public override bool TryUpdatePosition(
FontMetrics fontMetrics,
GPosTable table,
GlyphPositioningCollection collection,
Tag feature,
ushort index,
int count)
{
if (count <= 1)
{
return(false);
}
ushort glyphId = collection[index][0];
if (glyphId == 0)
{
return(false);
}
int coverage = this.coverageTable.CoverageIndexOf(glyphId);
if (coverage > -1)
{
PairSetTable pairSet = this.pairSets[coverage];
ushort glyphId2 = collection[index + 1][0];
if (glyphId2 == 0)
{
return(false);
}
if (pairSet.TryGetPairValueRecord(glyphId2, out PairValueRecord pairValueRecord))
{
ValueRecord record1 = pairValueRecord.ValueRecord1;
AdvancedTypographicUtils.ApplyPosition(collection, index, record1);
ValueRecord record2 = pairValueRecord.ValueRecord2;
AdvancedTypographicUtils.ApplyPosition(collection, (ushort)(index + 1), record2);
return(true);
}
}
return(false);
}
public static LookupType2Format1SubTable Load(BigEndianBinaryReader reader, long offset, LookupFlags lookupFlags)
{
// Pair Adjustment Positioning Subtable format 1.
// +-------------+------------------------------+------------------------------------------------+
// | Type | Name | Description |
// +=============+==============================+================================================+
// | uint16 | posFormat | Format identifier: format = 1 |
// +-------------+------------------------------+------------------------------------------------+
// | Offset16 | coverageOffset | Offset to Coverage table, from beginning of |
// | | | PairPos subtable. |
// +-------------+------------------------------+------------------------------------------------+
// | uint16 | valueFormat1 | Defines the types of data in valueRecord1 — |
// | | | for the first glyph in the pair (may be zero). |
// +-------------+------------------------------+------------------------------------------------+
// | uint16 | valueFormat2 | Defines the types of data in valueRecord2 — |
// | | | for the second glyph in the pair (may be zero).|
// +-------------+------------------------------+------------------------------------------------+
// | uint16 | pairSetCount | Number of PairSet tables |
// +-------------+------------------------------+------------------------------------------------+
// | Offset16 | pairSetOffsets[pairSetCount] | Array of offsets to PairSet tables. |
// | | | Offsets are from beginning of PairPos subtable,|
// | | | ordered by Coverage Index. |
// +-------------+------------------------------+------------------------------------------------+
ushort coverageOffset = reader.ReadOffset16();
ValueFormat valueFormat1 = reader.ReadUInt16 <ValueFormat>();
ValueFormat valueFormat2 = reader.ReadUInt16 <ValueFormat>();
ushort pairSetCount = reader.ReadUInt16();
using Buffer <ushort> pairSetOffsetsBuffer = new(pairSetCount);
Span <ushort> pairSetOffsets = pairSetOffsetsBuffer.GetSpan();
reader.ReadUInt16Array(pairSetOffsets);
var pairSets = new PairSetTable[pairSetCount];
for (int i = 0; i < pairSetCount; i++)
{
reader.Seek(offset + pairSetOffsets[i], SeekOrigin.Begin);
pairSets[i] = PairSetTable.Load(reader, offset + pairSetOffsets[i], valueFormat1, valueFormat2);
}
var coverageTable = CoverageTable.Load(reader, offset + coverageOffset);
return(new LookupType2Format1SubTable(coverageTable, pairSets, lookupFlags));
}
/// <summary>
/// Lookup Type 2: Pair Adjustment Positioning Subtable
/// </summary>
/// <param name="reader"></param>
void ReadLookupType2(BinaryReader reader)
{
//-----------------------------------------------
// USHORT PosFormat Format identifier-format = 1
//Offset Coverage Offset to Coverage table-from beginning of PairPos subtable-only the first glyph in each pair
//USHORT ValueFormat1 Defines the types of data in ValueRecord1-for the first glyph in the pair -may be zero (0)
//USHORT ValueFormat2 Defines the types of data in ValueRecord2-for the second glyph in the pair -may be zero (0)
//USHORT PairSetCount Number of PairSet tables
//Offset PairSetOffset
//[PairSetCount] Array of offsets to PairSet tables-from beginning of PairPos subtable-ordered by Coverage Index
// PairSet table
//Value Type Description
//USHORT PairValueCount Number of PairValueRecords
//struct PairValueRecord
//[PairValueCount] Array of PairValueRecords-ordered by GlyphID of the second glyph
//A PairValueRecord specifies the second glyph in a pair (SecondGlyph) and defines a ValueRecord for each glyph (Value1 and Value2). If ValueFormat1 is set to zero (0) in the PairPos subtable, ValueRecord1 will be empty; similarly, if ValueFormat2 is 0, Value2 will be empty.
