macOS: Dispose COM platform object on native app termination (#22200)

native/Avalonia.Native/src/OSX/app.mm

@@ -9,6 +9,34 @@
 NSApplicationActivationPolicy AvnDesiredActivationPolicy = NSApplicationActivationPolicyRegular;
 static NSMenu* s_dockMenu = nil;
 
+static bool IsOSShutdown()
+{
+    auto evt = [[NSAppleEventManager sharedAppleEventManager] currentAppleEvent];
+    if ([evt eventClass] != kCoreEventClass || [evt eventID] != kAEQuitApplication)
+        return false;
+
+    auto reason = [evt paramDescriptorForKeyword:kAEQuitReason];
+    if (reason == nil)
+        reason = [evt attributeDescriptorForKeyword:kAEQuitReason];
+
+    auto reasonCode = [reason enumCodeValue];
+    if (reasonCode == 0)
+        reasonCode = [reason typeCodeValue];
+
+    switch (reasonCode)
+    {
+        case kAELogOut:
+        case kAEReallyLogOut:
+        case kAEShowRestartDialog:
+        case kAERestart:
+        case kAEShowShutdownDialog:
+        case kAEShutDown:
+            return true;
+        default:
+            return false;
+    }
+}
+
 @implementation AvnAppDelegate
 ComPtr<IAvnApplicationEvents> _events;
 
@@ -85,7 +113,33 @@ ComPtr<IAvnApplicationEvents> _events;
 
 - (NSApplicationTerminateReply)applicationShouldTerminate:(NSApplication *)sender
 {
-    return _events->TryShutdown() ? NSTerminateNow : NSTerminateCancel;
+    switch (_events->TryShutdown(IsOSShutdown()))
+    {
+        case ShutdownReplyCancel:
+            return NSTerminateCancel;
+            
+        // The managed dispatcher loop is exiting: let it handle the termination instead.
+        case ShutdownReplyDeferToManagedLoop:
+            return NSTerminateCancel;
+
+        case ShutdownReplyTerminateNow:
+            return NSTerminateNow;
+
+        // Shouldn't happen
+        default:
+            return NSTerminateNow;
+    }
+}
+
+- (void)applicationWillTerminate:(NSNotification *)notification
+{
+    if (!_events)
+        return;
+    
+    // The process is about to exit() so this is the last point where managed code can still safely be called.
+    // Keep the application events object alive for the duration of the call, it's about to be released by the managed side.
+    ComPtr<IAvnApplicationEvents> events(_events);
+    events->OnTerminating();
 }
 
 - (NSMenu *)applicationDockMenu:(NSApplication *)sender

src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs

@@ -227,6 +227,8 @@ namespace Avalonia.Controls.ApplicationLifetimes
 
                 if (!shutdownCancelled)
                 {
+                    e.WillExitMainLoop = _cts is not null;
+
                     _cts?.Cancel();
                     _cts = null;
                     Dispatcher.UIThread.InvokeShutdown();

src/Avalonia.Controls/ApplicationLifetimes/ShutdownRequestedEventArgs.cs

@@ -8,5 +8,10 @@ namespace Avalonia.Controls.ApplicationLifetimes
         /// Is the operating system shutting down
         /// </summary>
         internal bool IsOSShutdown { get; init; }
+
+        /// <summary>
+        /// Indicates that the accepted shutdown will exit the main loop.
+        /// </summary>
+        internal bool WillExitMainLoop { get; set; }
     }
 }

src/Avalonia.Native/AvaloniaNativeApplicationPlatform.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.ComponentModel;
 using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Controls.Platform;
 using Avalonia.Native.Interop;
@@ -10,7 +9,8 @@ using Avalonia.Platform.Storage.FileIO;
 
 namespace Avalonia.Native
 {
-    internal class AvaloniaNativeApplicationPlatform : NativeCallbackBase, IAvnApplicationEvents, IPlatformLifetimeEventsImpl
+    internal class AvaloniaNativeApplicationPlatform(AvaloniaNativePlatform platform)
+        : NativeCallbackBase, IAvnApplicationEvents, IPlatformLifetimeEventsImpl
     {
         public event EventHandler<ShutdownRequestedEventArgs>? ShutdownRequested;
 
