Change iOS SetNeedsLayout propagation mechanism

src/Controls/src/Core/Compatibility/Handlers/iOS/FrameRenderer.cs

@@ -217,34 +217,6 @@ protected override void Dispose(bool disposing)
 			}
 		}
 
-		bool _pendingSuperViewSetNeedsLayout;
-
-		public override void SetNeedsLayout()
-		{
-			base.SetNeedsLayout();
-
-			if (Window is not null)
-			{
-				_pendingSuperViewSetNeedsLayout = false;
-				this.Superview?.SetNeedsLayout();
-			}
-			else
-			{
-				_pendingSuperViewSetNeedsLayout = true;
-			}
-		}
-
-		public override void MovedToWindow()
-		{
-			base.MovedToWindow();
-			if (_pendingSuperViewSetNeedsLayout)
-			{
-				this.Superview?.SetNeedsLayout();
-			}
-
-			_pendingSuperViewSetNeedsLayout = false;
-		}
-
 		[Microsoft.Maui.Controls.Internals.Preserve(Conditional = true)]
 		class FrameView : Microsoft.Maui.Platform.ContentView
 		{

src/Controls/src/Core/Compatibility/Handlers/iOS/VisualElementRenderer.cs

@@ -1,14 +1,14 @@
 using System;
 using System.ComponentModel;
 using Microsoft.Maui.Controls.Platform;
-using Microsoft.Maui.Graphics;
 using UIKit;
 
 namespace Microsoft.Maui.Controls.Handlers.Compatibility
 {
-	public abstract partial class VisualElementRenderer<TElement> : UIView, IPlatformViewHandler, IElementHandler
+	public abstract partial class VisualElementRenderer<TElement> : UIView, IPlatformViewHandler, IElementHandler, IPlatformMeasureInvalidationController
 		where TElement : Element, IView
 	{
+		bool _invalidateParentWhenMovedToWindow;
 		object? IElementHandler.PlatformView => Subviews.Length > 0 ? Subviews[0] : this;
 
 		public virtual UIViewController? ViewController => null;
@@ -93,5 +93,22 @@ void OnSizeChanged(object? sender, EventArgs e)
 		{
 			UpdateNativeWidget();
 		}
+
+		void IPlatformMeasureInvalidationController.InvalidateAncestorsMeasuresWhenMovedToWindow()
+		{
+			_invalidateParentWhenMovedToWindow = true;
+		}
+
+		void IPlatformMeasureInvalidationController.InvalidateMeasure(bool isPropagating) => SetNeedsLayout();
+
+		public override void MovedToWindow()
+		{
+			base.MovedToWindow();
+			if (_invalidateParentWhenMovedToWindow)
+			{
+				_invalidateParentWhenMovedToWindow = false;
+				this.InvalidateAncestorsMeasures();
+			}
+		}
 	}
 }

src/Controls/src/Core/Handlers/Items/iOS/MauiCollectionView.cs

@@ -5,8 +5,10 @@
 
 namespace Microsoft.Maui.Controls.Handlers.Items;
 
-internal class MauiCollectionView : UICollectionView, IUIViewLifeCycleEvents
+internal class MauiCollectionView : UICollectionView, IUIViewLifeCycleEvents, IPlatformMeasureInvalidationController
 {
+	bool _invalidateParentWhenMovedToWindow;
+
 	WeakReference<ICustomMauiCollectionViewDelegate>? _customDelegate;
 	public MauiCollectionView(CGRect frame, UICollectionViewLayout layout) : base(frame, layout)
 	{
@@ -18,8 +20,22 @@ public override void ScrollRectToVisible(CGRect rect, bool animated)
 			base.ScrollRectToVisible(rect, animated);
 	}
 
+	void IPlatformMeasureInvalidationController.InvalidateAncestorsMeasuresWhenMovedToWindow()
+	{
+		_invalidateParentWhenMovedToWindow = true;
+	}
+
+	void IPlatformMeasureInvalidationController.InvalidateMeasure(bool isPropagating)
+	{
+		if (!isPropagating)
+		{
+			SetNeedsLayout();
+		}
+	}
+
 	[UnconditionalSuppressMessage("Memory", "MEM0002", Justification = IUIViewLifeCycleEvents.UnconditionalSuppressMessage)]
 	EventHandler? _movedToWindow;
+
 	event EventHandler? IUIViewLifeCycleEvents.MovedToWindow
 	{
 		add => _movedToWindow += value;
@@ -35,6 +51,12 @@ public override void MovedToWindow()
 		{
 			target.MovedToWindow(this);
 		}
+
+		if (_invalidateParentWhenMovedToWindow)
+		{
+			_invalidateParentWhenMovedToWindow = false;
+			this.InvalidateAncestorsMeasures();
+		}
 	}
 
