Fix crash with unbounded sizing for WrapLayout.

Microsoft.Toolkit.Uwp.SampleApp/SamplePages/StaggeredLayout/StaggeredLayoutPage.xaml.cs

@@ -34,7 +34,7 @@ public StaggeredLayoutPage()
 
         public void OnXamlRendered(FrameworkElement control)
         {
-            var repeater = control.FindChildByName("StaggeredRepeater") as ItemsRepeater;
+            var repeater = control.FindDescendantByName("StaggeredRepeater") as ItemsRepeater;
 
             if (repeater != null)
             {

Microsoft.Toolkit.Uwp.SampleApp/SamplePages/WrapLayout/WrapLayout.bind

@@ -19,7 +19,7 @@
 
   <Grid Padding="48">
     <winui:ItemsRepeaterScrollHost> <!-- Needed for 1803 and below -->
-      <ScrollViewer>
+      <ScrollViewer x:Name="WrapScrollParent">
         <winui:ItemsRepeater x:Name="WrapRepeater"
                              Background="{ThemeResource Brush-Grey-04}"
                              ItemTemplate="{StaticResource WrapTemplate}">

Microsoft.Toolkit.Uwp.SampleApp/SamplePages/WrapLayout/WrapLayoutPage.xaml

@@ -6,10 +6,17 @@
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
     xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
     xmlns:controls="using:Microsoft.Toolkit.Uwp.UI.Controls"
+    xmlns:winui="using:Microsoft.UI.Xaml.Controls"
     mc:Ignorable="d"
     Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
 
     <Page.Resources>
         <controls:WrapLayout x:Key="WrapLayoutPlaceholder"/>
     </Page.Resources>
+
+    <winui:ItemsRepeaterScrollHost>
+        <ScrollViewer x:Name="WrapScrollParent">
+            <winui:ItemsRepeater x:Name="WrapRepeater"/>
+        </ScrollViewer>
+    </winui:ItemsRepeaterScrollHost>
 </Page>

Microsoft.Toolkit.Uwp.SampleApp/SamplePages/WrapLayout/WrapLayoutPage.xaml.cs

@@ -4,6 +4,7 @@
 
 using System;
 using System.Collections.ObjectModel;
+using Microsoft.Toolkit.Uwp.UI.Controls;
 using Microsoft.Toolkit.Uwp.UI.Extensions;
 using Microsoft.UI.Xaml.Controls;
 using Windows.UI;
@@ -19,11 +20,15 @@ public sealed partial class WrapLayoutPage : Page, IXamlRenderListener
     {
         private ObservableCollection<Item> _items = new ObservableCollection<Item>();
         private Random _random;
+        private ScrollViewer _wrapScrollParent;
+        private WrapLayout _wrapLayout;
 
         public WrapLayoutPage()
         {
             this.InitializeComponent();
 
+            SampleController.Current.RegisterNewCommand("Switch Orientation", SwitchButton_Click);
+
             _random = new Random(DateTime.Now.Millisecond);
             for (int i = 0; i < _random.Next(1000, 5000); i++)
             {
@@ -34,12 +39,16 @@ public WrapLayoutPage()
 
         public void OnXamlRendered(FrameworkElement control)
         {
-            var repeater = control.FindChildByName("WrapRepeater") as ItemsRepeater;
+            var repeater = control.FindDescendantByName("WrapRepeater") as ItemsRepeater;
 
             if (repeater != null)
             {
                 repeater.ItemsSource = _items;
+
+                _wrapLayout = repeater.Layout as WrapLayout;
             }
+
+            _wrapScrollParent = control.FindDescendantByName("WrapScrollParent") as ScrollViewer;
         }
 
         private class Item
@@ -52,5 +61,28 @@ private class Item
 
             public Color Color { get; internal set; }
         }
+
+        private void SwitchButton_Click(object sender, Windows.UI.Xaml.RoutedEventArgs e)
+        {
+            if (_wrapLayout != null && _wrapScrollParent != null)
+            {
+                if (_wrapLayout.Orientation == Orientation.Horizontal)
+                {
+                    _wrapLayout.Orientation = Orientation.Vertical;
+                    ScrollViewer.SetVerticalScrollMode(_wrapScrollParent, ScrollMode.Disabled);
+                    ScrollViewer.SetVerticalScrollBarVisibility(_wrapScrollParent, ScrollBarVisibility.Disabled);
+                    ScrollViewer.SetHorizontalScrollMode(_wrapScrollParent, ScrollMode.Auto);
+                    ScrollViewer.SetHorizontalScrollBarVisibility(_wrapScrollParent, ScrollBarVisibility.Auto);
+                }
+                else
+                {
+                    _wrapLayout.Orientation = Orientation.Horizontal;
+                    ScrollViewer.SetVerticalScrollMode(_wrapScrollParent, ScrollMode.Auto);
+                    ScrollViewer.SetVerticalScrollBarVisibility(_wrapScrollParent, ScrollBarVisibility.Auto);
+                    ScrollViewer.SetHorizontalScrollMode(_wrapScrollParent, ScrollMode.Disabled);
+                    ScrollViewer.SetHorizontalScrollBarVisibility(_wrapScrollParent, ScrollBarVisibility.Disabled);
+                }
+            }
+        }
     }
 }

Microsoft.Toolkit.Uwp.UI.Controls.Layout/WrapLayout/WrapLayout.cs

@@ -254,10 +254,18 @@ protected override Size MeasureOverride(VirtualizingLayoutContext context, Size
             // for the last condition it is zeros so adding it will make no difference
             // this way is faster than an if condition in every loop for checking the last item
             totalMeasure.U = parentMeasure.U;
+
+            // Propagating an infinite size causes a crash. This can happen if the parent is scrollable and infinite in the opposite
+            // axis to the panel. Clearing to zero prevents the crash.
+            // This is likely an incorrect use of the control by the developer, however we need stability here so setting a default that wont crash.
+            if (double.IsInfinity(totalMeasure.U))
+            {
+                totalMeasure.U = 0.0;
+            }
+
             totalMeasure.V = state.GetHeight();
 
             totalMeasure.U = Math.Ceiling(totalMeasure.U);
-
             return Orientation == Orientation.Horizontal ? new Size(totalMeasure.U, totalMeasure.V) : new Size(totalMeasure.V, totalMeasure.U);
         }