Lib/fontTools/merge.py

# Copyright 2013 Google, Inc. All Rights Reserved.
#
# Google Author(s): Behdad Esfahbod, Roozbeh Pournader

"""Font merger.
"""

from __future__ import print_function, division, absolute_import
from fontTools.misc.py23 import *
from fontTools.misc.timeTools import timestampNow
from fontTools import ttLib, cffLib
from fontTools.ttLib.tables import otTables, _h_e_a_d
from fontTools.ttLib.tables.DefaultTable import DefaultTable
from fontTools.misc.loggingTools import Timer
from fontTools.pens.recordingPen import DecomposingRecordingPen
from functools import reduce
import sys
import time
import operator
import logging


log = logging.getLogger("fontTools.merge")
timer = Timer(logger=logging.getLogger(__name__+".timer"), level=logging.INFO)


def _add_method(*clazzes, **kwargs):
	"""Returns a decorator function that adds a new method to one or
	more classes."""
	allowDefault = kwargs.get('allowDefaultTable', False)
	def wrapper(method):
		done = []
		for clazz in clazzes:
			if clazz in done: continue # Support multiple names of a clazz
			done.append(clazz)
			assert allowDefault or clazz != DefaultTable, 'Oops, table class not found.'
			assert method.__name__ not in clazz.__dict__, \
				"Oops, class '%s' has method '%s'." % (clazz.__name__, method.__name__)
			setattr(clazz, method.__name__, method)
		return None
	return wrapper

# General utility functions for merging values from different fonts

def equal(lst):
	lst = list(lst)
	t = iter(lst)
	first = next(t)
	assert all(item == first for item in t), "Expected all items to be equal: %s" % lst
	return first

def first(lst):
	return next(iter(lst))

def recalculate(lst):
	return NotImplemented

def current_time(lst):
	return timestampNow()

def bitwise_and(lst):
	return reduce(operator.and_, lst)

def bitwise_or(lst):
	return reduce(operator.or_, lst)

def avg_int(lst):
	lst = list(lst)
	return sum(lst) // len(lst)

def onlyExisting(func):
	"""Returns a filter func that when called with a list,
	only calls func on the non-NotImplemented items of the list,
	and only so if there's at least one item remaining.
	Otherwise returns NotImplemented."""

	def wrapper(lst):
		items = [item for item in lst if item is not NotImplemented]
		return func(items) if items else NotImplemented

	return wrapper

def sumLists(lst):
	l = []
	for item in lst:
		l.extend(item)
	return l

def sumDicts(lst):
	d = {}
	for item in lst:
		d.update(item)
	return d

def mergeObjects(lst):
	lst = [item for item in lst if item is not NotImplemented]
	if not lst:
		return NotImplemented
	lst = [item for item in lst if item is not None]
	if not lst:
		return None

	clazz = lst[0].__class__
	assert all(type(item) == clazz for item in lst), lst

	logic = clazz.mergeMap
	returnTable = clazz()
	returnDict = {}

	allKeys = set.union(set(), *(vars(table).keys() for table in lst))
	for key in allKeys:
		try:
			mergeLogic = logic[key]
		except KeyError:
			try:
				mergeLogic = logic['*']
			except KeyError:
				raise Exception("Don't know how to merge key %s of class %s" %
						(key, clazz.__name__))
		if mergeLogic is NotImplemented:
			continue
		value = mergeLogic(getattr(table, key, NotImplemented) for table in lst)
		if value is not NotImplemented:
			returnDict[key] = value

	returnTable.__dict__ = returnDict

	return returnTable

def mergeBits(bitmap):

	def wrapper(lst):
		lst = list(lst)
		returnValue = 0
		for bitNumber in range(bitmap['size']):
			try:
				mergeLogic = bitmap[bitNumber]
			except KeyError:
				try:
					mergeLogic = bitmap['*']
				except KeyError:
					raise Exception("Don't know how to merge bit %s" % bitNumber)
			shiftedBit = 1 << bitNumber
			mergedValue = mergeLogic(bool(item & shiftedBit) for item in lst)
			returnValue |= mergedValue << bitNumber
		return returnValue

	return wrapper


@_add_method(DefaultTable, allowDefaultTable=True)
def merge(self, m, tables):
	if not hasattr(self, 'mergeMap'):
		log.info("Don't know how to merge '%s'.", self.tableTag)
		return NotImplemented

	logic = self.mergeMap

	if isinstance(logic, dict):
		return m.mergeObjects(self, self.mergeMap, tables)
	else:
		return logic(tables)


ttLib.getTableClass('maxp').mergeMap = {
	'*': max,
	'tableTag': equal,
	'tableVersion': equal,
	'numGlyphs': sum,
	'maxStorage': first,
	'maxFunctionDefs': first,
	'maxInstructionDefs': first,
	# TODO When we correctly merge hinting data, update these values:
	# maxFunctionDefs, maxInstructionDefs, maxSizeOfInstructions
}

