Bug: Make TargetType support abstract classes

[mfkl]

Describe the bug

Hi,

While trying to add support for MAUI WinUI in LibVLCSharp (videolan/libvlcsharp#370), I've ran into what I believe is a regression. Indeed this behavior is supported in other XAML/UI flavors so I believe it should also work in WinUI MAUI.

Given this style:

<ResourceDictionary
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:vlc="using:LibVLCSharp.Platforms.Windows">

    <Style TargetType="vlc:VideoViewBase">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="vlc:VideoViewBase">
                    <SwapChainPanel x:Name="SwapChainPanel" />
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>

And this base class:

[TemplatePart(Name = PartSwapChainPanelName, Type = typeof(SwapChainPanel))]
public abstract class VideoViewBase : Control, IVideoView
{
/// stuff
}

This works fine in UWP, WinUI and Uno. But in WinUI for MAUI, I get the following error logs and stack trace:

Exception thrown at 0x00007FFE1316B699 (KernelBase.dll) in LibVLCSharp.MAUI.Sample.exe: WinRT originate error - 0x800F1000 : 'Cannot apply a Style with TargetType 'LibVLCSharp.Platforms.Windows.VideoViewBase' to an object of type 'Microsoft.UI.Xaml.Controls.Control'.'.
Microsoft.ui.xaml.dll!00007FFD09D843D2: 800F1000 - E_NER_INVALID_OPERATION
Exception thrown: 'System.Runtime.InteropServices.COMException' in WinRT.Runtime.dll
Exception thrown at 0x00007FFE1316B699 (KernelBase.dll) in LibVLCSharp.MAUI.Sample.exe: WinRT originate error - 0x800F1000 : 'No installed components were detected.

stack:

 	KernelBase.dll!00007ff95768b699()	Unknown
 	Microsoft.UI.Xaml.Controls.dll!00007ff8c616f5bf()	Unknown
 	Microsoft.UI.Xaml.Controls.dll!00007ff8c5d6d0b3()	Unknown
 	Microsoft.UI.Xaml.Controls.dll!00007ff8c5d82e9e()	Unknown
 	Microsoft.UI.Xaml.Controls.dll!00007ff8c5dc42c1()	Unknown
 	Microsoft.UI.Xaml.Controls.dll!00007ff8c5dd89a8()	Unknown
 	[Managed to Native Transition]	
>	Microsoft.WinUI.dll!ABI.Microsoft.UI.Xaml.IFrameworkElementOverridesMethods.MeasureOverride(WinRT.IObjectReference _obj, Windows.Foundation.Size availableSize) Line 30	C#
 	Microsoft.WinUI.dll!Microsoft.UI.Xaml.FrameworkElement.MeasureOverride(Windows.Foundation.Size availableSize) Line 673	C#
 	Microsoft.WinUI.dll!Microsoft.UI.Xaml.FrameworkElement.Microsoft.UI.Xaml.IFrameworkElementOverrides.MeasureOverride(Windows.Foundation.Size availableSize) Line 678	C#
 	Microsoft.WinUI.dll!ABI.Microsoft.UI.Xaml.IFrameworkElementOverrides.Do_Abi_MeasureOverride_0(nint thisPtr, Windows.Foundation.Size availableSize, Windows.Foundation.Size* result) Line 33	C#

This looks like the same issue as CommunityToolkit/Windows#273.

I can reproduce the error 90% of the time when running the sample app.

Steps to reproduce the bug

1. Clone Maui winui videolan/libvlcsharp#370
2. Run the sample without videolan/libvlcsharp@267bf18
3. Observe native exception on start

Expected behavior

Support abstract classes in Style TargetType in MAUI WinUI. Like in regular WinUI/UWP.

Screenshots

No response

NuGet package version

WinUI 3 - Windows App SDK 1.6.3: 1.6.241114003

Windows version

Windows 10 (21H2): Build 19044

Additional context

No response

[karkarl]

This seems to be an issue with maui. Please re-file the bug with their repo:
https://github.com/dotnet/maui