Fix TextWrapping

src/Avalonia.Controls/TextBlock.cs

@@ -118,6 +118,8 @@ namespace Avalonia.Controls
         {
             ClipToBoundsProperty.OverrideDefaultValue<TextBlock>(true);
 
+            AffectsRender<TextBlock>(BackgroundProperty);
+
             Observable.Merge(
                 TextProperty.Changed,
                 ForegroundProperty.Changed,
@@ -438,7 +440,9 @@ namespace Avalonia.Controls
 
             _constraint = availableSize;
 
-            return TextLayout?.Bounds.Size ?? Size.Empty;
+            var measuredSize = TextLayout?.Bounds.Size ?? Size.Empty;
+
+            return measuredSize.Inflate(padding);
         }
 
         protected override void OnAttachedToLogicalTree(LogicalTreeAttachmentEventArgs e)

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

@@ -201,18 +201,17 @@ namespace Avalonia.Media.TextFormatting
             var availableWidth = paragraphWidth;
             var currentWidth = 0.0;
             var runIndex = 0;
+            var length = 0;
 
             while (runIndex < textRuns.Count)
             {
                 var currentRun = textRuns[runIndex];
 
-                currentWidth += currentRun.GlyphRun.Bounds.Width;
-
-                if (currentWidth > availableWidth)
+                if (currentWidth + currentRun.GlyphRun.Bounds.Width > availableWidth)
                 {
-                    var measuredLength = MeasureText(currentRun, paragraphWidth);
+                    var measuredLength = MeasureText(currentRun, paragraphWidth - currentWidth);
 
-                    if (measuredLength < text.End)
+                    if (measuredLength < currentRun.Text.Length)
                     {
                         var currentBreakPosition = -1;
 
@@ -241,15 +240,19 @@ namespace Avalonia.Media.TextFormatting
                         }
                     }
 
-                    var splitResult = SplitTextRuns(textRuns, measuredLength);
+                    length += measuredLength;
+
+                    var splitResult = SplitTextRuns(textRuns, length);
 
                     var textLineMetrics =
                         TextLineMetrics.Create(splitResult.First, paragraphWidth, paragraphProperties.TextAlignment);
 
-                    return new SimpleTextLine(text.Take(measuredLength), splitResult.First, textLineMetrics);
+                    return new SimpleTextLine(text.Take(length), splitResult.First, textLineMetrics);
                 }
 
-                availableWidth -= currentRun.GlyphRun.Bounds.Width;
+                currentWidth += currentRun.GlyphRun.Bounds.Width;
+
+                length += currentRun.GlyphRun.Characters.Length;
 
                 runIndex++;
             }
@@ -281,12 +284,18 @@ namespace Avalonia.Media.TextFormatting
 
                 if (measuredWidth + advance > availableWidth)
                 {
+                    index--;
                     break;
                 }
 
                 measuredWidth += advance;
             }
 
+            if(index < 0)
+            {
+                return 0;
+            }
+
             var cluster = textRun.GlyphRun.GlyphClusters[index];
 
             var characterHit = textRun.GlyphRun.FindNearestCharacterHit(cluster, out _);
@@ -355,7 +364,7 @@ namespace Avalonia.Media.TextFormatting
                     continue;
                 }
 
-                var firstCount = currentRun.GlyphRun.Characters.Length > 1 ? i + 1 : i;
+                var firstCount = currentRun.GlyphRun.Characters.Length >= 1 ? i + 1 : i;
 
                 var first = new ShapedTextRun[firstCount];
 

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

@@ -233,6 +233,11 @@ namespace Avalonia.Media.TextFormatting
 
                         var textLine = TextFormatter.Current.FormatLine(textSource, 0, MaxWidth, _paragraphProperties);
 
+                        if (!double.IsPositiveInfinity(MaxHeight) && bottom + textLine.LineMetrics.Size.Height > MaxHeight)
+                        {
+                            break;
+                        }
+
                         UpdateBounds(textLine, ref left, ref right, ref bottom);
 
                         textLines.Add(textLine);
@@ -253,17 +258,17 @@ namespace Avalonia.Media.TextFormatting
                     {
                         var emptyTextLine = CreateEmptyTextLine(currentPosition);
 
+                        if (!double.IsPositiveInfinity(MaxHeight) && bottom + emptyTextLine.LineMetrics.Size.Height > MaxHeight)
+                        {
+                            break;
+                        }
+
                         UpdateBounds(emptyTextLine, ref left, ref right, ref bottom);
 
                         textLines.Add(emptyTextLine);
 
                         break;
                     }
-
-                    if (!double.IsPositiveInfinity(MaxHeight) && MaxHeight < Bounds.Height)
-                    {
-                        break;
-                    }
                 }
 
                 Bounds = new Rect(left, 0, right, bottom);