fix(library): restore Material playlist drag and drop

lib/screens/queue_tab.dart

@@ -16,6 +16,7 @@ import 'package:spotiflac_android/widgets/app_search_field.dart';
 import 'package:spotiflac_android/widgets/app_snack_bar.dart';
 import 'package:spotiflac_android/widgets/library_search_results.dart';
 import 'package:spotiflac_android/widgets/library_track_selection_bar.dart';
+import 'package:spotiflac_android/widgets/library_playlist_drag_source.dart';
 import 'package:spotiflac_android/widgets/mornye_chrome.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
@@ -238,6 +239,7 @@ class _QueueTabState extends ConsumerState<QueueTab> {
   final ValueNotifier<int> _embeddedCoverVersion = ValueNotifier<int>(0);
 
   bool _isSelectionMode = false;
+  bool _isDraggingLibraryTrack = false;
   final Set<String> _selectedIds = {};
   String? _selectionAnchorId;
   final SelectionOverlayController _selectionOverlay =

lib/screens/queue_tab_filter_widgets.dart

@@ -509,29 +509,14 @@ extension _QueueTabFilterWidgets on _QueueTabState {
                       final item = filteredUnifiedItems[trackIndex];
                       return KeyedSubtree(
                         key: ValueKey(item.id),
-                        child: LongPressDraggable<UnifiedLibraryItem>(
+                        child: LibraryPlaylistDragSource<UnifiedLibraryItem>(
                           data: item,
-                          feedback: _buildDragFeedback(
-                            context,
-                            item,
-                            colorScheme,
-                          ),
-                          childWhenDragging: Opacity(
-                            opacity: 0.4,
-                            child: _buildUnifiedGridItem(
-                              context,
-                              item,
-                              colorScheme,
-                              downloadedNavigationItems:
-                                  downloadedNavigationItems,
-                              downloadedNavigationIndex:
-                                  downloadedNavigationIndexByUnifiedId[item.id],
-                              localNavigationItems: localNavigationItems,
-                              localNavigationIndex:
-                                  localNavigationIndexByUnifiedId[item.id],
-                              libraryItems: filteredUnifiedItems,
-                            ),
-                          ),
+                          onSelect: () =>
+                              _selectDraggedTrack(item, filteredUnifiedItems),
+                          onDragStarted: _startLibraryTrackDrag,
+                          onDragEnd: _endLibraryTrackDrag,
+                          feedbackBuilder: (context) =>
+                              _buildDragFeedback(context, item, colorScheme),
                           child: _buildUnifiedGridItem(
                             context,
                             item,
@@ -544,6 +529,7 @@ extension _QueueTabFilterWidgets on _QueueTabState {
                             localNavigationIndex:
                                 localNavigationIndexByUnifiedId[item.id],
                             libraryItems: filteredUnifiedItems,
+                            playlistDragEnabled: true,
                           ),
                         ),
                       );
@@ -579,29 +565,14 @@ extension _QueueTabFilterWidgets on _QueueTabState {
                       final item = filteredUnifiedItems[trackIndex];
                       return KeyedSubtree(
                         key: ValueKey(item.id),
-                        child: LongPressDraggable<UnifiedLibraryItem>(
+                        child: LibraryPlaylistDragSource<UnifiedLibraryItem>(
                           data: item,
-                          feedback: _buildDragFeedback(
-                            context,
-                            item,
-                            colorScheme,
-                          ),
-                          childWhenDragging: Opacity(
-                            opacity: 0.4,
-                            child: _buildUnifiedLibraryItem(
-                              context,
-                              item,
-                              colorScheme,
-                              downloadedNavigationItems:
-                                  downloadedNavigationItems,
-                              downloadedNavigationIndex:
-                                  downloadedNavigationIndexByUnifiedId[item.id],
-                              localNavigationItems: localNavigationItems,
-                              localNavigationIndex:
-                                  localNavigationIndexByUnifiedId[item.id],
-                              libraryItems: filteredUnifiedItems,
-                            ),
-                          ),
+                          onSelect: () =>
+                              _selectDraggedTrack(item, filteredUnifiedItems),
+                          onDragStarted: _startLibraryTrackDrag,
+                          onDragEnd: _endLibraryTrackDrag,
+                          feedbackBuilder: (context) =>
+                              _buildDragFeedback(context, item, colorScheme),
                           child: _buildUnifiedLibraryItem(
                             context,
                             item,
@@ -614,6 +585,7 @@ extension _QueueTabFilterWidgets on _QueueTabState {
                             localNavigationIndex:
                                 localNavigationIndexByUnifiedId[item.id],
                             libraryItems: filteredUnifiedItems,
+                            playlistDragEnabled: true,
                           ),
                         ),
                       );

