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| GlyphIterator = require './GlyphIterator'
Script = require '../layout/Script'
class OpenTypeProcessor
constructor: (@font, @table) ->
@script = null
@scriptTag = null
@language = null
@languageTag = null
@features = {}
@lookups = {}
# initialize to default script + language
@selectScript()
# current context (set by applyFeatures)
@glyphs = []
@positions = [] # only used by GPOS
@ligatureID = 1
findScript: (script) ->
for entry in @table.scriptList when entry.tag is script
return entry
return null
selectScript: (script, language) ->
changed = false
if not @script? or script isnt @scriptTag
if script?
Iif Array.isArray(script)
for s in script
entry = @findScript s
break if entry
else
entry = @findScript script
entry ?= @findScript 'DFLT'
entry ?= @findScript 'dflt'
entry ?= @findScript 'latn'
return unless entry?
@scriptTag = entry.tag
@script = entry.script
@direction = Script.direction script
@language = null
changed = true
Iif language? and language isnt @langugeTag
for lang in @script.langSysRecords when lang.tag is language
@language = lang.langSys
@langugeTag = lang.tag
changed = true
break
@language ?= @script.defaultLangSys
# Build a feature lookup table
if changed
@features = {}
Eif @language?
for featureIndex in @language.featureIndexes
record = @table.featureList[featureIndex]
@features[record.tag] = record.feature
return
lookupsForFeatures: (userFeatures = [], exclude) ->
lookups = []
for tag in userFeatures
feature = @features[tag]
continue unless feature
for lookupIndex in feature.lookupListIndexes
Icontinue if exclude and lookupIndex in exclude
lookups.push
feature: tag
index: lookupIndex
lookup: @table.lookupList.get(lookupIndex)
lookups.sort (a, b) ->
a.index - b.index
return lookups
applyFeatures: (userFeatures, glyphs, advances) ->
lookups = @lookupsForFeatures userFeatures
@applyLookups lookups, glyphs, advances
applyLookups: (lookups, @glyphs, @positions) ->
@glyphIterator = new GlyphIterator @glyphs
for {feature, lookup} in lookups
@glyphIterator.reset lookup.flags
while @glyphIterator.index < @glyphs.length
unless feature of @glyphIterator.cur.features
@glyphIterator.index++
continue
for table in lookup.subTables
res = @applyLookup lookup.lookupType, table
break if res
@glyphIterator.index++
return
applyLookup: (lookup, table) ->
throw new Error "applyLookup must be implemented by subclasses"
applyLookupList: (lookupRecords) ->
glyphIndex = @glyphIterator.index
for lookupRecord in lookupRecords
@glyphIterator.index = glyphIndex + lookupRecord.sequenceIndex
lookup = @table.lookupList.get(lookupRecord.lookupListIndex)
for table in lookup.subTables
@applyLookup lookup.lookupType, table
@glyphIterator.index = glyphIndex
return
coverageIndex: (coverage, glyph) ->
glyph ?= @glyphIterator.cur.id
switch coverage.version
when 1
return coverage.glyphs.indexOf(glyph)
when 2
for range, i in coverage.rangeRecords
if range.start <= glyph <= range.end
return range.startCoverageIndex + glyph - range.start
return -1
match: (sequenceIndex, sequence, fn, matched) ->
pos = @glyphIterator.index
glyph = @glyphIterator.increment sequenceIndex
idx = 0
while idx < sequence.length and glyph and fn(sequence[idx], glyph.id)
matched?.push @glyphIterator.index
idx++
glyph = @glyphIterator.next()
@glyphIterator.index = pos
if idx < sequence.length
return false
return matched or true
sequenceMatches: (sequenceIndex, sequence) ->
@match sequenceIndex, sequence, (component, glyph) ->
component is glyph
sequenceMatchIndices: (sequenceIndex, sequence) ->
@match sequenceIndex, sequence, (component, glyph) ->
component is glyph
, []
coverageSequenceMatches: (sequenceIndex, sequence) ->
@match sequenceIndex, sequence, (coverage, glyph) =>
@coverageIndex(coverage, glyph) >= 0
getClassID: (glyph, classDef) ->
switch classDef.version
when 1 # Class array
glyphID = classDef.startGlyph
for classID in classDef.classValueArray
return classID if glyph is glyphID++
when 2
for range in classDef.classRangeRecord
return range.class if range.start <= glyph <= range.end
return -1
classSequenceMatches: (sequenceIndex, sequence, classDef) ->
@match sequenceIndex, sequence, (classID, glyph) =>
classID is @getClassID glyph, classDef
applyContext: (table) ->
switch table.version
when 1
index = @coverageIndex table.coverage
return if index is -1
set = table.ruleSets[index]
for rule in set when @sequenceMatches 1, rule.input
return @applyLookupList rule.lookupRecords
when 2
return if @coverageIndex(table.coverage) is -1
index = @getClassID @glyphIterator.cur.id, table.classDef
Ireturn if index is -1
set = table.classSet[index]
for rule in set when @classSequenceMatches 1, rule.classes, table.classDef
return @applyLookupList rule.lookupRecords
when 3
if @coverageSequenceMatches 0, table.coverages
@applyLookupList table.lookupRecords
applyChainingContext: (table) ->
switch table.version
when 1
index = @coverageIndex table.coverage
return if index is -1
set = table.chainRuleSets[index]
for rule in set
Iif @sequenceMatches(-rule.backtrack.length, rule.backtrack) and
@sequenceMatches(1, rule.input) and
@sequenceMatches(1 + rule.input.length, rule.lookahead)
return @applyLookupList rule.lookupRecords
when 2
return if @coverageIndex(table.coverage) is -1
index = @getClassID @glyphIterator.cur.id, table.inputClassDef
Ireturn if index is -1
rules = table.chainClassSet[index]
for rule in rules
if @classSequenceMatches(-rule.backtrack.length, rule.backtrack, table.backtrackClassDef) and
@classSequenceMatches(1, rule.input, table.inputClassDef) and
@classSequenceMatches(1 + rule.input.length, rule.lookahead, table.lookaheadClassDef)
return @applyLookupList rule.lookupRecords
when 3
if @coverageSequenceMatches(-table.backtrackGlyphCount, table.backtrackCoverage) and
@coverageSequenceMatches(0, table.inputCoverage) and
@coverageSequenceMatches(table.inputGlyphCount, table.lookaheadCoverage)
return @applyLookupList table.lookupRecords
module.exports = OpenTypeProcessor
|