Adding ScrollViewer to ContextMenu (#10239)

* Adding scrollviewer in ContextMenu

* Reverting SystemColorWindowColor key creation in Fluent.HC.xaml

Author: siagupta0202

src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Styles/ContextMenu.xaml

@@ -38,11 +38,16 @@
                         <Border.RenderTransform>
                             <TranslateTransform />
                         </Border.RenderTransform>
-                        <StackPanel
-                            ClipToBounds="True"
-                            IsItemsHost="True"
-                            KeyboardNavigation.DirectionalNavigation="Cycle"
-                            Orientation="Vertical" />
+                        <ScrollViewer
+                            CanContentScroll="True"
+                            HorizontalScrollBarVisibility="Disabled"
+                            VerticalScrollBarVisibility="Auto">
+                            <StackPanel
+                                ClipToBounds="True"
+                                IsItemsHost="True"
+                                KeyboardNavigation.DirectionalNavigation="Cycle"
+                                Orientation="Vertical" />
+                        </ScrollViewer>
                     </Border>
                     <ControlTemplate.Triggers>
                         <Trigger Property="IsOpen" Value="True">

src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Themes/Fluent.Dark.xaml

@@ -1536,7 +1536,9 @@
             <Border.RenderTransform>
               <TranslateTransform />
             </Border.RenderTransform>
-            <StackPanel ClipToBounds="True" IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle" Orientation="Vertical" />
+            <ScrollViewer CanContentScroll="True" HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Auto">
+              <StackPanel ClipToBounds="True" IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle" Orientation="Vertical" />
+            </ScrollViewer>
           </Border>
           <ControlTemplate.Triggers>
             <Trigger Property="IsOpen" Value="True">

src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Themes/Fluent.HC.xaml

@@ -1517,7 +1517,9 @@
             <Border.RenderTransform>
               <TranslateTransform />
             </Border.RenderTransform>
-            <StackPanel ClipToBounds="True" IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle" Orientation="Vertical" />
+            <ScrollViewer CanContentScroll="True" HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Auto">
+              <StackPanel ClipToBounds="True" IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle" Orientation="Vertical" />
+            </ScrollViewer>
           </Border>
           <ControlTemplate.Triggers>
             <Trigger Property="IsOpen" Value="True">

src/Microsoft.DotNet.Wpf/src/Themes/PresentationFramework.Fluent/Themes/Fluent.Light.xaml

@@ -1533,7 +1533,9 @@
             <Border.RenderTransform>
               <TranslateTransform />
             </Border.RenderTransform>
-            <StackPanel ClipToBounds="True" IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle" Orientation="Vertical" />
+            <ScrollViewer CanContentScroll="True" HorizontalScrollBarVisibility="Disabled" VerticalScrollBarVisibility="Auto">
+              <StackPanel ClipToBounds="True" IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle" Orientation="Vertical" />
+            </ScrollViewer>
           </Border>
           <ControlTemplate.Triggers>
             <Trigger Property="IsOpen" Value="True">