fluent 2 - add listbox selection indicator keys

src/Avalonia.Themes.Fluent2/Controls/ListBoxItem.xaml

@@ -25,6 +25,9 @@
   <Thickness x:Key="ListBoxItemPadding">12,9,12,12</Thickness>
   <x:Double x:Key="ListBoxItemMinHeight">40</x:Double>
   <x:Double x:Key="ListBoxItemMinWidth">88</x:Double>
+  <x:Double x:Key="ListBoxItemSelectionIndicatorWidth">3</x:Double>
+  <x:Double x:Key="ListBoxItemSelectionIndicatorHeight">16</x:Double>
+  <x:Double x:Key="ListBoxItemSelectionIndicatorRadius">2</x:Double>
   <ControlTheme x:Key="{x:Type ListBoxItem}" TargetType="ListBoxItem" BasedOn="{StaticResource FluentListBoxItemTheme}"/>
   <ControlTheme x:Key="FluentListBoxItemTheme" TargetType="ListBoxItem">
     <Setter Property="Background" Value="Transparent" />
@@ -40,27 +43,27 @@
         <!-- WinUI's ListViewItemPresenter insets the rounded backplate from the item bounds. -->
         <Panel Margin="4,2">
           <ContentPresenter Name="PART_ContentPresenter"
-                Background="{TemplateBinding Background}"
-                BorderBrush="{TemplateBinding BorderBrush}"
-                BorderThickness="{TemplateBinding BorderThickness}"
+                            Background="{TemplateBinding Background}"
+                            BorderBrush="{TemplateBinding BorderBrush}"
+                            BorderThickness="{TemplateBinding BorderThickness}"
                             CornerRadius="{TemplateBinding CornerRadius}"
-                                ContentTemplate="{TemplateBinding ContentTemplate}"
-                                Content="{TemplateBinding Content}"
+                            ContentTemplate="{TemplateBinding ContentTemplate}"
+                            Content="{TemplateBinding Content}"
                             Padding="{TemplateBinding Padding}"
                             VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
                             HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" />
           <!-- Selection pill: WinUI animates its height 0 -> 16 over 167ms when the item is selected;
-               expressed here as a scaleY render transform so the animation doesn't run layout every
-               frame (technique from FluentAvalonia). ListViewItemSelectionIndicatorBrush is not aliased
-               in this theme yet, so the Fluent 2 token AccentFillColorDefaultBrush is referenced directly. -->
+          expressed here as a scaleY render transform so the animation doesn't run layout every
+          frame (technique from FluentAvalonia). ListViewItemSelectionIndicatorBrush is not aliased
+          in this theme yet, so the Fluent 2 token AccentFillColorDefaultBrush is referenced directly. -->
           <Rectangle Name="SelectionIndicator"
                      IsVisible="False"
-                     Width="3"
-                     Height="16"
-                     RadiusX="1.5"
-                     RadiusY="1.5"
+                     Width="{DynamicResource ListBoxItemSelectionIndicatorWidth}"
+                     Height="{DynamicResource ListBoxItemSelectionIndicatorHeight}"
+                     RadiusX="{DynamicResource ListBoxItemSelectionIndicatorRadius}"
+                     RadiusY="{DynamicResource ListBoxItemSelectionIndicatorRadius}"
                      HorizontalAlignment="Left"
-                    VerticalAlignment="Center"
+                     VerticalAlignment="Center"
                      IsHitTestVisible="False"
                      UseLayoutRounding="False"
                      RenderTransform="scaleY(0)"