From 498c183f975f1d50f6491359ccd336c7e843a56f Mon Sep 17 00:00:00 2001
From: Julien Lebosquain <julien@lebosquain.net>
Date: Wed, 27 May 2026 14:47:57 +0100
Subject: [PATCH] Add a resource for title bar background (#21440)

---
 src/Avalonia.Themes.Fluent/Accents/FluentControlResources.xaml  | 2 ++
 src/Avalonia.Themes.Fluent/Controls/WindowDrawnDecorations.xaml | 2 +-
 src/Avalonia.Themes.Simple/Accents/Base.xaml                    | 2 ++
 src/Avalonia.Themes.Simple/Controls/WindowDrawnDecorations.xaml | 2 +-
 4 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Themes.Fluent/Accents/FluentControlResources.xaml b/src/Avalonia.Themes.Fluent/Accents/FluentControlResources.xaml
index 2613a0a133..80778a50db 100644
--- a/src/Avalonia.Themes.Fluent/Accents/FluentControlResources.xaml
+++ b/src/Avalonia.Themes.Fluent/Accents/FluentControlResources.xaml
@@ -825,6 +825,7 @@
       <SolidColorBrush x:Key="CaptionButtonForeground" Color="Black" />
       <SolidColorBrush x:Key="CaptionButtonBackground" Color="#ffe5e5e5" />
       <SolidColorBrush x:Key="CaptionButtonBorderBrush" Color="#ffcacaca" />
+      <StaticResource x:Key="TitleBarBackgroundBrush" ResourceKey="SystemControlBackgroundAltHighBrush" />
     </ResourceDictionary>
     <ResourceDictionary x:Key="Dark">
       <!-- Resources for Button.xaml -->
@@ -1652,6 +1653,7 @@
       <SolidColorBrush x:Key="CaptionButtonForeground" Color="White" />
       <SolidColorBrush x:Key="CaptionButtonBackground" Color="#ffe5e5e5" />
       <SolidColorBrush x:Key="CaptionButtonBorderBrush" Color="#ffcacaca" />
+      <StaticResource x:Key="TitleBarBackgroundBrush" ResourceKey="SystemControlBackgroundAltHighBrush" />
     </ResourceDictionary>
   </ResourceDictionary.ThemeDictionaries>
 </ResourceDictionary>
diff --git a/src/Avalonia.Themes.Fluent/Controls/WindowDrawnDecorations.xaml b/src/Avalonia.Themes.Fluent/Controls/WindowDrawnDecorations.xaml
index d774ef8ef2..d9af9faf79 100644
--- a/src/Avalonia.Themes.Fluent/Controls/WindowDrawnDecorations.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/WindowDrawnDecorations.xaml
@@ -48,7 +48,7 @@
               <!-- Titlebar: background, title text, and drag area live in underlay -->
               <Panel x:Name="PART_TitleBar" VerticalAlignment="Top"
                      Height="{TemplateBinding TitleBarHeight}"
-                     Background="{DynamicResource SystemControlTransparentBrush}"
+                     Background="{DynamicResource TitleBarBackgroundBrush}"
                      IsVisible="{TemplateBinding HasTitleBar}"
                      WindowDecorationProperties.ElementRole="TitleBar" />
 
diff --git a/src/Avalonia.Themes.Simple/Accents/Base.xaml b/src/Avalonia.Themes.Simple/Accents/Base.xaml
index 35f8abf64b..c81ba824d8 100644
--- a/src/Avalonia.Themes.Simple/Accents/Base.xaml
+++ b/src/Avalonia.Themes.Simple/Accents/Base.xaml
@@ -46,6 +46,7 @@
       <SolidColorBrush x:Key="CaptionButtonForeground" Color="Black" />
       <SolidColorBrush x:Key="CaptionButtonBackground" Color="#ffe5e5e5" />
       <SolidColorBrush x:Key="CaptionButtonBorderBrush" Color="#ffcacaca" />
+      <StaticResource x:Key="TitleBarBackgroundBrush" ResourceKey="ThemeBackgroundBrush" />
       
     </ResourceDictionary>
     <ResourceDictionary x:Key="Dark">
@@ -91,6 +92,7 @@
       <SolidColorBrush x:Key="CaptionButtonForeground" Color="White" />
       <SolidColorBrush x:Key="CaptionButtonBackground" Color="#ffe5e5e5" />
       <SolidColorBrush x:Key="CaptionButtonBorderBrush" Color="#ffcacaca" />
+      <StaticResource x:Key="TitleBarBackgroundBrush" ResourceKey="ThemeBackgroundBrush" />
     </ResourceDictionary>
   </ResourceDictionary.ThemeDictionaries>
   <FontFamily x:Key="ContentControlThemeFontFamily">fonts:Inter#Inter, $Default</FontFamily>
diff --git a/src/Avalonia.Themes.Simple/Controls/WindowDrawnDecorations.xaml b/src/Avalonia.Themes.Simple/Controls/WindowDrawnDecorations.xaml
index 944ff90e7f..3d76f8b277 100644
--- a/src/Avalonia.Themes.Simple/Controls/WindowDrawnDecorations.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/WindowDrawnDecorations.xaml
@@ -48,7 +48,7 @@
               <!-- Titlebar: background, title text, and drag area live in underlay -->
               <Panel x:Name="PART_TitleBar" VerticalAlignment="Top"
                      Height="{TemplateBinding TitleBarHeight}"
-                     Background="Transparent"
+                     Background="{DynamicResource TitleBarBackgroundBrush}"
                      IsVisible="{TemplateBinding HasTitleBar}"
                      WindowDecorationProperties.ElementRole="TitleBar" />
             </Panel>