 	internal void SetCustomDelegate(ICustomMauiCollectionViewDelegate customDelegate)

src/Controls/src/Core/ImageButton/ImageButton.iOS.cs

@@ -25,7 +25,7 @@ Size ICrossPlatformLayout.CrossPlatformMeasure(double widthConstraint, double he
 			if (platformButton.ImageView.Image is not null)
 			{
 				return platformButton.ImageView
-					.SizeThatFitsImage(constraintSize, Padding.IsNaN ? null : Padding).ToSize();
+					.SizeThatFitsImage(constraintSize, Padding.IsNaN ? default : Padding).ToSize();
 			}
 
 			return platformButton.SizeThatFits(constraintSize).ToSize();

src/Controls/src/Core/PublicAPI/net-ios/PublicAPI.Unshipped.txt

@@ -340,5 +340,7 @@ virtual Microsoft.Maui.Controls.Handlers.Items2.ItemsViewController2<TItemsView>
 virtual Microsoft.Maui.Controls.Handlers.Items2.ItemsViewController2<TItemsView>.UpdateVisibility() -> void
 virtual Microsoft.Maui.Controls.Handlers.Items2.ItemsViewDelegator2<TItemsView, TViewController>.GetVisibleItemsIndex() -> (bool VisibleItems, int First, int Center, int Last)
 virtual Microsoft.Maui.Controls.Handlers.Items2.ItemsViewHandler2<TItemsView>.UpdateLayout() -> void
-override Microsoft.Maui.Controls.Handlers.Compatibility.FrameRenderer.MovedToWindow() -> void
-~Microsoft.Maui.Controls.Internals.TypedBindingBase.UpdateSourceEventName.set -> void
+~Microsoft.Maui.Controls.Internals.TypedBindingBase.UpdateSourceEventName.set -> void
+*REMOVED*override Microsoft.Maui.Controls.Handlers.Compatibility.FrameRenderer.SetNeedsLayout() -> void
+*REMOVED*override Microsoft.Maui.Controls.Handlers.Compatibility.FrameRenderer.MovedToWindow() -> void
+override Microsoft.Maui.Controls.Handlers.Compatibility.VisualElementRenderer<TElement>.MovedToWindow() -> void

src/Controls/src/Core/PublicAPI/net-maccatalyst/PublicAPI.Unshipped.txt

@@ -341,4 +341,6 @@ virtual Microsoft.Maui.Controls.Handlers.Items2.ItemsViewController2<TItemsView>
 virtual Microsoft.Maui.Controls.Handlers.Items2.ItemsViewController2<TItemsView>.UpdateVisibility() -> void
 virtual Microsoft.Maui.Controls.Handlers.Items2.ItemsViewDelegator2<TItemsView, TViewController>.GetVisibleItemsIndex() -> (bool VisibleItems, int First, int Center, int Last)
 virtual Microsoft.Maui.Controls.Handlers.Items2.ItemsViewHandler2<TItemsView>.UpdateLayout() -> void
-override Microsoft.Maui.Controls.Handlers.Compatibility.FrameRenderer.MovedToWindow() -> void
+*REMOVED*override Microsoft.Maui.Controls.Handlers.Compatibility.FrameRenderer.SetNeedsLayout() -> void
+*REMOVED*override Microsoft.Maui.Controls.Handlers.Compatibility.FrameRenderer.MovedToWindow() -> void
+override Microsoft.Maui.Controls.Handlers.Compatibility.VisualElementRenderer<TElement>.MovedToWindow() -> void

src/Controls/tests/DeviceTests/Elements/CarouselView/CarouselViewTests.cs

@@ -147,7 +147,10 @@ await CreateHandlerAndAddToWindow<CarouselViewHandler>(carouselView, async (hand
 				Assert.False(data.IsCollectionChangedEventEmpty);
 			});
 
-			carouselView.Handler?.DisconnectHandler();
+			await InvokeOnMainThreadAsync(() =>
+			{
+				carouselView.Handler?.DisconnectHandler();
+			});
 
