fixed issue with DPI not updating

samples/NotificationFlyoutSample.Launcher/NotificationFlyoutSample.Launcher.csproj

@@ -7,6 +7,7 @@
     <StartupObject>NotificationFlyoutSample.Host.Program</StartupObject>
     <AssetTargetFallback>uap10.0.19041</AssetTargetFallback>
     <Platforms>x64</Platforms>
+    <ApplicationManifest>app.manifest</ApplicationManifest>
   </PropertyGroup>
 
   <ItemGroup>

src/TheXamlGuy.NotificationFlyout.Uwp.UI.Controls/NotificationFlyout/NotificationFlyout.xaml

@@ -51,7 +51,7 @@
                                     </TransitionCollection>
                                 </Border.Transitions>
                                 <Grid>
-                                
+
 
                                     <ScrollViewer
                                         x:Name="ScrollViewer"

src/TheXamlGuy.NotificationFlyout.Wpf.UI.Controls/NotificationFlyout/NotificationFlyoutApplication.cs

@@ -9,6 +9,10 @@ using System.Windows.Media.Imaging;
 using TheXamlGuy.NotificationFlyout.Common.Extensions;
 using Microsoft.Windows.Sdk;
 using TheXamlGuy.NotificationFlyout.Shared.UI;
+using System.Windows.Media;
+using System.Threading.Tasks;
+using Microsoft.Win32;
+using System.Windows.Threading;
 
 namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Controls
 {
@@ -24,6 +28,7 @@ namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Controls
         private readonly NotificationIconHelper _notificationIconHelper;
         private readonly SystemPersonalisationHelper _systemPersonalisationHelper;
         private readonly TaskbarHelper _taskbarHelper;
+        private bool _isDpiChanging;
         private TransparentXamlHost<ContentControl> _notificationFlyoutXamlHost;
 
         public NotificationFlyoutApplication()
@@ -58,12 +63,15 @@ namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Controls
         public void CloseFlyout() => CloseFlyout(false);
 
         public void Exit() => _notificationFlyoutXamlHost.Close();
+
         public void OpenAsWindow<TUIElement>() where TUIElement : Windows.UI.Xaml.UIElement
         {
             var window = new XamlHost<TUIElement>();
+            window.Hidden();
             window.Show();
         }
 
+
         public void OpenFlyout()
         {
             if (Flyout == null) return;
@@ -104,6 +112,29 @@ namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Controls
 
         private void OnNotificationFlyoutXamlHostDeactivated(object sender, EventArgs args) => CloseFlyout(true);
 
+        private async void OnNotificationFlyoutXamlHostDpiChanged(object sender, DpiChangedEventArgs args)
+        {
+            if (_isDpiChanging)
+                return;
+
+            _isDpiChanging = true;
+
+            UpdateIcons();
+            _notificationFlyoutXamlHost.Visibility = Visibility.Visible;
+
+            await Dispatcher.BeginInvoke(new Action(() =>
+            {
+                VisualTreeHelper.SetRootDpi(_notificationFlyoutXamlHost, args.OldDpi);
+                VisualTreeHelper.SetRootDpi(_notificationFlyoutXamlHost, args.NewDpi);
+            }), DispatcherPriority.ContextIdle, null);
+
+            await Dispatcher.BeginInvoke(new Action(() =>
+            {
+                _notificationFlyoutXamlHost.Visibility = Visibility.Hidden;
+                _isDpiChanging = false;
+            }), DispatcherPriority.ContextIdle, null);
+        }
+
         private void OnTaskbarChanged(object sender, EventArgs args) => UpdateFlyoutPlacement();
 
         private void OnThemeChanged(object sender, SystemPersonalisationChangedEventArgs args)
@@ -115,6 +146,7 @@ namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Controls
         private void PrepareFlyout()
         {
             if (Flyout == null) return;
+
             Flyout.IconSourcePropertyChanged += OnFlyoutIconSourcePropertyChanged;
             Flyout.PlacementPropertyChanged += OnFlyoutPlacementPropertyChanged;
             Flyout.InteractedWith += OnFlyoutInteractedWith;
@@ -131,6 +163,8 @@ namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Controls
         private void PrepareFlyoutHost()
         {
             _notificationFlyoutXamlHost = new TransparentXamlHost<ContentControl>();
+
+            _notificationFlyoutXamlHost.DpiChanged += OnNotificationFlyoutXamlHostDpiChanged;
             _notificationFlyoutXamlHost.Closed += OnNotificationFlyoutXamlHostClosed;
             _notificationFlyoutXamlHost.Deactivated += OnNotificationFlyoutXamlHostDeactivated;
 
