Replacing source in TreeDataGrid makes UI blank

[DanPristupov]

Adding new data source to an initialized TreeDataGrid makes it completely blank. The data only becomes visible after a short scrolling. Calling treeDataGrid.InvalidateVisual() doesn't help.

https://user-images.githubusercontent.com/618115/151990475-b4b5e13d-5339-40de-9889-ba086bed6796.mov

Steps to reproduce:

.xaml

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        x:Class="AvaloniaTest.MainWindow"
        Title="AvaloniaTest">
      <DockPanel>
        <Button DockPanel.Dock="Bottom" Click="PopulateClick">Populate</Button>
        <TreeDataGrid Name="treeDataGrid"/>
      </DockPanel>
</Window>

.cs

using System;
using Avalonia;
using Avalonia.Controls;
using Avalonia.Controls.Models.TreeDataGrid;
using Avalonia.Interactivity;
using Avalonia.Markup.Xaml;

namespace AvaloniaTest;

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
#if DEBUG
        this.AttachDevTools();
#endif
    }

    private void InitializeComponent()
    {
        AvaloniaXamlLoader.Load(this);
    }

    public void PopulateClick(object sender, RoutedEventArgs e)
    {
        var treeDataGrid = this.FindControl<TreeDataGrid>("treeDataGrid");

        var rootCount = 100;
        var items = new Item[rootCount];
        for (var i = 0; i < rootCount; i += 1)
        {
            items[i] = new Item($"Item {i} {DateTime.UtcNow.Ticks}", null);
        }

        var source = new HierarchicalTreeDataGridSource<Item>(items)
        {
            Columns =
            {
                new HierarchicalExpanderColumn<Item>(
                    new TextColumn<Item, string>(
                        "Title",
                        x => x.Title,
                        new GridLength(1, GridUnitType.Star)
                    ),
                    x => x.Children,
                    x => x.Children != null
                )
            }
        };
        treeDataGrid.Source = source;
    }
}

public class Item
{
    public Item[]? Children { get; }
    public string Title { get; }

    public Item(string title, Item[]? children = null)
    {
        Title = title;
        Children = children;
    }
}

[grokys]

Unable to repro this in the same way as you're seeing it, though I do see that the grid isn't laid out properly when pressing "Populate" multiple times.

[DanPristupov]

I confirm what you say. On the latest version items don't disappear anymore, but the layout gets horizontally trimmed.