Prevent infinite loop

samples/Sandbox/MainWindow.axaml

@@ -1,4 +1,5 @@
 <Window xmlns="https://github.com/avaloniaui"
         xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
         x:Class="Sandbox.MainWindow">
+  <TextBox Text="אבג ABC אבג 123"/>
 </Window>

src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs

@@ -371,14 +371,16 @@ namespace Avalonia.Media.TextFormatting
 
                 IndexedTextRun currentIndexedRun = _indexedTextRuns[i];
 
-                while(currentIndexedRun.TextSourceCharacterIndex != currentPosition)
+                while (currentIndexedRun.TextSourceCharacterIndex != currentPosition)
                 {
-                    if(i + 1 < _indexedTextRuns.Count)
+                    if (i + 1 == _indexedTextRuns.Count)
                     {
-                        i++;
-
-                        currentIndexedRun = _indexedTextRuns[i];
+                        break;
                     }
+
+                    i++;
+
+                    currentIndexedRun = _indexedTextRuns[i];
                 }
 
                 return currentIndexedRun;
@@ -604,12 +606,14 @@ namespace Avalonia.Media.TextFormatting
 
                 while (currentIndexedRun.TextSourceCharacterIndex != currentPosition)
                 {
-                    if (i + 1 < _indexedTextRuns.Count)
+                    if (i + 1 == _indexedTextRuns.Count)
                     {
-                        i++;
-
-                        currentIndexedRun = _indexedTextRuns[i];
+                        break;
                     }
+
+                    i++;
+
+                    currentIndexedRun = _indexedTextRuns[i];
                 }
 
                 return currentIndexedRun;

tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLineTests.cs

@@ -9,6 +9,7 @@ using Avalonia.Media.TextFormatting;
 using Avalonia.UnitTests;
 using Avalonia.Utilities;
 using Xunit;
+using static System.Net.Mime.MediaTypeNames;
 
 namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 {
@@ -1072,7 +1073,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
         }
 
         [Fact]
-        public void Should_GetTextBounds_BiDi()
+        public void Should_GetTextBounds_Bidi()
         {
             var text = "אבגדה 12345 ABCDEF אבגדה";
 
@@ -1120,6 +1121,31 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
             }
         }
 
+        [Fact]
+        public void Should_GetTextBounds_Bidi_2()
+        {
+            var text = "אבג ABC אבג 123";
+
+            using (Start())
+            {
+                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
+                var textSource = new SingleBufferTextSource(text, defaultProperties, true);
+
+                var formatter = new TextFormatterImpl();
+
+                var textLine =
+                    formatter.FormatLine(textSource, 0, double.PositiveInfinity,
+                        new GenericTextParagraphProperties(FlowDirection.LeftToRight, TextAlignment.Left,
+                        true, true, defaultProperties, TextWrapping.NoWrap, 0, 0, 0));
+
+                var bounds = textLine.GetTextBounds(0, text.Length);
+
+                Assert.Equal(5, bounds.Count);
+
+                Assert.Equal(textLine.WidthIncludingTrailingWhitespace, bounds.Last().Rectangle.Right);
+            }
+        }
+
         private class FixedRunsTextSource : ITextSource
         {
             private readonly IReadOnlyList<TextRun> _textRuns;