@@ -105,12 +105,31 @@ namespace Avalonia.Native
             }
         }
 
-        public int TryShutdown()
+        void IAvnApplicationEvents.OnTerminating()
         {
-            if (ShutdownRequested is null) return 1;
-            var e = new ShutdownRequestedEventArgs();
-            ShutdownRequested(this, e);
-            return (!e.Cancel).AsComBool();
+            // The OS is terminating us directly: AppDomain.ProcessExit won't run, dispose now.
+            platform.Dispose();
+        }
+
+        public AvnShutdownReply TryShutdown(int isOSShutdown)
+        {
+            if (ShutdownRequested is not { } shutdownRequested)
+                return AvnShutdownReply.ShutdownReplyTerminateNow;
+
+            var isOSShutdownBool = isOSShutdown.FromComBool();
+            var e = new ShutdownRequestedEventArgs { IsOSShutdown = isOSShutdownBool };
+            shutdownRequested.Invoke(this, e);
+
+            if (e.Cancel)
+                return AvnShutdownReply.ShutdownReplyCancel;
+
+            // If we know the main loop is going to exit (e.g. via a ClassicDesktopApplicationLifetime),
+            // tell the native side it doesn't have to exit, allowing the managed side to complete its shutdown.
+            if (e.WillExitMainLoop && !isOSShutdownBool)
+                return AvnShutdownReply.ShutdownReplyDeferToManagedLoop;
+
+            return AvnShutdownReply.ShutdownReplyTerminateNow;
+
         }
     }
 }

src/Avalonia.Native/AvaloniaNativePlatform.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Runtime.InteropServices;
+using System.Threading;
 using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Controls.Platform;
 using Avalonia.Input;
@@ -14,11 +15,12 @@ using MicroCom.Runtime;
 
 namespace Avalonia.Native
 {
-    class AvaloniaNativePlatform : IWindowingPlatform
+    internal sealed class AvaloniaNativePlatform : IWindowingPlatform, IDisposable
     {
         private readonly IAvaloniaNativeFactory _factory;
         private AvaloniaNativePlatformOptions? _options;
         private IPlatformGraphics? _platformGraphics;
+        private int _isDisposed;
 
         [DllImport("libAvaloniaNative")]
         static extern IntPtr CreateAvaloniaNative();
@@ -94,7 +96,7 @@ namespace Avalonia.Native
         {
             _options = options;
 
-            var applicationPlatform = new AvaloniaNativeApplicationPlatform();
+            var applicationPlatform = new AvaloniaNativeApplicationPlatform(this);
 
             var macOpts = AvaloniaLocator.Current.GetService<MacOSPlatformOptions>() ?? new MacOSPlatformOptions();
             
@@ -191,6 +193,15 @@ namespace Avalonia.Native
 
         private void OnProcessExit(object? sender, EventArgs e)
         {
+            // Self-dispose on exit, ensuring COM objects are properly released before the CLR shuts down.
+            Dispose();
+        }
+
+        public void Dispose()
+        {
+            if (Interlocked.CompareExchange(ref _isDisposed, 1, 0) != 0)
+                return;
+
             AppDomain.CurrentDomain.ProcessExit -= OnProcessExit;
             _factory.Dispose();
         }

src/Avalonia.Native/avn.idl

@@ -1237,17 +1237,25 @@ interface IAvnNativeControlHostTopLevelAttachment : IUnknown
      void ReleaseChild();
 }
 
+enum AvnShutdownReply
+{
+    ShutdownReplyCancel,
+    ShutdownReplyTerminateNow,
+    ShutdownReplyDeferToManagedLoop
+}
+
 [uuid(6575b5af-f27a-4609-866c-f1f014c20f79)]
 interface IAvnApplicationEvents : IUnknown
 {
      void FilesOpened (IAvnStringArray* args);
      void UrlsOpened (IAvnStringArray* urls);
-     bool TryShutdown();
+     AvnShutdownReply TryShutdown(bool isOSShutdown);
      void OnReopen ();
      void OnHide ();
      void OnUnhide ();
      void OnActivate();
      void OnDeactivate();
+     void OnTerminating();
 }
 
 [uuid(b4284791-055b-4313-8c2e-50f0a8c72ce9)]