//Example 4 at the end of this chapter shows a PairPosFormat1 subtable that defines two cases of pair kerning.
//PairValueRecord
//Value Type Description
//GlyphID SecondGlyph GlyphID of second glyph in the pair-first glyph is listed in the Coverage table
//ValueRecord Value1 Positioning data for the first glyph in the pair
//ValueRecord Value2 Positioning data for the second glyph in the pair
//-----------------------------------------------
// PairPosFormat2 subtable: Class pair adjustment
//Value Type Description
//USHORT PosFormat Format identifier-format = 2
//Offset Coverage Offset to Coverage table-from beginning of PairPos subtable-for the first glyph of the pair
//USHORT ValueFormat1 ValueRecord definition-for the first glyph of the pair-may be zero (0)
//USHORT ValueFormat2 ValueRecord definition-for the second glyph of the pair-may be zero (0)
//Offset ClassDef1 Offset to ClassDef table-from beginning of PairPos subtable-for the first glyph of the pair
//Offset ClassDef2 Offset to ClassDef table-from beginning of PairPos subtable-for the second glyph of the pair
//USHORT Class1Count Number of classes in ClassDef1 table-includes Class0
//USHORT Class2Count Number of classes in ClassDef2 table-includes Class0
//struct Class1Record
//[Class1Count] Array of Class1 records-ordered by Class1
//Each Class1Record contains an array of Class2Records (Class2Record), which also are ordered by class value.
//One Class2Record must be declared for each class in the ClassDef2 table, including Class 0.
//Class1Record
//Value Type Description
//struct Class2Record[Class2Count] Array of Class2 records-ordered by Class2
//A Class2Record consists of two ValueRecords,
//one for the first glyph in a class pair (Value1) and one for the second glyph (Value2).
//If the PairPos subtable has a value of zero (0) for ValueFormat1 or ValueFormat2,
//the corresponding record (ValueRecord1 or ValueRecord2) will be empty.
//Example 5 at the end of this chapter demonstrates pair kerning with glyph classes in a PairPosFormat2 subtable.
//Class2Record
//Value Type Description
//ValueRecord Value1 Positioning for first glyph-empty if ValueFormat1 = 0
//ValueRecord Value2 Positioning for second glyph-empty if ValueFormat2 = 0
long thisLookupTablePos = reader.BaseStream.Position;
int j = subTableOffsets.Length;
for (int i = 0; i < j; ++i)
{
//move to read pos
long subTableStartAt = lookupTablePos + subTableOffsets[i];
reader.BaseStream.Seek(subTableStartAt, SeekOrigin.Begin);
//-----------------------
ushort format = reader.ReadUInt16();
switch (format)
{
default: throw new NotSupportedException();
case 1:
{
short coverage = reader.ReadInt16();
ushort value1Format = reader.ReadUInt16();
ushort value2Format = reader.ReadUInt16();
ushort pairSetCount = reader.ReadUInt16();
short[] pairSetOffsetArray = Utils.ReadInt16Array(reader, pairSetCount);
PairSetTable[] pairSetTables = new PairSetTable[pairSetCount];
for (int n = 0; n < pairSetCount; ++n)
{
//read each pair set table
reader.BaseStream.Seek(thisLookupTablePos + pairSetOffsetArray[i], SeekOrigin.Begin);
var pairSetTable = new PairSetTable();
pairSetTable.ReadFrom(reader, value1Format, value2Format);
pairSetTables[n] = pairSetTable;
}
var subTable = new LkSubTableType2(pairSetTables);
//coverage
subTable.CoverageTable = CoverageTable.CreateFrom(reader, subTableStartAt + coverage);
subTables.Add(subTable);
} break;
case 2:
{
short coverage = reader.ReadInt16();
ushort value1Format = reader.ReadUInt16();
ushort value2Format = reader.ReadUInt16();
short classDef1Offset = reader.ReadInt16();
short classDef2Offset = reader.ReadInt16();
ushort class1Count = reader.ReadUInt16();
ushort class2Count = reader.ReadUInt16();
throw new NotImplementedException();
}
break;
}
}
}
public LkSubTableType2(PairSetTable[] pairSetTables)
{
this.pairSetTables = pairSetTables;
}