Combined Window styles (#9425)

Author: dipeshmsft

src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Window.cs

@@ -3583,14 +3583,7 @@ private void Initialize()
             // TODO : Remove when Fluent theme is enabled by default
             if (ThemeManager.IsFluentThemeEnabled)
             {
-                if(WindowBackdropManager.IsBackdropEnabled)
-                {
-                    SetResourceReference(StyleProperty, typeof(Window));
-                }
-                else
-                {
-                    SetResourceReference(StyleProperty, "BackdropDisabledWindowStyle");
-                }
+                SetResourceReference(StyleProperty, typeof(Window));
             }
         }
 

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

@@ -8,6 +8,7 @@
 <ResourceDictionary
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:framework="clr-namespace:MS.Internal;assembly=PresentationFramework"
     xmlns:controls="clr-namespace:Fluent.Controls">
 
     <ControlTemplate x:Key="WindowTemplateKey"
@@ -71,13 +72,15 @@
                 <Setter Property="Template"
                         Value="{StaticResource WindowTemplateKey}"/>
             </Trigger>
+            <DataTrigger Binding="{Binding Path=(SystemParameters.HighContrast)}" Value="True">
+                <Setter Property="Background" Value="{DynamicResource WindowBackground}" />
+            </DataTrigger>
+            <DataTrigger Binding="{Binding Path=(framework:FrameworkAppContextSwitches.DisableFluentThemeWindowBackdrop)}" Value="True">
+                <Setter Property="Background" Value="{DynamicResource WindowBackground}" />
+            </DataTrigger>  
         </Style.Triggers>
     </Style>
 
-    <Style x:Key="BackdropDisabledWindowStyle" BasedOn="{StaticResource DefaultWindowStyle}" TargetType="{x:Type Window}" >
-        <Setter Property="Background" Value="{DynamicResource WindowBackground}" />
-    </Style>
-
     <Style BasedOn="{StaticResource DefaultWindowStyle}" TargetType="{x:Type Window}" />
 
 </ResourceDictionary>