Setting MaximumRowsOrColumns property of UniformGridLayout causes holes and crashes in ItemsRepeater.

[MilesChing]

Describe the bug

Setting MaximumRowsOrColumns property of UniformGridLayout causes holes and crashes in ItemsRepeater. Holes appear in the upper right corner when using the latest stable version 2.3.191211002 of Microsoft.UI.Xaml.Controls on Nuget. Sliding errors with the ScrollViewer occur as well. The application crashed directly when scrolling the ScrollViewer using the latest prereleased version 2.4.0-prerelease.200113001.

Steps to reproduce the bug

The test code is as follows

<!--MainPage.xaml-->
<Page
    x:Class="TestApplication.MainPage"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:TestApplication"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:muxc="using:Microsoft.UI.Xaml.Controls"
    mc:Ignorable="d"
    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

    <Page.Resources>
        <!-- The Layout specifications used: -->
        <muxc:UniformGridLayout x:Name="UniformGridLayout"
                                MinRowSpacing="8" MinColumnSpacing="8"
                                MaximumRowsOrColumns="4"/>

        <!-- The DataTemplate used: CircularTemplate-->

        <DataTemplate x:Key="CircularTemplate" x:DataType="local:Bar">
            <Grid Background="Red"
                  Width="100"
                  Height="100">
                <TextBlock Text="{x:Bind str}" 
                           FontSize="20"/>
            </Grid>
        </DataTemplate>
    </Page.Resources>

    <ScrollViewer HorizontalScrollBarVisibility="Auto" 
        HorizontalScrollMode="Auto" 
        IsVerticalScrollChainingEnabled="False"
        MaxHeight="500">
        <muxc:ItemsRepeater
            ItemsSource="{x:Bind collection}"
            Layout="{StaticResource UniformGridLayout}"
            ItemTemplate="{StaticResource CircularTemplate}"
        />
    </ScrollViewer>
</Page>

//MainPage.xaml.cs
using System;
using System.Collections.ObjectModel;
using Windows.UI.Xaml.Controls;

namespace TestApplication
{
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
            for (int i = 0; i < 40; ++i)
                collection.Add(new Bar(i.ToString()));
        }

        public ObservableCollection<Bar> collection
            = new ObservableCollection<Bar>();
    }

    public class Bar
    {
        public Bar(string str) { this.str = str; }

        public String str;
    }
}

Screenshots

Version Info

Windows 10 18363.592

NuGet package version:

• Microsoft.UI.Xaml 2.4.0-prerelease.200113001
• Microsoft.UI.Xaml 2.3.191211002

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
November 2019 Update (18363)	Yes
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Mobile
Xbox
Surface Hub
IoT

[ranjeshj]

@MilesChing Is this specifically when using MaximumRowsOrColumns?
Which OS are you running on ? For this scenario to work downlevel, you will need to add ItemsRepeaterScrollHost, since ScrollViewer does not perform anchoring downlevel. ItemsRepeaterScrollhost is the interim solution until WinUI3 at which point it will not be needed.

[MilesChing]

@MilesChing Is this specifically when using MaximumRowsOrColumns?
Which OS are you running on ? For this scenario to work downlevel, you will need to add ItemsRepeaterScrollHost, since ScrollViewer does not perform anchoring downlevel. ItemsRepeaterScrollhost is the interim solution until WinUI3 at which point it will not be needed.

Yes and it don't happen when MaximumRowsOrColumns is not set.
I'm running the test code on version 1909. It seems that this version does not require an ItemsRepeaterScrollHost, and using it doesn't work.

[marcelwgn]

I would like to look into this issue (feel free to assign this to me),