WIP: Compact Font Format (CFF) Version 2

src/SixLabors.Fonts/BigEndianBinaryReader.cs

@@ -356,7 +356,7 @@ public string ReadTag()
     }
 
     /// <summary>
-    /// Reads an offset consuming the given nuber of bytes.
+    /// Reads an offset consuming the given number of bytes.
     /// </summary>
     /// <param name="size">The offset size in bytes.</param>
     /// <returns>The 32-bit signed integer representing the offset.</returns>
@@ -393,6 +393,7 @@ private void ReadInternal(byte[] data, int size)
         }
     }
 
+    /// <inheritdoc />
     public void Dispose()
     {
         if (!this.leaveOpen)

src/SixLabors.Fonts/FileFontMetrics.cs

@@ -5,6 +5,7 @@
 using System.Numerics;
 using SixLabors.Fonts.Tables;
 using SixLabors.Fonts.Tables.AdvancedTypographic;
+using SixLabors.Fonts.Tables.AdvancedTypographic.Variations;
 using SixLabors.Fonts.Unicode;
 
 namespace SixLabors.Fonts;
@@ -115,6 +116,10 @@ internal override bool TryGetGlyphClass(ushort glyphId, [NotNullWhen(true)] out
     internal override bool TryGetMarkAttachmentClass(ushort glyphId, [NotNullWhen(true)] out GlyphClassDef? markAttachmentClass)
         => this.fontMetrics.Value.TryGetMarkAttachmentClass(glyphId, out markAttachmentClass);
 
+    /// <inheritdoc/>
+    public override bool TryGetVariationAxes(out VariationAxis[]? variationAxes)
+        => this.fontMetrics.Value.TryGetVariationAxes(out variationAxes);
+
     /// <inheritdoc />
     public override bool TryGetGlyphMetrics(
         CodePoint codePoint,

src/SixLabors.Fonts/FontMetrics.cs

@@ -4,6 +4,7 @@
 using System.Diagnostics.CodeAnalysis;
 using System.Numerics;
 using SixLabors.Fonts.Tables.AdvancedTypographic;
+using SixLabors.Fonts.Tables.AdvancedTypographic.Variations;
 using SixLabors.Fonts.Unicode;
 
 namespace SixLabors.Fonts;
@@ -159,6 +160,14 @@ internal FontMetrics()
     /// <returns>true, if the mark attachment class could be retrieved.</returns>
     internal abstract bool TryGetMarkAttachmentClass(ushort glyphId, [NotNullWhen(true)] out GlyphClassDef? markAttachmentClass);
 
+    /// <summary>
+    /// Tries to get the variation axes that this font supports.
+    /// The font needs to have a fvar table.
+    /// </summary>
+    /// <param name="variationAxes">An array with Variation axes.</param>
+    /// <returns>True, if fvar table is present.</returns>
+    public abstract bool TryGetVariationAxes(out VariationAxis[]? variationAxes);
+
     /// <summary>
     /// Gets the glyph metrics for a given code point.
     /// </summary>

src/SixLabors.Fonts/FontReader.cs

@@ -138,18 +138,16 @@ public FontReader(Stream stream)
         {
             return (TTableType)table;
         }
-        else
+
+        TTableType? loadedTable = this.loader.Load<TTableType>(this);
+        if (loadedTable is null)
         {
-            TTableType? loadedTable = this.loader.Load<TTableType>(this);
-            if (loadedTable is null)
-            {
-                return null;
-            }
-
-            table = loadedTable;
-            this.loadedTables.Add(typeof(TTableType), loadedTable);
+            return null;
         }
 
+        table = loadedTable;
+        this.loadedTables.Add(typeof(TTableType), loadedTable);
+
         return (TTableType)table;
     }
 

src/SixLabors.Fonts/StreamFontMetrics.Cff.cs

@@ -2,6 +2,7 @@
 // Licensed under the Six Labors Split License.
 
