Fix Inlines clear handling (#14247)

* Make sure to clean up VisualChildren and created text runs when the TextLayout is invalidate

* Remove localized comment

---------

Co-authored-by: Tim <47110241+timunie@users.noreply.github.com>
#Conflicts:
#	src/Avalonia.Controls/TextBlock.cs

src/Avalonia.Controls/TextBlock.cs

@@ -671,9 +671,12 @@ namespace Avalonia.Controls
         {
             _textLayout?.Dispose();
             _textLayout = null;
+            
+            VisualChildren.Clear();
 
-            InvalidateVisual();
+            _textRuns = null;
 
+            InvalidateVisual();
             InvalidateMeasure();
         }
 
@@ -690,8 +693,6 @@ namespace Avalonia.Controls
 
             if (HasComplexContent)
             {
-                VisualChildren.Clear();
-
                 var textRuns = new List<TextRun>();
 
                 foreach (var inline in inlines!)
@@ -875,7 +876,9 @@ namespace Avalonia.Controls
             }
         }
 
-        private readonly struct InlinesTextSource : ITextSource
+#pragma warning disable CA1815
+        protected readonly struct InlinesTextSource : ITextSource
+#pragma warning restore CA1815
         {
             private readonly IReadOnlyList<TextRun> _textRuns;
 

tests/Avalonia.Controls.UnitTests/TextBlockTests.cs

@@ -224,5 +224,21 @@ namespace Avalonia.Controls.UnitTests
                 Assert.Equal(underline, target.Inlines[0].TextDecorations);
             }
         }
+        
+        [Fact]
+        public void TextBlock_TextLines_Should_Be_Empty()
+        {
+            using (UnitTestApplication.Start(TestServices.MockPlatformRenderInterface))
+            {
+                var textblock = new TextBlock();
+                textblock.Inlines?.Add(new Run("123"));
+                textblock.Measure(new Size(200, 200));
+                int count = textblock.TextLayout.TextLines[0].TextRuns.Count;
+                textblock.Inlines?.Clear();
+                textblock.Measure(new Size(200, 200));
+                int count1 = textblock.TextLayout.TextLines[0].TextRuns.Count;
+                Assert.NotEqual(count, count1);
+            }
+        }
     }
 }