public static LigatureAttachTable ReadFrom(BinaryReader reader, ushort classCount)
{
LigatureAttachTable table = new LigatureAttachTable();
ushort componentCount = reader.ReadUInt16();
ComponentRecord[] componentRecs = new ComponentRecord[componentCount];
table.records = componentRecs;
for (int i = 0; i < componentCount; ++i)
{
componentRecs[i] = new ComponentRecord(
Utils.ReadInt16Array(reader, classCount));
}
return(table);
}
public void ReadFrom(BinaryReader reader, ushort classCount)
{
long startPos = reader.BaseStream.Position;
ushort ligatureCount = reader.ReadUInt16();
short[] offsets = Utils.ReadInt16Array(reader, ligatureCount);
ligatures = new LigatureAttachTable[ligatureCount];
for (int i = 0; i < ligatureCount; ++i)
{
//each ligature table
reader.BaseStream.Seek(startPos + offsets[i], SeekOrigin.Begin);
ligatures[i] = LigatureAttachTable.ReadFrom(reader, classCount);
}
}
public static LigatureAttachTable ReadFrom(BinaryReader reader, ushort classCount)
{
LigatureAttachTable table = new LigatureAttachTable();
ushort componentCount = reader.ReadUInt16();
ComponentRecord[] componentRecs = new ComponentRecord[componentCount];
table.records = componentRecs;
for (int i = 0; i < componentCount; ++i)
{
componentRecs[i] = new ComponentRecord(
Utils.ReadInt16Array(reader, classCount));
}
return table;
}
public override bool TryUpdatePosition(
FontMetrics fontMetrics,
GPosTable table,
GlyphPositioningCollection collection,
Tag feature,
ushort index,
int count)
{
// Mark-to-Ligature Attachment Positioning.
// Implements: https://docs.microsoft.com/en-us/typography/opentype/spec/gpos#lookup-type-5-mark-to-ligature-attachment-positioning-subtable
ushort glyphId = collection[index][0];
if (glyphId == 0)
{
return(false);
}
int markIndex = this.markCoverage.CoverageIndexOf(glyphId);
if (markIndex < 0)
{
return(false);
}
// Search backward for a base glyph.
int baseGlyphIndex = index;
while (--baseGlyphIndex >= 0)
{
GlyphShapingData data = collection.GetGlyphShapingData(baseGlyphIndex);
if (!AdvancedTypographicUtils.IsMarkGlyph(fontMetrics, data.GlyphIds[0], data))
{
break;
}
}
if (baseGlyphIndex < 0)
{
return(false);
}
ushort baseGlyphId = collection[baseGlyphIndex][0];
int ligatureIndex = this.ligatureCoverage.CoverageIndexOf(baseGlyphId);
if (ligatureIndex < 0)
{
return(false);
}
// We must now check whether the ligature ID of the current mark glyph
// is identical to the ligature ID of the found ligature.
// If yes, we can directly use the component index. If not, we attach the mark
// glyph to the last component of the ligature.
LigatureAttachTable ligatureAttach = this.ligatureArrayTable.LigatureAttachTables[ligatureIndex];
GlyphShapingData markGlyph = collection.GetGlyphShapingData(index);
GlyphShapingData ligGlyph = collection.GetGlyphShapingData(baseGlyphIndex);
int compIndex = ligGlyph.LigatureId > 0 && ligGlyph.LigatureId == markGlyph.LigatureId && markGlyph.LigatureComponent > 0
? Math.Min(markGlyph.LigatureComponent, ligGlyph.CodePointCount) - 1
: ligGlyph.CodePointCount - 1;
MarkRecord markRecord = this.markArrayTable.MarkRecords[markIndex];
AnchorTable baseAnchor = ligatureAttach.ComponentRecords[compIndex].LigatureAnchorTables[markRecord.MarkClass];
AdvancedTypographicUtils.ApplyAnchor(collection, index, baseAnchor, markRecord, baseGlyphIndex);
return(true);
}
