Properly arrange Embedded controls during ArrangeOverride

src/Avalonia.Controls/Documents/IInlineHost.cs

@@ -4,8 +4,6 @@ namespace Avalonia.Controls.Documents
 {
     internal interface IInlineHost : ILogical
     {
-        void AddVisualChild(IControl child);
-
         void Invalidate();
     }
 }

src/Avalonia.Controls/Documents/InlineRun.cs

@@ -0,0 +1,42 @@
+using Avalonia.Media;
+using Avalonia.Media.TextFormatting;
+using Avalonia.Utilities;
+
+namespace Avalonia.Controls.Documents
+{
+    internal class EmbeddedControlRun : DrawableTextRun
+    {
+        public EmbeddedControlRun(IControl control, TextRunProperties properties)
+        {
+            Control = control;
+            Properties = properties;
+        }
+
+        public IControl Control { get; }
+
+        public override TextRunProperties? Properties { get; }
+
+        public override Size Size => Control.DesiredSize;
+
+        public override double Baseline
+        {
+            get
+            {
+                double baseline = Size.Height;
+                double baselineOffsetValue = Control.GetValue<double>(TextBlock.BaselineOffsetProperty);
+
+                if (!MathUtilities.IsZero(baselineOffsetValue))
+                {
+                    baseline = baselineOffsetValue;
+                }
+
+                return -baseline;
+            }
+        }
+
+        public override void Draw(DrawingContext drawingContext, Point origin)
+        {
+            //noop            
+        }
+    }
+}

src/Avalonia.Controls/Documents/InlineUIContainer.cs

@@ -3,7 +3,6 @@ using System.Text;
 using Avalonia.Media;
 using Avalonia.Media.TextFormatting;
 using Avalonia.Metadata;
-using Avalonia.Utilities;
 
 namespace Avalonia.Controls.Documents
 {
@@ -59,56 +58,11 @@ namespace Avalonia.Controls.Documents
 
         internal override void BuildTextRun(IList<TextRun> textRuns)
         {
-            if(InlineHost == null)
-            {
-                return;
-            }
-
-            ((ISetLogicalParent)Child).SetParent(InlineHost);
-
-            InlineHost.AddVisualChild(Child);
-
-            textRuns.Add(new InlineRun(Child, CreateTextRunProperties()));
+            textRuns.Add(new EmbeddedControlRun(Child, CreateTextRunProperties()));
         }
 
         internal override void AppendText(StringBuilder stringBuilder)
         {
         }
-
-        private class InlineRun : DrawableTextRun
-        {
-            public InlineRun(IControl control, TextRunProperties properties)
-            {
-                Control = control;
-                Properties = properties;
-            }
-
-            public IControl Control { get; }
-
-            public override TextRunProperties? Properties { get; }
-
-            public override Size Size => Control.DesiredSize;
-
-            public override double Baseline
-            {
-                get
-                {
-                    double baseline = Size.Height;
-                    double baselineOffsetValue = Control.GetValue<double>(TextBlock.BaselineOffsetProperty);
-
-                    if (!MathUtilities.IsZero(baselineOffsetValue))
-                    {
-                        baseline = baselineOffsetValue;
-                    }
-
-                    return -baseline;
-                }
-            }
-
-            public override void Draw(DrawingContext drawingContext, Point origin)
-            {             
-                //noop            
-            }
-        }
     }
 }

src/Avalonia.Controls/RichTextBlock.cs

@@ -61,6 +61,7 @@ namespace Avalonia.Controls
         private int _selectionStart;
         private int _selectionEnd;
         private int _wordSelectionStart = -1;
+        private IReadOnlyList<TextRun>? _textRuns;
 
         static RichTextBlock()
         {
@@ -277,8 +278,8 @@ namespace Avalonia.Controls
         protected override void SetText(string? text)
         {
             var oldValue = GetText();
-      
-            AddText(text);        
+
+            AddText(text);
 
             RaisePropertyChanged(TextProperty, oldValue, text);
         }
@@ -301,18 +302,9 @@ namespace Avalonia.Controls
 
             ITextSource textSource;
 
