[iOS] Improve background layer frame mapping performance

src/Compatibility/Core/src/iOS/Renderers/FrameRenderer.cs

@@ -136,7 +136,6 @@ public override void LayoutSubviews()
 			if (_previousSize != Bounds.Size)
 			{
 				SetNeedsDisplay();
-				this.UpdateBackgroundLayer();
 			}
 
 			base.LayoutSubviews();

src/Compatibility/Core/src/iOS/Renderers/PageRenderer.cs

@@ -135,9 +135,6 @@ public override void ViewDidLayoutSubviews()
 
 			if (_safeAreasSet || !Forms.IsiOS11OrNewer)
 				UpdateUseSafeArea();
-
-			if (Element.Background != null && !Element.Background.IsEmpty)
-				NativeView?.UpdateBackgroundLayer();
 		}
 
 		[SupportedOSPlatform("ios11.0")]

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

@@ -252,11 +252,6 @@ public override void LayoutSubviews()
 				if (_blur.Superview == null)
 					Superview.Add(_blur);
 			}
-
-			bool hasBackground = Element?.Background != null && !Element.Background.IsEmpty;
-
-			if (hasBackground)
-				NativeView.UpdateBackgroundLayer();
 		}
 
 #else

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

@@ -158,7 +158,6 @@ public override void LayoutSubviews()
 			if (_previousSize != Bounds.Size)
 			{
 				SetNeedsDisplay();
-				this.UpdateBackgroundLayer();
 			}
 
 			base.LayoutSubviews();

src/Controls/src/Core/Platform/iOS/Extensions/BrushExtensions.cs

@@ -148,6 +148,8 @@ public static void InsertBackgroundLayer(this CALayer layer, CALayer backgroundL
 					layer.InsertSublayer(backgroundLayer, index);
 				else
 					layer.AddSublayer(backgroundLayer);
+
+				(backgroundLayer as IAutoSizableCALayer)?.AutoSizeToSuperLayer();
 			}
 		}
 
@@ -176,6 +178,7 @@ public static void RemoveBackgroundLayer(this CALayer layer)
 			}
 		}
 
+		[Obsolete("MAUI background layers now automatically update their Frame when their SuperLayer Frame changes. This method will be removed in a future release.")]
 		public static void UpdateBackgroundLayer(this UIView view) =>
 			view.UpdateBackgroundLayerFrame(BackgroundLayer);
 

src/Core/src/Handlers/View/ViewHandler.iOS.cs

@@ -55,7 +55,6 @@ internal static void MapContextFlyout(IElementHandler handler, IContextFlyoutEle
 		static partial void MappingFrame(IViewHandler handler, IView view)
 		{
 			UpdateTransformation(handler, view);
-			handler.ToPlatform().UpdateBackgroundLayerFrame();
 		}
 
 		public static void MapTranslationX(IViewHandler handler, IView view)

src/Core/src/Platform/iOS/ContentView.cs

@@ -27,7 +27,6 @@ public override void LayoutSubviews()
 			base.LayoutSubviews();
 
 			UpdateClip();
-			this.UpdateBackgroundLayerFrame();
 		}
 
 		internal IBorderStroke? Clip

src/Core/src/Platform/iOS/IAutoSizableCALayer.cs

@@ -0,0 +1,13 @@
+namespace Microsoft.Maui.Platform
+{
+	/// <summary>
+	/// Provides a way to automatically size a CALayer to its super layer.
+	/// </summary>
+	public interface IAutoSizableCALayer
+	{
+		/// <summary>
+		/// Automatically sizes the CALayer to its super layer.
+		/// </summary>
+		void AutoSizeToSuperLayer();
+	}
+}

src/Core/src/Platform/iOS/LayerExtensions.cs

@@ -18,6 +18,8 @@ public static void InsertBackgroundLayer(this UIView control, CALayer background
 					layer.InsertSublayer(backgroundLayer, index);
 				else
 					layer.AddSublayer(backgroundLayer);
+
+				(backgroundLayer as IAutoSizableCALayer)?.AutoSizeToSuperLayer();
 			}
 		}
 

src/Core/src/Platform/iOS/MauiCALayer.cs

@@ -3,13 +3,14 @@
 using System.Diagnostics.CodeAnalysis;
 using CoreAnimation;
 using CoreGraphics;
+using Foundation;
 using Microsoft.Maui.Graphics;
 using Microsoft.Maui.Graphics.Platform;
 using UIKit;
 
 namespace Microsoft.Maui.Platform
 {
-	public class MauiCALayer : CALayer
+	public class MauiCALayer : CALayer, IAutoSizableCALayer
 	{
 		CGRect _bounds;
 		[UnconditionalSuppressMessage("Memory", "MEM0002", Justification = "IShape is a non-NSObject in MAUI.")]
@@ -30,13 +31,41 @@ public class MauiCALayer : CALayer
 
 		nfloat _strokeMiterLimit;
 
