fix(ui): make snackbars transient and replace stale messages

Limit transient messages to three seconds, keep action snackbars on a timer, and provide close controls. Apply one latest-message policy to the app and metadata sheet while preserving glass animations.

lib/app.dart

@@ -14,6 +14,7 @@ import 'package:spotiflac_android/theme/dynamic_color_wrapper.dart';
 import 'package:spotiflac_android/l10n/app_localizations.dart';
 import 'package:spotiflac_android/l10n/supported_locales.dart';
 import 'package:spotiflac_android/utils/adaptive_layout.dart';
+import 'package:spotiflac_android/widgets/app_snack_bar.dart';
 
 String initialLocationForAppState({
   required bool isFirstLaunch,
@@ -203,7 +204,9 @@ class SpotiFLACApp extends ConsumerWidget {
           builder: (context, child) {
             final mediaQuery = MediaQuery.of(context);
             final appContent = _OrientationFade(
-              child: child ?? const SizedBox.shrink(),
+              child: AppScaffoldMessenger(
+                child: child ?? const SizedBox.shrink(),
+              ),
             );
             return MediaQuery(
               data: mediaQuery.copyWith(displayFeatures: const []),

lib/screens/track_metadata_edit_sheet.dart

@@ -2174,7 +2174,7 @@ class _EditMetadataSheetState extends State<_EditMetadataSheet> {
         minChildSize: 0.5,
         maxChildSize: 0.95,
         expand: false,
-        builder: (context, scrollController) => ScaffoldMessenger(
+        builder: (context, scrollController) => AppScaffoldMessenger(
           key: _sheetMessengerKey,
           child: Scaffold(
             backgroundColor: Colors.transparent,

lib/widgets/app_snack_bar.dart

@@ -3,6 +3,73 @@ import 'package:spotiflac_android/l10n/l10n.dart';
 import 'package:spotiflac_android/theme/mornye_theme.dart';
 import 'package:spotiflac_android/widgets/mornye_chrome.dart';
 
