ItemsRepeater extremely slow

[Leon99]

Describe the bug
Even with ~20 items, ItemsRepeater takes a few seconds to scroll.

To Reproduce

    <DockPanel>
        <TextBox
            Name="SearchTextBox"
            Margin="15,5,15,10"
            Classes="clearButton"
            DockPanel.Dock="Top"
            Text="{Binding SearchTerm}"
            Watermark="Filter" />
        <ScrollViewer Padding="15,0">
            <ItemsRepeater ItemsSource="{Binding Types}">
                <ItemsRepeater.ItemTemplate>
                    <DataTemplate DataType="model:TypeExtract">
                        <controls:SettingsExpander
                            Margin="0,1"
                            Description="{Binding Namespace}"
                            Header="{Binding Name}" />
                    </DataTemplate>
                </ItemsRepeater.ItemTemplate>
            </ItemsRepeater>
        </ScrollViewer>
    </DockPanel>

Desktop (please complete the following information):

• OS: Windows 11
• Version 11.0.1

Additional context
Debug output constantly shows

[Layout]Layout cycle detected. Item 'Avalonia.Controls.StackPanel' was enqueued '10' times.(LayoutQueue`1 #12819582)
[Layout]Layout cycle detected. Item 'Avalonia.Controls.TextBlock' was enqueued '10' times.(LayoutQueue`1 #12819582)
[Layout]Layout cycle detected. Item 'Avalonia.Controls.Presenters.ContentPresenter' was enqueued '10' times.(LayoutQueue`1 #12819582)

[timunie]

please attach or link a very minimal sample to reproduce. Thx.

[IanRawley]

I've had something similar occur when two controls from two adjacent rows in the ItemsRepeater were touching. Specifically Buttons that took up the full height of their row. Try adding small margins to the outermost layout elements and see if that fixes the cycles.

Specifically the outermost layout elements of the controls:SettingsExpander

[timunie]

@IanRawley interesting. Probably you can share a sample of your edge-case? Then we can investigate it further.

[Leon99]

Seems to be caused by FluentAvalonia.UI.Controls.NavigationView. Created amwx/FluentAvalonia#445 instead.

[IanRawley]

@IanRawley interesting. Probably you can share a sample of your edge-case? Then we can investigate it further.

Sorry, it was a while back and I don't have the code any more, or remember enough about the specifics to confidently reproduce it. It was also part of my first attempt at a custom control having just started using Avalonia, so no doubt there were many more issues contributing to it. I just remember that adding margins to a button in the datatemplate solved all my layout cycles.

[Leon99]

Hey @timunie, @amwx believes it's an Avalonia issue after all. Could you check it? I made a minimal repro.

[timunie]

minimal repro is in deed often useful. We can add it to samples/Sandbox and maybe debug it.