Prevent measure in flexlayout during arrange pass

src/Controls/src/Core/Layout/FlexLayout.cs

@@ -497,22 +497,32 @@ void AddFlexItem(int index, IView child)
 			{
 				item.SelfSizing = (Flex.Item it, ref float w, ref float h) =>
 				{
-					var sizeConstraints = item.GetConstraints();
+					Size request;
 
-					sizeConstraints.Width = (InMeasureMode && sizeConstraints.Width == 0) ? double.PositiveInfinity : sizeConstraints.Width;
-					sizeConstraints.Height = (InMeasureMode && sizeConstraints.Height == 0) ? double.PositiveInfinity : sizeConstraints.Height;
-
-					if (child is Image)
+					if (InMeasureMode)
 					{
-						// This is a hack to get FlexLayout to behave like it did in Forms
-						// Forms always did its initial image measure unconstrained, which would return
-						// the intrinsic size of the image (no scaling or aspect ratio adjustments)
+						var sizeConstraints = item.GetConstraints();
 
-						sizeConstraints.Width = double.PositiveInfinity;
-						sizeConstraints.Height = double.PositiveInfinity;
-					}
+						sizeConstraints.Width = (InMeasureMode && sizeConstraints.Width == 0) ? double.PositiveInfinity : sizeConstraints.Width;
+						sizeConstraints.Height = (InMeasureMode && sizeConstraints.Height == 0) ? double.PositiveInfinity : sizeConstraints.Height;
+
+						if (child is Image)
+						{
+							// This is a hack to get FlexLayout to behave like it did in Forms
+							// Forms always did its initial image measure unconstrained, which would return
+							// the intrinsic size of the image (no scaling or aspect ratio adjustments)
+
+							sizeConstraints.Width = double.PositiveInfinity;
+							sizeConstraints.Height = double.PositiveInfinity;
+						}
 
-					var request = child.Measure(sizeConstraints.Width, sizeConstraints.Height);
+						request = child.Measure(sizeConstraints.Width, sizeConstraints.Height);
+					}
+					else
+					{
+						// Arrange pass, do not ever run a measure here!
+						request = child.DesiredSize;
+					}
 					w = (float)request.Width;
 					h = (float)request.Height;
 				};

src/Controls/tests/Core.UnitTests/Layouts/FlexLayoutTests.cs

@@ -43,8 +43,7 @@ public void FlexLayoutMeasuresImagesUnconstrained()
 			root.Add(flexLayout);
 			flexLayout.Add(image as IView);
 
-			var manager = new FlexLayoutManager(flexLayout);
-			_ = manager.Measure(1000, 1000);
+			flexLayout.CrossPlatformMeasure(1000, 1000);
 
 			Assert.True(image.Passed, "Image should be measured unconstrained even if the FlexLayout is constrained.");
 		}
@@ -61,21 +60,19 @@ public void FlexLayoutRecognizesVisibilityChange()
 			flexLayout.Add(view as IView);
 			flexLayout.Add(view2 as IView);
 
-			var manager = new FlexLayoutManager(flexLayout);
-
 			// Measure and arrange the layout while the first view is visible
-			var measure = manager.Measure(1000, 1000);
-			manager.ArrangeChildren(new Rect(Point.Zero, measure));
+			var measure = flexLayout.CrossPlatformMeasure(1000, 1000);
+			flexLayout.CrossPlatformArrange(new Rect(Point.Zero, measure));
 
 			// Keep track of where the second view is arranged
 			var whenVisible = view2.Frame.X;
 
 			// Change the visibility
 			view.IsVisible = false;
 
-			// Measure and arrange againg
-			measure = manager.Measure(1000, 1000);
-			manager.ArrangeChildren(new Rect(Point.Zero, measure));
+			// Measure and arrange again
+			measure = flexLayout.CrossPlatformMeasure(1000, 1000);
+			flexLayout.CrossPlatformArrange(new Rect(Point.Zero, measure));
 
 			var whenInvisible = view2.Frame.X;
 

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue20696.cs

@@ -0,0 +1,30 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue20696 : _IssuesUITest
+	{
+		public override string Issue => "[iOS] FlyoutHeader does not change its size after adding new content";
+
+		public Issue20696(TestDevice device) : base(device)
+		{
+		}
+
+		#if IOS
+		[Test]
+		#endif
+		public void FlyoutHeaderShouldBeResized()
+		{
+			_ = App.WaitForElement("GoToTest");
+			App.Tap("GoToTest");
+
+			_ = App.WaitForElement("button");
+			App.Tap("button");
+
+			//The test passes if the second button is visible in the flyout header
+			_ = App.WaitForElement("TestButton2");
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue9075.cs