@@ -140,7 +174,6 @@ namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Controls
 
             _notificationFlyoutXamlHost.Show();
         }
-
         private void ShowContextMenu()
         {
             var dpiX = _notificationFlyoutXamlHost.DpiX();

src/TheXamlGuy.NotificationFlyout.Wpf.UI.Controls/XamlHost/TransparentXamlHost.cs

@@ -1,18 +1,17 @@
 using Microsoft.Toolkit.Wpf.UI.XamlHost;
+using System;
 using System.Windows;
 using System.Windows.Media;
-using System;
-using TheXamlGuy.NotificationFlyout.Wpf.UI.Extensions;
 
 namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Controls
 {
     internal class TransparentXamlHost<TXamlContent> : XamlHost<TXamlContent> where TXamlContent : Windows.UI.Xaml.UIElement
     {
-        internal const double WindowSize = 0;
+        internal const double WindowSize = 10;
 
         public TransparentXamlHost() => PrepareDefaultWindow();
 
-        protected override void OnContentRendered(EventArgs args) => Visibility = Visibility.Hidden;
+        protected override void OnContentRendered(EventArgs args) => Hide();
 
         protected override WindowsXamlHost OnPreparingXamlHost(WindowsXamlHost xamlHost)
         {
@@ -21,6 +20,7 @@ namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Controls
 
             return base.OnPreparingXamlHost(xamlHost);
         }
+
         private void PrepareDefaultWindow()
         {
             ShowInTaskbar = false;

src/TheXamlGuy.NotificationFlyout.Wpf.UI.Controls/XamlHost/XamlHost.cs

@@ -6,13 +6,11 @@ namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Controls
 {
     internal class XamlHost<TXamlContent> : Window where TXamlContent : Windows.UI.Xaml.UIElement
     {
-        protected new bool IsLoaded;
         private WindowsXamlHost _xamlHost;
 
         public XamlHost()
         {
             PrepareWindowsXamlHost();
-            ContentRendered += OnContentRendered;
         }
 
         internal TXamlContent GetHostContent()
@@ -21,11 +19,6 @@ namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Controls
             return _xamlHost.GetUwpInternalObject() as TXamlContent;
         }
 
-        protected virtual void OnContentLoaded()
-        {
-            
-        }
-
         protected virtual WindowsXamlHost OnPreparingXamlHost(WindowsXamlHost xamlHost)
         {
             xamlHost.InitialTypeName = typeof(TXamlContent).FullName;
@@ -35,12 +28,6 @@ namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Controls
             return xamlHost;
         }
 
-        private void OnContentRendered(object sender, EventArgs args)
-        {
-            IsLoaded = true;
-            OnContentLoaded();
-        }
-
         private void PrepareWindowsXamlHost()
         {
             _xamlHost = new WindowsXamlHost();

src/TheXamlGuy.NotificationFlyout.Wpf.UI/Extensions/WindowExtensions.cs

@@ -7,6 +7,8 @@ namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Extensions
 {
     public static class WindowExtensions
     {
+        private const int GWL_EX_STYLE = -20;
+
         [Flags]
         private enum WindowFlag : uint
         {
@@ -26,6 +28,12 @@ namespace TheXamlGuy.NotificationFlyout.Wpf.UI.Extensions
             return helper.Handle;
         }
 
+        public static void Hidden(this Window window)
+        {
+            var handle = window.GetHandle();
+            PInvoke.SetWindowLong((HWND)handle, GWL_EX_STYLE, (PInvoke.GetWindowLong((HWND)handle, GWL_EX_STYLE) | (int)WindowFlag.WS_EX_TOOLWINDOW) & ~(int)WindowFlag.WS_EX_APPWINDOW);
+        }
+
         public static void SetTopAll(this Window window)
         {
             PInvoke.SetWindowPos((HWND)window.GetHandle(), (HWND)new IntPtr(-1), 0, 0, 0, 0, (uint)WindowFlag.SWP_NOMOVE | (uint)WindowFlag.SWP_NOSIZE | (uint)WindowFlag.WS_EX_NOACTIVATE);