Changing ItemsView Layout.Orientation removes the item from ItemsRepeater

[ghost1372]

Describe the bug

<SelectorBar local:SelectorAttach.Orientation="Horizontal"/>

WinUI 3 SelectorBar Source Code:

<Style TargetType="SelectorBar">
    <Setter Property="Padding" Value="{ThemeResource SegmentedPadding}" />
    <Setter Property="Background" Value="{ThemeResource SegmentedBackground}" />
    <Setter Property="BorderBrush" Value="{ThemeResource SegmentedBorderBrush}" />
    <Setter Property="BorderThickness" Value="1" />
    <Setter Property="CornerRadius" Value="{ThemeResource ControlCornerRadius}" />
    <Setter Property="HorizontalAlignment" Value="Left" />
    <Setter Property="VerticalAlignment" Value="Top" />
    <Setter Property="IsTabStop" Value="False" />
    <Setter Property="TabNavigation" Value="Once" />
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="SelectorBar">
                <Grid
                    Background="{TemplateBinding Background}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    ColumnDefinitions="Auto"
                    CornerRadius="{TemplateBinding CornerRadius}"
                    RowDefinitions="Auto">
                    <Grid.ChildrenTransitions>
                        <TransitionCollection>
                            <RepositionThemeTransition />
                        </TransitionCollection>
                    </Grid.ChildrenTransitions>

                    <ItemsView
                        x:Name="PART_ItemsView"
                        MaxWidth="{TemplateBinding MaxWidth}"
                        MaxHeight="{TemplateBinding MaxHeight}"
                        Padding="{TemplateBinding Padding}"
                        ItemsSource="{TemplateBinding Items}"
                        TabNavigation="{TemplateBinding TabNavigation}">
                        <ItemsView.Layout>
                            <StackLayout Orientation="Horizontal" />
                        </ItemsView.Layout>
                    </ItemsView>
                </Grid>
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>

Steps to reproduce the bug

1.Create a ItemsView with a StackLayout
2.Try to Change StackLayout Orientation in Runtime
3.Select Different Items
4.Change Orientation again

Expected behavior

No response

Screenshots

No response

NuGet package version

WinUI 3 - Windows App SDK 1.5.0: 1.5.240227000

Windows version

Windows 11 (22H2): Build 22621

Additional context

No response

[github-actions]

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Please view the issues below to see if they solve your problem, and if the issue describes your problem please consider closing this one. Thank you!

Closed similar issues:

• ListView/ItemsRepeater layout broken (#6989), similarity score: 0.75
• ItemsRepeater within ListView causing layout cycles (#544), similarity score: 0.70

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[ranjeshj]

@ghost1372 can you please share your repro project?

[ghost1372]

Hi @ranjeshj
Please Download sample
1.Run App
2.Select item
3.Change Orientation in runtime

4.Select another item
5.Change Orientation Again
6.you can see crash

App5.zip

[karkarl]

Fixed in internal repo: Pull Request 10572937: Changing ItemsView Layout.Orientation removes the item from ItemsRepeater Fix

[karkarl]

Description of fix:

Repro has created a custom attached property to SelectorBar, where it toggles ItemsView's Layout.Orientation:

ItemsView itemsView = FindChild<ItemsView>(selectorBar, "PART_ItemsView");
itemsView.Layout = new StackLayout { Orientation = Orientation.Horizontal };

This implementation manually sets a new StackLayout with different orientations compared to simply toggling ItemsView.Layout.Orientation = Horizontal. As such, ItemsRepeater treats it as changing its layout completely, and goes through the whole virtualization process in recycling and re-realizing the elements.

There are multiple layers to this issue:

• ItemsRepeater::OnLayoutChanged goes through and clears each element in the collection. If pinned, it goes to m_pinnedPool when cleared.
• In this situation, the pinned element is added to m_pinnedPool twice. Once at line 694, and again when manually cleared at 706:
  
• When ViewManager goes through m_pinnedPool after layout changed at ViewManager::GetElementFromPinnedElements, the first is cleared properly, but the extra element in m_pinnedPool remains and is never cleared.
• If one swaps the layout more times, the size in m_pinnedPool actually slowly creeps up.
• When user goes to select another element, it falsely starts checking in pinnedPool at ViewManager::PrunePinnedElements() since there is an element that shouldn't be there.
• The previously selected element is no longer pinned, thus the element is mistakenly removed from the Collection.

Fix: adds a check for uniqueness when adding to m_pinnedPool so there will be no duplicates. After layoutChanged, size of m_pinnedPool is reset to 0 as designed.

[ghost1372]

Thank you
Can we expect it in v1.5.x?
Or we should wait for 1.6?