TreeView Virtualization seems to be broken under .NET 7

[akade]

Environment: SDKs 7.0.100 & 6.0.301 on Win 10 22H2

.NET SDK: Version: 7.0.100 Commit: e12b7af219

Runtime Environment:
OS Name: Windows
OS Version: 10.0.19045
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\7.0.100\

Host:
Version: 7.0.0
Architecture: x64
Commit: d099f075e4

.NET SDKs installed:
6.0.301 [C:\Program Files\dotnet\sdk]
7.0.100 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 7.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 3.1.22 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.10 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.22 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.10 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
Not set

global.json file:
Not found

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download

Problem description:

If a TreeView is within a StackPanel and has Virtualization turned on, it fails to render more than one item on the second or deeper level of the treeview:

While the same under .NET 6 works as expected:

Minimal repro:
WpfApp2.zip
Just change the TFM, clean & rebuild in VS to reproduce the bug.

[lindexi]

I can repro this issues. But I haven't pinpointed the specific problem yet.

[Laniusexcubitor]

The same happens when grouping in an ItemsControl and enabling virtualization for grouping.
There seems to be an issue with hierarchical virtualization.

See this gist for a repro with a simple items control with virtualization and grouping.
All items get realized in dotnet 6 but only the first item in each group gets realized in dotnet 7

[zlatanov]

I can confirm that this happens with ItemsControl with virtualization enabled as @Laniusexcubitor said. This is a major setback, why is no one on the WPF team responding to this?

[batzen]

It's not limited to the TreeView. Virtualized grouping is also affected, so i guess nested virtualization is affected completely.

[batzen]

@dipeshmsft any chance someone from the WPF team can have a look at this?

[pchaurasia14]

@batzen - Yes. We're checking on this. Will update this thread asap.

[singhashish-wpf]

InternalChildren Property is showing up wrong value along with other properties related to the size and height. Still debugging it further to check for the root cause.