CursorLang.Agent.Tests/EndToEndTests.cs

@@ -133,6 +133,34 @@ public sealed partial class EndToEndTests
         Assert.False(launch.Process.HasExited);
     }
 
+    /// <summary>
+    /// "Exit" in the tray menu ends the application whole: the settings window goes with
+    /// the agent instead of staying on the screen belonging to nothing.
+    /// </summary>
+    /// <remarks>
+    /// The menu itself is out of reach of a test — it is a <c>TrackPopupMenuEx</c> menu
+    /// with a modal loop of its own — so what is checked is the request the menu makes.
+    /// The settings window here is the real one, started by the agent, and it must be
+    /// listening by the time it is on the screen.
+    /// </remarks>
+    [Fact]
+    public void The_agents_exit_closes_the_settings_window()
+    {
+        using Launch launch = Launch.Start();
+        launch.WaitForSettingsWindow();
+
+        Process settings = Launch.SettingsProcesses().Single();
+        try
+        {
+            Assert.True(SettingsCloseSignal.RequestClose(), "the settings window was not listening");
+            Assert.True(settings.WaitForExit(ExitTimeout), "the settings window outlived the agent's exit");
+        }
+        finally
+        {
+            settings.Dispose();
+        }
+    }
+
     /// <summary>A started application that shuts down together with the check.</summary>
     private sealed class Launch : IDisposable
     {

CursorLang.Agent/Agent.cs

@@ -125,5 +125,12 @@ internal sealed class Agent : IDisposable
 
     private void OnOpenRequested(object? sender, EventArgs e) => SettingsLauncher.Open();
 
-    private void OnExitRequested(object? sender, EventArgs e) => _window.Quit();
+    // "Exit" means the application, not just the background half of it. A settings
+    // window left open would outlive the tray icon it was opened from, so it is asked
+    // to close first — it may be the very window the user is looking at
+    private void OnExitRequested(object? sender, EventArgs e)
+    {
+        SettingsCloseSignal.RequestClose();
+        _window.Quit();
+    }
 }

CursorLang.Core.Tests/Services/SettingsCloseSignalTests.cs

@@ -0,0 +1,115 @@
+using System.Collections.Concurrent;
+using CursorLang.Core.Services;
+using CursorLang.Tests.Shared;
+
+namespace CursorLang.Core.Tests.Services;
+
+/// <summary>
+/// The one thing the agent says to the settings window: quit with me.
+/// </summary>
+/// <remarks>
+/// The event names here are the tests' own. The application's name is fixed, and a test
+/// listening on it would answer for a settings window someone is using — or, signalling,
+/// close it.
+/// </remarks>
+public sealed class SettingsCloseSignalTests
+{
+    [Fact]
+    public void The_request_reaches_the_settings_window()
+    {
+        string suffix = UniqueSuffix();
+        var signal = new SettingsCloseSignal(suffix);
+
+        ConcurrentQueue<EventArgs> requests = new();
+        signal.CloseRequested += (_, e) => requests.Enqueue(e);
+
+        try
+        {
+            signal.Listen();
+
+            Assert.True(RequestApart(suffix), "the request found nobody listening");
+            Pump.WaitFor(() => !requests.IsEmpty, "the settings window got the request to close");
+        }
+        finally
+        {
+            signal.Dispose();
+        }
+    }
+
+    // The usual case: the user quits from the tray with no settings window on the screen
+    [Fact]
+    public void A_request_with_no_settings_window_open_passes_without_consequence()
+    {
+        Assert.False(RequestApart(UniqueSuffix()));
+    }
+
+    // The window has closed on its own, and the process is on its way out anyway
+    [Fact]
+    public void No_request_arrives_after_the_window_is_gone()
+    {
+        string suffix = UniqueSuffix();
+        var signal = new SettingsCloseSignal(suffix);
+
+        ConcurrentQueue<EventArgs> requests = new();
+        signal.CloseRequested += (_, e) => requests.Enqueue(e);
+
+        signal.Listen();
+        signal.Dispose();
+
+        RequestApart(suffix);
+        Pump.Pause(TimeSpan.FromMilliseconds(80));
+
+        Assert.Empty(requests);
+    }
+
+    [Fact]
+    public void Listening_twice_leaves_one_listener()
+    {
+        string suffix = UniqueSuffix();
+        var signal = new SettingsCloseSignal(suffix);
+
+        var requests = 0;
+        signal.CloseRequested += (_, _) => Interlocked.Increment(ref requests);
+
+        try
+        {
+            signal.Listen();
+            signal.Listen();
+
+            Assert.True(RequestApart(suffix));
+            Pump.WaitFor(() => Volatile.Read(ref requests) > 0, "the request arrived");
+            Pump.Pause(TimeSpan.FromMilliseconds(80));
+
+            Assert.Equal(1, Volatile.Read(ref requests));
+        }
+        finally
+        {
+            signal.Dispose();
+        }
+    }
+
+    [Fact]
+    public void Closing_without_listening_passes_without_consequence()
+    {
+        var signal = new SettingsCloseSignal(UniqueSuffix());
+
+        signal.Dispose();
+        signal.Dispose();
+    }
+
+    // Every test gets a namespace of kernel objects of its own
+    private static string UniqueSuffix() => "." + Guid.NewGuid().ToString("N");
+
+    /// <summary>
+    /// Asks for the close the way the agent does it — from another process, and here
+    /// from another thread, which is as foreign as a test can get.
+    /// </summary>
+    private static bool RequestApart(string suffix)
+    {
+        var heard = false;
+
+        Pump.RunApart(() => heard = SettingsCloseSignal.RequestClose(suffix));
+
+        return heard;
+    }
+}

