public static bool ApplyChainedClassSequenceRule(
SkippingGlyphIterator iterator,
ChainedClassSequenceRuleTable rule,
ClassDefinitionTable inputClassDefinitionTable,
ClassDefinitionTable backtrackClassDefinitionTable,
ClassDefinitionTable lookaheadClassDefinitionTable)
{
if (rule.BacktrackSequence.Length > 0 &&
!MatchClassSequence(iterator, -rule.BacktrackSequence.Length, rule.BacktrackSequence, backtrackClassDefinitionTable))
{
return(false);
}
if (rule.InputSequence.Length > 0 &&
!MatchClassSequence(iterator, 1, rule.InputSequence, inputClassDefinitionTable))
{
return(false);
}
if (rule.LookaheadSequence.Length > 0 &&
!MatchClassSequence(iterator, 1 + rule.InputSequence.Length, rule.LookaheadSequence, lookaheadClassDefinitionTable))
{
return(false);
}
return(true);
}
public static bool MatchClassSequence(
SkippingGlyphIterator iterator,
int increment,
ushort[] sequence,
ClassDefinitionTable classDefinitionTable)
=> Match(
increment,
sequence,
iterator,
(component, data) => component == classDefinitionTable.ClassIndexOf(data.GlyphIds[0]),
default);
internal static CoverageTable LoadSequenceContextFormat2(BigEndianBinaryReader reader, long offset, out ClassDefinitionTable classDefTable, out ClassSequenceRuleSetTable[] classSeqRuleSets)
{
// https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#sequence-context-format-2-class-based-glyph-contexts
// Context Positioning Subtable Format 2: Class-based Glyph Contexts.
// +----------+----------------------------------------------+--------------------------------------------------------------------+
// | Type | Name | Description |
// +==========+==============================================+====================================================================+
// | uint16 | format | Format identifier: format = 2 |
// +----------+----------------------------------------------+--------------------------------------------------------------------+
// | Offset16 | coverageOffset | Offset to Coverage table, from beginning of |
// | | | SequenceContextFormat2 table. |
// +----------+----------------------------------------------+--------------------------------------------------------------------+
// | Offset16 | classDefOffset | Offset to ClassDef table, from beginning of |
// | | | SequenceContextFormat2 table. |
// +----------+----------------------------------------------+--------------------------------------------------------------------+
// | uint16 | classSeqRuleSetCount | Number of ClassSequenceRuleSet tables. |
// +----------+----------------------------------------------+--------------------------------------------------------------------+
// | Offset16 | classSeqRuleSetOffsets[classSeqRuleSetCount] | Array of offsets to ClassSequenceRuleSet tables, from beginning of |
// | | | SequenceContextFormat2 table (may be NULL). |
// +----------+----------------------------------------------+--------------------------------------------------------------------+
ushort coverageOffset = reader.ReadOffset16();
ushort classDefOffset = reader.ReadOffset16();
ushort classSeqRuleSetCount = reader.ReadUInt16();
using Buffer <ushort> classSeqRuleSetOffsetsBuffer = new(classSeqRuleSetCount);
Span <ushort> classSeqRuleSetOffsets = classSeqRuleSetOffsetsBuffer.GetSpan();
reader.ReadUInt16Array(classSeqRuleSetOffsets);
var coverageTable = CoverageTable.Load(reader, offset + coverageOffset);
classDefTable = ClassDefinitionTable.Load(reader, offset + classDefOffset);
classSeqRuleSets = new ClassSequenceRuleSetTable[classSeqRuleSetCount];
for (int i = 0; i < classSeqRuleSets.Length; i++)
{
ushort ruleSetOffset = classSeqRuleSetOffsets[i];
if (ruleSetOffset > 0)
{
classSeqRuleSets[i] = ClassSequenceRuleSetTable.Load(reader, offset + classSeqRuleSetOffsets[i]);
}
}
return(coverageTable);
}
internal static ChainedClassSequenceRuleSetTable[] LoadChainedSequenceContextFormat2(
BigEndianBinaryReader reader,
long offset,
out CoverageTable coverageTable,
out ClassDefinitionTable backtrackClassDefTable,
out ClassDefinitionTable inputClassDefTable,
out ClassDefinitionTable lookaheadClassDefTable)
{
// https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#chained-sequence-context-format-2-class-based-glyph-contexts
// ChainedSequenceContextFormat2
// +----------+------------------------------------------------------------+---------------------------------------------------------------------+
