Sounds: survive an audio device that crashes the app on open

A Windows friend's 1.3.0 dies about a second in on every start, right
around the 2 s audio warm-up (no Dart error, no close lines). Opening the
device is now logged and leaves audio-init.pending until it returns; a
start that finds it skips sounds instead of crashing again, and a sound
preview in Settings tries once more.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/desktop/lib/main.dart

@@ -49,6 +49,8 @@ Future<void> main(List<String> args) async {
   await AppSettings.instance.ensureLoaded();
   // The composition root: every system, made once.
   final graph = AppGraph.build();
+  // Sounds stay off after an audio-device crash (see SoundEngine.crashMark).
+  graph.sfx.engine.crashMark = '${dirs.support}${Platform.pathSeparator}audio-init.pending';
   final ports = graph.ports;
   // Close button / Alt+F4: the orderly close ([shutDownApp]), so others
   // see "left", your server shuts down and no player outlives the engine.

apps/desktop/lib/src/platform/audio/sound_engine.dart

@@ -1,4 +1,5 @@
 import 'dart:async';
+import 'dart:io';
 import 'dart:typed_data';
 
 import 'package:flutter_soloud/flutter_soloud.dart';
@@ -50,6 +51,13 @@ class SoundEngine {
 
   Future<bool>? _ready;
   var _disposed = false;
+
+  /// A file that exists only while the audio device is opening (set by the
+  /// app). Found at the next start, the last open took the app down (a
+  /// native crash in the driver or miniaudio, seen on Windows): sounds stay
+  /// off rather than crash every start, until [retry] (Settings' preview).
+  String? crashMark;
+  var _skipped = false;
   /// Per slot: the loaded key and its sound (null: failed to load).
   final Map<String, (String, Future<Object?>)> _slots = {};
   /// Load names are unique: SoLoud hands back the old sound for a name it
@@ -61,15 +69,43 @@ class SoundEngine {
 
   Future<bool> _init() async {
     if (_disposed) return false;
+    final mark = crashMark == null ? null : File(crashMark!);
+    try {
+      if (mark != null && mark.existsSync()) {
+        _skipped = true;
+        _log.warning('no sounds: opening the audio device crashed the app last time '
+            '(${mark.path}); a sound preview in Settings tries again');
+        return false;
+      }
+      mark?.writeAsStringSync('opening the audio device');
+    } catch (_) {}
+    _log.info('opening the audio device');
     try {
       await _backend.init();
+      _log.info('audio device open');
       return true;
     } catch (e) {
       _log.warning('no sounds: audio init failed: $e');
       return false;
+    } finally {
+      try {
+        if (mark != null && mark.existsSync()) mark.deleteSync();
+      } catch (_) {}
     }
   }
 
+  /// Opens the device again after a crash mark kept sounds off (the user
+  /// asked for a sound). A real crash leaves the mark again.
+  void retry() {
+    if (!_skipped) return;
+    _skipped = false;
+    try {
+      final m = crashMark;
+      if (m != null) File(m).deleteSync();
+    } catch (_) {}
+    _ready = null;
+  }
+
   /// Plays the sound of [slot] at [volume] (linear gain). [key] names what
   /// [wav] renders: the same key reuses the loaded sound; another key, or
   /// [fresh], renders and loads it again.

apps/desktop/lib/src/sfx/synth_sfx.dart

@@ -37,8 +37,11 @@ class SynthSfx implements SfxService {
 
   /// Plays [kind] even when it is switched off (Settings' preview), always
   /// freshly rendered: an edited spec plays after a hot reload.
-  Future<void> preview(SfxKind kind, {int readyIndex = 1, SoundPreset? preset}) =>
-      _play(kind, readyIndex, preset ?? presetFor(kind), fresh: true);
+  Future<void> preview(SfxKind kind, {int readyIndex = 1, SoundPreset? preset}) {
+    // Asked for: try the device again even after a crash kept it closed.
+    engine.retry();
+    return _play(kind, readyIndex, preset ?? presetFor(kind), fresh: true);
+  }
 
   /// One slot per sound and ready step: a new preset replaces it.
   Future<void> _play(SfxKind kind, int readyIndex, SoundPreset preset, {bool fresh = false}) {

apps/desktop/test/sound_engine_test.dart

@@ -1,3 +1,4 @@
+import 'dart:io';
 import 'dart:typed_data';
 
 import 'package:flutter_test/flutter_test.dart';
@@ -147,4 +148,46 @@ void main() {
       expect(b.deinits, 1);
     });
   });
+
+  group('crash mark', () {
+    late Directory dir;
+    setUp(() => dir = Directory.systemTemp.createTempSync('sound_mark'));
+    tearDown(() => dir.deleteSync(recursive: true));
+
+    test('exists only while the device opens', () async {
+      final mark = '${dir.path}/audio-init.pending';
+      var seen = false;
+      final b = _MarkBackend(() => seen = File(mark).existsSync());
+      final e = SoundEngine(backend: b)..crashMark = mark;
+      expect(await e.warmUp(), isTrue);
+      expect(seen, isTrue, reason: 'there while opening');
+      expect(File(mark).existsSync(), isFalse, reason: 'gone once open');
+    });
+
+    test('left by a crash: sounds stay off, a preview tries again', () async {
+      final mark = '${dir.path}/audio-init.pending';
+      File(mark).writeAsStringSync('opening the audio device');
+      final b = _FakeBackend();
+      final e = SoundEngine(backend: b)..crashMark = mark;
+      await e.play('chat', 'k', _bytes, volume: 1);
+      expect(b.inits, 0, reason: 'never opened after a crash');
+      expect(b.plays, isEmpty);
+      e.retry();
+      await e.play('chat', 'k', _bytes, volume: 1);
+      expect(b.inits, 1);
+      expect(b.plays, hasLength(1));
+      expect(File(mark).existsSync(), isFalse);
+    });
+  });
+}
+
+class _MarkBackend extends _FakeBackend {
+  final void Function() onInit;
+  _MarkBackend(this.onInit);
+
+  @override
+  Future<void> init() async {
+    onInit();
+    await super.init();
+  }
 }