 			Assert.True(data.IsCollectionChangedEventEmpty);
 		}

src/Controls/tests/TestCases.HostApp/Issues/Issue24996.xaml

@@ -0,0 +1,39 @@
+<?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"
+             xmlns:issues="clr-namespace:Maui.Controls.Sample.Issues"
+             x:Class="Maui.Controls.Sample.Issues.Issue24996"
+             Title="Issue24996"
+             x:Name="Self">
+  <AbsoluteLayout BackgroundColor="DarkSlateBlue">
+    <AbsoluteLayout.GestureRecognizers>
+      <TapGestureRecognizer Tapped="OnTapped" />
+    </AbsoluteLayout.GestureRecognizers>
+    <Grid RowDefinitions="*" ColumnDefinitions="*">
+      <issues:ObservedLayout24996 x:Name="Lvl1" BackgroundColor="BlueViolet">
+        <issues:ObservedLayout24996 x:Name="Lvl2" BackgroundColor="AliceBlue">
+          <issues:ObservedLayout24996 x:Name="Lvl3"
+                                      BackgroundColor="Aqua"
+                                      HeightRequest="200"
+                                      WidthRequest="200">
+            <Border BackgroundColor="GreenYellow" HeightRequest="100" WidthRequest="100" />
+          </issues:ObservedLayout24996>
+        </issues:ObservedLayout24996>
+      </issues:ObservedLayout24996>
+    </Grid>
+    <VerticalStackLayout AbsoluteLayout.LayoutFlags="PositionProportional"
+                         AbsoluteLayout.LayoutBounds="0,1,-1,-1"
+                         BackgroundColor="#222222">
+      <Label x:Name="Coords"
+             HeightRequest="40"
+             WidthRequest="{Binding Width, Source={x:Reference Self}}"
+             AutomationId="Coords"
+             TextColor="White"/>
+      <Label x:Name="Stats"
+             HeightRequest="40"
+             WidthRequest="{Binding Width, Source={x:Reference Self}}"
+             AutomationId="Stats"
+             TextColor="White"/>
+    </VerticalStackLayout>
+  </AbsoluteLayout>
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issue24996.xaml.cs

@@ -0,0 +1,73 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 24996, "Changing Translation of an element causes Maui in iOS to constantly run Measure & ArrangeChildren", PlatformAffected.All)]
+public partial class Issue24996 : ContentPage
+{
+	Point[] _translations = [
+		new(40, 80),
+		new(1000, 20),
+		new(20, 1000),
+		new(1000, 1000),
+	];
+
+	int _index = -1;
+
+	public Issue24996()
+	{
+		InitializeComponent();
+		UpdateText();
+
+		SizeChanged += delegate {
+			if (Width > 0) {
+				// For some reason, constraining this layout to a fixed size causes a `SetNeedsLayout` to be called
+				// when translating the Lvl2 view outside the bottom boundary.
+				// This causes a layout pass to be called on the Root, Lvl1, Lvl2, and Lvl3.
+				Lvl1.WidthRequest = Width;
+				Lvl1.HeightRequest = Height;
+			}
+		};
+	}
+
+	protected override async void OnAppearing()
+	{
+		base.OnAppearing();
+		await Task.Delay(250);
+		Lvl1.MeasurePasses = Lvl1.ArrangePasses = 0;
+		Lvl2.MeasurePasses = Lvl2.ArrangePasses = 0;
+		Lvl3.MeasurePasses = Lvl3.ArrangePasses = 0;
+		UpdateText();
+	}
+
+	public async void OnTapped(object sender, EventArgs e)
+	{
+		var testPoint = _translations[++_index % _translations.Length];
+		Coords.Text = $"X: {testPoint.X}, Y: {testPoint.Y}";
+		Lvl2.TranslationX = testPoint.X;
+		Lvl2.TranslationY = testPoint.Y;
+		await Task.Delay(100);
+		UpdateText();
+	}
+
+	void UpdateText()
+	{
+		Stats.Text = $"Lvl1[{Lvl1.MeasurePasses}/{Lvl1.ArrangePasses}] - Lvl2[{Lvl2.MeasurePasses}/{Lvl2.ArrangePasses}] - Lvl3[{Lvl3.MeasurePasses}/{Lvl3.ArrangePasses}]";
+	}
+}
+
+public class ObservedLayout24996 : AbsoluteLayout
+{
+	public int MeasurePasses { get; set; }
+	public int ArrangePasses { get; set; }
+
+	protected override Size MeasureOverride(double widthConstraint, double heightConstraint)
+	{
+		MeasurePasses++;
+		return base.MeasureOverride(widthConstraint, heightConstraint);
+	}
+
+	protected override Size ArrangeOverride(Rect bounds)
+	{
+		ArrangePasses++;
+		return base.ArrangeOverride(bounds);
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue24996.cs

