[desktop_multi_window] Failed to send message on startup

[subzero911]

the app seemingly works correct, but I always have this message on startup

embedder.cc (2977): 'FlutterEngineSendPlatformMessage' returned 'kInvalidArguments'. Invalid engine handle.
2025-11-09 20:27:01.620 foilcap_app[78298:125658879] Failed to send message to Flutter engine on channel 'mixin.one/desktop_multi_window' (2).
2025-11-09 20:27:01.624 foilcap_app[78298:125658879] Running with merged UI and platform thread. Experimental.

My main.dart:

void main(List<String> args) async {
  WidgetsFlutterBinding.ensureInitialized();

  // Get the current window controller (for multi-window initialization)
  final windowController = await WindowController.fromCurrentEngine();

  print('window id: ${windowController.windowId}');
  print('window args: ${windowController.arguments}');

  // Parse arguments to determine window position and UUID
  Offset? windowPosition;
  String? windowUuid;
  
  if (windowController.arguments.isNotEmpty) {
    // This is an additional window - parse arguments
    try {
      final parts = windowController.arguments.split(',');
      if (parts.length >= 2) {
        final x = double.parse(parts[0]);
        final y = double.parse(parts[1]);
        windowPosition = Offset(x, y);
        
        // If there's a third parameter - it's the UUID
        if (parts.length >= 3) {
          windowUuid = parts[2];
        }
      }
    } catch (e) {
      print('Error parsing window arguments: $e');
    }
  } else {
    // This is the main window - check for temporary files
    final tempFiles = await SaveLoadStore.getAllTempFiles();
    if (tempFiles.isNotEmpty) {
      // Use UUID from the first temporary file for the main window
      final firstFile = tempFiles[0];
      final fileName = firstFile.path.split('/').last;
      windowUuid = fileName.replaceAll('.tmp.cap', '');
      print('Main window using UUID from first temp file: $windowUuid');
      
      // Create additional windows for remaining temporary files
      await _restoreWindowsFromTempFiles();
    }
  }

  // Initialize window manager
  await windowManager.ensureInitialized();

  WindowOptions windowOptions = WindowOptions(
    size: const Size(800, 600),
    minimumSize: const Size(640, 480),
    center: windowPosition == null, // Center only if position is not specified
    backgroundColor: Colors.transparent,
    skipTaskbar: false,
    titleBarStyle: TitleBarStyle.normal,
    title: 'FoilCap',
  );

  windowManager.waitUntilReadyToShow(windowOptions, () async {
    // If position is specified, set it
    if (windowPosition != null) {
      await windowManager.setPosition(windowPosition);
    }
    // Enable close interception to show save dialog
    await windowManager.setPreventClose(true);
    await windowManager.show();
    await windowManager.focus();
  });

  runApp(
    .....
    ),
  );
}

/// Restores windows from autosave temporary files
Future<void> _restoreWindowsFromTempFiles() async {
  try {
    final tempFiles = await SaveLoadStore.getAllTempFiles();
    print('Found temporary files: ${tempFiles.length}');

    if (tempFiles.isEmpty) {
      return;
    }

    // Create additional windows for each temporary file (except the first one)
    // The first file will be loaded in the main window automatically
    for (int i = 1; i < tempFiles.length; i++) {
      final file = tempFiles[i];
      // Extract UUID from filename (format: {uuid}.tmp.cap)
      final fileName = file.path.split('/').last;
      final uuid = fileName.replaceAll('.tmp.cap', '');
      
      final offset = 30.0 * i;
      await WindowController.create(
        WindowConfiguration(
          hiddenAtLaunch: false,
          arguments: '$offset,$offset,$uuid', // Pass position and UUID
        ),
      );
    }
  } catch (e) {
    print('Error restoring windows: $e');
  }
}