sliver clip tests

main.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/rendering.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  testWidgets('SliverClipRRect uses correctheight for clip calculation', (WidgetTester tester) async {
    final ScrollController controller = ScrollController();
    await tester.pumpWidget(
      WidgetsApp(
        color: const Color(0xffffffff),
        onGenerateRoute: (settings) => PageRouteBuilder(
          pageBuilder: (_, _, _) => CustomScrollView(
            controller: controller,
            slivers: <Widget>[
              const SliverPersistentHeader(
                delegate: _SliverPersistentHeaderDelegate(100), // 100px Pinned Header
                pinned: true,
              ),
              SliverClipRRect(
                borderRadius: const BorderRadius.all(Radius.circular(40)),
                sliver: SliverToBoxAdapter(
                  child: Container(
                    height: 100, // Total Height: 100px. middleRect.height is 20px (100 - 40 - 40).
                    color: const Color(0xFF2196F3),
                  ),
                ),
              ),
              const SliverToBoxAdapter(child: SizedBox(height: 1000)),
            ],
          ),
        ),
      ),
    );

    // Scroll by 50px. 
    // The header covers 0-100px in the viewport. 
    // The SliverClipRRect starts at 50px in the viewport (100px header - 50px scroll).
    // The overlap is 50px. The clip should start at local y=50.
    controller.jumpTo(50);
    await tester.pump();
    
    final RenderSliverClipRRect renderSliver = tester.renderObject(find.byType(SliverClipRRect).first);
    final RRect clip = renderSliver.getClip()!;

    // ACTUAL: clip.top was 20.0 instead of 50.0.
    // REASON: It used middleRect.height (20) instead of total height (100).
    expect(
      clip.top, 
      50.0, 
      reason: 'clip.top should be 50.0 to cover the overlap. Using middleRect.height (20) results in a miscalculated clip origin.'
    );
  });

  testWidgets('SliverClipRRect rounded overlap cut causes content leak', (WidgetTester tester) async {
    final ScrollController controller = ScrollController();
    await tester.pumpWidget(
      WidgetsApp(
        color: const Color(0xffffffff),
        onGenerateRoute: (settings) => PageRouteBuilder(
          pageBuilder: (_, _, _) => CustomScrollView(
            controller: controller,
            slivers: <Widget>[
              const SliverPersistentHeader(
                delegate: _SliverPersistentHeaderDelegate(100),
                pinned: true,
              ),
              SliverClipRRect(
                borderRadius: const BorderRadius.all(Radius.circular(40)),
                sliver: SliverToBoxAdapter(
                  child: Container(
                    height: 100,
                    color: const Color(0xFF2196F3),
                  ),
                ),
              ),
              const SliverToBoxAdapter(child: SizedBox(height: 1000)),
            ],
          ),
        ),
      ),
    );

    controller.jumpTo(20);
    await tester.pump();
    
    final RenderSliverClipRRect renderSliver = tester.renderObject(find.byType(SliverClipRRect).first);
    
    // Test point (1, 21) in local coordinates. 
    // If the cut is rounded, this point is clipped (hit=false).
    // This confirms that content is visible (or hidden) following a curve, 
    // which leaves "gaps" against a straight pinned header.
    final SliverHitTestResult result = SliverHitTestResult();
    final bool hit = renderSliver.hitTest(result, mainAxisPosition: 21, crossAxisPosition: 1);
    
    expect(
      hit, 
      isTrue, 
      reason: 'Content at (1, 21) is clipped because the overlap cut is rounded, leaving visual gaps under the header.'
    );
  });

  testWidgets('SliverClipRRect reverse scroll overlap calculation', (WidgetTester tester) async {
    final ScrollController controller = ScrollController();
    await tester.pumpWidget(
      WidgetsApp(
        color: const Color(0xffffffff),
        onGenerateRoute: (settings) => PageRouteBuilder(
          pageBuilder: (_, _, _) => CustomScrollView(
            reverse: true, // REVERSE SCROLLING
            controller: controller,
            slivers: <Widget>[
              const SliverToBoxAdapter(child: SizedBox(height: 1000)),
              SliverClipRRect(
                borderRadius: const BorderRadius.all(Radius.circular(40)),
                sliver: SliverToBoxAdapter(
                  child: Container(
                    height: 100,
                    color: const Color(0xFF2196F3),
                  ),
                ),
              ),
              const SliverPersistentHeader(
                delegate: _SliverPersistentHeaderDelegate(100), // Pinned Header at the BOTTOM
                pinned: true,
              ),
            ],
          ),
        ),
      ),
    );

    // Scroll so there is 50px overlap at the bottom.
    controller.jumpTo(50);
    await tester.pump();
    
    final RenderSliverClipRRect renderSliver = tester.renderObject(find.byType(SliverClipRRect).first);
    expect(renderSliver.constraints.overlap, 50.0);
    
    final RRect clip = renderSliver.getClip()!;

    // For AxisDirection.up, it uses newClip.copyWith(bottom: geometry!.paintExtent - clipOrigin)
    // If clipOrigin is wrong (20 instead of 50), the bottom clip will be misplaced.
    expect(
      clip.bottom, 
      50.0, 
      reason: 'Reverse scroll overlap clipping is incorrect.'
    );
  });
}

class _SliverPersistentHeaderDelegate extends SliverPersistentHeaderDelegate {
  const _SliverPersistentHeaderDelegate(this.height);
  final double height;
  @override
  Widget build(BuildContext context, double shrinkOffset, bool overlapsContent) => SizedBox(height: height);
  @override
  double get maxExtent => height;
  @override
  double get minExtent => height;
  @override
  bool shouldRebuild(covariant _SliverPersistentHeaderDelegate oldDelegate) => height != oldDelegate.height;
}