@@ -0,0 +1,30 @@
+using NUnit.Framework;
+using NUnit.Framework.Legacy;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue24996 : _IssuesUITest
+	{
+		public Issue24996(TestDevice testDevice) : base(testDevice)
+		{
+		}
+
+		public override string Issue => "Changing Translation of an element causes Maui in iOS to constantly run Measure & ArrangeChildren";
+
+		[Test]
+		[Category(UITestCategories.Layout)]
+		public async Task ChangingTranslationShouldNotCauseLayoutPassOnAncestors()
+		{
+			var element = App.WaitForElement("Stats");
+			// Tries to translate the element in different positions, on-screen and off-screen.
+			for (int i = 0; i < 4; i++)
+			{
+				element.Tap();
+				await Task.Delay(150);
+				ClassicAssert.True(element.GetText()!.StartsWith("Lvl1[0/0]"));
+			}
+		}
+	}
+}

src/Core/src/Handlers/Button/ButtonHandler.iOS.cs

@@ -218,6 +218,11 @@ public override void SetImageSource(UIImage? platformImage)
 				platformImage = platformImage?.ImageWithRenderingMode(UIImageRenderingMode.AlwaysOriginal);
 
 				button.SetImage(platformImage, UIControlState.Normal);
+
+				// UIButton.SetImage(image, forState:) does not immediately assign the image to UIButton.ImageView.Image.
+				// Instead, the image is set internally and only applied to ImageView when the button is rendered.
+				// To ensure SizeThatFits is correct, and avoid race conditions, we have to force a layout.
+				button.LayoutIfNeeded();
 			}
 		}
 	}

src/Core/src/Handlers/ImageButton/ImageButtonHandler.iOS.cs

@@ -83,6 +83,11 @@ public override void SetImageSource(UIImage? platformImage)
 				button.SetImage(platformImage, UIControlState.Normal);
 				button.HorizontalAlignment = UIControlContentHorizontalAlignment.Fill;
 				button.VerticalAlignment = UIControlContentVerticalAlignment.Fill;
+
+				// UIButton.SetImage(image, forState:) does not immediately assign the image to UIButton.ImageView.Image.
+				// Instead, the image is set internally and only applied to ImageView when the button is rendered.
+				// To ensure SizeThatFits is correct, and avoid race conditions, we have to force a layout.
+				button.LayoutIfNeeded();
 			}
 		}
 

src/Core/src/Handlers/Layout/LayoutHandler.iOS.cs

@@ -38,6 +38,8 @@ public override void SetVirtualView(IView view)
 			{
 				PlatformView.AddSubview(child.ToPlatform(MauiContext));
 			}
+
+			PlatformView.InvalidateAncestorsMeasures();
 		}
 
 		public void Add(IView child)
@@ -54,6 +56,8 @@ public void Add(IView child)
 			{
 				childPlatformView.UpdateFlowDirection(child);
 			}
+
+			PlatformView.InvalidateAncestorsMeasures();
 		}
 
 		public void Remove(IView child)
@@ -65,11 +69,14 @@ public void Remove(IView child)
 			{
 				childView.RemoveFromSuperview();
 			}
+
+			PlatformView.InvalidateAncestorsMeasures();
 		}
 
 		public void Clear()
 		{
 			PlatformView.ClearSubviews();
+			PlatformView.InvalidateAncestorsMeasures();
 		}
 
 		public void Insert(int index, IView child)
@@ -86,6 +93,8 @@ public void Insert(int index, IView child)
 			{
 				childPlatformView.UpdateFlowDirection(child);
 			}
+
+			PlatformView.InvalidateAncestorsMeasures();
 		}
 
 		public void Update(int index, IView child)
@@ -99,6 +108,7 @@ public void Update(int index, IView child)
 			var targetIndex = VirtualView.GetLayoutHandlerIndex(child);
 			PlatformView.InsertSubview(child.ToPlatform(MauiContext), targetIndex);
 			PlatformView.SetNeedsLayout();
+			PlatformView.InvalidateAncestorsMeasures();
 		}
 
 		public void UpdateZIndex(IView child)
@@ -137,6 +147,7 @@ void EnsureZIndexOrder(IView child)
 			{
 				PlatformView.Subviews.RemoveAt(currentIndex);
 				PlatformView.InsertSubview(nativeChildView, targetIndex);
+				PlatformView.InvalidateAncestorsMeasures();
 			}
 		}