chore: Progress on Leave

Author: Youssef1313

src/Uno.UI.RuntimeTests/Tests/BindingTests/BindingTests.cs

@@ -43,6 +43,8 @@ public async Task When_Binding_By_Programmatically_Setting_Name()
 			},
 		};
 
+		Assert.AreEqual(null, button.Content);
+
 		await UITestHelper.Load(sp);
 
 #if UNO_HAS_ENHANCED_LIFECYCLE || WINAPPSDK
@@ -51,6 +53,72 @@ public async Task When_Binding_By_Programmatically_Setting_Name()
 		// Unfortunate wrong behavior on Android and iOS.
 		Assert.AreEqual(null, button.Content);
 #endif
+
+		tb.DataContext = "Hello World Updated";
+
+#if UNO_HAS_ENHANCED_LIFECYCLE || WINAPPSDK
+		Assert.AreEqual("Hello World Updated", button.Content);
+#else
+		// Unfortunate wrong behavior on Android and iOS.
+		Assert.AreEqual(null, button.Content);
+#endif
+
+		sp.Children.Remove(tb);
+
+#if UNO_HAS_ENHANCED_LIFECYCLE || WINAPPSDK
+		Assert.AreEqual("Hello World Updated", button.Content);
+#else
+		// Unfortunate wrong behavior on Android and iOS.
+		Assert.AreEqual(null, button.Content);
+#endif
+
+		// At this point, the textBox name is was unregistered as it's removed from the visual tree.
+		// However, on WinUI, the binding have already solved the target for ElementName and the binding will continue to work.
+		tb.DataContext = "Hello World Updated 2";
+
+#if UNO_HAS_ENHANCED_LIFECYCLE || WINAPPSDK
+		Assert.AreEqual("Hello World Updated 2", button.Content);
+#else
+		// Unfortunate wrong behavior on Android and iOS.
+		Assert.AreEqual(null, button.Content);
+#endif
+	}
+
+	[TestMethod]
+	public async Task When_Binding_Is_Set_After_RegisterName_And_UnregisterName()
+	{
+		var tb = new TextBox();
+		tb.Name = "textBox";
+		tb.Text = "Text";
+		tb.DataContext = "Hello World";
+
+		var button = new Button();
+		button.Name = "button";
+
+		var sp = new StackPanel()
+		{
+			Children =
+			{
+				tb,
+				button,
+			},
+		};
+
+		Assert.AreEqual(null, button.Content);
+
+		await UITestHelper.Load(sp);
+
+		sp.Children.Remove(tb);
+
+		// The remove call will UnregisterName for the textBox.
+		// The binding shouldn't be able to find the target for ElementName
+		button.SetBinding(Button.ContentProperty, new Binding()
+		{
+			ElementName = "textBox",
+			Path = new PropertyPath("DataContext")
+		});
+
+		Assert.AreEqual(null, button.Content);
 	}
 
 	[TestMethod]

src/Uno.UI/UI/Xaml/Controls/FlipView/FlipView.managed.cs

@@ -129,9 +129,9 @@ internal override void Enter(INameScope nameScope, EnterParams @params, int dept
 			HookTemplate();
 		}
 
-		internal override void Leave(LeaveParams @params)
+		internal override void Leave(INameScope nameScope, LeaveParams @params)
 		{
-			base.Leave(@params);
+			base.Leave(nameScope, @params);
 
 			UnhookTemplate();
 		}

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

@@ -902,16 +902,21 @@ private void ArrangeNative(Point offset, Rect? clippedFrame)
 #endif
 		}
 