// | Type | Name | Description |
// +==========+============================================================+=====================================================================+
// | uint16 | format | Format identifier: format = 2 |
// +----------+------------------------------------------------------------+---------------------------------------------------------------------+
// | Offset16 | coverageOffset | Offset to Coverage table, from beginning |
// | | | of ChainedSequenceContextFormat2 table |
// +----------+------------------------------------------------------------+---------------------------------------------------------------------+
// | Offset16 | backtrackClassDefOffset | Offset to ClassDef table containing |
// | | | backtrack sequence context, from |
// | | | beginning of ChainedSequenceContextFormat2 table |
// +----------+------------------------------------------------------------+---------------------------------------------------------------------+
// | Offset16 | inputClassDefOffset | Offset to ClassDef table containing input |
// | | | sequence context, from beginning of |
// | | | ChainedSequenceContextFormat2 table |
// +----------+------------------------------------------------------------+---------------------------------------------------------------------+
// | Offset16 | lookaheadClassDefOffset | Offset to ClassDef table containing |
// | | | lookahead sequence context, from |
// | | | beginning of ChainedSequenceContextFormat2 table |
// +----------+------------------------------------------------------------+---------------------------------------------------------------------+
// | uint16 | chainedClassSeqRuleSetCount | Number of ChainedClassSequenceRuleSet tables |
// +----------+------------------------------------------------------------+---------------------------------------------------------------------+
// | Offset16 | chainedClassSeqRuleSetOffsets[chainedClassSeqRuleSetCount] | Array of offsets to ChainedClassSequenceRuleSet tables, |
// | | | from beginning of ChainedSequenceContextFormat2 table (may be NULL) |
// +----------+------------------------------------------------------------+---------------------------------------------------------------------+
ushort coverageOffset = reader.ReadOffset16();
ushort backtrackClassDefOffset = reader.ReadOffset16();
ushort inputClassDefOffset = reader.ReadOffset16();
ushort lookaheadClassDefOffset = reader.ReadOffset16();
ushort chainedClassSeqRuleSetCount = reader.ReadUInt16();
ChainedClassSequenceRuleSetTable[] seqRuleSets = Array.Empty <ChainedClassSequenceRuleSetTable>();
if (chainedClassSeqRuleSetCount != 0)
{
ushort[] chainedClassSeqRuleSetOffsets = new ushort[chainedClassSeqRuleSetCount];
for (int i = 0; i < chainedClassSeqRuleSetCount; i++)
{
chainedClassSeqRuleSetOffsets[i] = reader.ReadOffset16();
}
seqRuleSets = new ChainedClassSequenceRuleSetTable[chainedClassSeqRuleSetCount];
for (int i = 0; i < seqRuleSets.Length; i++)
{
if (chainedClassSeqRuleSetOffsets[i] > 0)
{
seqRuleSets[i] =
ChainedClassSequenceRuleSetTable.Load(reader, offset + chainedClassSeqRuleSetOffsets[i]);
}
}
}
coverageTable = CoverageTable.Load(reader, offset + coverageOffset);
backtrackClassDefTable = ClassDefinitionTable.Load(reader, offset + backtrackClassDefOffset);
inputClassDefTable = ClassDefinitionTable.Load(reader, offset + inputClassDefOffset);
lookaheadClassDefTable = ClassDefinitionTable.Load(reader, offset + lookaheadClassDefOffset);
return(seqRuleSets);
}
public static GlyphDefinitionTable Load(BigEndianBinaryReader reader)
{
// Header version 1.0
// Type | Name | Description
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// uint16 | majorVersion | Major version of the GDEF table, = 1
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// uint16 | minorVersion | Minor version of the GDEF table, = 0
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | glyphClassDefOffset | Offset to class definition table for glyph type, from beginning of GDEF header(may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | attachListOffset | Offset to attachment point list table, from beginning of GDEF header(may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | ligCaretListOffset | Offset to ligature caret list table, from beginning of GDEF header(may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | markAttachClassDefOffset | Offset to class definition table for mark attachment type, from beginning of GDEF header(may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Header version 1.2
