Fix TextBlock TextAlignment issues when a HorizontalAlignment is defined (#17402)

* Always measure TextBlock with infinite width

* Make sure the constraint is always fulfilled

* Add some tests

* Adjust tests because we no longer retain the TextLayout in the arrange pass

src/Avalonia.Controls/TextBlock.cs

@@ -653,7 +653,7 @@ namespace Avalonia.Controls
                 TextDecorations,
                 Foreground);
 
-            var paragraphProperties = new GenericTextParagraphProperties(FlowDirection, TextAlignment, true, false,
+            var paragraphProperties = new GenericTextParagraphProperties(FlowDirection, IsMeasureValid ? TextAlignment : TextAlignment.Left, true, false,
                 defaultProperties, TextWrapping, LineHeight, 0, LetterSpacing)
             {
                 LineSpacing = LineSpacing
@@ -703,7 +703,7 @@ namespace Avalonia.Controls
             var padding = LayoutHelper.RoundLayoutThickness(Padding, scale, scale);
             var deflatedSize = availableSize.Deflate(padding);
 
-            if(_constraint != deflatedSize)
+            if (_constraint != deflatedSize)
             {
                 //Reset TextLayout when the constraint is not matching.
                 _textLayout?.Dispose();
@@ -733,9 +733,7 @@ namespace Avalonia.Controls
 
             var width = textLayout.OverhangLeading + textLayout.WidthIncludingTrailingWhitespace + textLayout.OverhangTrailing;
 
-            var size = LayoutHelper.RoundLayoutSizeUp(new Size(width, textLayout.Height).Inflate(padding), 1, 1);   
+            var size = LayoutHelper.RoundLayoutSizeUp(new Size(width, textLayout.Height).Inflate(padding), 1, 1);
-
-            _constraint = size;
 
             return size;
         }
@@ -747,15 +745,12 @@ namespace Avalonia.Controls
 
             var availableSize = finalSize.Deflate(padding);
 
-            //Fixes: #11019
+            //ToDo: Introduce a text run cache to be able to reuse shaped runs etc.
-            if (availableSize != _constraint)
+            _textLayout?.Dispose();
-            {
+            _textLayout = null;
-                _textLayout?.Dispose();
+            _constraint = availableSize;
-                _textLayout = null;
-                _constraint = availableSize;
-            }
 
-            //This implicitly recreated the TextLayout with a new constraint if we previously reset it.
+            //This implicitly recreated the TextLayout with a new constraint.
             var textLayout = TextLayout;
 
             if (HasComplexContent)

tests/Avalonia.Controls.UnitTests/TextBlockTests.cs

@@ -27,7 +27,7 @@ namespace Avalonia.Controls.UnitTests
         }
 
         [Fact]
-        public void Calling_Measure_Should_Update_Constraint_And_TextLayout()
+        public void Calling_Measure_Should_Update_TextLayout()
         {
             using (UnitTestApplication.Start(TestServices.MockPlatformRenderInterface))
             {
@@ -39,8 +39,6 @@ namespace Avalonia.Controls.UnitTests
 
                 var textLayout = textBlock.TextLayout;
 
-                Assert.Equal(new Size(110, 10), textBlock.Constraint);
-
                 textBlock.Measure(new Size(50, 100));
 
                 Assert.NotEqual(textLayout, textBlock.TextLayout);
@@ -60,13 +58,12 @@ namespace Avalonia.Controls.UnitTests
 
                 var constraint = LayoutHelper.RoundLayoutSizeUp(new Size(textLayout.WidthIncludingTrailingWhitespace, textLayout.Height), 1, 1);
 
-                Assert.Equal(constraint, textBlock.Constraint);
-
                 textBlock.Arrange(new Rect(constraint));
 
-                Assert.Equal(constraint, textBlock.Constraint);
+                //TextLayout is recreated after arrange
+                textLayout = textBlock.TextLayout;
 
-                Assert.Equal(textLayout, textBlock.TextLayout);
+                Assert.Equal(constraint, textBlock.Constraint);
 
                 textBlock.Measure(constraint);
 
@@ -78,6 +75,7 @@ namespace Avalonia.Controls.UnitTests
 
                 Assert.Equal(constraint, textBlock.Constraint);
 
+                //TextLayout is recreated after arrange
                 Assert.NotEqual(textLayout, textBlock.TextLayout);
             }
         }
@@ -93,8 +91,6 @@ namespace Avalonia.Controls.UnitTests
 
                 var textLayout = textBlock.TextLayout;
 
