fix: Exit VRCFT when SteamVR shuts down

VRCFaceTracking/Services/OpenVRService.cs

@@ -1,31 +1,37 @@
-using System.Reflection;
+using System.Diagnostics;
+using System.Reflection;
 using Microsoft.Extensions.Logging;
 using Valve.VR;
+using VRCFaceTracking.Core.Contracts.Services;
 
 namespace VRCFaceTracking.Services;
 
 public class OpenVRService
 {
     private CVRSystem _system;
     private readonly ILogger<OpenVRService> _logger;
-
-    public OpenVRService(ILogger<OpenVRService> logger)
+    private readonly IMainService _mainService;
+    private Thread? _eventPollingThread;
+    private readonly CancellationTokenSource _pollingCts = new();
+
+    public OpenVRService(ILogger<OpenVRService> logger, IMainService mainService)
     {
         _logger = logger;
+        _mainService = mainService;
     }
 
     public bool Initialize()
     {
         EVRInitError error = EVRInitError.None;
         _system = OpenVR.Init(ref error, EVRApplicationType.VRApplication_Background);
-        
+
         if (error != EVRInitError.None)
         {
             _logger.LogWarning("Failed to initialize OpenVR: {0}", error);
             IsInitialized = false;
             return IsInitialized;
         }
-        
+
         // Our app.vrmanifest is next to the executable, so we can just use the current directory of the executable
         var currentDirectory = Path.GetDirectoryName(Assembly.GetEntryAssembly()?.Location);
         var fullManifestPath = Path.Combine(currentDirectory, "app.vrmanifest"); // Replace is for Linux
@@ -36,21 +42,59 @@ public bool Initialize()
             IsInitialized = false;
             return IsInitialized;
         }
-        
+
         _logger.LogInformation("Successfully initialized OpenVR");
-        
+
         IsInitialized = true;
+
+        StartEventPolling();
+
         return IsInitialized;
     }
 
+    private void StartEventPolling()
+    {
+        _eventPollingThread = new Thread(() =>
+        {
+            var vrEvent = new VREvent_t();
+            var eventSize = (uint)System.Runtime.InteropServices.Marshal.SizeOf(typeof(VREvent_t));
+
+            while (!_pollingCts.IsCancellationRequested)
+            {
+                while (_system.PollNextEvent(ref vrEvent, eventSize))
+                {
+                    if ((EVREventType)vrEvent.eventType == EVREventType.VREvent_Quit)
+                    {
+                        _logger.LogInformation("SteamVR is shutting down. Exiting VRCFT.");
+                        _system.AcknowledgeQuit_Exiting();
+
+                        // Teardown modules first to kill child processes,
+                        // then force-exit the application.
+                        _mainService.Teardown().GetAwaiter().GetResult();
+                        Core.Utils.KillAllProcessesOfName("VRCFaceTracking.ModuleProcess");
+                        Environment.Exit(0);
+                        return;
+                    }
+                }
+
+                Thread.Sleep(200);
+            }
+        })
+        {
+            IsBackground = true,
+            Name = "OpenVR Event Polling"
+        };
+        _eventPollingThread.Start();
+    }
+
     public void InitIfNotAlready()
     {
         if (!IsInitialized)
         {
             Initialize();
         }
     }
-    
+
     public bool IsInitialized { get; private set; }
 
     public bool AutoStart