+		[UnconditionalSuppressMessage("Memory", "MEM0002", Justification = "Sublayer already holds a reference to SuperLayer by design.")]
+		IDisposable? _boundsObserver;
+
 		public MauiCALayer()
 		{
 			_bounds = new CGRect();
-
 			ContentsScale = UIScreen.MainScreen.Scale;
 		}
 
+		protected override void Dispose(bool disposing)
+		{
+			base.Dispose(disposing);
+			_boundsObserver?.Dispose();
+			_boundsObserver = null;
+		}
+
+		public override void RemoveFromSuperLayer()
+		{
+			_boundsObserver?.Dispose();
+			_boundsObserver = null;
+			base.RemoveFromSuperLayer();
+		}
+
+		public void AutoSizeToSuperLayer()
+		{
+			var superLayer = SuperLayer ?? throw new InvalidOperationException("SuperLayer should be set before calling AutoSizeToSuperLayer");
+			_boundsObserver?.Dispose();
+			_boundsObserver = superLayer.AddObserver("bounds", NSKeyValueObservingOptions.New, _ =>
+			{
+				Frame = SuperLayer?.Bounds ?? CGRect.Empty;
+			});
+
+			Frame = superLayer.Bounds;
+		}
+
 		public override void AddAnimation(CAAnimation animation, string? key)
 		{
 			// Do nothing, we don't want animations here

src/Core/src/Platform/iOS/StaticCAGradientLayer.cs

@@ -1,9 +1,42 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
 using CoreAnimation;
+using CoreGraphics;
+using Foundation;
 
 namespace Microsoft.Maui.Platform;
 
-class StaticCAGradientLayer : CAGradientLayer
+class StaticCAGradientLayer : CAGradientLayer, IAutoSizableCALayer
 {
+	[UnconditionalSuppressMessage("Memory", "MEM0002", Justification = "Sublayer already holds a reference to SuperLayer by design.")]
+	IDisposable? _boundsObserver;
+
+	protected override void Dispose(bool disposing)
+	{
+		base.Dispose(disposing);
+		_boundsObserver?.Dispose();
+		_boundsObserver = null;
+	}
+
+	public override void RemoveFromSuperLayer()
+	{
+		_boundsObserver?.Dispose();
+		_boundsObserver = null;
+		base.RemoveFromSuperLayer();
+	}
+
+	public void AutoSizeToSuperLayer()
+	{
+		var superLayer = SuperLayer ?? throw new InvalidOperationException("SuperLayer should be set before calling AutoSizeToSuperLayer");
+		_boundsObserver?.Dispose();
+		_boundsObserver = superLayer.AddObserver("bounds", NSKeyValueObservingOptions.New, _ =>
+		{
+			Frame = SuperLayer?.Bounds ?? CGRect.Empty;
+		});
+
+		Frame = superLayer.Bounds;
+	}
+
 	public override void AddAnimation(CAAnimation animation, string? key)
 	{
 		// Do nothing, we don't want animations here

src/Core/src/Platform/iOS/StaticCALayer.cs

@@ -1,9 +1,42 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
 using CoreAnimation;
+using CoreGraphics;
+using Foundation;
 
 namespace Microsoft.Maui.Platform;
 
-class StaticCALayer : CALayer
+class StaticCALayer : CALayer, IAutoSizableCALayer
 {
+	[UnconditionalSuppressMessage("Memory", "MEM0002", Justification = "Sublayer already holds a reference to SuperLayer by design.")]
+	IDisposable? _boundsObserver;
+
+	protected override void Dispose(bool disposing)
+	{
+		base.Dispose(disposing);
+		_boundsObserver?.Dispose();
+		_boundsObserver = null;
+	}
+
+	public override void RemoveFromSuperLayer()
+	{
+		_boundsObserver?.Dispose();
+		_boundsObserver = null;
+		base.RemoveFromSuperLayer();
+	}
+
+	public void AutoSizeToSuperLayer()
+	{
+		var superLayer = SuperLayer ?? throw new InvalidOperationException("SuperLayer should be set before calling AutoSizeToSuperLayer");
+		_boundsObserver?.Dispose();
+		_boundsObserver = superLayer.AddObserver("bounds", NSKeyValueObservingOptions.New, _ =>
+		{
+			Frame = SuperLayer?.Bounds ?? CGRect.Empty;
+		});
+
+		Frame = superLayer.Bounds;
+	}
+
 	public override void AddAnimation(CAAnimation animation, string? key)
 	{
 		// Do nothing, we don't want animations here

src/Core/src/Platform/iOS/StaticCAShapeLayer.cs

@@ -1,9 +1,42 @@
+using System;
+using System.Diagnostics.CodeAnalysis;
 using CoreAnimation;
+using CoreGraphics;
+using Foundation;
 
 namespace Microsoft.Maui.Platform;
 