+/// Applies the same transient-message policy to existing snackbar call sites.
+/// A new message replaces the old one instead of building a stale FIFO queue.
+class AppScaffoldMessenger extends ScaffoldMessenger {
+  const AppScaffoldMessenger({super.key, required super.child});
+
+  @override
+  ScaffoldMessengerState createState() => _AppScaffoldMessengerState();
+}
+
+class _AppScaffoldMessengerState extends ScaffoldMessengerState {
+  @override
+  ScaffoldFeatureController<SnackBar, SnackBarClosedReason> showSnackBar(
+    SnackBar snackBar, {
+    AnimationStyle? snackBarAnimationStyle,
+  }) {
+    removeCurrentSnackBar();
+    return super.showSnackBar(
+      _TransientSnackBar(snackBar),
+      snackBarAnimationStyle: snackBarAnimationStyle,
+    );
+  }
+}
+
+class _TransientSnackBar extends SnackBar {
+  _TransientSnackBar(this.original)
+    : super(
+        content: original.content,
+        duration: original.duration > const Duration(seconds: 3)
+            ? const Duration(seconds: 3)
+            : original.duration,
+        persist: false,
+      );
+
+  final SnackBar original;
+
+  @override
+  SnackBar withAnimation(Animation<double> newAnimation, {Key? fallbackKey}) {
+    // Delegate first so custom glass animations remain intact.
+    final animated = original.withAnimation(
+      newAnimation,
+      fallbackKey: fallbackKey,
+    );
+    return SnackBar(
+      key: animated.key,
+      content: animated.content,
+      backgroundColor: animated.backgroundColor,
+      elevation: animated.elevation,
+      margin: animated.margin,
+      padding: animated.padding,
+      width: animated.width,
+      shape: animated.shape,
+      hitTestBehavior: animated.hitTestBehavior,
+      behavior: animated.behavior,
+      action: animated.action,
+      actionOverflowThreshold: animated.actionOverflowThreshold,
+      showCloseIcon: animated.showCloseIcon ?? true,
+      closeIconColor: animated.closeIconColor,
+      duration: duration,
+      persist: false,
+      animation: animated.animation,
+      onVisible: animated.onVisible,
+      dismissDirection: animated.dismissDirection,
+      clipBehavior: animated.clipBehavior,
+    );
+  }
+}
+
 /// Reports a failure to open a local file with a plain Material snackbar.
 void showCannotOpenFileSnackBar(BuildContext context, Object error) {
   ScaffoldMessenger.of(context).showSnackBar(
@@ -18,13 +85,19 @@ void showCannotOpenFileSnackBar(BuildContext context, Object error) {
 ScaffoldFeatureController<SnackBar, SnackBarClosedReason> showAppSnackBar(
   BuildContext context, {
   required Widget content,
-  Duration duration = const Duration(seconds: 4),
+  Duration duration = const Duration(seconds: 3),
   SnackBarBehavior? behavior,
 }) {
   final messenger = ScaffoldMessenger.of(context);
   if (!context.isMornye) {
     return messenger.showSnackBar(
-      SnackBar(content: content, duration: duration, behavior: behavior),
+      SnackBar(
+        content: content,
+        duration: duration,
+        behavior: behavior,
+        persist: false,
+        showCloseIcon: true,
+      ),
     );
   }
   final theme = Theme.of(context);
@@ -44,7 +117,17 @@ ScaffoldFeatureController<SnackBar, SnackBarClosedReason> showAppSnackBar(
             style: theme.textTheme.bodyMedium!.copyWith(
               color: theme.colorScheme.onSurface,
             ),
-            child: content,
+            child: Row(
+              children: [
+                Expanded(child: content),
+                IconButton(
+                  tooltip: MaterialLocalizations.of(context).closeButtonTooltip,
+                  color: theme.colorScheme.onSurface,
+                  onPressed: messenger.hideCurrentSnackBar,
+                  icon: const Icon(Icons.close, size: 20),
+                ),
+              ],
+            ),
           ),
         ),
       ),
@@ -63,6 +146,8 @@ class _MornyeSnackBar extends SnackBar {
          backgroundColor: Colors.transparent,
          elevation: 0,
          clipBehavior: Clip.none,
+         persist: false,
+         showCloseIcon: false,
          padding: EdgeInsets.zero,
          margin: const EdgeInsets.fromLTRB(20, 8, 20, 12),
          shape: const RoundedRectangleBorder(
@@ -79,6 +164,8 @@ class _MornyeSnackBar extends SnackBar {
     return SnackBar(
       key: key ?? fallbackKey,
       duration: duration,
+      persist: false,
+      showCloseIcon: false,
       behavior: behavior,
       backgroundColor: backgroundColor,
       elevation: elevation,

lib/widgets/view_queue_snackbar_action.dart

@@ -18,6 +18,9 @@ void showAddedToQueueSnackBar(BuildContext context, String trackName) {
     SnackBar(
       content: Text(context.l10n.snackbarAddedToQueue(trackName)),
       action: buildViewQueueSnackBarAction(context),
+      duration: const Duration(seconds: 3),
+      persist: false,
+      showCloseIcon: true,
     ),
   );
 }

test/app_snack_bar_test.dart

@@ -4,9 +4,11 @@ import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:spotiflac_android/l10n/l10n.dart';
 import 'package:spotiflac_android/theme/mornye_theme.dart';
 import 'package:spotiflac_android/widgets/app_snack_bar.dart';
 import 'package:spotiflac_android/widgets/mornye_chrome.dart';
+import 'package:spotiflac_android/widgets/view_queue_snackbar_action.dart';
 
 void main() {
   for (final brightness in Brightness.values) {
@@ -22,7 +24,10 @@ void main() {
         ProviderScope(
           child: MaterialApp(
             theme: MornyeTheme.build(brightness),
-            builder: (_, child) => RepaintBoundary(key: capture, child: child),
+            builder: (_, child) => RepaintBoundary(
+              key: capture,
+              child: AppScaffoldMessenger(child: child!),
+            ),
             home: Builder(
               builder: (context) => Scaffold(
                 body: Stack(
@@ -102,13 +107,14 @@ void main() {
 