CursorLang.Core/Services/SettingsCloseSignal.cs

@@ -0,0 +1,98 @@
+namespace CursorLang.Core.Services;
+
+/// <summary>
+/// Tells the settings window that the agent is quitting and it is to close with it.
+/// </summary>
+/// <remarks>
+/// The one thing the agent says to the settings window, and the mirror image of
+/// <see cref="SettingsSignal"/>. "Exit" in the tray menu means the application is done
+/// with, and a settings window left alone on the screen after it is a window belonging
+/// to nothing: the tray icon it was opened from is gone, and closing it would be the
+/// user's only remaining move.
+///
+/// A named event rather than a window message, because the agent has no handle to send
+/// one to: the settings window lives in a process the agent starts and deliberately
+/// does not keep hold of. The name has no <c>Global</c> prefix, so it lives in the
+/// session namespace — same reasoning as <see cref="SingleInstanceGate"/>, and the same
+/// consequence: with fast user switching each user's halves talk to their own.
+///
+/// Only the settings window creates the object; the agent opens what is already there
+/// and stays silent when there is nothing. Were it the other way round, the request
+/// would sit in an auto-reset event waiting for the next settings window to open and
+/// close it the moment it did.
+/// </remarks>
+internal sealed class SettingsCloseSignal : IDisposable
+{
+    private const string EventName = "CursorLang.CloseSettings";
+
+    private readonly string _eventName;
+
+    private EventWaitHandle? _request;
+    private RegisteredWaitHandle? _wait;
+
+    /// <summary>
+    /// Listens on the name the two halves agree on.
+    /// </summary>
+    /// <param name="nameSuffix">
+    /// A namespace of its own. Empty for the application; the tests pass one so that
+    /// they do not answer for — or worse, close — a settings window someone is using.
+    /// </param>
+    internal SettingsCloseSignal(string nameSuffix = "") => _eventName = EventName + nameSuffix;
+
+    /// <summary>The agent asks for the window to be closed.</summary>
+    /// <remarks>
+    /// Raised on a thread pool thread, wherever the wait happened to be answered — a
+    /// window obeys only its own, so the handler has to get back to it.
+    /// </remarks>
+    internal event EventHandler? CloseRequested;
+
+    /// <summary>
+    /// Asks the settings window of this session, if one is open, to close. Silence is
+    /// a normal answer: most of the time the user quits with no window on the screen.
+    /// </summary>
+    /// <returns>Whether there was anybody to hear it.</returns>
+    internal static bool RequestClose(string nameSuffix = "")
+    {
+        if (!EventWaitHandle.TryOpenExisting(EventName + nameSuffix, out EventWaitHandle? request))
+        {
+            return false;
+        }
+
+        using (request)
+        {
+            return request.Set();
+        }
+    }
+
+    /// <summary>Starts waiting for the request. Called once, by the settings window.</summary>
+    internal void Listen()
+    {
+        if (_request is not null)
+        {
+            return;
+        }
+
+        _request = new EventWaitHandle(false, EventResetMode.AutoReset, _eventName);
+
+        // As in the gate: the thread pool holds the wait, there is no reason to keep a
+        // thread of our own for a request that may never come
+        _wait = ThreadPool.RegisterWaitForSingleObject(
+            _request,
+            OnCloseSignalled,
+            state: null,
+            Timeout.Infinite,
+            executeOnlyOnce: false);
+    }
+
+    public void Dispose()
+    {
+        _wait?.Unregister(null);
+        _wait = null;
+
+        _request?.Dispose();
+        _request = null;
+    }
+
+    private void OnCloseSignalled(object? state, bool timedOut) =>
+        CloseRequested?.Invoke(this, EventArgs.Empty);
+}

CursorLang.Settings/App.xaml.cs

@@ -26,6 +26,7 @@ public partial class App : Application
 {
     private ServiceProvider? _services;
     private SingleInstanceGate? _instanceGate;
+    private SettingsCloseSignal? _closeSignal;
 
     protected override void OnStartup(StartupEventArgs e)
     {
@@ -42,6 +43,10 @@ public partial class App : Application
         _instanceGate = gate;
         _instanceGate.ActivationRequested += OnActivationRequested;
 
