Fix UI thread blocking and potential deadlocks in NotificationService and MainWindow

src/Service/NotificationService.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Drawing;
 using System.Drawing.Drawing2D;
 using System.Drawing.Text;
@@ -479,8 +479,8 @@ public void Loading(bool running)
             if (WpfApplication.Current == null || WpfApplication.Current.Dispatcher == null)
                 return;
 
-            // Multi-threading trick
-            WpfApplication.Current.Dispatcher.Invoke((Action)delegate
+            // Multi-threading safe dispatch
+            WpfApplication.Current.Dispatcher.BeginInvoke((Action)delegate
             {
                 Mouse.OverrideCursor = running ? Cursors.Wait : null;
 
@@ -572,7 +572,7 @@ private void StartRotationAnimation()
 
             try
             {
-                WpfApplication.Current.Dispatcher.Invoke((Action)delegate
+                WpfApplication.Current.Dispatcher.BeginInvoke((Action)delegate
                 {
                     try
                     {
@@ -610,7 +610,7 @@ private void StopRotationAnimation()
                     return;
                 }
 
-                WpfApplication.Current.Dispatcher.Invoke((Action)delegate
+                WpfApplication.Current.Dispatcher.BeginInvoke((Action)delegate
                 {
                     CleanupRotationTimer();
                 });

src/View/Window/MainWindow.xaml.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Linq;
 using System.Threading;
 using System.Windows;
@@ -213,21 +213,25 @@ private void OnOptimizeCommandCompleted()
                 }
                 else
                 {
-                    Thread.Sleep(1000);
-                    App.Shutdown();
+                    var timer = new System.Windows.Threading.DispatcherTimer { Interval = TimeSpan.FromSeconds(1) };
+                    timer.Tick += (sender, args) =>
+                    {
+                        timer.Stop();
+                        App.Shutdown();
+                    };
+                    timer.Start();
                 }
             }
             else
             {
                 _viewModel.IsBusy = false;
 
-             // Wait for the button to be enabled before trying to refocus it
-           // The button is disabled while IsOptimizationRunning = true
+                // Wait for the button to be enabled before trying to refocus it
                 Dispatcher.BeginInvoke(new Action(() =>
-             {
-              SetFocusTo(Optimize, force: true);
-           }), System.Windows.Threading.DispatcherPriority.Loaded);
- }
+                {
+                    SetFocusTo(Optimize, force: true);
+                }), System.Windows.Threading.DispatcherPriority.Loaded);
+            }
         }
 
         /// <summary>
@@ -348,7 +352,6 @@ private void SetFocusTo(object element, bool force = false)
             else
             {
                 // Normal focus - immediate
-                Keyboard.ClearFocus();
                 Keyboard.Focus(uiElement);
                 FocusManager.SetFocusedElement(this, inputElement);
             }

src/ViewModel/MainViewModel.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
@@ -1706,7 +1706,12 @@ private void MonitorComputer()
                 {
                     // Check if it's busy
                     if (IsBusy)
+                    {
+                        if (_cancellationTokenSource.Token.WaitHandle.WaitOne(1000))
+                            break;
+
                         continue;
+                    }
 
                     lock (_lockObject)
                     {