lib/screens/queue_tab_item_widgets.dart

@@ -742,6 +742,7 @@ extension _QueueTabItemWidgets on _QueueTabState {
     required List<LocalLibraryItem> localNavigationItems,
     required int? localNavigationIndex,
     required List<UnifiedLibraryItem> libraryItems,
+    bool playlistDragEnabled = false,
   }) {
     final fileExistsListenable = _fileExistsListenable(item.filePath);
     final isSelected = _selectedIds.contains(item.id);
@@ -788,7 +789,9 @@ extension _QueueTabItemWidgets on _QueueTabState {
                 album: item.albumName,
                 coverUrl: item.coverUrl ?? item.localCoverPath ?? '',
               ),
-        onLongPress: _isSelectionMode
+        onLongPress: playlistDragEnabled
+            ? null
+            : _isSelectionMode
             ? () => _selectRangeTo(item.id, libraryItems)
             : () => _enterSelectionMode(item.id),
         leading: Hero(
@@ -892,6 +895,7 @@ extension _QueueTabItemWidgets on _QueueTabState {
     required List<LocalLibraryItem> localNavigationItems,
     required int? localNavigationIndex,
     required List<UnifiedLibraryItem> libraryItems,
+    bool playlistDragEnabled = false,
   }) {
     final fileExistsListenable = _fileExistsListenable(item.filePath);
     final isSelected = _selectedIds.contains(item.id);
@@ -925,7 +929,9 @@ extension _QueueTabItemWidgets on _QueueTabState {
               album: item.albumName,
               coverUrl: item.coverUrl ?? item.localCoverPath ?? '',
             ),
-      onLongPress: _isSelectionMode
+      onLongPress: playlistDragEnabled
+          ? null
+          : _isSelectionMode
           ? () => _selectRangeTo(item.id, libraryItems)
           : () => _enterSelectionMode(item.id),
       cover: Hero(

lib/screens/queue_tab_selection.dart

@@ -1,6 +1,30 @@
 part of 'queue_tab.dart';
 
 extension _QueueTabSelectionActions on _QueueTabState {
+  void _selectDraggedTrack(
+    UnifiedLibraryItem item,
+    List<UnifiedLibraryItem> visibleItems,
+  ) {
+    // Holding an already-selected track drags the existing batch without
+    // extending the range back to the selection anchor.
+    if (_isSelectionMode && _selectedIds.contains(item.id)) return;
+    if (_isSelectionMode) {
+      _selectRangeTo(item.id, visibleItems);
+    } else {
+      _enterSelectionMode(item.id);
+    }
+  }
+
+  void _startLibraryTrackDrag() {
+    _setState(() => _isDraggingLibraryTrack = true);
+    _hideSelectionOverlay();
+  }
+
+  void _endLibraryTrackDrag() {
+    if (!mounted) return;
+    _setState(() => _isDraggingLibraryTrack = false);
+  }
+
   void _enterSelectionMode(String itemId) {
     HapticFeedback.mediumImpact();
     _setState(() {
@@ -71,6 +95,7 @@ extension _QueueTabSelectionActions on _QueueTabState {
   }) {
     if (!mounted) return;
     if (_suppressSelectionOverlay ||
+        _isDraggingLibraryTrack ||
         !_isSelectionMode ||
         _isPlaylistSelectionMode) {
       _hideSelectionOverlay();

lib/widgets/library_playlist_drag_source.dart

@@ -0,0 +1,41 @@
+import 'package:flutter/material.dart';
+
+/// Owns the long press for both selection and playlist dragging. The card
+/// inside must not register a competing onLongPress gesture.
+class LibraryPlaylistDragSource<T extends Object> extends StatelessWidget {
+  const LibraryPlaylistDragSource({
+    super.key,
+    required this.data,
+    required this.onSelect,
+    required this.onDragStarted,
+    required this.onDragEnd,
+    required this.feedbackBuilder,
+    required this.child,
+  });
+
+  final T data;
+  final VoidCallback onSelect;
+  final VoidCallback onDragStarted;
+  final VoidCallback onDragEnd;
+  final WidgetBuilder feedbackBuilder;
+  final Widget child;
+
+  @override
+  Widget build(BuildContext context) => Semantics(
+    onLongPress: onSelect,
+    child: LongPressDraggable<T>(
+      data: data,
+      maxSimultaneousDrags: 1,
+      hapticFeedbackOnStart: false,
+      onDragStarted: () {
+        onDragStarted();
+        onSelect();
+      },
+      onDragEnd: (_) => onDragEnd(),
+      // Build after onSelect so the feedback reflects the selected batch.
+      feedback: Builder(builder: feedbackBuilder),
+      childWhenDragging: Opacity(opacity: 0.4, child: child),
+      child: child,
+    ),
+  );
+}