+        _closeSignal = new SettingsCloseSignal();
+        _closeSignal.CloseRequested += OnCloseRequested;
+        _closeSignal.Listen();
+
         var services = new ServiceCollection();
         ConfigureServices(services);
         _services = services.BuildServiceProvider();
@@ -61,6 +66,12 @@ public partial class App : Application
     {
         _services?.Dispose();
 
+        if (_closeSignal is not null)
+        {
+            _closeSignal.CloseRequested -= OnCloseRequested;
+            _closeSignal.Dispose();
+        }
+
         if (_instanceGate is not null)
         {
             _instanceGate.ActivationRequested -= OnActivationRequested;
@@ -95,6 +106,27 @@ public partial class App : Application
     private void OnActivationRequested(object? sender, EventArgs e) =>
         Dispatcher.BeginInvoke(ShowMainWindow);
 
+    // The agent is quitting. Answered on a thread pool thread, and the window is closed
+    // on its own one
+    private void OnCloseRequested(object? sender, EventArgs e) =>
+        Dispatcher.BeginInvoke(CloseMainWindow);
+
+    /// <summary>
+    /// Closes the window the way the title bar button does, so that everything hanging
+    /// off closing happens; <see cref="ShutdownMode.OnMainWindowClose"/> ends the process
+    /// after it. Without a window there is nothing to close and the process simply ends.
+    /// </summary>
+    private void CloseMainWindow()
+    {
+        if (MainWindow is { } window)
+        {
+            window.Close();
+            return;
+        }
+
+        Shutdown();
+    }
+
     private void ShowMainWindow()
     {
         if (MainWindow is not { } window)

README.RU.md

@@ -84,20 +84,28 @@ MSIX всегда выполняются в контексте вошедшег
 раскладкой. Без UI, и так должно остаться: всё, что попадёт туда, попадёт и
 в фоновый процесс.
 
-Связь между ними — только `settings.json`. Окно пишет его целиком, во временный
+Всё, что окно сообщает агенту, идёт только через `settings.json`. Окно пишет его
-файл, который одним движением встаёт на место, и посылает агенту
+целиком, во временный файл, который одним движением встаёт на место, и посылает
-зарегистрированное оконное сообщение, по которому тот перечитывает файл.
+агенту зарегистрированное оконное сообщение, по которому тот перечитывает файл.
 Сообщение не несёт данных: пересылка самих изменений лишила бы файл роли
 единственного источника правды. Работающий агент необязателен — без него окно
 работает так же. За файлом никто не следит: писатель у него один, и он сам
 сообщает о записи.
 
+В обратную сторону агент говорит одно слово, и то последнее: пункт «Выход» в меню
+трея просит открытое окно настроек закрыться, прежде чем агент уйдёт, — чтобы на
+экране не осталось окна, которому больше ничего не принадлежит. Просьба идёт
+именованным событием сессии, а не оконным сообщением: агент запускает этот процесс
+и намеренно не держит на него ссылки. Чаще всего слушать её некому, и это
+нормальный ответ.
+
 ## Трей
 
 Окно настроек — гость на экране, а не само приложение: оно показывается после
 установки и всякий раз, когда его просят иконка или её меню. Обе кнопки в
 заголовке окна означают ровно то, что написано: окно закрывается, а его процесс
-завершается. Выход из самого приложения — пункт «Выход» в меню трея.
+завершается. Выход из самого приложения — пункт «Выход» в меню трея, и открытое
+окно настроек он закрывает вместе с агентом.
 
 Меню иконки системное, его рисует Windows. Надписи по-прежнему следуют языку,
 выбранному в настройках, а тема до меню больше не дотягивается: меню на WPF

README.md

@@ -81,19 +81,26 @@ the next time the window is asked for.
 the layout tracking. No UI, and it must stay that way — whatever lands there lands
 in the background process.
 
-The connection between the two is `settings.json` and nothing else. The window
+Everything the window has to say to the agent goes through `settings.json` and
-writes it — whole, into a temporary file moved into place in one step — and then
+nothing else. The window writes it — whole, into a temporary file moved into place in one step — and then
 posts a registered window message to the agent, which re-reads. The message carries
 no data: sending the changed values along would make the file stop being the only
 source of truth. An agent that is not running is a normal case — the window works the
 same. Nobody watches the file: it has one writer, and that writer speaks up.
 
+The one word in the other direction is the last one: Exit in the tray menu asks an
+open settings window to close before the agent goes, so that no window is left
+belonging to nothing. It travels as a named event of the session rather than a
+window message — the agent starts that process and deliberately keeps no handle to
+it. Nobody listening is the usual case, and it is a normal answer.
+
 ## The tray
 
 The settings window is a guest on the screen rather than the app itself: it shows
 up after the installation and whenever the icon or its menu is asked for. Both
 buttons in its title bar mean what they say — the window closes and its process
-ends. The way out of the app itself is the Exit item of the tray menu.
+ends. The way out of the app itself is the Exit item of the tray menu — and it
+closes an open settings window along with the agent.
 
 The menu of the icon is a system one, drawn by Windows. Its captions still follow
 the language chosen in the settings, but the theme no longer reaches it: a WPF