headFlagsMergeBitMap = {
	'size': 16,
	'*': bitwise_or,
	1: bitwise_and, # Baseline at y = 0
	2: bitwise_and, # lsb at x = 0
	3: bitwise_and, # Force ppem to integer values. FIXME?
	5: bitwise_and, # Font is vertical
	6: lambda bit: 0, # Always set to zero
	11: bitwise_and, # Font data is 'lossless'
	13: bitwise_and, # Optimized for ClearType
	14: bitwise_and, # Last resort font. FIXME? equal or first may be better
	15: lambda bit: 0, # Always set to zero
}

ttLib.getTableClass('head').mergeMap = {
	'tableTag': equal,
	'tableVersion': max,
	'fontRevision': max,
	'checkSumAdjustment': lambda lst: 0, # We need *something* here
	'magicNumber': equal,
	'flags': mergeBits(headFlagsMergeBitMap),
	'unitsPerEm': equal,
	'created': current_time,
	'modified': current_time,
	'xMin': min,
	'yMin': min,
	'xMax': max,
	'yMax': max,
	'macStyle': first,
	'lowestRecPPEM': max,
	'fontDirectionHint': lambda lst: 2,
	'indexToLocFormat': recalculate,
	'glyphDataFormat': equal,
}

ttLib.getTableClass('hhea').mergeMap = {
	'*': equal,
	'tableTag': equal,
	'tableVersion': max,
	'ascent': max,
	'descent': min,
	'lineGap': max,
	'advanceWidthMax': max,
	'minLeftSideBearing': min,
	'minRightSideBearing': min,
	'xMaxExtent': max,
	'caretSlopeRise': first,
	'caretSlopeRun': first,
	'caretOffset': first,
	'numberOfHMetrics': recalculate,
}

ttLib.getTableClass('vhea').mergeMap = {
	'*': equal,
	'tableTag': equal,
	'tableVersion': max,
	'ascent': max,
	'descent': min,
	'lineGap': max,
	'advanceHeightMax': max,
	'minTopSideBearing': min,
	'minBottomSideBearing': min,
	'yMaxExtent': max,
	'caretSlopeRise': first,
	'caretSlopeRun': first,
	'caretOffset': first,
	'numberOfVMetrics': recalculate,
}

os2FsTypeMergeBitMap = {
	'size': 16,
	'*': lambda bit: 0,
	1: bitwise_or, # no embedding permitted
	2: bitwise_and, # allow previewing and printing documents
	3: bitwise_and, # allow editing documents
	8: bitwise_or, # no subsetting permitted
	9: bitwise_or, # no embedding of outlines permitted
}

def mergeOs2FsType(lst):
	lst = list(lst)
	if all(item == 0 for item in lst):
		return 0

	# Compute least restrictive logic for each fsType value
	for i in range(len(lst)):
		# unset bit 1 (no embedding permitted) if either bit 2 or 3 is set
		if lst[i] & 0x000C:
			lst[i] &= ~0x0002
		# set bit 2 (allow previewing) if bit 3 is set (allow editing)
		elif lst[i] & 0x0008:
			lst[i] |= 0x0004
		# set bits 2 and 3 if everything is allowed
		elif lst[i] == 0:
			lst[i] = 0x000C

	fsType = mergeBits(os2FsTypeMergeBitMap)(lst)
	# unset bits 2 and 3 if bit 1 is set (some font is "no embedding")
	if fsType & 0x0002:
		fsType &= ~0x000C
	return fsType


ttLib.getTableClass('OS/2').mergeMap = {
	'*': first,
	'tableTag': equal,
	'version': max,
	'xAvgCharWidth': avg_int, # Apparently fontTools doesn't recalc this
	'fsType': mergeOs2FsType, # Will be overwritten
	'panose': first, # FIXME: should really be the first Latin font
	'ulUnicodeRange1': bitwise_or,
	'ulUnicodeRange2': bitwise_or,
	'ulUnicodeRange3': bitwise_or,
	'ulUnicodeRange4': bitwise_or,
	'fsFirstCharIndex': min,
	'fsLastCharIndex': max,
	'sTypoAscender': max,
	'sTypoDescender': min,
	'sTypoLineGap': max,
	'usWinAscent': max,
	'usWinDescent': max,
	# Version 2,3,4
	'ulCodePageRange1': onlyExisting(bitwise_or),
	'ulCodePageRange2': onlyExisting(bitwise_or),
	'usMaxContex': onlyExisting(max),
	# TODO version 5
}

