Set default SelectionForegroundBrush in default style resource instead of code

src/Avalonia.Controls/Presenters/TextPresenter.cs

@@ -262,13 +262,12 @@ namespace Avalonia.Controls.Presenters
             var selectionEnd = SelectionEnd;
             var start = Math.Min(selectionStart, selectionEnd);
             var length = Math.Max(selectionStart, selectionEnd) - start;
-            var selectionForegroundBrush = SelectionForegroundBrush ?? Brushes.White;
 
             if (length > 0)
             {
                 result.Spans = new[]
                 {
-                    new FormattedTextStyleSpan(start, length, foregroundBrush: selectionForegroundBrush),
+                    new FormattedTextStyleSpan(start, length, SelectionForegroundBrush),
                 };
             }
 

src/Avalonia.Themes.Default/Accents/BaseDark.xaml

@@ -22,6 +22,7 @@
         <Color x:Key="ThemeForegroundLowColor">#FF808080</Color>
 
         <Color x:Key="HighlightColor">#FF119EDA</Color>
+        <Color x:Key="HighlightForegroundColor">#FFFFFFFF</Color>
         <Color x:Key="ErrorColor">#FFFF0000</Color>
         <Color x:Key="ErrorLowColor">#10FF0000</Color>
 
@@ -39,6 +40,7 @@
         <SolidColorBrush x:Key="ThemeForegroundLowBrush" Color="{DynamicResource ThemeForegroundLowColor}"></SolidColorBrush>
 
         <SolidColorBrush x:Key="HighlightBrush" Color="{DynamicResource HighlightColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="HighlightForegroundBrush" Color="{DynamicResource HighlightForegroundColor}"></SolidColorBrush>
         <SolidColorBrush x:Key="ThemeAccentBrush" Color="{DynamicResource ThemeAccentColor}"></SolidColorBrush>
         <SolidColorBrush x:Key="ThemeAccentBrush2" Color="{DynamicResource ThemeAccentColor2}"></SolidColorBrush>
         <SolidColorBrush x:Key="ThemeAccentBrush3" Color="{DynamicResource ThemeAccentColor3}"></SolidColorBrush>

src/Avalonia.Themes.Default/Accents/BaseLight.xaml

@@ -22,6 +22,7 @@
         <Color x:Key="ThemeForegroundLowColor">#FF808080</Color>
 
         <Color x:Key="HighlightColor">#FF086F9E</Color>
+        <Color x:Key="HighlightForegroundColor">#FFFFFFFF</Color>
         <Color x:Key="ErrorColor">#FFFF0000</Color>
         <Color x:Key="ErrorLowColor">#10FF0000</Color>
 
@@ -39,6 +40,7 @@
         <SolidColorBrush x:Key="ThemeForegroundLowBrush" Color="{DynamicResource ThemeForegroundLowColor}"></SolidColorBrush>
 
         <SolidColorBrush x:Key="HighlightBrush" Color="{DynamicResource HighlightColor}"></SolidColorBrush>
+        <SolidColorBrush x:Key="HighlightForegroundBrush" Color="{DynamicResource HighlightForegroundColor}"></SolidColorBrush>
         <SolidColorBrush x:Key="ThemeAccentBrush" Color="{DynamicResource ThemeAccentColor}"></SolidColorBrush>
         <SolidColorBrush x:Key="ThemeAccentBrush2" Color="{DynamicResource ThemeAccentColor2}"></SolidColorBrush>
         <SolidColorBrush x:Key="ThemeAccentBrush3" Color="{DynamicResource ThemeAccentColor3}"></SolidColorBrush>

src/Avalonia.Themes.Default/TextBox.xaml

@@ -4,6 +4,7 @@
     <Setter Property="BorderBrush" Value="{DynamicResource ThemeBorderMidBrush}"/>
     <Setter Property="BorderThickness" Value="{DynamicResource ThemeBorderThickness}"/>
     <Setter Property="SelectionBrush" Value="{DynamicResource HighlightBrush}"/>
+    <Setter Property="SelectionForegroundBrush" Value="{DynamicResource HighlightForegroundBrush}"/>
     <Setter Property="Padding" Value="4"/>
     <Setter Property="Template">
       <ControlTemplate>