fix!: Change Measure/Arrange to not be virtual

build/PackageDiffIgnore.xml

@@ -1257,7 +1257,8 @@
 			<Member fullName="System.Void Windows.UI.Xaml.Media.Animation.Timeline.Dispose()" reason="Api alignments" />
 
 			<Member fullName="System.Void Windows.UI.Xaml.Window.set_Visible(System.Boolean value)" reason="Does not exist in UWP and WinUI" />
-
+			<Member fullName="System.Void Windows.UI.Xaml.UIElement.Arrange(Windows.Foundation.Rect finalRect)" reason="Api alignments" />
+			<Member fullName="System.Void Windows.UI.Xaml.UIElement.Measure(Windows.Foundation.Size availableSize)" reason="Api alignments" />
 			<Member fullName="System.Object Uno.UI.Svg.GlobalStaticResources.FindResource(System.String name)" reason="API Alignment" />
 			<Member fullName="System.Void Windows.Devices.Sensors.SimpleOrientationSensor.OnAccuracyChanged(Android.Hardware.Sensor sensor, Android.Hardware.SensorStatus accuracy)" reason="Api alignments" />
 			<Member fullName="System.Void Windows.Devices.Sensors.SimpleOrientationSensor.OnSensorChanged(Android.Hardware.SensorEvent e)" reason="Api alignments" />

src/Uno.UI/UI/Xaml/FrameworkElement.cs

@@ -268,50 +268,6 @@ protected virtual Size ArrangeOverride(Size finalSize)
 			}
 		}
 
-#if !UNO_REFERENCE_API
-		/// <summary>
-		/// Updates the DesiredSize of a UIElement. Typically, objects that implement custom layout for their
-		/// layout children call this method from their own MeasureOverride implementations to form a recursive layout update.
-		/// </summary>
-		/// <param name="availableSize">
-		/// The available space that a parent can allocate to a child object. A child object can request a larger
-		/// space than what is available; the provided size might be accommodated if scrolling or other resize behavior is
-		/// possible in that particular container.
-		/// </param>
-		/// <returns>The measured size.</returns>
-		/// <remarks>
-		/// Under Uno.UI, this method should not be called during the normal layouting phase. Instead, use the
-		/// <see cref="MeasureElement(View, Size)"/> methods, which handles native view properly.
-		/// </remarks>
-		public override void Measure(Size availableSize)
-		{
-			if (double.IsNaN(availableSize.Width) || double.IsNaN(availableSize.Height))
-			{
-				throw new InvalidOperationException($"Cannot measure [{GetType()}] with NaN");
-			}
-
-			_layouter.Measure(availableSize);
-#if IS_UNIT_TESTS
-			OnMeasurePartial(availableSize);
-#endif
-		}
-
-		/// <summary>
-		/// Positions child objects and determines a size for a UIElement. Parent objects that implement custom layout
-		/// for their child elements should call this method from their layout override implementations to form a recursive layout update.
-		/// </summary>
-		/// <param name="finalRect">The final size that the parent computes for the child in layout, provided as a <see cref="Windows.Foundation.Rect"/> value.</param>
-		public override void Arrange(Rect finalRect)
-		{
-			_layouter.Arrange(finalRect);
-			_layouter.ArrangeChild(this, finalRect);
-		}
-#endif
-
-#if IS_UNIT_TESTS
-		partial void OnMeasurePartial(Size slotSize);
-#endif
-
 		/// <summary>
 		/// Measures an native element, in the same way <see cref="Measure"/> would do.
 		/// </summary>

src/Uno.UI/UI/Xaml/FrameworkElement.net.cs

@@ -83,26 +83,6 @@ protected internal override void OnInvalidateMeasure()
 			base.OnInvalidateMeasure();
 		}
 
