feat(player): 增加进度条拖动画面预览

test/playback/seek_progress_bar_test.dart

@@ -1,8 +1,12 @@
 // Author: fruit.com.cn
 
+import 'dart:typed_data';
+
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:fruitshorts/core/data/services/playback_thumbnail_service.dart';
 import 'package:fruitshorts/core/theme/app_colors.dart';
+import 'package:fruitshorts/pages/player/widgets/scrub_preview_card.dart';
 import 'package:fruitshorts/pages/player/widgets/seek_progress_bar.dart';
 import 'package:video_player/video_player.dart';
 
@@ -17,6 +21,18 @@ void main() {
     expect(seekPositionForFraction(1, duration), lessThan(duration));
   });
 
+  test('should_clamp_preview_card_inside_track_safe_margins', () {
+    expect(
+      scrubPreviewLeft(trackWidth: 300, fraction: 0),
+      scrubPreviewSafeMargin,
+    );
+    expect(
+      scrubPreviewLeft(trackWidth: 300, fraction: 1),
+      300 - scrubPreviewWidth - scrubPreviewSafeMargin,
+    );
+    expect(scrubPreviewLeft(trackWidth: 100, fraction: 0.5), 0);
+  });
+
   testWidgets('should_show_inactive_track_when_video_is_not_initialized', (
     tester,
   ) async {
@@ -233,6 +249,59 @@ void main() {
     },
   );
 
+  testWidgets('should_show_frame_card_with_cover_then_hide_on_release', (
+    tester,
+  ) async {
+    final video = ValueNotifier<VideoPlayerValue>(
+      const VideoPlayerValue(
+        duration: Duration(seconds: 12),
+        position: Duration(seconds: 3),
+        isInitialized: true,
+      ),
+    );
+    final service = _thumbnailService();
+    addTearDown(video.dispose);
+    addTearDown(service.dispose);
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: Center(
+            child: SizedBox(
+              width: 300,
+              child: SeekProgressBar(
+                valueListenable: video,
+                semanticsLabel: 'Seek video',
+                episodeId: 'episode-1',
+                posterUrl: '',
+                thumbnailService: service,
+                onSeek: (_) async {},
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    final gesture = await tester.startGesture(
+      tester.getCenter(find.byType(Slider)),
+    );
+    await gesture.moveBy(const Offset(80, 0));
+    await tester.pump();
+
+    expect(find.byKey(const Key('scrub-preview-card')), findsOneWidget);
+    expect(find.byKey(const Key('scrub-preview-poster')), findsOneWidget);
+    expect(find.byKey(const Key('scrub-preview-frame')), findsNothing);
+    expect(find.textContaining('/ 00:12'), findsOneWidget);
+    expect(
+      tester.getSize(find.byKey(const Key('scrub-preview-card'))).width,
+      120,
+    );
+
+    await gesture.up();
+    await tester.pump();
+    expect(find.byKey(const Key('scrub-preview-card')), findsNothing);
+  });
+
   testWidgets('should_show_time_only_while_dragging_when_seek_bar_is_compact', (
     tester,
   ) async {
@@ -267,3 +336,20 @@ void main() {
     expect(find.textContaining('00:12'), findsNothing);
   });
 }
+
+PlaybackThumbnailService _thumbnailService() {
+  return PlaybackThumbnailService(
+    frameLoader: _NullThumbnailLoader(),
+    sourceResolver: (_) =>
+        const PlaybackThumbnailSource(remoteUrl: 'https://example/video.mp4'),
+    prefetchDelay: const Duration(hours: 1),
+  );
+}
+
+class _NullThumbnailLoader implements PlaybackThumbnailFrameLoader {
+  @override
+  Future<ByteData?> load(PlaybackThumbnailFrameRequest request) async => null;
+
+  @override
+  void dispose() {}
+}