Include the TextLine's Start offset to the TextLayout's size calculation.

src/Avalonia.Visuals/Media/TextFormatting/TextLayout.cs

@@ -305,9 +305,11 @@ namespace Avalonia.Media.TextFormatting
         /// <param name="height">The current height.</param>
         private static void UpdateBounds(TextLine textLine, ref double width, ref double height)
         {
-            if (width < textLine.Width)
+            var lineWidth = textLine.Width + textLine.Start * 2;
+            
+            if (width < lineWidth)
             {
-                width = textLine.Width;
+                width = lineWidth;
             }
 
             height += textLine.Height;