-            if (HasComplexContent)
+            if (_textRuns != null)
             {
-                var inlines = Inlines!;
-
-                var textRuns = new List<TextRun>();
-
-                foreach (var inline in inlines)
-                {
-                    inline.BuildTextRun(textRuns);
-                }
-
-                textSource = new InlinesTextSource(textRuns);
+                textSource = new InlinesTextSource(_textRuns);
             }
             else
             {
@@ -546,27 +538,72 @@ namespace Avalonia.Controls
 
         protected override Size MeasureOverride(Size availableSize)
         {
-            foreach (var child in VisualChildren)
+            LogicalChildren.Clear();
+
+            VisualChildren.Clear();
+
+            if (Inlines != null && Inlines.Count > 0)
             {
-                if (child is Control control)
+                var inlines = Inlines;
+
+                var textRuns = new List<TextRun>();
+
+                foreach (var inline in inlines)
                 {
-                    control.Measure(Size.Infinity);
+                    inline.BuildTextRun(textRuns);
+                }
+
+                foreach (var textRun in textRuns)
+                {
+                    if (textRun is EmbeddedControlRun controlRun &&
+                        controlRun.Control is Control control)
+                    {
+                        ((ISetLogicalParent)control).SetParent(this);
+
+                        VisualChildren.Add(control);
+
+                        control.Measure(Size.Infinity);
+                    }
                 }
+
+                _textRuns = textRuns;
+            }
+            else
+            {
+                _textRuns = null;
             }
-            
+
             return base.MeasureOverride(availableSize);
         }
 
         protected override Size ArrangeOverride(Size finalSize)
         {
-            foreach (var child in VisualChildren)
+            if (HasComplexContent)
             {
-                if (child is Control control)
+                var currentY = 0.0;
+
+                foreach (var textLine in TextLayout.TextLines)
                 {
-                    control.Arrange(new Rect(control.DesiredSize));
+                    var currentX = textLine.Start;
+
+                    foreach (var run in textLine.TextRuns)
+                    {
+                        if (run is DrawableTextRun drawable)
+                        {
+                            if (drawable is EmbeddedControlRun controlRun
+                                && controlRun.Control is Control control)
+                            {
+                                control.Arrange(new Rect(new Point(currentX, currentY), control.DesiredSize));
+                            }
+
+                            currentX += drawable.Size.Width;
+                        }
+                    }
+
+                    currentY += textLine.Height;
                 }
             }
-            
+           
             return base.ArrangeOverride(finalSize);
         }
 
@@ -618,14 +655,6 @@ namespace Avalonia.Controls
             }
         }
 
-        void IInlineHost.AddVisualChild(IControl child)
-        {
-            if (child.VisualParent == null)
-            {
-                VisualChildren.Add(child);
-            }
-        }
-
         void IInlineHost.Invalidate()
         {
             InvalidateTextLayout();

tests/Avalonia.Controls.UnitTests/RichTextBlockTests.cs

@@ -1,4 +1,6 @@
 using Avalonia.Controls.Documents;
+using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Templates;
 using Avalonia.Media;
 using Avalonia.UnitTests;
 using Xunit;
@@ -92,5 +94,39 @@ namespace Avalonia.Controls.UnitTests
                 Assert.Equal(target, run.Parent);
             }
         }
+
+        [Fact]
+        public void InlineUIContainer_Child_Schould_Be_Arranged()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var target = new RichTextBlock();
+
+                var button = new Button { Content = "12345678" };
+
+                button.Template = new FuncControlTemplate<Button>((parent, scope) =>           
+                        new TextBlock
+                        {
+                            Name = "PART_ContentPresenter",
+                            [!TextBlock.TextProperty] = parent[!ContentControl.ContentProperty],
+                        }.RegisterInNameScope(scope)                                       
+                );
+
+                target.Inlines!.Add("123456");
+                target.Inlines.Add(new InlineUIContainer(button));
+                target.Inlines.Add("123456");
+
+                target.Measure(Size.Infinity);
+
+                Assert.True(button.IsMeasureValid);
+                Assert.Equal(80, button.DesiredSize.Width);
+
+                target.Arrange(new Rect(new Size(200, 50)));
+
+                Assert.True(button.IsArrangeValid);
+
+                Assert.Equal(60, button.Bounds.Left);
+            }
+        }
     }
 }