-		partial void OnMeasurePartial(Size slotSize)
-		{
-			MeasureCallCount++;
-			AvailableMeasureSize = slotSize;
-
-			if (DesiredSizeSelector != null)
-			{
-				var desiredSize = DesiredSizeSelector(slotSize);
-
-				LayoutInformation.SetDesiredSize(this, desiredSize);
-				RequestedDesiredSize = desiredSize;
-			}
-			else if (RequestedDesiredSize != null)
-			{
-				var desiredSize = RequestedDesiredSize.Value;
-
-				LayoutInformation.SetDesiredSize(this, desiredSize);
-			}
-		}
-
 		internal void InternalArrange(Rect frame)
 		{
 			_layouter.Arrange(frame);

src/Uno.UI/UI/Xaml/UIElement.cs

@@ -883,12 +883,60 @@ internal static string SetDependencyPropertyValueInternal(DependencyObject owner
 		internal Rect? ClippedFrame;
 #endif
 
-		public virtual void Measure(Size availableSize)
+		/// <summary>
+		/// Updates the DesiredSize of a UIElement. Typically, objects that implement custom layout for their
+		/// layout children call this method from their own MeasureOverride implementations to form a recursive layout update.
+		/// </summary>
+		/// <param name="availableSize">
+		/// The available space that a parent can allocate to a child object. A child object can request a larger
+		/// space than what is available; the provided size might be accommodated if scrolling or other resize behavior is
+		/// possible in that particular container.
+		/// </param>
+		/// <returns>The measured size.</returns>
+		/// <remarks>
+		/// Under Uno.UI, this method should not be called during the normal layouting phase. Instead, use the
+		/// <see cref="MeasureElement(View, Size)"/> methods, which handles native view properly.
+		/// </remarks>
+		public void Measure(Size availableSize)
 		{
+#if !UNO_REFERENCE_API
+			if (this is not FrameworkElement fwe)
+			{
+				return;
+			}
+
+			if (double.IsNaN(availableSize.Width) || double.IsNaN(availableSize.Height))
+			{
+				throw new InvalidOperationException($"Cannot measure [{GetType()}] with NaN");
+			}
+
+			((ILayouterElement)fwe).Layouter.Measure(availableSize);
+#if IS_UNIT_TESTS
+			OnMeasurePartial(availableSize);
+#endif
+#endif
 		}
 
-		public virtual void Arrange(Rect finalRect)
+#if IS_UNIT_TESTS
+		partial void OnMeasurePartial(Size slotSize);
+#endif
+
+		/// <summary>
+		/// Positions child objects and determines a size for a UIElement. Parent objects that implement custom layout
+		/// for their child elements should call this method from their layout override implementations to form a recursive layout update.
+		/// </summary>
+		/// <param name="finalRect">The final size that the parent computes for the child in layout, provided as a <see cref="Windows.Foundation.Rect"/> value.</param>
+		public void Arrange(Rect finalRect)
 		{
+#if !UNO_REFERENCE_API
+			if (this is not FrameworkElement fwe)
+			{
+				return;
+			}
+
+			((ILayouterElement)fwe).Layouter.Arrange(finalRect);
+			((ILayouterElement)fwe).Layouter.ArrangeChild(fwe, finalRect);
+#endif
 		}
 
 		public void InvalidateMeasure()

src/Uno.UI/UI/Xaml/UIElement.net.cs

@@ -4,6 +4,7 @@
 using Uno;
 using Uno.Extensions;
 using Windows.Foundation;
+using Windows.UI.Xaml.Controls.Primitives;
 using Windows.UI.Xaml.Input;
 using Windows.UI.Xaml.Media;
 
@@ -60,5 +61,25 @@ internal void AddChild(UIElement child, int? index = null)
 		{
 			child.SetParent(this);
 		}
+
+		partial void OnMeasurePartial(Size slotSize)
+		{
+			MeasureCallCount++;
+			AvailableMeasureSize = slotSize;
+
+			if (DesiredSizeSelector != null)
+			{
+				var desiredSize = DesiredSizeSelector(slotSize);
+
+				LayoutInformation.SetDesiredSize(this, desiredSize);
+				RequestedDesiredSize = desiredSize;
+			}
+			else if (RequestedDesiredSize != null)
+			{
+				var desiredSize = RequestedDesiredSize.Value;
+
+				LayoutInformation.SetDesiredSize(this, desiredSize);
+			}
+		}
 	}
 }