SliverPhysicalShape

readme.md

SliverPhysicalShape

Created with <3 with dartpad.dev.

main.dart

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

void main() => runApp(
      const MaterialApp(
        debugShowCheckedModeBanner: false,
        home: SliverPhysicalShapeDemo(),
      ),
    );

class SliverPhysicalShapeDemo extends StatefulWidget {
  const SliverPhysicalShapeDemo({super.key});

  @override
  State<SliverPhysicalShapeDemo> createState() => _SliverPhysicalShapeDemoState();
}

class _SliverPhysicalShapeDemoState extends State<SliverPhysicalShapeDemo> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('SliverPhysicalShape'),
      ),
      body: CustomScrollView(
        slivers: [
          SliverPhysicalShape(
            color: Colors.white,
            borderRadius: const BorderRadius.only(
              topLeft: Radius.circular(16),
              topRight: Radius.circular(16),
            ),
            child: SliverList(
              delegate: SliverChildBuilderDelegate(
                (context, index) => ListTile(
                  leading: const Icon(Icons.code),
                  title: Text('Index ${index + 1}'),
                ),
                childCount: 50,
              ),
            ),
          ),
        ],
      ),
    );
  }
}

class SliverPhysicalShape extends SingleChildRenderObjectWidget {
  const SliverPhysicalShape({
    super.key,
    this.color = const Color(0xFFFFFFFF),
    this.elevation = 0.0,
    this.shadowColor = const Color(0x00000000),
    this.borderRadius,
    super.child,
  });

  final Color color;
  final double elevation;
  final Color shadowColor;
  final BorderRadius? borderRadius;

  @override
  RenderSliverPhysicalShape createRenderObject(BuildContext context) =>
      RenderSliverPhysicalShape(
        color: color,
        elevation: elevation,
        shadowColor: shadowColor,
        borderRadius: borderRadius,
      );

  @override
  void updateRenderObject(
          BuildContext context, RenderSliverPhysicalShape renderObject) =>
      renderObject
        ..color = color
        ..elevation = elevation
        ..shadowColor = shadowColor
        ..borderRadius = borderRadius;
}

class RenderSliverPhysicalShape extends RenderSliver
    with RenderObjectWithChildMixin<RenderSliver> {
  RenderSliverPhysicalShape({
    required Color color,
    required double elevation,
    required Color shadowColor,
    BorderRadius? borderRadius,
  })  : _color = color,
        _elevation = elevation,
        _shadowColor = shadowColor,
        _borderRadius = borderRadius;

  Color get color => _color;
  Color _color;

  set color(Color value) {
    if (_color == value) {
      return;
    }
    final bool didNeedCompositing = alwaysNeedsCompositing;
    _color = value;
    if (didNeedCompositing != alwaysNeedsCompositing) {
      markNeedsCompositingBitsUpdate();
    }
    markNeedsPaint();
  }

  double get elevation => _elevation;
  double _elevation;

  set elevation(double value) {
    if (_elevation == value) {
      return;
    }
    final bool didNeedCompositing = alwaysNeedsCompositing;
    _elevation = value;
    if (didNeedCompositing != alwaysNeedsCompositing) {
      markNeedsCompositingBitsUpdate();
    }
    markNeedsPaint();
  }

  Color get shadowColor => _shadowColor;
  Color _shadowColor;

  set shadowColor(Color value) {
    if (_shadowColor == value) {
      return;
    }
    final bool didNeedCompositing = alwaysNeedsCompositing;
    _shadowColor = value;
    if (didNeedCompositing != alwaysNeedsCompositing) {
      markNeedsCompositingBitsUpdate();
    }
    markNeedsPaint();
  }

  BorderRadius? get borderRadius => _borderRadius;
  BorderRadius? _borderRadius;

  set borderRadius(BorderRadius? value) {
    if (_borderRadius == value) {
      return;
    }
    final bool didNeedCompositing = alwaysNeedsCompositing;
    _borderRadius = value;
    if (didNeedCompositing != alwaysNeedsCompositing) {
      markNeedsCompositingBitsUpdate();
    }
    markNeedsPaint();
  }

  @override
  PhysicalModelLayer? get layer => super.layer as PhysicalModelLayer?;

  @override
  void applyPaintTransform(RenderObject child, Matrix4 transform) {
    final SliverPhysicalParentData childParentData =
        child.parentData as SliverPhysicalParentData;
    childParentData.applyPaintTransform(transform);
  }

  @override
  void performLayout() {
    assert(child != null);
    child!.layout(constraints, parentUsesSize: true);
    geometry = child!.geometry;
  }

  @override
  void setupParentData(RenderObject child) {
    if (child.parentData is! SliverPhysicalParentData) {
      child.parentData = SliverPhysicalParentData();
    }
  }

  @override
  bool hitTestChildren(
    SliverHitTestResult result, {
    required double mainAxisPosition,
    required double crossAxisPosition,
  }) =>
      child != null &&
      child!.geometry!.hitTestExtent > 0 &&
      child!.hitTest(result,
          mainAxisPosition: mainAxisPosition,
          crossAxisPosition: crossAxisPosition);

  @override
  double childMainAxisPosition(RenderSliver child) {
    assert(child == this.child);
    return 0.0;
  }

  @override
  void paint(PaintingContext context, Offset offset) {
    layer ??= PhysicalModelLayer();

    final clipPath = Path();
    if (borderRadius != null) {
      clipPath.addRRect(borderRadius!.toRRect(offset & getAbsoluteSize()));
    }

    layer!
      ..color = color
      ..elevation = elevation
      ..shadowColor = shadowColor
      ..clipPath = clipPath;

    context.pushLayer(layer!, child!.paint, offset);
  }
}