591: minor update on variable fonts (work-in-progress)

Author: prepare

Demo/Windows/TestFonts/AmstelvarAlpha-VF.ttf

@@ -0,0 +1 @@
+SIL , https://github.com/TypeNetwork/Amstelvar/blob/master/COPYRIGHT.md

Demo/Windows/TestFonts/AmstelvarAlpha_LICENSE.txt

@@ -0,0 +1 @@
+OFL, https://fonts.google.com/specimen/Comfortaa#standard-styles

Demo/Windows/TestFonts/Comfortaa-VariableFont_wght.ttf

@@ -20,6 +20,8 @@ The FreeType Project LICENSE (3-clauses BSD style),2003-2016, David Turner, Robe
 
 Apache2, 2018, Apache/PDFBox Authors,  https://github.com/apache/pdfbox
 
+Apache2, 2020, Adobe Font Development Kit for OpenType (AFDKO), https://github.com/adobe-type-tools/afdko
+
 **Text Processing**
 
 Unicode (BSD style), 2020, _UNICODE, INC_, https://www.unicode.org/license.html

Demo/Windows/TestFonts/Comfortaa-VariableFont_wght_LICENSE.txt

@@ -12,9 +12,12 @@ namespace Typography.OpenFont.Tables
     class CVar : TableEntry
     {
         public const string _N = "cvar";
-        public override string Name => _N; 
+        public override string Name => _N;
         public CVar()
         {
+            //The control value table (CVT) variations table is used in variable fonts to provide variation data for CVT values.
+            //For a general overview of OpenType Font Variations
+
 
         }
         protected override void ReadContentFrom(BinaryReader reader)

LICENSE.md

@@ -86,7 +86,8 @@ namespace Typography.OpenFont.Tables
 
     //The tupleVariationCount field contains a packed value that includes flags and the number of logical tuple variation tables — which is also the number of physical tuple variation headers.The format of the tupleVariationCount value is as follows:
     //Mask      Name                    Description
-    //0x8000 	SHARED_POINT_NUMBERS    Flag indicating that some or all tuple variation tables reference a shared set of “point” numbers.These shared numbers are represented as packed point number data at the start of the serialized data.
+    //0x8000 	SHARED_POINT_NUMBERS    Flag indicating that some or all tuple variation tables reference a shared set of “point” numbers.
+    //                              These shared numbers are represented as packed point number data at the start of the serialized data.
     //0x7000 	Reserved                Reserved for future use — set to 0.
     //0x0FFF 	COUNT_MASK              Mask     for the low bits to give the number of tuple variation tables.
 
@@ -109,22 +110,58 @@ class TupleVariationHeader
     {
         //TupleVariationHeader:
         //Type      Name                    Description
-        //int16     variationDataSize       The size in bytes of the serialized data for this tuple variation table.
+        //uint16    variationDataSize       The size in bytes of the serialized data for this tuple variation table.
         //uint16    tupleIndex              A packed field.
         //                                  The high 4 bits are flags(see below).
         //                                  The low 12 bits are an index into a shared tuple records array.
-        //Tuple     peakTuple               Peak tuple record for this tuple variation table — optional, 
-        //                                  determined by flags in the tupleIndex value.
+        //Tuple     peakTuple               Peak tuple record for this tuple variation table — optional, determined by flags in the tupleIndex value.
         //                                  Note that this must always be included in the 'cvar' table.
         //Tuple     intermediateStartTuple  Intermediate start tuple record for this tuple variation table — optional, determined by flags in the tupleIndex value.
         //Tuple     intermediateEndTuple    Intermediate end tuple record for this tuple variation table — optional, determined by flags in the tupleIndex value.
 