@@ -0,0 +1,25 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue9075 : _IssuesUITest
+{
+	public override string Issue => "FlexLayout trigger Cycle GUI exception";
+
+	public Issue9075(TestDevice device)
+		: base(device)
+	{ }
+
+	#if WINDOWS
+	[Test]
+	[Category(UITestCategories.Layout)]
+	#endif
+	public void FlexLayoutCycleException()
+	{
+		App.WaitForElement("Item2");
+
+		// Without exceptions, the test has passed.
+	}
+}

src/Controls/tests/TestCases/Issues/Issue9075.xaml

@@ -0,0 +1,78 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage
+    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+    x:Class="Maui.Controls.Sample.Issues.Issue9075">
+  <ScrollView>
+    <Grid 
+      BackgroundColor="LightCoral">
+      <Grid.RowDefinitions>
+        <RowDefinition Height="410"/>
+        <RowDefinition Height="60"/>
+      </Grid.RowDefinitions>
+      <CarouselView 
+        ItemsSource="{Binding CarouselGrids}" 
+        IndicatorView="indic"
+        HorizontalOptions="Center"
+        VerticalOptions="Center" 
+        HeightRequest="400"
+        Loop="False" 
+        BackgroundColor="PaleGoldenrod">
+        <CarouselView.ItemTemplate>
+          <DataTemplate>
+            <Grid>
+              <Border
+                Margin="10,0,10,10" 
+                Stroke="Blue" 
+                HeightRequest="300" 
+                WidthRequest="300"    
+                Background="WhiteSmoke" 
+                StrokeThickness="8" 
+                StrokeShape="RoundRectangle 5">
+                <Border.Shadow>
+                  <Shadow 
+                    Brush="Black" 
+                    Offset="10,10" 
+                    Radius="20" 
+                    Opacity="0.8"/>
+                </Border.Shadow>
+                <CollectionView ItemsSource="{Binding}">
+                  <CollectionView.ItemTemplate>
+                    <DataTemplate>
+                      <FlexLayout>
+                        <Border
+                          Margin="1" 
+                          Stroke="Red" 
+                          HeightRequest="30" 
+                          WidthRequest="30"            
+                          Background="WhiteSmoke" 
+                          StrokeThickness="2">
+                          <Label 
+                            Text="{Binding}" 
+                            AutomationId="{Binding}" 
+                            TextColor="Red" 
+                            FontSize="12" 
+                            FontAttributes="Bold"      
+                            HorizontalTextAlignment="Center" 
+                            VerticalTextAlignment="Center"/>
+                        </Border>
+                      </FlexLayout>
+                    </DataTemplate>
+                  </CollectionView.ItemTemplate>
+                </CollectionView>
+              </Border>
+            </Grid>
+          </DataTemplate>
+        </CarouselView.ItemTemplate>
+      </CarouselView>
+      <IndicatorView
+        Grid.Row="1" 
+        HorizontalOptions="Center" 
+        IndicatorSize="22" 
+        IndicatorsShape="Circle"
+        IndicatorColor="Gainsboro" 
+        SelectedIndicatorColor="#006EFF"
+        x:Name="indic" />
+    </Grid>
+  </ScrollView>
+</ContentPage>

src/Controls/tests/TestCases/Issues/Issue9075.xaml.cs

@@ -0,0 +1,60 @@
+using System.Collections.ObjectModel;
+using Microsoft.Maui.Controls.Internals;
+using Microsoft.Maui.Controls;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.None, 9075, "FlexLayout trigger Cycle GUI exception", PlatformAffected.UWP)]
+	public partial class Issue9075 : ContentPage
+	{
+		public Issue9075()
+		{
+			InitializeComponent();
+
+			BindingContext = new Issue9075ViewModel();
+		}
+	}
+
+	[Preserve(AllMembers = true)]
+	public partial class Issue9075ViewModel : BindableObject
+	{
+		List<int> _carouselCards = new()
+		{
+			49,
+			12,
+			50,
+			10,
+			25,
+			9,
+			99,
+			77
+		};
+
+		ObservableCollection<ObservableCollection<string>> _carouselGrids = new();
+
+		public ObservableCollection<ObservableCollection<string>> CarouselGrids
+		{ 
+			get => _carouselGrids; 
+			set
+			{
+				_carouselGrids = value;
+				OnPropertyChanged();
+			}
+		}
+
+		public Issue9075ViewModel()
+		{
+			_InitGrids();
+		}
+
+		private void _InitGrids()
+		{
+			foreach (var card in _carouselCards)
+			{
+				_carouselGrids.Add(new ObservableCollection<string>(Enumerable.Range(1, card).Select(x=> $"Item{x}")));
+			}
+		}
+	}
+}