Recreate TextLayout on measure to make sure constraint is updated (#14705)

* Recreate TextLayout on measure to make sure constraint is updated

* Add failing test

src/Avalonia.Controls/TextBlock.cs

@@ -677,7 +677,6 @@ namespace Avalonia.Controls
         {
             _textLayout?.Dispose();
             _textLayout = null;
-
             _textRuns = null;
 
             base.OnMeasureInvalidated();
@@ -690,6 +689,10 @@ namespace Avalonia.Controls
 
             _constraint = availableSize.Deflate(padding);
 
+            //Reset TextLayout otherwise constraint might be outdated.
+            _textLayout?.Dispose();
+            _textLayout = null;
+
             var inlines = Inlines;
 
             if (HasComplexContent)
@@ -819,15 +822,19 @@ namespace Avalonia.Controls
             {
                 oldValue.LogicalChildren = null;
                 oldValue.InlineHost = null;
-                oldValue.Invalidated -= (s, e) => InvalidateMeasure();
+                oldValue.Invalidated -= Invalidated;
             }
 
             if (newValue is not null)
             {
                 newValue.LogicalChildren = LogicalChildren;
                 newValue.InlineHost = this;
-                newValue.Invalidated += (s, e) => InvalidateMeasure();
+                newValue.Invalidated += Invalidated;
             }
+
+            return;
+
+            void Invalidated(object? sender, EventArgs e) => InvalidateMeasure();
         }
 
         void IInlineHost.Invalidate()

tests/Avalonia.Controls.UnitTests/TextBlockTests.cs

@@ -30,6 +30,27 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(null, textBlock.Text);
         }
 
+        [Fact]
+        public void Calling_Measure_Should_Update_Constraint_And_TextLayout()
+        {
+            using (UnitTestApplication.Start(TestServices.MockPlatformRenderInterface))
+            {
+                var textBlock = new TestTextBlock { Text = "Hello World" };
+
+                textBlock.Measure(new Size(100, 100));
+
+                var textLayout = textBlock.TextLayout;
+
+                Assert.Equal(new Size(100,100), textBlock.Constraint);
+
+                textBlock.Measure(new Size(50, 100));
+
+                Assert.Equal(new Size(50, 100), textBlock.Constraint);
+
+                Assert.NotEqual(textLayout, textBlock.TextLayout);
+            }
+        }
+
         [Fact]
         public void Changing_InlinesCollection_Should_Invalidate_Measure()
         {
@@ -328,5 +349,10 @@ namespace Avalonia.Controls.UnitTests
                 Assert.NotEqual(count, count1);
             }
         }
+
+        private class TestTextBlock : TextBlock
+        {
+            public Size Constraint => _constraint;
+        }
     }
 }