-class StaticCAShapeLayer : CAShapeLayer
+class StaticCAShapeLayer : CAShapeLayer, IAutoSizableCALayer
 {
+	[UnconditionalSuppressMessage("Memory", "MEM0002", Justification = "Sublayer already holds a reference to SuperLayer by design.")]
+	IDisposable? _boundsObserver;
+
+	protected override void Dispose(bool disposing)
+	{
+		base.Dispose(disposing);
+		_boundsObserver?.Dispose();
+		_boundsObserver = null;
+	}
+
+	public override void RemoveFromSuperLayer()
+	{
+		_boundsObserver?.Dispose();
+		_boundsObserver = null;
+		base.RemoveFromSuperLayer();
+	}
+
+	public void AutoSizeToSuperLayer()
+	{
+		var superLayer = SuperLayer ?? throw new InvalidOperationException("SuperLayer should be set before calling AutoSizeToSuperLayer");
+		_boundsObserver?.Dispose();
+		_boundsObserver = superLayer.AddObserver("bounds", NSKeyValueObservingOptions.New, _ =>
+		{
+			Frame = SuperLayer?.Bounds ?? CGRect.Empty;
+		});
+
+		Frame = superLayer.Bounds;
+	}
+
 	public override void AddAnimation(CAAnimation animation, string? key)
 	{
 		// Do nothing, we don't want animations here

src/Core/src/Platform/iOS/ViewExtensions.cs

@@ -248,9 +248,11 @@ public static void UpdateBorder(this UIView platformView, IView view)
 		public static T? FindDescendantView<T>(this UIView view) where T : UIView =>
 			FindDescendantView<T>(view, (_) => true);
 
+		[Obsolete("MAUI background layers now automatically update their Frame when their SuperLayer Frame changes. This method will be removed in a future release.")]
 		public static void UpdateBackgroundLayerFrame(this UIView view) =>
 			view.UpdateBackgroundLayerFrame(BackgroundLayerName);
 
+		[Obsolete("MAUI background layers now automatically update their Frame when their SuperLayer Frame changes. This method will be removed in a future release.")]
 		internal static void UpdateBackgroundLayerFrame(this UIView view, string layerName)
 		{
 			if (view.Frame.IsEmpty)

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

@@ -61,3 +61,8 @@ static Microsoft.Maui.Platform.UIWindowExtensions.GetWindow(this UIKit.UIWindowS
 static Microsoft.Maui.ViewExtensions.DisconnectHandlers(this Microsoft.Maui.IView! view) -> void
 override Microsoft.Maui.Platform.MauiCALayer.AddAnimation(CoreAnimation.CAAnimation! animation, string? key) -> void
 *REMOVED*override Microsoft.Maui.Handlers.BorderHandler.ConnectHandler(Microsoft.Maui.Platform.ContentView! platformView) -> void
+Microsoft.Maui.Platform.IAutoSizableCALayer
+Microsoft.Maui.Platform.IAutoSizableCALayer.AutoSizeToSuperLayer() -> void
+Microsoft.Maui.Platform.MauiCALayer.AutoSizeToSuperLayer() -> void
+override Microsoft.Maui.Platform.MauiCALayer.Dispose(bool disposing) -> void
+override Microsoft.Maui.Platform.MauiCALayer.RemoveFromSuperLayer() -> void

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

@@ -61,3 +61,8 @@ static Microsoft.Maui.Platform.UIWindowExtensions.GetWindow(this UIKit.UIWindowS
 static Microsoft.Maui.ViewExtensions.DisconnectHandlers(this Microsoft.Maui.IView! view) -> void
 override Microsoft.Maui.Platform.MauiCALayer.AddAnimation(CoreAnimation.CAAnimation! animation, string? key) -> void
 *REMOVED*override Microsoft.Maui.Handlers.BorderHandler.ConnectHandler(Microsoft.Maui.Platform.ContentView! platformView) -> void
+Microsoft.Maui.Platform.IAutoSizableCALayer
+Microsoft.Maui.Platform.IAutoSizableCALayer.AutoSizeToSuperLayer() -> void
+Microsoft.Maui.Platform.MauiCALayer.AutoSizeToSuperLayer() -> void
+override Microsoft.Maui.Platform.MauiCALayer.Dispose(bool disposing) -> void
+override Microsoft.Maui.Platform.MauiCALayer.RemoveFromSuperLayer() -> void