fix: [TextBlock] Prevent Text value overriding when it isn't necessary

- Once the Inlines collection is initialized, changes to Text via binding no longer causes the binding to be overridden.
- The inlines text cached on the TextBlock is no longer updated when non-Text properties change on Runs.
- WASM Inlines collections now properly invalidate their owners when changed.

Author: mikernet

src/Uno.UI/UI/Xaml/Controls/TextBlock/TextBlock.cs

@@ -36,6 +36,7 @@ public partial class TextBlock : DependencyObject
 		private string _inlinesText; // Text derived from the content of Inlines
 		private readonly SerialDisposable _foregroundChanged = new SerialDisposable();
 
+		private bool _skipInlinesChangedTextSetter;
 
 #if !UNO_REFERENCE_API
 		public TextBlock()
@@ -87,15 +88,29 @@ public InlineCollection Inlines
 			}
 		}
 
-		internal void InvalidateInlines() => OnInlinesChanged();
-
-		private void OnInlinesChanged()
-		{
-			Text = _inlinesText = string.Concat(Inlines.Select(InlineExtensions.GetText));
-			UpdateHyperlinks();
+		internal void InvalidateInlines(bool updateText)
+		{
+			if (updateText)
+			{
+				if (Inlines.Count == 1 && Inlines[0] is Run run)
+				{
+					_inlinesText = run.Text;
+				}
+				else
+				{
+					_inlinesText = string.Concat(Inlines.Select(InlineExtensions.GetText));
+				}
+
+				if (!_skipInlinesChangedTextSetter)
+				{
+					Text = _inlinesText;
+				}
+
+				UpdateHyperlinks();
+			}
 
 			OnInlinesChangedPartial();
-			InvalidateTextBlock();
+			InvalidateTextBlock();
 		}
 
 		partial void OnInlinesChangedPartial();
@@ -700,16 +715,21 @@ private void UpdateInlines(string text)
 			}
 
 			if (ReadLocalValue(TextProperty) is UnsetValue)
-			{
-				Inlines.Clear();
+			{
+				_skipInlinesChangedTextSetter = true;
+				Inlines.Clear();
+				_skipInlinesChangedTextSetter = false;
 				ClearTextPartial();
 			}
 			else if (text != _inlinesText)
-			{
-				// Inlines must be updated
+			{
+				// Inlines must be updated
+				_skipInlinesChangedTextSetter = true;
 				Inlines.Clear();
-				ClearTextPartial();
-				Inlines.Add(new Run { Text = text });
+				ClearTextPartial();
+				_skipInlinesChangedTextSetter = true;
+				Inlines.Add(new Run { Text = text });
+				_skipInlinesChangedTextSetter = false;
 			}
 		}
 

src/Uno.UI/UI/Xaml/Controls/TextBlock/TextBlock.skia.cs

@@ -30,7 +30,7 @@ public TextBlock()
 
 		private int GetCharacterIndexAtPoint(Point point)
 		{
-			throw new NotSupportedException();
+			return -1; // Not supported yet
 		}
 
 		protected override Size MeasureOverride(Size availableSize)

src/Uno.UI/UI/Xaml/Documents/Inline.cs

@@ -8,16 +8,16 @@ namespace Windows.UI.Xaml.Documents
 {
 	public abstract partial class Inline : TextElement
 	{
-		internal void InvalidateInlines()
+		internal void InvalidateInlines(bool updateText)
 		{
 #if !NET461
 			switch (this.GetParent())
 			{
 				case Span span:
-					span.InvalidateInlines();
+					span.InvalidateInlines(updateText);
 					break;
 				case TextBlock textBlock:
-					textBlock.InvalidateInlines();
+					textBlock.InvalidateInlines(updateText);
 					break;
 				default:
 					break;

src/Uno.UI/UI/Xaml/Documents/InlineCollection.cs

@@ -24,10 +24,10 @@ private void OnCollectionChanged()
 			switch (_collection.GetParent())
 			{
 				case TextBlock textBlock:
-					textBlock.InvalidateInlines();
+					textBlock.InvalidateInlines(true);
 					break;
 				case Inline inline:
-					inline.InvalidateInlines();
+					inline.InvalidateInlines(true);
 					break;
 				default:
 					break;

src/Uno.UI/UI/Xaml/Documents/InlineCollection.wasm.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
+using System.Collections.Specialized;
 using System.Linq;
 using Windows.UI.Xaml.Controls;
 
@@ -13,8 +14,24 @@ partial class InlineCollection : IList<Inline>, IEnumerable<Inline>
 		internal InlineCollection(UIElement containerElement)
 		{
 			_collection = new UIElementCollection(containerElement);
-		}
-
+			_collection.CollectionChanged += OnCollectionChanged;
+		}
+
+		private void OnCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+		{
+			switch (_collection.Owner)
+			{
+				case TextBlock textBlock:
+					textBlock.InvalidateInlines(true);
+					break;
+				case Inline inline:
+					inline.InvalidateInlines(true);
+					break;
+				default:
+					break;
+			}
+		}
+
 		/// <inheritdoc />
 		public IEnumerator<Inline> GetEnumerator() => _collection.OfType<Inline>().GetEnumerator();
 

src/Uno.UI/UI/Xaml/Documents/Run.cs

@@ -33,7 +33,7 @@ public string Text
 		public void OnTextChanged()
 		{
 			OnTextChangedPartial();
-			InvalidateInlines();
+			InvalidateInlines(true);
 			InvalidateSegmentsPartial();
 		}
 
@@ -44,54 +44,54 @@ public void OnTextChanged()
 		protected override void OnForegroundChanged()
 		{
 			base.OnForegroundChanged();
-			InvalidateInlines();
+			InvalidateInlines(false);
 		}
 
 		protected override void OnFontFamilyChanged()
 		{
 			base.OnFontFamilyChanged();
-			InvalidateInlines();
+			InvalidateInlines(false);
 			InvalidateSegmentsPartial();
 		}
 
 		protected override void OnFontSizeChanged()
 		{
 			base.OnFontSizeChanged();
-			InvalidateInlines();
+			InvalidateInlines(false);
 			InvalidateSegmentsPartial();
 		}
 
 		protected override void OnFontStyleChanged()
 		{
 			base.OnFontStyleChanged();
-			InvalidateInlines();
+			InvalidateInlines(false);
 			InvalidateSegmentsPartial();
 		}
 
 		protected override void OnFontWeightChanged()
 		{
 			base.OnFontWeightChanged();
-			InvalidateInlines();
+			InvalidateInlines(false);
 			InvalidateSegmentsPartial();
 		}
 
 		protected override void OnBaseLineAlignmentChanged()
 		{
 			base.OnBaseLineAlignmentChanged();
-			InvalidateInlines();
+			InvalidateInlines(false);
 		}
 
 		protected override void OnCharacterSpacingChanged()
 		{
 			base.OnCharacterSpacingChanged();
-			InvalidateInlines();
+			InvalidateInlines(false);
 			InvalidateSegmentsPartial();
 		}
 
 		protected override void OnTextDecorationsChanged()
 		{
 			base.OnTextDecorationsChanged();
-			InvalidateInlines();
+			InvalidateInlines(false);
 		}
 
 		partial void InvalidateSegmentsPartial();