added sending closing event message to settings windows (#7)

Reviewed-on: #7
Co-authored-by: Aleksandr Neychev <alexnejchev73@gmail.com>

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)