fix(flutter): 优化分类弧线与自动滚动

test/discover/home_all_dramas_grid_test.dart

@@ -12,6 +12,7 @@ import 'package:fruitshorts/core/data/repositories/playback_repository.dart';
 import 'package:fruitshorts/core/data/repositories/watch_history_repository.dart';
 import 'package:fruitshorts/core/theme/app_colors.dart';
 import 'package:fruitshorts/core/widgets/app_pull_to_refresh.dart';
+import 'package:fruitshorts/pages/discover/discover_view.dart';
 import 'package:shared_preferences_platform_interface/in_memory_shared_preferences_async.dart';
 import 'package:shared_preferences_platform_interface/shared_preferences_async_platform_interface.dart';
 
@@ -274,23 +275,54 @@ void main() {
 
   testWidgets('should_show_category_underline_for_selection', (tester) async {
     await _pumpTheater(tester, categoryRepository: _GridCategoryRepository());
-    Color underline(String id) =>
-        (tester
-                    .widget<Container>(
-                      find.byKey(Key('theater-category-underline-$id')),
-                    )
-                    .decoration!
-                as BoxDecoration)
-            .color!;
+    CategoryUnderlinePainter underline(String id) =>
+        tester
+                .widget<CustomPaint>(
+                  find.byKey(Key('theater-category-underline-$id')),
+                )
+                .painter!
+            as CategoryUnderlinePainter;
 
-    expect(underline('all'), AppColors.blue);
-    expect(underline('7'), Colors.transparent);
+    expect(
+      tester
+          .widget<CustomPaint>(
+            find.byKey(const Key('theater-category-underline-all')),
+          )
+          .size,
+      const Size(20, 3),
+    );
+    expect(underline('all').color, AppColors.blue);
+    expect(underline('7').color, Colors.transparent);
 
     await tester.tap(find.byKey(const Key('theater-category-7')));
     await tester.pumpAndSettle();
 
-    expect(underline('all'), Colors.transparent);
-    expect(underline('7'), AppColors.blue);
+    expect(underline('all').color, Colors.transparent);
+    expect(underline('7').color, AppColors.blue);
+  });
+
+  testWidgets('should_scroll_offscreen_category_into_view_when_tapped', (
+    tester,
+  ) async {
+    final categories = [
+      for (var index = 0; index < 12; index++)
+        ContentCategory(id: '$index', name: 'Long category $index'),
+    ];
+    await _pumpTheater(
+      tester,
+      categoryRepository: _GridCategoryRepository(categories: categories),
+    );
+
+    final target = find.byKey(const Key('theater-category-11'));
+    expect(tester.getRect(target).right, greaterThan(390));
+
+    tester.widget<GestureDetector>(target).onTap!();
+    await tester.pump();
+    await tester.pumpAndSettle();
+
+    final rect = tester.getRect(target);
+    expect(rect.left, greaterThanOrEqualTo(0));
+    expect(rect.right, lessThanOrEqualTo(390));
   });
 
   testWidgets('should_use_text_pull_to_refresh', (tester) async {
@@ -344,15 +376,16 @@ Future<void> _pumpTheater(
 }
 
 class _GridCategoryRepository implements CategoryRepository {
-  _GridCategoryRepository({HomeFeed? discoverFeed})
-    : discoverFeed = discoverFeed ?? _defaultDiscoverFeed;
+  _GridCategoryRepository({
+    HomeFeed? discoverFeed,
+    this.categories = const [ContentCategory(id: '7', name: 'Romance')],
+  }) : discoverFeed = discoverFeed ?? _defaultDiscoverFeed;
 
   final HomeFeed discoverFeed;
+  final List<ContentCategory> categories;
 
   @override
-  Future<List<ContentCategory>> fetchCategories() async => const [
-    ContentCategory(id: '7', name: 'Romance'),
-  ];
+  Future<List<ContentCategory>> fetchCategories() async => categories;
 
   @override
   Future<HomeFeed> fetchDiscoverFeed() async => discoverFeed;