test/library_playlist_drag_test.dart

@@ -0,0 +1,118 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:spotiflac_android/l10n/l10n.dart';
+import 'package:spotiflac_android/theme/app_theme.dart';
+import 'package:spotiflac_android/widgets/library_playlist_drag_source.dart';
+import 'package:spotiflac_android/widgets/track_card.dart';
+
+void main() {
+  for (final grid in [false, true]) {
+    testWidgets('Material ${grid ? 'grid' : 'list'} selects and drops tracks', (
+      tester,
+    ) async {
+      tester.view.physicalSize = const Size(800, 1000);
+      tester.view.devicePixelRatio = 1;
+      addTearDown(tester.view.reset);
+      final selected = <String>{};
+      final playlist = <String>[];
+      final dropped = <String>[];
+      var taps = 0;
+      var dragging = false;
+      await tester.pumpWidget(
+        MaterialApp(
+          theme: AppTheme.light(),
+          localizationsDelegates: AppLocalizations.localizationsDelegates,
+          supportedLocales: AppLocalizations.supportedLocales,
+          home: Scaffold(
+            body: StatefulBuilder(
+              builder: (context, setState) => Column(
+                children: [
+                  DragTarget<String>(
+                    onAcceptWithDetails: (details) {
+                      dropped.add(details.data);
+                      playlist.addAll(selected);
+                    },
+                    builder: (_, candidates, _) => SizedBox(
+                      key: const ValueKey('playlist'),
+                      width: 240,
+                      height: 100,
+                      child: Text(
+                        candidates.isEmpty ? 'Playlist' : 'Drop here',
+                      ),
+                    ),
+                  ),
+                  for (final id in ['a', 'b'])
+                    SizedBox(
+                      width: 240,
+                      height: grid ? 280 : 100,
+                      child: LibraryPlaylistDragSource<String>(
+                        key: ValueKey(id),
+                        data: id,
+                        onSelect: () => setState(() => selected.add(id)),
+                        onDragStarted: () => setState(() => dragging = true),
+                        onDragEnd: () => setState(() => dragging = false),
+                        feedbackBuilder: (_) => Material(
+                          child: Text('Dragging ${selected.length}'),
+                        ),
+                        child: grid
+                            ? TrackGridCard(
+                                cover: const ColoredBox(color: Colors.blue),
+                                title: 'Song $id',
+                                isSelected: selected.contains(id),
+                                onTap: () => taps++,
+                              )
+                            : TrackCard(
+                                leading: const SizedBox.square(dimension: 56),
+                                title: 'Song $id',
+                                isSelectionMode: selected.isNotEmpty,
+                                isSelected: selected.contains(id),
+                                onTap: () => taps++,
+                              ),
+                      ),
+                    ),
+                ],
+              ),
+            ),
+          ),
+        ),
+      );
+      // A normal tap still opens track details.
+      await tester.tap(find.text('Song a'));
+      await tester.pumpAndSettle();
+      expect(taps, 1);
+
+      // Holding without moving selects; releasing outside a target retains it.
+      var gesture = await tester.startGesture(
+        tester.getCenter(find.text('Song a')),
+      );
+      await tester.pump(const Duration(milliseconds: 600));
+      expect(selected, {'a'});
+      expect(dragging, isTrue);
+      expect(find.text('Dragging 1'), findsOneWidget);
+      await gesture.up();
+      await tester.pumpAndSettle();
+      expect(selected, {'a'});
+      expect(playlist, isEmpty);
+      expect(dragging, isFalse);
+
+      // Another hold can select and drag the batch directly onto its playlist.
+      gesture = await tester.startGesture(
+        tester.getCenter(find.text('Song b')),
+      );
+      await tester.pump(const Duration(milliseconds: 600));
+      expect(find.text('Dragging 2'), findsOneWidget);
+      await gesture.moveTo(
+        tester.getCenter(find.byKey(const ValueKey('playlist'))),
+      );
+      await tester.pump();
+      expect(find.text('Drop here'), findsOneWidget);
+      await gesture.up();
+      await tester.pumpAndSettle();
+      expect(playlist, ['a', 'b']);
+      expect(dropped, ['b']);
+      expect(dragging, isFalse);
+      expect(taps, 1);
+      expect(tester.takeException(), isNull);
+    });
+  }
+}