Figured out the lark with first display transition and transitions based on taskbar pos

NotificationFlyout.Sample/NotificationFlyout.Sample.csproj

@@ -130,6 +130,9 @@
     <PackageReference Include="Microsoft.NETCore.UniversalWindowsPlatform">
       <Version>6.2.11</Version>
     </PackageReference>
+    <PackageReference Include="Microsoft.UI.Xaml">
+      <Version>2.6.0-prerelease.210113001</Version>
+    </PackageReference>
   </ItemGroup>
   <ItemGroup>
     <Page Include="MyUserControl1.xaml">

NotificationFlyout.Uwp.UI.Controls/NotificationFlyout.Uwp.UI.Controls.csproj

@@ -128,6 +128,9 @@
     <PackageReference Include="Microsoft.NETCore.UniversalWindowsPlatform">
       <Version>6.2.11</Version>
     </PackageReference>
+    <PackageReference Include="Microsoft.UI.Xaml">
+      <Version>2.6.0-prerelease.210113001</Version>
+    </PackageReference>
   </ItemGroup>
   <ItemGroup>
     <Page Include="NotificationFlyoutPresenter\NotificationFlyoutPresenter.xaml">

NotificationFlyout.Uwp.UI.Controls/NotificationFlyoutPresenter/NotificationFlyoutPresenter.cs

@@ -26,13 +26,6 @@ namespace NotificationFlyout.Uwp.UI.Controls
             flyout.ShowAt(_root, new FlyoutShowOptions { Placement = placementMode, ShowMode = FlyoutShowMode.Standard });
         }
 
-        public void ShowFlyout()
-        {
-            if (_root == null) return;
-            var flyout = FlyoutBase.GetAttachedFlyout(_root);
-            flyout.ShowAt(_root);
-        }
-
         protected override void OnApplyTemplate()
         {
             _root = GetTemplateChild("Root") as Grid;

NotificationFlyout.Uwp.UI.Controls/NotificationFlyoutPresenter/NotificationFlyoutPresenter.xaml

@@ -8,7 +8,46 @@
                 <ControlTemplate TargetType="controls:NotificationFlyoutPresenter">
                     <Grid x:Name="Root">
                         <FlyoutBase.AttachedFlyout>
-                            <Flyout ShouldConstrainToRootBounds="False">
+                            <Flyout AreOpenCloseAnimationsEnabled="False" ShouldConstrainToRootBounds="False">
+                                <Flyout.FlyoutPresenterStyle>
+                                    <Style TargetType="FlyoutPresenter">
+                                        <Setter Property="BorderThickness" Value="0" />
+                                        <Setter Property="Template">
+                                            <Setter.Value>
+                                                <ControlTemplate TargetType="FlyoutPresenter">
+                                                    <Border
+                                                        Background="{TemplateBinding Background}"
+                                                        BackgroundSizing="InnerBorderEdge"
+                                                        BorderBrush="{TemplateBinding BorderBrush}"
+                                                        BorderThickness="{TemplateBinding BorderThickness}"
+                                                        CornerRadius="{TemplateBinding CornerRadius}">
+                                                        <Border.Transitions>
+                                                            <TransitionCollection>
+                                                                <EntranceThemeTransition FromHorizontalOffset="200" FromVerticalOffset="0" />
+                                                            </TransitionCollection>
+                                                        </Border.Transitions>
+                                                        <ScrollViewer
+                                                            x:Name="ScrollViewer"
+                                                            AutomationProperties.AccessibilityView="Raw"
+                                                            HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}"
+                                                            HorizontalScrollMode="{TemplateBinding ScrollViewer.HorizontalScrollMode}"
+                                                            VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}"
+                                                            VerticalScrollMode="{TemplateBinding ScrollViewer.VerticalScrollMode}"
+                                                            ZoomMode="{TemplateBinding ScrollViewer.ZoomMode}">
+                                                            <ContentPresenter
+                                                                Margin="{TemplateBinding Padding}"
+                                                                HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
+                                                                VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
+                                                                Content="{TemplateBinding Content}"
+                                                                ContentTemplate="{TemplateBinding ContentTemplate}"
+                                                                ContentTransitions="{TemplateBinding ContentTransitions}" />
+                                                        </ScrollViewer>
+                                                    </Border>
+                                                </ControlTemplate>
+                                            </Setter.Value>
+                                        </Setter>
+                                    </Style>
+                                </Flyout.FlyoutPresenterStyle>
                                 <ContentControl Content="{TemplateBinding Content}" ContentTemplate="{TemplateBinding ContentTemplate}" />
                             </Flyout>
                         </FlyoutBase.AttachedFlyout>

NotificationFlyout.Wpf.UI.Controls/NotificationFlyout/NotificationFlyoutXamlHost.cs

@@ -51,35 +51,29 @@ namespace NotificationFlyout.Wpf.UI.Controls
 
         internal void ShowFlyout()
         {
-            var flyoutContentControl = GetNotificationFlyoutPresenter();
+            var notificationFlyoutPresenter = GetNotificationFlyoutPresenter();
-            if (flyoutContentControl != null)
+            if (notificationFlyoutPresenter != null)
             {
                 var taskbarState = _taskbarHelper.GetCurrentState();
-
+                var flyoutPlacement = taskbarState.Position switch
-                var flyoutPlacement = FlyoutPlacementMode.Auto;
-                switch (taskbarState.Position)
                 {
-                    case TaskbarPosition.Left:
+                    TaskbarPosition.Left => FlyoutPlacementMode.Right,
-                        flyoutPlacement = FlyoutPlacementMode.Right;
+                    TaskbarPosition.Top => FlyoutPlacementMode.Bottom,
-                        break;
+                    TaskbarPosition.Right => FlyoutPlacementMode.Left,
-                    case TaskbarPosition.Top:
+                    TaskbarPosition.Bottom => FlyoutPlacementMode.Top,
-                        flyoutPlacement = FlyoutPlacementMode.Bottom;
+                    _ => throw new ArgumentOutOfRangeException(),
-                        break;
+                };
-                    case TaskbarPosition.Right:
-                        flyoutPlacement = FlyoutPlacementMode.Left;
-                        break;
-                    case TaskbarPosition.Bottom:
-                        flyoutPlacement = FlyoutPlacementMode.Top;
-                        break;
-                }
 
-                UpdateWindow();
                 Activate();
-
+                notificationFlyoutPresenter.ShowFlyout(flyoutPlacement);
-                flyoutContentControl.ShowFlyout(flyoutPlacement);
             }
         }
 
+        private void SetFlyoutPlacement(FlyoutPlacementMode placementMode)
+        {
+            var notificationFlyoutPresenter = GetNotificationFlyoutPresenter();
+        }
+
         private static void OnFlyoutContentPropertyChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
         {
             var sender = dependencyObject as NotificationFlyoutXamlHost;
@@ -171,6 +165,7 @@ namespace NotificationFlyout.Wpf.UI.Controls
             var windowHeight = DesiredSize.Height * this.DpiY();
 
             var taskbarRect = taskbarState.Rect;
+            var flyoutPlacement = FlyoutPlacementMode.Auto;
             switch (taskbarState.Position)
             {
                 case TaskbarPosition.Left:

NotificationFlyout.XamlHost/App.xaml

@@ -3,4 +3,7 @@
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:xamlhost="using:Microsoft.Toolkit.Win32.UI.XamlHost">
+    <xamlhost:XamlApplication.Resources>
+        <XamlControlsResources xmlns="using:Microsoft.UI.Xaml.Controls" />
+    </xamlhost:XamlApplication.Resources>
 </xamlhost:XamlApplication>