protected override void ReadContentFrom(BinaryReader reader)
{
gposTableStartAt = reader.BaseStream.Position;
//-------------------------------------------
// GPOS Header
//The GPOS 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 Header table definition.
//GPOS Header, Version 1.0
//Value Type Description
//USHORT MajorVersion Major version of the GPOS table, = 1
//USHORT MinorVersion Minor version of the GPOS table, = 0
//Offset ScriptList Offset to ScriptList table, from beginning of GPOS table
//Offset FeatureList Offset to FeatureList table, from beginning of GPOS table
//Offset LookupList Offset to LookupList table, from beginning of GPOS table
//GPOS Header, Version 1.1
//Value Type Description
//USHORT MajorVersion Major version of the GPOS table, = 1
//USHORT MinorVersion Minor version of the GPOS table, = 1
//Offset ScriptList Offset to ScriptList table, from beginning of GPOS table
//Offset FeatureList Offset to FeatureList table, from beginning of GPOS table
//Offset LookupList Offset to LookupList table, from beginning of GPOS table
//ULONG FeatureVariations Offset to FeatureVariations table, from beginning of GPOS table (may be NULL)
this.MajorVersion = reader.ReadUInt16();
this.MinorVersion = reader.ReadUInt16();
ushort scriptListOffset = reader.ReadUInt16();//from beginning of GSUB table
ushort featureListOffset = reader.ReadUInt16();//from beginning of GSUB table
ushort lookupListOffset = reader.ReadUInt16();//from beginning of GSUB table
uint featureVariations = (MinorVersion == 1) ? reader.ReadUInt32() : 0;//from beginning of GSUB table
//-----------------------
//1. scriptlist
scriptList = ScriptList.CreateFrom(reader, gposTableStartAt + scriptListOffset);
//-----------------------
//2. feature list
featureList = FeatureList.CreateFrom(reader, gposTableStartAt + featureListOffset);
//-----------------------
//3. lookup list
ReadLookupListTable(reader, gposTableStartAt + lookupListOffset);
//-----------------------
//4. feature variations
if (featureVariations > 0)
{
reader.BaseStream.Seek(this.Header.Offset + featureVariations, SeekOrigin.Begin);
ReadFeaureVariations(reader);
}
}
public static ScriptList CreateFrom(BinaryReader reader, long beginAt)
{
reader.BaseStream.Seek(beginAt, SeekOrigin.Begin);
//https://www.microsoft.com/typography/otspec/chapter2.htm
//ScriptList table
//Type Name Description
//USHORT ScriptCount Number of ScriptRecords
//struct ScriptRecord
//[ScriptCount] Array of ScriptRecords
//-listed alphabetically by ScriptTag
//ScriptRecord
//Type Name Description
//Tag ScriptTag 4-byte ScriptTag identifier
//Offset Script Offset to Script table-from beginning of ScriptList
ScriptList scriptList = new ScriptList();
ushort scriptCount = reader.ReadUInt16();
ScriptRecord[] scRecords = scriptList.scriptRecords = new ScriptRecord[scriptCount];
for (int i = 0; i < scriptCount; ++i)
{
//read script record
scRecords[i] = new ScriptRecord(
reader.ReadUInt32(), //tag
reader.ReadInt16());//offset
}
//-------------
ScriptTable[] scriptTables = scriptList.scriptTables = new ScriptTable[scriptCount];
//then read each
for (int i = 0; i < scriptCount; ++i)
{
ScriptRecord scriptRecord = scRecords[i];
//move to
ScriptTable scriptTable = ScriptTable.CreateFrom(reader, beginAt + scriptRecord.offset);
scriptTable.scriptTag = scriptRecord.scriptTag;
scriptTables[i] = scriptTable;
}
return scriptList;
}