   for (final mornye in [true, false]) {
     testWidgets(
-      'messages still queue, time out and dismiss (Mornye: $mornye)',
+      'new messages replace old ones and still dismiss (Mornye: $mornye)',
       (tester) async {
         late BuildContext messageContext;
         await tester.pumpWidget(
           ProviderScope(
             child: MaterialApp(
               theme: mornye ? MornyeTheme.build(Brightness.dark) : ThemeData(),
+              builder: (_, child) => AppScaffoldMessenger(child: child!),
               home: Builder(
                 builder: (context) {
                   messageContext = context;
@@ -123,16 +129,15 @@ void main() {
           content: const Text('First'),
           duration: const Duration(seconds: 1),
         );
+        await tester.pumpAndSettle();
+        expect(find.text('First'), findsOneWidget);
         final second = showAppSnackBar(
           messageContext,
           content: const Text('Second'),
         );
         await tester.pumpAndSettle();
-        expect(find.text('First'), findsOneWidget);
-        expect(find.text('Second'), findsNothing);
-        await tester.pump(const Duration(seconds: 1));
-        await tester.pumpAndSettle();
-        expect(await first.closed, SnackBarClosedReason.timeout);
+        expect(await first.closed, SnackBarClosedReason.remove);
+        expect(find.text('First'), findsNothing);
         expect(find.text('Second'), findsOneWidget);
         await tester.drag(find.text('Second'), const Offset(0, 300));
         await tester.pumpAndSettle();
@@ -141,5 +146,79 @@ void main() {
         expect(tester.takeException(), isNull);
       },
     );
+
+    testWidgets('View Queue times out and has a close button ($mornye)', (
+      tester,
+    ) async {
+      late BuildContext messageContext;
+      await tester.pumpWidget(
+        ProviderScope(
+          child: MaterialApp(
+            theme: mornye ? MornyeTheme.build(Brightness.dark) : ThemeData(),
+            builder: (_, child) => AppScaffoldMessenger(child: child!),
+            localizationsDelegates: AppLocalizations.localizationsDelegates,
+            supportedLocales: AppLocalizations.supportedLocales,
+            home: Builder(
+              builder: (context) {
+                messageContext = context;
+                return const Scaffold(body: SizedBox.expand());
+              },
+            ),
+          ),
+        ),
+      );
+      showAddedToQueueSnackBar(messageContext, 'Track');
+      await tester.pumpAndSettle();
+      expect(find.text('View Queue'), findsOneWidget);
+      expect(find.byTooltip('Close'), findsOneWidget);
+      await tester.pump(const Duration(seconds: 3));
+      await tester.pumpAndSettle();
+      expect(find.byType(SnackBar), findsNothing);
+
+      showAddedToQueueSnackBar(messageContext, 'Another track');
+      await tester.pumpAndSettle();
+      await tester.tap(find.byTooltip('Close'));
+      await tester.pumpAndSettle();
+      expect(find.byType(SnackBar), findsNothing);
+      expect(tester.takeException(), isNull);
+    });
   }
+
+  testWidgets('rapid messages never leave a backlog or persist an action', (
+    tester,
+  ) async {
+    late BuildContext messageContext;
+    await tester.pumpWidget(
+      MaterialApp(
+        builder: (_, child) => AppScaffoldMessenger(child: child!),
+        home: Builder(
+          builder: (context) {
+            messageContext = context;
+            return const Scaffold(body: SizedBox.expand());
+          },
+        ),
+      ),
+    );
+    final controllers = [
+      for (var i = 0; i < 10; i++)
+        ScaffoldMessenger.of(messageContext).showSnackBar(
+          SnackBar(
+            content: Text('Message $i'),
+            action: SnackBarAction(label: 'Action', onPressed: () {}),
+            duration: const Duration(minutes: 1),
+          ),
+        ),
+    ];
+    await tester.pumpAndSettle();
+    expect(find.text('Message 9'), findsOneWidget);
+    expect(find.text('Message 0'), findsNothing);
+    for (final controller in controllers.take(9)) {
+      expect(await controller.closed, SnackBarClosedReason.remove);
+    }
+    await tester.pump(const Duration(seconds: 3));
+    await tester.pumpAndSettle();
+    expect(await controllers.last.closed, SnackBarClosedReason.timeout);
+    expect(find.byType(SnackBar), findsNothing);
+    expect(tester.takeException(), isNull);
+  });
 }