Check for existing instance on startup using sockets.

lib/desktop/single_instance.dart

@@ -0,0 +1,79 @@
+import 'dart:io';
+import 'package:logging/logging.dart';
+import 'package:path/path.dart' as path;
+
+import 'package:path_provider/path_provider.dart';
+import 'package:window_manager/window_manager.dart';
+
+const _lockFileName = 'lockfile';
+const _pingMessage = 'YA-PING';
+const _pongMessage = 'YA-PONG';
+
+final log = Logger('single_instance');
+
+void _startServer(File lockfile) async {
+  ServerSocket socket;
+  if (Platform.isWindows) {
+    socket = await ServerSocket.bind(InternetAddress.loopbackIPv4, 0);
+    lockfile.writeAsString('${socket.port}');
+  } else {
+    socket = await ServerSocket.bind(
+        InternetAddress(lockfile.path, type: InternetAddressType.unix), 0);
+  }
+
+  log.info('Lock file and socket created.');
+  socket.listen((client) {
+    client.listen((data) async {
+      final message = String.fromCharCodes(data);
+      if (message == _pingMessage) {
+        log.info('Got incomming connection');
+
+        if (!await WindowManager.instance.isMinimized()) {
+          await WindowManager.instance.setAlwaysOnTop(true);
+          await WindowManager.instance.setAlwaysOnTop(false);
+        } else {
+          await WindowManager.instance.restore();
+        }
+
+        // This doesn't seem to always work
+        await WindowManager.instance.focus();
+        client.write(_pongMessage);
+      }
+      client.close();
+    }, cancelOnError: true);
+  });
+}
+
+Future<void> ensureSingleInstance() async {
+  final appSupport = await getApplicationSupportDirectory();
+  final lockfile = File(path.join(appSupport.path, _lockFileName));
+  log.info('Lock file: $lockfile');
+
+  if (await lockfile.exists()) {
+    try {
+      Socket client;
+      if (Platform.isWindows) {
+        final port = int.parse(await lockfile.readAsString());
+        client = await Socket.connect(InternetAddress.loopbackIPv4, port);
+      } else {
+        client = await Socket.connect(
+            InternetAddress(lockfile.path, type: InternetAddressType.unix), 0);
+      }
+      client.write(_pingMessage);
+      await client.flush();
+      client.listen((data) async {
+        final message = String.fromCharCodes(data);
+        await client.close();
+        if (message == _pongMessage) {
+          log.info('Other application instance already running, exit.');
+          exit(0);
+        }
+      }, cancelOnError: true);
+    } on Exception {
+      await lockfile.delete();
+      _startServer(lockfile);
+    }
+  } else {
+    _startServer(lockfile);
+  }
+}

lib/main.dart

@@ -6,6 +6,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:logging/logging.dart';
 import 'package:window_manager/window_manager.dart';
+import 'package:yubico_authenticator/desktop/single_instance.dart';
 
 import 'app/app.dart';
 import 'app/views/main_page.dart';
@@ -17,7 +18,11 @@ import 'error_page.dart';
 final log = Logger('main');
 
 void main() async {
+  _initLogging(Level.INFO);
+
   WidgetsFlutterBinding.ensureInitialized();
+  log.info('Ensuring single instance...');
+  await ensureSingleInstance();
   await windowManager.ensureInitialized();
 
   // Either use the _YKMAN_EXE environment variable, or look relative to executable.
@@ -43,8 +48,8 @@ void main() async {
   try {
     var rpc = await RpcSession.launch(exe!);
     // Enable logging TODO: Make this configurable
-    _initLogging(Level.INFO, rpc);
     log.info('ykman process started', exe);
+    rpc.setLogLevel(Logger.root.level);
     overrides.add(rpcProvider.overrideWithValue(rpc));
     page = const MainPage();
   } catch (e) {
@@ -52,8 +57,8 @@ void main() async {
     page = ErrorPage(error: e.toString());
   }
 
-  // Only MacOS supports hiding the window at start currently.
-  // For now, this size should match windows/runner/main.cpp and linux/flutter/my_application.cc
+  // Linux doesn't currently support hiding the window at start currently.
+  // For now, this size should match linux/flutter/my_application.cc to avoid window flicker at startup.
   windowManager.waitUntilReadyToShow().then((_) async {
     await windowManager.setSize(const Size(400, 720));
     windowManager.show();
@@ -65,7 +70,7 @@ void main() async {
   ));
 }
 
-void _initLogging(Level level, RpcSession rpc) {
+void _initLogging(Level level) {
   //TODO: Add support for logging to stderr and file
   Logger.root.onRecord.listen((record) {
     developer.log(
@@ -78,7 +83,6 @@ void _initLogging(Level level, RpcSession rpc) {
   });
 
   Logger.root.level = level;
-  rpc.setLogLevel(level);
 }
 
 //TODO: Remove below this

macos/Flutter/GeneratedPluginRegistrant.swift

@@ -5,10 +5,12 @@
 import FlutterMacOS
 import Foundation
 
+import path_provider_macos
 import shared_preferences_macos
 import window_manager
 
 func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
+  PathProviderPlugin.register(with: registry.registrar(forPlugin: "PathProviderPlugin"))
   SharedPreferencesPlugin.register(with: registry.registrar(forPlugin: "SharedPreferencesPlugin"))
   WindowManagerPlugin.register(with: registry.registrar(forPlugin: "WindowManagerPlugin"))
 }

pubspec.lock

@@ -352,6 +352,27 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "1.8.0"
+  path_provider:
+    dependency: "direct main"
+    description:
+      name: path_provider
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.8"
+  path_provider_android:
+    dependency: transitive
+    description:
+      name: path_provider_android
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.11"
+  path_provider_ios:
+    dependency: transitive
+    description:
+      name: path_provider_ios
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.7"
   path_provider_linux:
     dependency: transitive
     description:
@@ -359,6 +380,13 @@ packages:
       url: "https://pub.dartlang.org"
     source: hosted
     version: "2.1.5"
+  path_provider_macos:
+    dependency: transitive
+    description:
+      name: path_provider_macos
+      url: "https://pub.dartlang.org"
+    source: hosted
+    version: "2.0.5"
   path_provider_platform_interface:
     dependency: transitive
     description:

pubspec.yaml

@@ -37,6 +37,7 @@ dependencies:
 
   async: ^2.8.2
   logging: ^1.0.2
+  path_provider: ^2.0.8
   shared_preferences: ^2.0.12
   flutter_riverpod: ^1.0.0
   json_annotation: ^4.4.0

windows/runner/win32_window.cpp

@@ -117,7 +117,8 @@ bool Win32Window::CreateAndShow(const std::wstring& title,
   double scale_factor = dpi / 96.0;
 
   HWND window = CreateWindow(
-      window_class, title.c_str(), WS_OVERLAPPEDWINDOW | WS_VISIBLE,
+      //original line: window_class, title.c_str(), WS_OVERLAPPEDWINDOW | WS_VISIBLE,
+      window_class, title.c_str(), WS_OVERLAPPEDWINDOW,
       Scale(origin.x, scale_factor), Scale(origin.y, scale_factor),
       Scale(size.width, scale_factor), Scale(size.height, scale_factor),
       nullptr, nullptr, GetModuleHandle(nullptr), this);