DataGrid Header loses fluent styling when HorizontalContentAlignment property applied

[leeaa-s-thermal]

Description

DataGrid Header loses fluent styling when HorizontalContentAlignment property applied Without any props on the datagrid header the header style is ok :

<Window.Resources>
    <!--<Style TargetType="{x:Type DataGridColumnHeader}">
        <Setter Property="HorizontalContentAlignment" Value="Center"/>
    </Style>-->
    <Style TargetType="{x:Type DataGridCell}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type DataGridCell}">
                    <Grid Background="{TemplateBinding Background}">
                        <ContentPresenter HorizontalAlignment="Center" />
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</Window.Resources>

once

    <Style TargetType="{x:Type DataGridColumnHeader}">
        <Setter Property="HorizontalContentAlignment" Value="Center"/>
    </Style>

is enabled:

only the header becomes light theme

Reproduction Steps

use this with a datagrid that has column headers and toggle the disabled prop:

<Window.Resources>
    <!--<Style TargetType="{x:Type DataGridColumnHeader}">
        <Setter Property="HorizontalContentAlignment" Value="Center"/>
    </Style>-->
    <Style TargetType="{x:Type DataGridCell}">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type DataGridCell}">
                    <Grid Background="{TemplateBinding Background}">
                        <ContentPresenter HorizontalAlignment="Center" />
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</Window.Resources>

maybe relevant .csproj:

	<PropertyGroup>
		<OutputType>WinExe</OutputType>
		<TargetFramework>net9.0-windows</TargetFramework>
		<Nullable>enable</Nullable>
		<ImplicitUsings>enable</ImplicitUsings>
		<UseWPF>true</UseWPF>
		<UseWindowsForms>False</UseWindowsForms>
		<StartupObject></StartupObject>
		<AllowUnsafeBlocks>true</AllowUnsafeBlocks>
		<NoWarn>$(NoWarn);WPF0001</NoWarn>
		<ApplicationIcon>Properties\icon.ico</ApplicationIcon>

	</PropertyGroup>

this is how I'm applying the theme:

    public MainWindow() {
        InitializeComponent();

        Application.Current.ThemeMode = ThemeMode.System;
        //...
}

Expected behavior

The header should remain in dark mode, even if the text is centered. Works just fine for the datagrid cells, only the headers break.

Actual behavior

Header goes to light theme, no errors that I've seen.

Regression?

No response

Known Workarounds

No response

Impact

No response

Configuration

dotnet --version
9.0.101

systeminfo:

systeminfo

Host Name:                     
OS Name:                       Microsoft Windows 11 Business
OS Version:                    10.0.26100 N/A Build 26100
OS Manufacturer:               Microsoft Corporation
OS Configuration:              Member Workstation
OS Build Type:                 Multiprocessor Free
System Manufacturer:           Dell Inc.
System Model:                  Precision 5770
System Type:                   x64-based PC
Processor(s):                  1 Processor(s) Installed.
                               [01]: Intel64 Family 6 Model 154 Stepping 3 GenuineIntel ~2400 Mhz
BIOS Version:                  Dell Inc. 1.28.0, 9/26/2024
Windows Directory:             C:\WINDOWS
System Directory:              C:\WINDOWS\system32
Boot Device:                   \Device\HarddiskVolume1
System Locale:                 en-us;English (United States)
Input Locale:                  en-us;English (United States)
Time Zone:                     (UTC-08:00) Pacific Time (US & Canada)
Total Physical Memory:         32,453 MB
Available Physical Memory:     10,831 MB
Virtual Memory: Max Size:      44,229 MB
Virtual Memory: Available:     16,083 MB
Virtual Memory: In Use:        28,146 MB
Page File Location(s):         C:\pagefile.sys

Logon Server:                  \\SERVER-ST-1
Hotfix(s):                     4 Hotfix(s) Installed.
                               [01]: KB5054979
                               [02]: KB5058411
                               [03]: KB5058538
                               [04]: KB5058523

Virtualization-based security: Status: Running
                               Required Security Properties:
                               Available Security Properties:
                                     Base Virtualization Support
                                     Secure Boot
                                     DMA Protection
                                     UEFI Code Readonly
                                     SMM Security Mitigations 1.0
                                     Mode Based Execution Control
                                     APIC Virtualization
                               Services Configured:
                                     Hypervisor enforced Code Integrity
                               Services Running:
                                     Hypervisor enforced Code Integrity
                                     Hypervisor-Enforced Paging Translation
                               App Control for Business policy: Enforced
                               App Control for Business user mode policy: Off
                               Security Features Enabled:
Hyper-V Requirements:          A hypervisor has been detected. Features required for Hyper-V will not be displayed.

Other information

On light theme, it seems to be a slightly different control object (has highlighting on select, has arrows)

the sorting arrows work on light theme, but not dark. My guess is that it might be falling back to light theme because the dark ones are missing certain properties?

[IoBebe]

I just ran into the same problem, any updates ?

I'm also experiencing the same behaviour if I Bind the IsEnabled property of the DataGrid. While it switches to the default style for when IsEnabled = false, it looses the Fluent style