 using SixLabors.Fonts.Tables.AdvancedTypographic;
+using SixLabors.Fonts.Tables.AdvancedTypographic.Variations;
 using SixLabors.Fonts.Tables.Cff;
 using SixLabors.Fonts.Tables.General;
 using SixLabors.Fonts.Tables.General.Colr;
@@ -21,15 +22,14 @@ private static StreamFontMetrics LoadCompactFont(FontReader reader)
     {
         // Load using recommended order for best performance.
         // https://www.microsoft.com/typography/otspec/recom.htm#TableOrdering
-        // 'head', 'hhea', 'maxp', OS/2, 'name', 'cmap', 'post', 'CFF '
+        // 'head', 'hhea', 'maxp', OS/2, 'name', 'cmap', 'post', 'CFF ' / 'CFF2'
         HeadTable head = reader.GetTable<HeadTable>();
         HorizontalHeadTable hhea = reader.GetTable<HorizontalHeadTable>();
         MaximumProfileTable maxp = reader.GetTable<MaximumProfileTable>();
         OS2Table os2 = reader.GetTable<OS2Table>();
         NameTable name = reader.GetTable<NameTable>();
         CMapTable cmap = reader.GetTable<CMapTable>();
         PostTable post = reader.GetTable<PostTable>();
-
         ICffTable? cff = reader.TryGetTable<Cff1Table>() ?? (ICffTable?)reader.TryGetTable<Cff2Table>();
 
         // TODO: VORG
@@ -50,6 +50,21 @@ private static StreamFontMetrics LoadCompactFont(FontReader reader)
         ColrTable? colr = reader.TryGetTable<ColrTable>();
         CpalTable? cpal = reader.TryGetTable<CpalTable>();
 
+        // Variations related tables.
+        FVarTable? fVar = reader.TryGetTable<FVarTable>();
+        AVarTable? aVar = reader.TryGetTable<AVarTable>();
+        GVarTable? gVar = reader.TryGetTable<GVarTable>();
+        GlyphVariationProcessor? glyphVariationProcessor = null;
+        if (cff?.ItemVariationStore != null)
+        {
+            if (fVar is null)
+            {
+                throw new InvalidFontFileException("missing fvar table required for glyph variations processing");
+            }
+
+            glyphVariationProcessor = new GlyphVariationProcessor(cff.ItemVariationStore, fVar, aVar, gVar);
+        }
+
         CompactFontTables tables = new(cmap, head, hhea, htmx, maxp, name, os2, post, cff!)
         {
             Kern = kern,
@@ -60,9 +75,12 @@ private static StreamFontMetrics LoadCompactFont(FontReader reader)
             GPos = gPos,
             Colr = colr,
             Cpal = cpal,
+            FVar = fVar,
+            AVar = aVar,
+            GVar = gVar,
         };
 
-        return new StreamFontMetrics(tables);
+        return new StreamFontMetrics(tables, glyphVariationProcessor);
     }
 
     private GlyphMetrics CreateCffGlyphMetrics(
@@ -78,8 +96,14 @@ private GlyphMetrics CreateCffGlyphMetrics(
         ICffTable cff = tables.Cff;
         HorizontalMetricsTable htmx = tables.Htmx;
         VerticalMetricsTable? vtmx = tables.Vmtx;
+        FVarTable? fVar = tables.FVar;
+        AVarTable? aVar = tables.AVar;
+        GVarTable? gVar = tables.GVar;
 
         CffGlyphData vector = cff.GetGlyph(glyphId);
+        vector.FVar = fVar;
+        vector.AVar = aVar;
+        vector.GVar = gVar;
         Bounds bounds = vector.GetBounds();
         ushort advanceWidth = htmx.GetAdvancedWidth(glyphId);
         short lsb = htmx.GetLeftSideBearing(glyphId);

src/SixLabors.Fonts/StreamFontMetrics.TrueType.cs

@@ -3,6 +3,7 @@
 
 using System.Numerics;
 using SixLabors.Fonts.Tables.AdvancedTypographic;
+using SixLabors.Fonts.Tables.AdvancedTypographic.Variations;
 using SixLabors.Fonts.Tables.General;
 using SixLabors.Fonts.Tables.General.Colr;
 using SixLabors.Fonts.Tables.General.Kern;
@@ -64,6 +65,12 @@ internal void ApplyTrueTypeHinting(HintingMode hintingMode, GlyphMetrics metrics
 
