverList.builder(
                        itemCount: 20,
                        itemBuilder: (BuildContext context, int index) => ListTile(
                          title: Text('Item $index', style: const TextStyle(color: Colors.white)),
                        ),
                      ),
                    ),
                  ],
                ),
              ),
            ),
          ),
        ),
      ],
    ),
  ),
)