public static bool ApplyLookupList(
FontMetrics fontMetrics,
GSubTable table,
Tag feature,
LookupFlags lookupFlags,
SequenceLookupRecord[] records,
GlyphSubstitutionCollection collection,
ushort index,
int count)
{
bool hasChanged = false;
SkippingGlyphIterator iterator = new(fontMetrics, collection, index, lookupFlags);
int currentCount = collection.Count;
foreach (SequenceLookupRecord lookupRecord in records)
{
ushort sequenceIndex = lookupRecord.SequenceIndex;
ushort lookupIndex = lookupRecord.LookupListIndex;
iterator.Index = index;
iterator.Increment(sequenceIndex);
GSub.LookupTable lookup = table.LookupList.LookupTables[lookupIndex];
hasChanged |= lookup.TrySubstitution(fontMetrics, table, collection, feature, iterator.Index, count - (iterator.Index - index));
// Account for substitutions changing the length of the collection.
if (collection.Count != currentCount)
{
count -= currentCount - collection.Count;
currentCount = collection.Count;
}
}
return(hasChanged);
}
public override bool TrySubstitution(
FontMetrics fontMetrics,
GSubTable table,
GlyphSubstitutionCollection collection,
Tag feature,
ushort index,
int count)
=> false;
public bool TrySubstitution(
FontMetrics fontMetrics,
GSubTable table,
GlyphSubstitutionCollection collection,
Tag feature,
ushort index,
int count)
{
foreach (LookupSubTable subTable in this.LookupSubTables)
{
if (subTable.TrySubstitution(fontMetrics, table, collection, feature, index, count))
{
// A lookup is finished for a glyph after the client locates the target
// glyph or glyph context and performs a substitution, if specified.
return(true);
}
}
return(false);
}
public void ApplySubstitution(FontMetrics fontMetrics, GlyphSubstitutionCollection collection, KerningMode kerningMode)
{
for (ushort i = 0; i < collection.Count; i++)
{
// Choose a shaper based on the script.
// This determines which features to apply to which glyphs.
ScriptClass current = CodePoint.GetScriptClass(collection.GetGlyphShapingData(i).CodePoint);
BaseShaper shaper = ShaperFactory.Create(current, kerningMode);
ushort index = i;
ushort count = 1;
while (i < collection.Count - 1)
{
// We want to assign the same feature lookups to individual sections of the text rather
// than the text as a whole to ensure that different language shapers do not interfere
// with each other when the text contains multiple languages.
GlyphShapingData nextData = collection.GetGlyphShapingData(i + 1);
ScriptClass next = CodePoint.GetScriptClass(nextData.CodePoint);
if (next is not ScriptClass.Common and not ScriptClass.Unknown and not ScriptClass.Inherited && next != current)
{
break;
}
i++;
count++;
}
// Assign Substitution features to each glyph.
shaper.AssignFeatures(collection, index, count);
IEnumerable <Tag> stageFeatures = shaper.GetShapingStageFeatures();
int currentCount = collection.Count;
SkippingGlyphIterator iterator = new(fontMetrics, collection, index, default);
foreach (Tag stageFeature in stageFeatures)
{
List <(Tag Feature, ushort Index, LookupTable LookupTable)> lookups = this.GetFeatureLookups(in stageFeature, current);
if (lookups.Count == 0)
{
continue;
}
// Apply features in order.
foreach ((Tag Feature, ushort Index, LookupTable LookupTable)featureLookup in lookups)
{
Tag feature = featureLookup.Feature;
iterator.Reset(index, featureLookup.LookupTable.LookupFlags);
while (iterator.Index < index + count)
{
List <TagEntry> glyphFeatures = collection.GetGlyphShapingData(iterator.Index).Features;
if (!HasFeature(glyphFeatures, in feature))
{
iterator.Next();
continue;
}
featureLookup.LookupTable.TrySubstitution(fontMetrics, this, collection, featureLookup.Feature, iterator.Index, count - (iterator.Index - index));
iterator.Next();
// Account for substitutions changing the length of the collection.
if (collection.Count != currentCount)
{
count = (ushort)(count - (currentCount - collection.Count));
currentCount = collection.Count;
}
}
}
}
}
}
