public override bool TryUpdatePosition(
FontMetrics fontMetrics,
GPosTable table,
GlyphPositioningCollection collection,
Tag feature,
ushort index,
int count)
{
// Implements Chained Contexts Substitution, Format 1:
// https://docs.microsoft.com/en-us/typography/opentype/spec/gsub#61-chained-contexts-substitution-format-1-simple-glyph-contexts
ushort glyphId = collection[index][0];
if (glyphId == 0)
{
return(false);
}
// Search for the current glyph in the Coverage table.
int offset = this.coverageTable.CoverageIndexOf(glyphId);
if (offset <= -1)
{
return(false);
}
if (this.seqRuleSetTables is null || this.seqRuleSetTables.Length is 0)
{
return(false);
}
ChainedSequenceRuleSetTable seqRuleSet = this.seqRuleSetTables[offset];
if (seqRuleSet is null)
{
return(false);
}
// Apply ruleset for the given glyph id.
ChainedSequenceRuleTable[] rules = seqRuleSet.SequenceRuleTables;
SkippingGlyphIterator iterator = new(fontMetrics, collection, index, this.LookupFlags);
for (int lookupIndex = 0; lookupIndex < rules.Length; lookupIndex++)
{
ChainedSequenceRuleTable rule = rules[lookupIndex];
if (!AdvancedTypographicUtils.ApplyChainedSequenceRule(iterator, rule))
{
continue;
}
bool hasChanged = false;
for (int j = 0; j < rule.SequenceLookupRecords.Length; j++)
{
SequenceLookupRecord sequenceLookupRecord = rule.SequenceLookupRecords[j];
LookupTable lookup = table.LookupList.LookupTables[sequenceLookupRecord.LookupListIndex];
ushort sequenceIndex = sequenceLookupRecord.SequenceIndex;
if (lookup.TryUpdatePosition(fontMetrics, table, collection, feature, (ushort)(index + sequenceIndex), 1))
{
hasChanged = true;
}
}
return(hasChanged);
}
return(false);
}
public override bool TryUpdatePosition(
FontMetrics fontMetrics,
GPosTable table,
GlyphPositioningCollection collection,
Tag feature,
ushort index,
int count)
{
// Implements Chained Contexts Substitution for Format 2:
// https://docs.microsoft.com/en-us/typography/opentype/spec/gsub#62-chained-contexts-substitution-format-2-class-based-glyph-contexts
ushort glyphId = collection[index][0];
if (glyphId == 0)
{
return(false);
}
// Search for the current glyph in the Coverage table.
int offset = this.coverageTable.CoverageIndexOf(glyphId);
if (offset <= -1)
{
return(false);
}
// Search in the class definition table to find the class value assigned to the currently glyph.
int classId = this.inputClassDefinitionTable.ClassIndexOf(glyphId);
ChainedClassSequenceRuleTable[]? rules = classId >= 0 && classId < this.sequenceRuleSetTables.Length ? this.sequenceRuleSetTables[classId].SubRules : null;
if (rules is null)
{
return(false);
}
// Apply ruleset for the given glyph class id.
SkippingGlyphIterator iterator = new(fontMetrics, collection, index, this.LookupFlags);
for (int lookupIndex = 0; lookupIndex < rules.Length; lookupIndex++)
{
ChainedClassSequenceRuleTable rule = rules[lookupIndex];
if (!AdvancedTypographicUtils.ApplyChainedClassSequenceRule(iterator, rule, this.inputClassDefinitionTable, this.backtrackClassDefinitionTable, this.lookaheadClassDefinitionTable))
{
continue;
}
// It's a match. Perform position update and return true if anything changed.
bool hasChanged = false;
for (int j = 0; j < rule.SequenceLookupRecords.Length; j++)
{
SequenceLookupRecord sequenceLookupRecord = rule.SequenceLookupRecords[j];
LookupTable lookup = table.LookupList.LookupTables[sequenceLookupRecord.LookupListIndex];
ushort sequenceIndex = sequenceLookupRecord.SequenceIndex;
if (lookup.TryUpdatePosition(fontMetrics, table, collection, feature, (ushort)(index + sequenceIndex), 1))
{
hasChanged = true;
}
}
return(hasChanged);
}
return(false);
}