// Type | Name | Description
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// uint16 | majorVersion | Major version of the GDEF table, = 1
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// uint16 | minorVersion | Minor version of the GDEF table, = 0
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | glyphClassDefOffset | Offset to class definition table for glyph type, from beginning of GDEF header(may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | attachListOffset | Offset to attachment point list table, from beginning of GDEF header(may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | ligCaretListOffset | Offset to ligature caret list table, from beginning of GDEF header(may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | markAttachClassDefOffset | Offset to class definition table for mark attachment type, from beginning of GDEF header (may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | markGlyphSetsDefOffset | Offset to the table of mark glyph set definitions, from beginning of GDEF header (may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Header version 1.3
// Type | Name | Description
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// uint16 | majorVersion | Major version of the GDEF table, = 1
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// uint16 | minorVersion | Minor version of the GDEF table, = 0
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | glyphClassDefOffset | Offset to class definition table for glyph type, from beginning of GDEF header(may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | attachListOffset | Offset to attachment point list table, from beginning of GDEF header(may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | ligCaretListOffset | Offset to ligature caret list table, from beginning of GDEF header(may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | markAttachClassDefOffset | Offset to class definition table for mark attachment type, from beginning of GDEF header (may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset16 | markGlyphSetsDefOffset | Offset to the table of mark glyph set definitions, from beginning of GDEF header (may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
// Offset32 | itemVarStoreOffset | Offset to the Item Variation Store table, from beginning of GDEF header (may be NULL).
// ----------|--------------------------|--------------------------------------------------------------------------------------------------------
ushort majorVersion = reader.ReadUInt16();
ushort minorVersion = reader.ReadUInt16();
ushort glyphClassDefOffset = reader.ReadUInt16();
ushort attachListOffset = reader.ReadUInt16();
ushort ligatureCaretListOffset = reader.ReadUInt16();
ushort markAttachClassDefOffset = reader.ReadUInt16();
ushort markGlyphSetsDefOffset = 0;
uint itemVarStoreOffset = 0;
switch (minorVersion)
{
case 0:
break;
case 2:
markGlyphSetsDefOffset = reader.ReadUInt16();
break;
case 3:
markGlyphSetsDefOffset = reader.ReadUInt16();
itemVarStoreOffset = reader.ReadUInt32();
break;
default:
throw new InvalidFontFileException($"Invalid value for 'minor version' {minorVersion} of GDEF table. Should be '0', '2' or '3'.");
}
ClassDefinitionTable?classDefinitionTable = glyphClassDefOffset is 0 ? null : ClassDefinitionTable.Load(reader, glyphClassDefOffset);
AttachmentListTable? attachmentListTable = attachListOffset is 0 ? null : AttachmentListTable.Load(reader, attachListOffset);
LigatureCaretList? ligatureCaretList = ligatureCaretListOffset is 0 ? null : LigatureCaretList.Load(reader, ligatureCaretListOffset);
ClassDefinitionTable?markAttachmentClassDef = markAttachClassDefOffset is 0 ? null : ClassDefinitionTable.Load(reader, markAttachClassDefOffset);
MarkGlyphSetsTable? markGlyphSetsTable = markGlyphSetsDefOffset is 0 ? null : MarkGlyphSetsTable.Load(reader, markGlyphSetsDefOffset);
var glyphDefinitionTable = new GlyphDefinitionTable()
{
GlyphClassDefinition = classDefinitionTable,
AttachmentListTable = attachmentListTable,
LigatureCaretList = ligatureCaretList,
MarkAttachmentClassDef = markAttachmentClassDef,
MarkGlyphSetsTable = markGlyphSetsTable
};
// TODO: read itemVarStore.
return(glyphDefinitionTable);
}