correct theme gets applied when windows theme is changed while the app is running

code/TemplateStudioForWinUICs/Templates/Proj/Default/Param_ProjectName/App.xaml.cs

@@ -7,6 +7,7 @@ namespace Param_RootNamespace;
 public partial class App : Application
 {
     public static WindowEx MainWindow { get; } = new MainWindow();
+    public static UIElement? AppTitlebar;
 
     public App()
     {

code/TemplateStudioForWinUICs/Templates/Proj/Default/Param_ProjectName/Helpers/TitleBarHelper.cs

@@ -1,4 +1,4 @@
-using System.Runtime.InteropServices;
+using System.Runtime.InteropServices;
 using Microsoft.UI;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Media;
@@ -97,4 +97,24 @@ internal class TitleBarHelper
             }
         }
     }
+
+    public static void ApplySystemThemeToCaptionButtons()
+    {
+        var res = Application.Current.Resources;
+        var frame = App.AppTitlebar as FrameworkElement;
+        if (frame != null)
+        {
+            if (frame.ActualTheme == ElementTheme.Dark)
+            {
+                res["WindowCaptionForeground"] = Colors.White;
+            }
+            else
+            {
+                res["WindowCaptionForeground"] = Colors.Black;
+            }
+
+            UpdateTitleBar(frame.ActualTheme);
+        }
+    }
+
 }

code/TemplateStudioForWinUICs/Templates/Proj/Default/Param_ProjectName/MainWindow.xaml.cs

@@ -1,9 +1,11 @@
 using Param_RootNamespace.Helpers;
-
+using Windows.UI.ViewManagement;
 namespace Param_RootNamespace;
 
 public sealed partial class MainWindow : WindowEx
 {
+    public Microsoft.UI.Dispatching.DispatcherQueue dispatcherQueue;
+    private UISettings _settings;
     public MainWindow()
     {
         InitializeComponent();
@@ -11,5 +13,21 @@ public sealed partial class MainWindow : WindowEx
         AppWindow.SetIcon(Path.Combine(AppContext.BaseDirectory, "Assets/WindowIcon.ico"));
         Content = null;
         Title = "AppDisplayName".GetLocalized();
+
+        // Theme change code picked from https://github.com/microsoft/WinUI-Gallery/pull/1239
+        dispatcherQueue = Microsoft.UI.Dispatching.DispatcherQueue.GetForCurrentThread();
+        _settings = new UISettings();
+        _settings.ColorValuesChanged += _settings_ColorValuesChanged; // cannot use FrameworkElement.ActualThemeChanged event because the triggerTitleBarRepaint workaround no longer works
+    }
+
+    // this handles updating the caption button colors correctly when indows system theme is changed
+    // while the app is open
+    private void _settings_ColorValuesChanged(UISettings sender, object args)
+    {
+        // This calls comes off-thread, hence we will need to dispatch it to current app's thread
+        dispatcherQueue.TryEnqueue(() =>
+        {
+            TitleBarHelper.ApplySystemThemeToCaptionButtons();
+        });
     }
 }

code/TemplateStudioForWinUICs/Templates/_comp/MT/Project.MenuBar/Views/ShellPage.xaml.cs

@@ -45,6 +45,7 @@ public sealed partial class ShellPage : Page
         var resource = args.WindowActivationState == WindowActivationState.Deactivated ? "WindowCaptionForegroundDisabled" : "WindowCaptionForeground";
 
         AppTitleBarText.Foreground = (SolidColorBrush)App.Current.Resources[resource];
+        App.AppTitlebar = AppTitleBarText as UIElement;
     }
 
     private void OnUnloaded(object sender, RoutedEventArgs e)

code/TemplateStudioForWinUICs/Templates/_comp/MT/Project.NavView/Views/ShellPage.xaml.cs

@@ -47,6 +47,8 @@ public sealed partial class ShellPage : Page
         var resource = args.WindowActivationState == WindowActivationState.Deactivated ? "WindowCaptionForegroundDisabled" : "WindowCaptionForeground";
 
         AppTitleBarText.Foreground = (SolidColorBrush)App.Current.Resources[resource];
+        App.AppTitlebar = AppTitleBarText as UIElement;
+
     }
 
     private void NavigationViewControl_DisplayModeChanged(NavigationView sender, NavigationViewDisplayModeChangedEventArgs args)