-                Assert.Equal(new Size(110, 10), textBlock.Constraint);
-
                 var constraint = LayoutHelper.RoundLayoutSizeUp(new Size(textLayout.WidthIncludingTrailingWhitespace, textLayout.Height), 1, 1);
 
                 Assert.Equal(constraint, textBlock.DesiredSize);

tests/Avalonia.RenderTests/Controls/TextBlockTests.cs

@@ -5,6 +5,7 @@ using Avalonia.Controls.Documents;
 using Avalonia.Layout;
 using Avalonia.Media;
 using Xunit;
+using static System.Net.Mime.MediaTypeNames;
 
 #if AVALONIA_SKIA
 namespace Avalonia.Skia.RenderTests
@@ -176,5 +177,106 @@ namespace Avalonia.Direct2D1.RenderTests.Controls
             await RenderToFile(target);
             CompareImages();
         }
+
+
+        [InlineData(150, 200, TextWrapping.NoWrap)]
+        [InlineData(44, 200, TextWrapping.NoWrap)]
+        [InlineData(44, 400, TextWrapping.Wrap)]
+        [Win32Theory("Has text")]
+        public async Task Should_Measure_Arrange_TextBlock(double width, double height, TextWrapping textWrapping)
+        {
+            var text = "Hello World";
+
+            var target = new StackPanel { Width = 200, Height = height };
+
+            target.Children.Add(new TextBlock 
+            { 
+                Text = text, 
+                Background = Brushes.Red, 
+                HorizontalAlignment = HorizontalAlignment.Left, 
+                TextAlignment = TextAlignment.Left,
+                Width = width, 
+                TextWrapping = textWrapping 
+            });
+            target.Children.Add(new TextBlock 
+            { 
+                Text = text,
+                Background = Brushes.Red, 
+                HorizontalAlignment = HorizontalAlignment.Left, 
+                TextAlignment = TextAlignment.Center, 
+                Width = width, 
+                TextWrapping = textWrapping 
+            });
+            target.Children.Add(new TextBlock 
+            { 
+                Text = text, 
+                Background = Brushes.Red, 
+                HorizontalAlignment = HorizontalAlignment.Left, 
+                TextAlignment = TextAlignment.Right, 
+                Width = width, 
+                TextWrapping = textWrapping 
+            });
+
+            target.Children.Add(new TextBlock 
+            {
+                Text = text,
+                Background = Brushes.Red,
+                HorizontalAlignment = HorizontalAlignment.Center,
+                TextAlignment = TextAlignment.Left, 
+                Width = width, 
+                TextWrapping = textWrapping
+            });
+            target.Children.Add(new TextBlock 
+            { 
+                Text = text, 
+                Background = Brushes.Red, 
+                HorizontalAlignment = HorizontalAlignment.Center, 
+                TextAlignment = TextAlignment.Center, 
+                Width = width,
+                TextWrapping = textWrapping
+            });
+            target.Children.Add(new TextBlock 
+            { 
+                Text = text,
+                Background = Brushes.Red,
+                HorizontalAlignment = HorizontalAlignment.Center,
+                TextAlignment = TextAlignment.Right, 
+                Width = width,
+                TextWrapping = textWrapping 
+            });
+
+            target.Children.Add(new TextBlock 
+            { 
+                Text = text,
+                Background = Brushes.Red, 
+                HorizontalAlignment = HorizontalAlignment.Right,
+                TextAlignment = TextAlignment.Left, 
+                Width = width, 
+                TextWrapping = textWrapping
+            });
+            target.Children.Add(new TextBlock 
+            { 
+                Text = text, 
+                Background = Brushes.Red, 
+                HorizontalAlignment = HorizontalAlignment.Right, 
+                TextAlignment = TextAlignment.Center, 
+                Width = width, 
+                TextWrapping = textWrapping 
+            });
+            target.Children.Add(new TextBlock 
+            { 
+                Text = text, 
+                Background = Brushes.Red, 
+                HorizontalAlignment = HorizontalAlignment.Right, 
+                TextAlignment = TextAlignment.Right, 
+                Width = width, 
+                TextWrapping = textWrapping 
+            });
+
+            var testName = $"Should_Measure_Arrange_TextBlock_{width}_{textWrapping}";
+
+            await RenderToFile(target, testName);
+            CompareImages(testName);
+        }
     }
 }

tests/Avalonia.RenderTests/TestSkip.cs

@@ -17,5 +17,14 @@ namespace Avalonia.Direct2D1.RenderTests
                 Skip = message;
         }
     }
+
+    public class Win32Theory : TheoryAttribute
+    {
+        public Win32Theory(string message)
+        {
+            if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+                Skip = message;
+        }
+    }
 }