     private static StreamFontMetrics LoadTrueTypeFont(FontReader reader)
     {
+        // Load glyph variations related tables first, because glyph table needs them.
+        FVarTable? fvar = reader.TryGetTable<FVarTable>();
+        AVarTable? avar = reader.TryGetTable<AVarTable>();
+        GVarTable? gvar = reader.TryGetTable<GVarTable>();
+        HVarTable? hvar = reader.TryGetTable<HVarTable>();
+
         // Load using recommended order for best performance.
         // https://www.microsoft.com/typography/otspec/recom.htm#TableOrdering
         // 'head', 'hhea', 'maxp', OS/2, 'hmtx', LTSH, VDMX, 'hdmx', 'cmap', 'fpgm', 'prep', 'cvt ', 'loca', 'glyf', 'kern', 'name', 'post', 'gasp', PCLT, DSIG
@@ -109,6 +116,10 @@ private static StreamFontMetrics LoadTrueTypeFont(FontReader reader)
             GPos = gPos,
             Colr = colr,
             Cpal = cpal,
+            Fvar = fvar,
+            Gvar = gvar,
+            Hvar = hvar,
+            Avar = avar
         };
 
         return new StreamFontMetrics(tables);

src/SixLabors.Fonts/StreamFontMetrics.cs

@@ -3,9 +3,11 @@
 
 using System.Collections.Concurrent;
 using System.Diagnostics.CodeAnalysis;
+using System.Globalization;
 using System.Numerics;
 using SixLabors.Fonts.Tables;
 using SixLabors.Fonts.Tables.AdvancedTypographic;
+using SixLabors.Fonts.Tables.AdvancedTypographic.Variations;
 using SixLabors.Fonts.Tables.Cff;
 using SixLabors.Fonts.Tables.General;
 using SixLabors.Fonts.Tables.General.Colr;
@@ -76,11 +78,13 @@ internal StreamFontMetrics(TrueTypeFontTables tables)
     /// Initializes a new instance of the <see cref="StreamFontMetrics"/> class.
     /// </summary>
     /// <param name="tables">The Compact Font tables.</param>
-    internal StreamFontMetrics(CompactFontTables tables)
+    /// <param name="glyphVariationProcessor">Processor which handles glyph variations.</param>
+    internal StreamFontMetrics(CompactFontTables tables, GlyphVariationProcessor? glyphVariationProcessor = null)
     {
         this.compactFontTables = tables;
         this.outlineType = OutlineType.CFF;
         this.description = new FontDescription(tables.Name, tables.Os2, tables.Head);
+        this.GlyphVariationProcessor = glyphVariationProcessor;
         this.glyphIdCache = new();
         this.glyphCache = new();
         if (tables.Colr is not null)
@@ -95,6 +99,8 @@ internal StreamFontMetrics(CompactFontTables tables)
 
     public HeadTable.HeadFlags HeadFlags { get; private set; }
 
+    public GlyphVariationProcessor? GlyphVariationProcessor { get; private set; }
+
     /// <inheritdoc/>
     public override FontDescription Description => this.description;
 
@@ -196,6 +202,35 @@ internal override bool TryGetMarkAttachmentClass(ushort glyphId, [NotNullWhen(tr
         return gdef is not null && gdef.TryGetMarkAttachmentClass(glyphId, out markAttachmentClass);
     }
 
+    /// <inheritdoc/>
+    public override bool TryGetVariationAxes(out VariationAxis[]? variationAxes)
+    {
+        if (this.trueTypeFontTables?.Fvar == null)
+        {
+            variationAxes = Array.Empty<VariationAxis>();
+            return false;
+        }
+
+        FVarTable? fvar = this.trueTypeFontTables?.Fvar;
+        Tables.General.Name.NameTable? names = this.trueTypeFontTables?.Name;
+        variationAxes = new VariationAxis[fvar!.Axes.Length];
+        for (int i = 0; i < fvar.Axes.Length; i++)
+        {
+            VariationAxisRecord axis = fvar.Axes[i];
+            string name = names != null ? names.GetNameById(CultureInfo.InvariantCulture, axis.AxisNameId) : string.Empty;
+            variationAxes[i] = new VariationAxis()
+            {
+                Tag = axis.Tag,
+                Min = axis.MinValue,
+                Max = axis.MaxValue,
+                Default = axis.DefaultValue,
+                Name = name
+            };
+        }
+
+        return true;
+    }
+
     /// <inheritdoc/>
     public override bool TryGetGlyphMetrics(
         CodePoint codePoint,
@@ -367,10 +402,8 @@ internal static StreamFontMetrics LoadFont(FontReader reader)
         {
             return LoadTrueTypeFont(reader);
         }
-        else
-        {
-            return LoadCompactFont(reader);
-        }
+
+        return LoadCompactFont(reader);
     }
 
     private (HorizontalMetrics HorizontalMetrics, VerticalMetrics VerticalMetrics) Initialize<T>(T tables)

