static JstfScriptTable ReadJstfScriptTable(BinaryReader reader)
{
//A Justification Script(JstfScript) table describes the justification information for a single script.
//It consists of an offset to a table that defines extender glyphs(extenderGlyphOffset),
//an offset to a default justification table for the script (defJstfLangSysOffset),
//and a count of the language systems that define justification data(jstfLangSysCount).
//If a script uses the same justification information for all language systems,
//the font developer defines only the default JstfLangSys table and
//sets the jstfLangSysCount value to zero(0).
//However, if any language system has unique justification suggestions,
//jstfLangSysCount will be a positive value,
//and the JstfScript table must include an array of records(jstfLangSysRecords),
//one for each language system.Each JstfLangSysRecord contains a language system tag(jstfLangSysTag) and
//an offset to a justification language system table(jstfLangSysOffset).
//In the jstfLangSysRecords array, records are ordered alphabetically by jstfLangSysTag.
//JstfScript table
//Type Name Description
//Offset16 extenderGlyphOffset Offset to ExtenderGlyph table, from beginning of JstfScript table(may be NULL)
//Offset16 defJstfLangSysOffset Offset to default JstfLangSys table, from beginning of JstfScript table(may be NULL)
//uint16 jstfLangSysCount Number of JstfLangSysRecords in this table - may be zero(0)
//JstfLangSysRecord jstfLangSysRecords[jstfLangSysCount] Array of JstfLangSysRecords, in alphabetical order by JstfLangSysTag
JstfScriptTable jstfScriptTable = new JstfScriptTable();
long tableStartAt = reader.BaseStream.Position;
ushort extenderGlyphOffset = reader.ReadUInt16();
ushort defJstfLangSysOffset = reader.ReadUInt16();
ushort jstfLangSysCount = reader.ReadUInt16();
if (jstfLangSysCount > 0)
{
JstfLangSysRecord[] recs = new JstfLangSysRecord[jstfLangSysCount];
for (int i = 0; i < jstfLangSysCount; ++i)
{
recs[i] = ReadJstfLangSysRecord(reader);
}
jstfScriptTable.other = recs;
}
if (extenderGlyphOffset > 0)
{
reader.BaseStream.Position = tableStartAt + extenderGlyphOffset;
jstfScriptTable.extenderGlyphs = ReadExtenderGlyphTable(reader);
}
if (defJstfLangSysOffset > 0)
{
reader.BaseStream.Position = tableStartAt + defJstfLangSysOffset;
jstfScriptTable.defaultLangSys = ReadJstfLangSysRecord(reader);
}
return(jstfScriptTable);
}
//The Justification table(JSTF) provides font developers with additional control over glyph substitution and
//positioning in justified text.
//Text-processing clients now have more options to expand or
//shrink word and glyph spacing so text fills the specified line length.
protected override void ReadContentFrom(BinaryReader reader)
{
//test this with Arial font
//JSTF header
//Type Name Description
//uint16 majorVersion Major version of the JSTF table, = 1
//uint16 minorVersion Minor version of the JSTF table, = 0
//uint16 jstfScriptCount Number of JstfScriptRecords in this table
//JstfScriptRecord jstfScriptRecords[jstfScriptCount] Array of JstfScriptRecords, in alphabetical order by jstfScriptTag
//----------
//JstfScriptRecord
//Type Name Description
//Tag jstfScriptTag 4-byte JstfScript identification
//Offset16 jstfScriptOffset Offset to JstfScript table, from beginning of JSTF Header
long tableStartAt = reader.BaseStream.Position;
//
ushort majorVersion = reader.ReadUInt16();
ushort minorVersion = reader.ReadUInt16();
ushort jstfScriptCount = reader.ReadUInt16();
JstfScriptRecord[] recs = new JstfScriptRecord[jstfScriptCount];
for (int i = 0; i < recs.Length; ++i)
{
recs[i] = new JstfScriptRecord(
Utils.TagToString(reader.ReadUInt32()),
reader.ReadUInt16()
);
}
_jsftScriptTables = new JstfScriptTable[recs.Length];
for (int i = 0; i < recs.Length; ++i)
{
JstfScriptRecord rec = recs[i];
reader.BaseStream.Position = tableStartAt + rec.jstfScriptOffset;
JstfScriptTable jstfScriptTable = ReadJstfScriptTable(reader);
jstfScriptTable.ScriptTag = rec.jstfScriptTag;
_jsftScriptTables[i] = jstfScriptTable;
}
}
