Fix for invalid ClassDefinitionTable offset handling

samples/DrawWithImageSharp/DrawWithImageSharp.csproj

@@ -46,7 +46,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="SixLabors.ImageSharp.Drawing" Version="1.0.0-beta15.14" />
+    <PackageReference Include="SixLabors.ImageSharp.Drawing" Version="2.0.0" />
     <PackageReference Include="System.ValueTuple" Version="4.5.0" />
   </ItemGroup>
 

samples/DrawWithImageSharp/Program.cs

@@ -21,15 +21,15 @@
     {
         var fonts = new FontCollection();
         var woffFonts = new FontCollection();
         FontFamily font = fonts.Add(@"Fonts\SixLaborsSampleAB.ttf");
         FontFamily fontWoff = woffFonts.Add(@"Fonts\SixLaborsSampleAB.woff");
         FontFamily fontWoff2 = woffFonts.Add(@"Fonts\OpenSans-Regular.woff2");
         FontFamily carter = fonts.Add(@"Fonts\CarterOne.ttf");
         FontFamily wendyOne = fonts.Add(@"Fonts\WendyOne-Regular.ttf");
         FontFamily whitneyBook = fonts.Add(@"Fonts\whitney-book.ttf");
         FontFamily colorEmoji = fonts.Add(@"Fonts\Twemoji Mozilla.ttf");
         FontFamily font2 = fonts.Add(@"Fonts\OpenSans-Regular.ttf");
         FontFamily sunflower = fonts.Add(@"Fonts\Sunflower-Medium.ttf");
         FontFamily bugzilla = fonts.Add(@"Fonts\me_quran_volt_newmet.ttf");
 
         FontFamily notoKR = fonts.Add(@"Fonts\NotoSansKR-Regular.otf");
@@ -58,7 +58,7 @@
         RenderText(SystemFonts.Get("Arial"), "abcdef ghijk lmnopq rstuvwxyz", pointSize: 30);
         return;
 
         var textRuns = new List<RichTextRun>
         {
             new RichTextRun { Start = 4, End = 10, Font = uiFont.CreateFont(72, FontStyle.Bold), TextAttributes = TextAttributes.Superscript, TextDecorations = TextDecorations.Underline | TextDecorations.Strikeout | TextDecorations.Overline },
             new RichTextRun { Start = 26, End = 30, Font = uiFont.CreateFont(72, FontStyle.Italic), TextAttributes = TextAttributes.Subscript, TextDecorations = TextDecorations.Strikeout | TextDecorations.Underline | TextDecorations.Overline }
@@ -289,7 +289,7 @@
 
                 FontRectangle textSize = TextMeasurer.MeasureSize(text, textOptions);
                 using var img = new Image<Rgba32>(((int)textSize.Width * 2) + 20, ((int)textSize.Height * 2) + 20);
-                Size size = img.Size();
+                Size size = img.Size;
                 textOptions.Origin = new PointF(size.Width / 2F, size.Height / 2F);
 
                 img.Mutate(x => x.Fill(Color.Black).ApplyProcessor(
@@ -302,8 +302,8 @@
 
                 img[size.Width / 2, size.Height / 2] = Color.White;
 
                 string h = ha.ToString().Replace(nameof(HorizontalAlignment), string.Empty).ToLower();
                 string v = va.ToString().Replace(nameof(VerticalAlignment), string.Empty).ToLower();
 
                 string fullPath = CreatePath(font.Name, text + "-" + h + "-" + v + ".png");
                 Directory.CreateDirectory(IOPath.GetDirectoryName(fullPath));

src/SixLabors.Fonts/Tables/AdvancedTypographic/AttachmentListTable.cs

@@ -29,7 +29,7 @@ public static AttachmentListTable Load(BigEndianBinaryReader reader, long offset
         Span<ushort> attachPointOffsets = attachPointOffsetsBuffer.GetSpan();
         reader.ReadUInt16Array(attachPointOffsets);
 
-        var attachmentListTable = new AttachmentListTable
+        AttachmentListTable attachmentListTable = new()
         {
             CoverageTable = CoverageTable.Load(reader, offset + coverageOffset),
             AttachPoints = new AttachPoint[glyphCount]

src/SixLabors.Fonts/Tables/AdvancedTypographic/ClassDefinitionTable.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using System.Diagnostics.CodeAnalysis;
+
 namespace SixLabors.Fonts.Tables.AdvancedTypographic;
 
 /// <summary>
@@ -20,6 +22,26 @@ internal abstract class ClassDefinitionTable
     /// <returns>The class id.</returns>
     public abstract int ClassIndexOf(ushort glyphId);
 