src/SixLabors.Fonts/Tables/AdvancedTypographic/Variations/AVarTable.cs

@@ -0,0 +1,73 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.Fonts.Tables.AdvancedTypographic.Variations;
+
+/// <summary>
+/// Implements reading the Font Variations Table `avar`.
+/// <see href="https://docs.microsoft.com/de-de/typography/opentype/spec/avar"/>
+/// </summary>
+internal class AVarTable : Table
+{
+    internal const string TableName = "avar";
+
+    public AVarTable(uint axisCount, SegmentMapRecord[] segmentMaps)
+    {
+        this.AxisCount = axisCount;
+        this.SegmentMaps = segmentMaps;
+    }
+
+    public uint AxisCount { get; }
+
+    public SegmentMapRecord[] SegmentMaps { get; }
+
+    public static AVarTable? Load(FontReader reader)
+    {
+        if (!reader.TryGetReaderAtTablePosition(TableName, out BigEndianBinaryReader? binaryReader))
+        {
+            return null;
+        }
+
+        using (binaryReader)
+        {
+            return Load(binaryReader);
+        }
+    }
+
+    public static AVarTable Load(BigEndianBinaryReader reader)
+    {
+        // VariationsTable `avar`
+        // +-----------------+----------------------------------------+-------------------------------------------------------------------------+
+        // | Type            | Name                                   | Description                                                             |
+        // +=================+========================================+=========================================================================+
+        // | uint16          | majorVersion                           | Major version number of the font variations table — set to 1.           |
+        // +-----------------+----------------------------------------+-------------------------------------------------------------------------+
+        // | uint16          | minorVersion                           | Minor version number of the font variations table — set to 0.           |
+        // +-----------------+----------------------------------------+-------------------------------------------------------------------------+
+        // | uint16          | (reserved)                             | This field is permanently reserved. Set to zero.                        |
+        // +-----------------+----------------------------------------+-------------------------------------------------------------------------+
+        // | uint16          | axisCount                              | The number of variation axes in the font                                |
+        // |                 |                                        | (the number of records in the axes array).                              |
+        // +-----------------+----------------------------------------+-------------------------------------------------------------------------+
+        // | SegmentMaps     | axisSegmentMaps[axisCount]             | The segment maps array — one segment map for each axis, in the order of |
+        // |                 |                                        | axes specified in the 'fvar' table.                                     |
+        // +-----------------+----------------------------------------+-------------------------------------------------------------------------+
+        ushort major = reader.ReadUInt16();
+        ushort minor = reader.ReadUInt16();
+        ushort reserved = reader.ReadUInt16();
+        ushort axisCount = reader.ReadUInt16();
+
+        if (major != 1)
+        {
+            throw new NotSupportedException("Only version 1 of avar table is supported");
+        }
+
+        var segmentMaps = new SegmentMapRecord[axisCount];
+        for (int i = 0; i < axisCount; i++)
+        {
+            segmentMaps[i] = SegmentMapRecord.Load(reader);
+        }
+
+        return new AVarTable(axisCount, segmentMaps);
+    }
+}

src/SixLabors.Fonts/Tables/AdvancedTypographic/Variations/AxisValueMapRecord.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.Fonts.Tables.AdvancedTypographic.Variations;
+
+internal class AxisValueMapRecord
+{
+    public AxisValueMapRecord(float fromCoordinate, float toCoordinate)
+    {
+        this.FromCoordinate = fromCoordinate;
+        this.ToCoordinate = toCoordinate;
+    }
+
+    public float FromCoordinate { get; }
+
+    public float ToCoordinate { get; }
+
+    public static AxisValueMapRecord Load(BigEndianBinaryReader reader)
+    {
+        // AxisValueMapRecord
+        // +-----------------+----------------------------------------+-------------------------------------------------------------------------+
+        // | Type            | Name                                   | Description                                                             |
+        // +=================+========================================+=========================================================================+
+        // | F2DOT14         | fromCoordinate                         | A normalized coordinate value obtained using default normalization.     |
+        // +-----------------+----------------------------------------+-------------------------------------------------------------------------+
+        // | F2DOT14         | toCoordinate                           | The modified, normalized coordinate value.                              |
+        // +-----------------+----------------------------------------+-------------------------------------------------------------------------+
+        float fromCoordinate = reader.ReadF2dot14();
+        float toCoordinate = reader.ReadF2dot14();
+
+        return new AxisValueMapRecord(fromCoordinate, toCoordinate);
+    }
+}