Merge pull request #5864 from Gillibald/fixes/TryGetRunProperties

Fix text tokenization for inherited scripts

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

@@ -109,7 +109,8 @@ namespace Avalonia.Media.TextFormatting
                 GlyphRun.GlyphAdvances.Take(glyphCount),
                 GlyphRun.GlyphOffsets.Take(glyphCount),
                 GlyphRun.Characters.Take(length),
-                GlyphRun.GlyphClusters.Take(glyphCount));
+                GlyphRun.GlyphClusters.Take(glyphCount),
+                GlyphRun.BiDiLevel);
 
             var firstTextRun = new ShapedTextCharacters(firstGlyphRun, Properties);
 
@@ -120,7 +121,8 @@ namespace Avalonia.Media.TextFormatting
                 GlyphRun.GlyphAdvances.Skip(glyphCount),
                 GlyphRun.GlyphOffsets.Skip(glyphCount),
                 GlyphRun.Characters.Skip(length),
-                GlyphRun.GlyphClusters.Skip(glyphCount));
+                GlyphRun.GlyphClusters.Skip(glyphCount),
+                GlyphRun.BiDiLevel);
 
             var secondTextRun = new ShapedTextCharacters(secondGlyphRun, Properties);
 

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

@@ -135,20 +135,20 @@ namespace Avalonia.Media.TextFormatting
 
             count = 0;
             var script = Script.Common;
-            //var direction = BiDiClass.LeftToRight;
+            var direction = BiDiClass.LeftToRight;
 
             var font = typeface.GlyphTypeface;
             var defaultFont = defaultTypeface.GlyphTypeface;
-
+            
             var enumerator = new GraphemeEnumerator(text);
 
             while (enumerator.MoveNext())
             {
-                var grapheme = enumerator.Current;
+                var currentGrapheme = enumerator.Current;
 
-                var currentScript = grapheme.FirstCodepoint.Script;
+                var currentScript = currentGrapheme.FirstCodepoint.Script;
 
-                //var currentDirection = grapheme.FirstCodepoint.BiDiClass;
+                var currentDirection = currentGrapheme.FirstCodepoint.BiDiClass;
 
                 //// ToDo: Implement BiDi algorithm
                 //if (currentScript.HorizontalDirection != direction)
@@ -161,36 +161,44 @@ namespace Avalonia.Media.TextFormatting
 
                 if (currentScript != script)
                 {
-                    if (currentScript != Script.Inherited && currentScript != Script.Common)
+                    if (script == Script.Inherited || script == Script.Common)
                     {
-                        if (script == Script.Inherited || script == Script.Common)
-                        {
-                            script = currentScript;
-                        }
-                        else
+                        script = currentScript;
+                    }
+                    else
+                    {
+                        if (currentScript != Script.Inherited && currentScript != Script.Common)
                         {
                             break;
                         }
                     }
                 }
 
-                if (isFallback)
+                if (currentScript != Script.Common && currentScript != Script.Inherited)
                 {
-                    if (defaultFont.TryGetGlyph(grapheme.FirstCodepoint, out _))
+                    if (isFallback && defaultFont.TryGetGlyph(currentGrapheme.FirstCodepoint, out _))
                     {
                         break;
                     }
-                }
 
-                if (!font.TryGetGlyph(grapheme.FirstCodepoint, out _))
-                {
-                    if (!grapheme.FirstCodepoint.IsWhiteSpace)
+                    if (!font.TryGetGlyph(currentGrapheme.FirstCodepoint, out _))
                     {
                         break;
                     }
                 }
 
-                count += grapheme.Text.Length;
+                if (!currentGrapheme.FirstCodepoint.IsWhiteSpace && !font.TryGetGlyph(currentGrapheme.FirstCodepoint, out _))
+                {
+                    break;
+                }
+
+                if (direction == BiDiClass.RightToLeft && currentDirection  == BiDiClass.CommonSeparator)
+                {
+                    break;
+                }
+
+                count += currentGrapheme.Text.Length;
+                direction = currentDirection;
             }
 
             return count > 0;

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

@@ -125,6 +125,27 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
             }
         }
 
+        [Fact]
+        public void Should_Produce_A_Single_Fallback_Run()
+        {
+            using (Start())
+            {
+                var defaultProperties = new GenericTextRunProperties(Typeface.Default);
+
+                const string text = "👍 👍 👍 👍";
+                
+                var textSource = new SingleBufferTextSource(text, defaultProperties);
+
+                var formatter = new TextFormatterImpl();
+
+                var textLine =
+                    formatter.FormatLine(textSource, 0, double.PositiveInfinity,
+                        new GenericTextParagraphProperties(defaultProperties));
+
+                Assert.Equal(1, textLine.TextRuns.Count);
+            } 
+        }
+
         [Fact]
         public void Should_Split_Run_On_Script()
         {