+    public static bool TryLoad(BigEndianBinaryReader reader, long offset, [NotNullWhen(true)] out ClassDefinitionTable? table)
+    {
+        if (offset == 0)
+        {
+            table = null;
+            return false;
+        }
+
+        reader.Seek(offset, SeekOrigin.Begin);
+        ushort classFormat = reader.ReadUInt16();
+        table = classFormat switch
+        {
+            1 => ClassDefinitionFormat1Table.Load(reader),
+            2 => ClassDefinitionFormat2Table.Load(reader),
+            _ => null
+        };
+
+        return table is not null;
+    }
+
     public static ClassDefinitionTable Load(BigEndianBinaryReader reader, long offset)
     {
         reader.Seek(offset, SeekOrigin.Begin);
@@ -97,7 +119,7 @@ public static ClassDefinitionFormat2Table Load(BigEndianBinaryReader reader)
         // |                  |                                    | startGlyphID                            |
         // +------------------+------------------------------------+-----------------------------------------+
         ushort classRangeCount = reader.ReadUInt16();
-        var records = new ClassRangeRecord[classRangeCount];
+        ClassRangeRecord[] records = new ClassRangeRecord[classRangeCount];
         for (int i = 0; i < records.Length; ++i)
         {
             // +--------+--------------+------------------------------------+

src/SixLabors.Fonts/Tables/AdvancedTypographic/GlyphDefinitionTable.cs

@@ -145,22 +145,20 @@ public static GlyphDefinitionTable Load(BigEndianBinaryReader reader)
                 throw new InvalidFontFileException($"Invalid value for 'minor version' {minorVersion} of GDEF table. Should be '0', '2' or '3'.");
         }
 
-        ClassDefinitionTable? classDefinitionTable = glyphClassDefOffset is 0 ? null : ClassDefinitionTable.Load(reader, glyphClassDefOffset);
+        ClassDefinitionTable.TryLoad(reader, glyphClassDefOffset, out ClassDefinitionTable? classDefinitionTable);
         AttachmentListTable? attachmentListTable = attachListOffset is 0 ? null : AttachmentListTable.Load(reader, attachListOffset);
         LigatureCaretList? ligatureCaretList = ligatureCaretListOffset is 0 ? null : LigatureCaretList.Load(reader, ligatureCaretListOffset);
-        ClassDefinitionTable? markAttachmentClassDef = markAttachClassDefOffset is 0 ? null : ClassDefinitionTable.Load(reader, markAttachClassDefOffset);
+        ClassDefinitionTable.TryLoad(reader, markAttachClassDefOffset, out ClassDefinitionTable? markAttachmentClassDef);
         MarkGlyphSetsTable? markGlyphSetsTable = markGlyphSetsDefOffset is 0 ? null : MarkGlyphSetsTable.Load(reader, markGlyphSetsDefOffset);
 
-        var glyphDefinitionTable = new GlyphDefinitionTable()
+        // TODO: read itemVarStore.
+        return new GlyphDefinitionTable()
         {
             GlyphClassDefinition = classDefinitionTable,
             AttachmentListTable = attachmentListTable,
             LigatureCaretList = ligatureCaretList,
             MarkAttachmentClassDef = markAttachmentClassDef,
             MarkGlyphSetsTable = markGlyphSetsTable
         };
-
-        // TODO: read itemVarStore.
-        return glyphDefinitionTable;
     }
 }

src/SixLabors.Fonts/Tables/AdvancedTypographic/MarkGlyphSetsTable.cs

@@ -13,7 +13,7 @@ public static MarkGlyphSetsTable Load(BigEndianBinaryReader reader, long offset)
     {
         reader.Seek(offset, SeekOrigin.Begin);
 
-        var markGlyphSetsTable = new MarkGlyphSetsTable
+        MarkGlyphSetsTable markGlyphSetsTable = new()
         {
             Format = reader.ReadUInt16()
         };

tests/SixLabors.Fonts.Tests/FontLoaderTests.cs

@@ -137,4 +137,16 @@ public void LoadFontWoff()
         // the test font only has characters .notdef, 'a' & 'b' defined
         Assert.Equal(6, r.ControlPoints.Distinct().Count());
     }
+
+    [Fact]
+    public void LoadFontWithIncorrectClassDefinitionTableOffset()
+    {
+        // The following font contains a ClassDefinitionTable with an invalid offset.
+        // See https://forum.stimulsoft.com/viewtopic.php?t=60972
+        Font font = new FontCollection().Add(TestFonts.THSarabunFile).CreateFont(12);
+
+        FontRectangle advance = TextMeasurer.MeasureAdvance("เราใช้คุกกี้เพื่อพัฒนาประสิทธิภาพ และประสบการณ์ที่ดีในการใช้เว็บไซต์ของคุณ คุณสามารถศึกษารายละเอียดได้ที่", new(font));
+
+        Assert.NotEqual(default, advance);
+    }
 }

tests/SixLabors.Fonts.Tests/TestFonts.cs

@@ -243,6 +243,8 @@
 
     public static string DFKaiSBFile => GetFullPath("kaiu.ttf");
 
+    public static string THSarabunFile => GetFullPath("THSarabun.ttf");
+
     public static Stream TwemojiMozillaData() => OpenStream(TwemojiMozillaFile);
 
     public static Stream SegoeuiEmojiData() => OpenStream(SegoeuiEmojiFile);
@@ -294,7 +296,7 @@
 
     private static string GetFullPath(string path)
     {
         string root = Path.GetDirectoryName(new Uri(typeof(TestFonts).GetTypeInfo().Assembly.CodeBase).LocalPath);
 
         string[] paths = new[]
         {