-        public short variableDataSize;
-        public ushort tupleIndex;
+        public ushort variableDataSize;
+
+        public int flags;
+        public ushort indexToSharedTupleRecArray;
+
         public TupleRecord peakTuple;
         public TupleRecord intermediateStartTuple;
         public TupleRecord intermediateEndTuple;
 
+
+        public static TupleVariationHeader Read(BinaryReader reader, int axisCount)
+        {
+            TupleVariationHeader header = new TupleVariationHeader();
+
+            header.variableDataSize = reader.ReadUInt16();
+            ushort tupleIndex = reader.ReadUInt16();
+            int flags = (tupleIndex >> 12) & 0xF; //The high 4 bits are flags(see below).
+            header.flags = flags; //The high 4 bits are flags(see below).
+            header.indexToSharedTupleRecArray = (ushort)(tupleIndex & 0x0FFF); // The low 12 bits are an index into a shared tuple records array.
+
+
+            if ((flags & ((int)TupleIndexFormat.EMBEDDED_PEAK_TUPLE >> 12)) == ((int)TupleIndexFormat.EMBEDDED_PEAK_TUPLE >> 12))
+            {
+                //TODO:...
+                header.peakTuple = TupleRecord.ReadTupleRecord(reader, axisCount);
+            }
+            if ((flags & ((int)TupleIndexFormat.INTERMEDIATE_REGION >> 12)) == ((int)TupleIndexFormat.INTERMEDIATE_REGION >> 12))
+            {
+                //TODO:...
+                header.intermediateStartTuple = TupleRecord.ReadTupleRecord(reader, axisCount);
+                header.intermediateEndTuple = TupleRecord.ReadTupleRecord(reader, axisCount);
+            }
+
+            return header;
+        }
+
+
+
+        //---------
+        public ushort[] PrivatePoints;
+        public short[] PackedDeltasXY;
+
+
         //Note that the size of the TupleVariationHeader is variable, 
         //depending on whether peak or intermediate tuple records are included. (See below for more information.)
 
@@ -208,9 +245,22 @@ enum TupleIndexFormat
         //    }
     }
 
-    struct TupleRecord
+    readonly struct TupleRecord
     {
-        public float[] coords;
+        public readonly float[] coords;
+        public TupleRecord(float[] coords) => this.coords = coords;
+#if DEBUG
+        public override string ToString() => coords?.Length.ToString() ?? "0";
+#endif
+        public static TupleRecord ReadTupleRecord(BinaryReader reader, int count)
+        {
+            float[] coords = new float[count];
+            for (int n = 0; n < coords.Length; ++n)
+            {
+                coords[n] = reader.ReadF2Dot14();
+            }
+            return new TupleRecord(coords);
+        }
     }
 
     //----------------------------------------------------------------

Typography.OpenFont/Tables.Variations/CVar.cs

@@ -145,6 +145,7 @@ public void ReadContent(BinaryReader reader)
 
             }
         }
+
         public class InstanceRecord
         {
             //InstanceRecord
@@ -166,23 +167,24 @@ public class InstanceRecord
             //Tuple     coordinates         The coordinates array for this instance.
             //uint16    postScriptNameID    Optional.The name ID for entries in the 'name' table that provide PostScript names for this instance.
 
-            public ushort subfamilyNameID;
+            public ushort subfamilyNameID;//point to name table, will be resolved later
             public ushort flags;
-            public float[] coordinates; //tuple record
-            public ushort postScriptNameID;
+            public TupleRecord coordinates;
+            public ushort postScriptNameID;//point to name table, will be resolved later
+
             public void ReadContent(BinaryReader reader, int axisCount, int instanceRecordSize)
             {
                 long expectedEndPos = reader.BaseStream.Position + instanceRecordSize;
                 subfamilyNameID = reader.ReadUInt16();
                 flags = reader.ReadUInt16();
-                coordinates = new float[axisCount];
+                float[] coords = new float[axisCount];
                 for (int i = 0; i < axisCount; ++i)
                 {
-                    coordinates[i] = reader.ReadFixed();
+                    coords[i] = reader.ReadFixed();
                 }
+                coordinates = new TupleRecord(coords);
 
-
-                if (reader.BaseStream.Position < instanceRecordSize)
+                if (reader.BaseStream.Position < expectedEndPos)
                 {
                     //optional field
                     postScriptNameID = reader.ReadUInt16();