protected override void ReadContentFrom(BinaryReader reader)
{
//-------------------------------------------
// GPOS/GSUB Header
// The GPOS/GSUB table begins with a header that contains a version number for the table. Two versions are defined.
// Version 1.0 contains offsets to three tables: ScriptList, FeatureList, and LookupList.
// Version 1.1 also includes an offset to a FeatureVariations table.
// For descriptions of these tables, see the chapter, OpenType Layout Common Table Formats .
// Example 1 at the end of this chapter shows a GPOS/GSUB Header table definition.
//
// GPOS/GSUB Header, Version 1.0
// Value Type Description
// uint16 MajorVersion Major version of the GPOS/GSUB table, = 1
// uint16 MinorVersion Minor version of the GPOS/GSUB table, = 0
// Offset16 ScriptList Offset to ScriptList table, from beginning of GPOS/GSUB table
// Offset16 FeatureList Offset to FeatureList table, from beginning of GPOS/GSUB table
// Offset16 LookupList Offset to LookupList table, from beginning of GPOS/GSUB table
//
// GPOS/GSUB Header, Version 1.1
// Value Type Description
// uint16 MajorVersion Major version of the GPOS/GSUB table, = 1
// uint16 MinorVersion Minor version of the GPOS/GSUB table, = 1
// Offset16 ScriptList Offset to ScriptList table, from beginning of GPOS/GSUB table
// Offset16 FeatureList Offset to FeatureList table, from beginning of GPOS/GSUB table
// Offset16 LookupList Offset to LookupList table, from beginning of GPOS/GSUB table
// Offset32 FeatureVariations Offset to FeatureVariations table, from beginning of GPOS/GSUB table (may be NULL)
long tableStartAt = reader.BaseStream.Position;
MajorVersion = reader.ReadUInt16();
MinorVersion = reader.ReadUInt16();
ushort scriptListOffset = reader.ReadUInt16(); // from beginning of table
ushort featureListOffset = reader.ReadUInt16(); // from beginning of table
ushort lookupListOffset = reader.ReadUInt16(); // from beginning of table
uint featureVariations = (MinorVersion == 1) ? reader.ReadUInt32() : 0; // from beginning of table
//-----------------------
//1. scriptlist
ScriptList = ScriptList.CreateFrom(reader, tableStartAt + scriptListOffset);
//-----------------------
//2. feature list
FeatureList = FeatureList.CreateFrom(reader, tableStartAt + featureListOffset);
//-----------------------
//3. lookup list
ReadLookupListTable(reader, tableStartAt + lookupListOffset);
//-----------------------
//4. feature variations
if (featureVariations > 0)
{
ReadFeatureVariations(reader, tableStartAt + featureVariations);
}
}
public static ScriptList CreateFrom(BinaryReader reader, long beginAt)
{
// https://www.microsoft.com/typography/otspec/chapter2.htm
//
// ScriptList table
// Type Name Description
// uint16 ScriptCount Number of ScriptRecords
// struct ScriptRecord[ScriptCount] Array of ScriptRecords
// -listed alphabetically by ScriptTag
// ScriptRecord
// Type Name Description
// Tag ScriptTag 4-byte ScriptTag identifier
// Offset16 Script Offset to Script table-from beginning of ScriptList
reader.BaseStream.Seek(beginAt, SeekOrigin.Begin);
ushort scriptCount = reader.ReadUInt16();
ScriptList scriptList = new ScriptList();
// Read records (tags and table offsets)
uint[] scriptTags = new uint[scriptCount];
ushort[] scriptOffsets = new ushort[scriptCount];
for (int i = 0; i < scriptCount; ++i)
{
scriptTags[i] = reader.ReadUInt32();
scriptOffsets[i] = reader.ReadUInt16();
}
// Read each table and add it to the dictionary
for (int i = 0; i < scriptCount; ++i)
{
ScriptTable scriptTable = ScriptTable.CreateFrom(reader, beginAt + scriptOffsets[i]);
scriptTable.scriptTag = scriptTags[i];
scriptList.Add(Utils.TagToString(scriptTags[i]), scriptTable);
}
return(scriptList);
}
