public override bool TryUpdatePosition(
FontMetrics fontMetrics,
GPosTable table,
GlyphPositioningCollection collection,
Tag feature,
ushort index,
int count)
{
// Mark-to-Base Attachment Positioning Subtable.
// Implements: https://docs.microsoft.com/en-us/typography/opentype/spec/gpos#lookup-type-4-mark-to-base-attachment-positioning-subtable
ushort glyphId = collection[index][0];
if (glyphId == 0)
{
return(false);
}
int markIndex = this.markCoverage.CoverageIndexOf(glyphId);
if (markIndex == -1)
{
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) && !(data.LigatureComponent > 0))
{
break;
}
}
if (baseGlyphIndex < 0)
{
return(false);
}
ushort baseGlyphId = collection[baseGlyphIndex][0];
int baseIndex = this.baseCoverage.CoverageIndexOf(baseGlyphId);
if (baseIndex < 0)
{
return(false);
}
MarkRecord markRecord = this.markArrayTable.MarkRecords[markIndex];
AnchorTable baseAnchor = this.baseArrayTable.BaseRecords[baseIndex].BaseAnchorTables[markRecord.MarkClass];
AdvancedTypographicUtils.ApplyAnchor(collection, index, baseAnchor, markRecord, baseGlyphIndex);
return(true);
}
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);
}
public override bool TryUpdatePosition(
FontMetrics fontMetrics,
GPosTable table,
GlyphPositioningCollection collection,
Tag feature,
ushort index,
int count)
{
// Mark to mark positioning.
// Implements: https://docs.microsoft.com/en-us/typography/opentype/spec/gpos#lookup-type-6-mark-to-mark-attachment-positioning-subtable
ushort glyphId = collection[index][0];
if (glyphId == 0)
{
return(false);
}
int mark1Index = this.mark1Coverage.CoverageIndexOf(glyphId);
if (mark1Index == -1)
{
return(false);
}
// Get the previous mark to attach to.
if (index < 1)
{
return(false);
}
int prevIdx = index - 1;
ushort prevGlyphId = collection[prevIdx][0];
GlyphShapingData prevGlyph = collection.GetGlyphShapingData(prevIdx);
if (!AdvancedTypographicUtils.IsMarkGlyph(fontMetrics, prevGlyphId, prevGlyph))
{
return(false);
}
// The following logic was borrowed from Harfbuzz,
// see: https://github.com/harfbuzz/harfbuzz/blob/3e635cf5e26e33d6210d3092256a49291752deec/src/hb-ot-layout-gpos-table.hh#L2525
bool good = false;
GlyphShapingData curGlyph = collection.GetGlyphShapingData(index);
if (curGlyph.LigatureId == prevGlyph.LigatureId)
{
if (curGlyph.LigatureId > 0)
{
// Marks belonging to the same base.
good = true;
}
else if (curGlyph.LigatureComponent == prevGlyph.LigatureComponent)
{
// Marks belonging to the same ligature component.
good = true;
}
}
else
{
// If ligature ids don't match, it may be the case that one of the marks
// itself is a ligature, in which case match.
if ((curGlyph.LigatureId > 0 && curGlyph.LigatureComponent <= 0) ||
(prevGlyph.LigatureId > 0 && prevGlyph.LigatureComponent <= 0))
{
good = true;
}
}
if (!good)
{
return(false);
}
int mark2Index = this.mark2Coverage.CoverageIndexOf(prevGlyphId);
if (mark2Index == -1)
{
return(false);
}
MarkRecord markRecord = this.mark1ArrayTable.MarkRecords[mark1Index];
AnchorTable baseAnchor = this.mark2ArrayTable.Mark2Records[mark2Index].MarkAnchorTable[markRecord.MarkClass];
AdvancedTypographicUtils.ApplyAnchor(collection, index, baseAnchor, markRecord, prevIdx);
return(true);
}