+		private void AdjustNameScope(ref INameScope? nameScope)
+		{
+			if (NameScope.GetNameScope(this) is { } currentNameScope)
+			{
+				nameScope = currentNameScope;
+			}
+		}
+
 		internal override void Enter(INameScope? nameScope, EnterParams @params, int depth)
 		{
 			// This should happen regardless of whether Name is null or not.
 			// What we need here is that once we find an element being entered that
 			// has its own NameScope, then we start using this namescope and use it for entering its children.
 			// For example, elements in a template where the template root will have its own NameScope.
-			if (NameScope.GetNameScope(this) is { } currentNameScope)
-			{
-				nameScope = currentNameScope;
-			}
+			AdjustNameScope(ref nameScope);
 
 			if (nameScope is not null)
 			{
@@ -963,8 +968,24 @@ internal override void Enter(INameScope? nameScope, EnterParams @params, int dep
 			m_firedLoadingEvent = false;
 		}
 
-		internal override void Leave(LeaveParams @params)
+		internal override void Leave(INameScope? nameScope, LeaveParams @params)
 		{
+			// This should happen regardless of whether Name is null or not.
+			// What we need here is that once we find an element leaving that
+			// has its own NameScope, then we start using this namescope and use it for leaving its children.
+			// For example, elements in a template where the template root will have its own NameScope.
+			AdjustNameScope(ref nameScope);
+
+			if (nameScope is not null)
+			{
+				var name = this.Name;
+
+				if (!string.IsNullOrEmpty(name))
+				{
+					nameScope.UnregisterName(name);
+				}
+			}
+
 			// The way this works on WinUI is that when an element enters the visual tree, all values
 			// of properties that are marked with MetaDataPropertyInfoFlags::IsSparse and MetaDataPropertyInfoFlags::IsVisualTreeProperty
 			// are entered as well.
@@ -975,12 +996,12 @@ internal override void Leave(LeaveParams @params)
 				{
 					if (resource is FrameworkElement resourceAsUIElement)
 					{
-						resourceAsUIElement.Leave(@params);
+						resourceAsUIElement.Leave(nameScope, @params);
 					}
 				}
 			}
 
-			base.Leave(@params);
+			base.Leave(nameScope, @params);
 
 			ReconfigureViewportPropagation(isLeavingTree: true);
 		}

src/Uno.UI/UI/Xaml/ResourceDictionary.cs

@@ -140,7 +140,7 @@ public bool Remove(object key)
 				if (value is FrameworkElement fe)
 				{
 #if UNO_HAS_ENHANCED_LIFECYCLE
-					fe.Leave(new LeaveParams());
+					fe.Leave(UIElement.FindNameScope(fe), new LeaveParams());
 #else
 					fe.PerformOnUnloaded(isFromResources: true);
 #endif

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

@@ -110,15 +110,15 @@ private void OnChildRemoved(UIElement child)
 
 #if UNO_HAS_ENHANCED_LIFECYCLE
 			var leaveParams = new LeaveParams(IsActiveInVisualTree);
-			child.Leave(leaveParams);
+			child.Leave(FindNameScope(this), leaveParams);
 #endif
 		}
 
 		internal Point GetPosition(Point position, UIElement relativeTo)
 			=> TransformToVisual(relativeTo).TransformPoint(position);
 
 #if UNO_HAS_ENHANCED_LIFECYCLE
-		private static INameScope FindNameScope(DependencyObject dependencyObject)
+		internal static INameScope FindNameScope(DependencyObject dependencyObject)
 		{
 			// In many cases, this will not traverse the entire visual tree, as the NameScope is often
 			// present on each element as the DP is inherited. However, it can happen that the DP inheritance

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

@@ -652,7 +652,7 @@ internal virtual void Enter(INameScope? nameScope, EnterParams @params, int dept
 			SetLayoutFlags(LayoutFlag.MeasureDirty | LayoutFlag.ArrangeDirty);
 		}
 
-		internal virtual void Leave(LeaveParams @params)
+		internal virtual void Leave(INameScope? nameScope, LeaveParams @params)
 		{
 			foreach (var child in _children)
 			{
@@ -666,7 +666,7 @@ internal virtual void Leave(LeaveParams @params)
 					continue;
 				}
 
-				child.Leave(@params);
+				child.Leave(nameScope, @params);
 			}
 
 			if (IsActiveInVisualTree)