@_add_method(ttLib.getTableClass('OS/2'))
def merge(self, m, tables):
	DefaultTable.merge(self, m, tables)
	if self.version < 2:
		# bits 8 and 9 are reserved and should be set to zero
		self.fsType &= ~0x0300
	if self.version >= 3:
		# Only one of bits 1, 2, and 3 may be set. We already take
		# care of bit 1 implications in mergeOs2FsType. So unset
		# bit 2 if bit 3 is already set.
		if self.fsType & 0x0008:
			self.fsType &= ~0x0004
	return self

ttLib.getTableClass('post').mergeMap = {
	'*': first,
	'tableTag': equal,
	'formatType': max,
	'isFixedPitch': min,
	'minMemType42': max,
	'maxMemType42': lambda lst: 0,
	'minMemType1': max,
	'maxMemType1': lambda lst: 0,
	'mapping': onlyExisting(sumDicts),
	'extraNames': lambda lst: [],
}

ttLib.getTableClass('vmtx').mergeMap = ttLib.getTableClass('hmtx').mergeMap = {
	'tableTag': equal,
	'metrics': sumDicts,
}

ttLib.getTableClass('name').mergeMap = {
	'tableTag': equal,
	'names': first, # FIXME? Does mixing name records make sense?
}

ttLib.getTableClass('loca').mergeMap = {
	'*': recalculate,
	'tableTag': equal,
}

ttLib.getTableClass('glyf').mergeMap = {
	'tableTag': equal,
	'glyphs': sumDicts,
	'glyphOrder': sumLists,
}

@_add_method(ttLib.getTableClass('glyf'))
def merge(self, m, tables):
	for i,table in enumerate(tables):
		for g in table.glyphs.values():
			if i:
				# Drop hints for all but first font, since
				# we don't map functions / CVT values.
				g.removeHinting()
			# Expand composite glyphs to load their
			# composite glyph names.
			if g.isComposite():
				g.expand(table)
	return DefaultTable.merge(self, m, tables)

ttLib.getTableClass('prep').mergeMap = lambda self, lst: first(lst)
ttLib.getTableClass('fpgm').mergeMap = lambda self, lst: first(lst)
ttLib.getTableClass('cvt ').mergeMap = lambda self, lst: first(lst)
ttLib.getTableClass('gasp').mergeMap = lambda self, lst: first(lst) # FIXME? Appears irreconcilable

def _glyphsAreSame(glyphSet1, glyphSet2, glyph1, glyph2):
	pen1 = DecomposingRecordingPen(glyphSet1)
	pen2 = DecomposingRecordingPen(glyphSet2)
	g1 = glyphSet1[glyph1]
	g2 = glyphSet2[glyph2]
	g1.draw(pen1)
	g2.draw(pen2)
	return (pen1.value == pen2.value and
		g1.width == g2.width and
		(not hasattr(g1, 'height') or g1.height == g2.height))

# Valid (format, platformID, platEncID) triplets for cmap subtables containing
# Unicode BMP-only and Unicode Full Repertoire semantics.
# Cf. OpenType spec for "Platform specific encodings":
# https://docs.microsoft.com/en-us/typography/opentype/spec/name
class CmapUnicodePlatEncodings:
	BMP = {(4, 3, 1), (4, 0, 3), (4, 0, 4), (4, 0, 6)}
	FullRepertoire = {(12, 3, 10), (12, 0, 4), (12, 0, 6)}

@_add_method(ttLib.getTableClass('cmap'))
def merge(self, m, tables):
	# TODO Handle format=14.
	# Only merge format 4 and 12 Unicode subtables, ignores all other subtables
	# If there is a format 12 table for the same font, ignore the format 4 table
	cmapTables = []
	for fontIdx,table in enumerate(tables):
		format4 = None
		format12 = None
		for subtable in table.tables:
			properties = (subtable.format, subtable.platformID, subtable.platEncID)
			if properties in CmapUnicodePlatEncodings.BMP:
				format4 = subtable
			elif properties in CmapUnicodePlatEncodings.FullRepertoire:
				format12 = subtable
			else:
				log.warning(
					"Dropped cmap subtable from font [%s]:\t"
					"format %2s, platformID %2s, platEncID %2s",
					fontIdx, subtable.format, subtable.platformID, subtable.platEncID
				)
		if format12 is not None:
			cmapTables.append((format12, fontIdx))
		elif format4 is not None:
			cmapTables.append((format4, fontIdx))

	# Build a unicode mapping, then decide which format is needed to store it.
	cmap = {}
	fontIndexForGlyph = {}
	glyphSets = [None for f in m.fonts] if hasattr(m, 'fonts') else None
	for table,fontIdx in cmapTables:
		# handle duplicates
		for uni,gid in table.cmap.items():
			oldgid = cmap.get(uni, None)
			if oldgid is None:
				cmap[uni] = gid
				fontIndexForGlyph[gid] = fontIdx
			elif oldgid != gid:
				# Char previously mapped to oldgid, now to gid.
				# Record, to fix up in GSUB 'locl' later.
				if m.duplicateGlyphsPerFont[fontIdx].get(oldgid) is None:
					if glyphSets is not None:
						oldFontIdx = fontIndexForGlyph[oldgid]
						for idx in (fontIdx, oldFontIdx):
							if glyphSets[idx] is None:
								glyphSets[idx] = m.fonts[idx].getGlyphSet()
						if _glyphsAreSame(glyphSets[oldFontIdx], glyphSets[fontIdx], oldgid, gid):
							continue
					m.duplicateGlyphsPerFont[fontIdx][oldgid] = gid
				elif m.duplicateGlyphsPerFont[fontIdx][oldgid] != gid:
					# Char previously mapped to oldgid but oldgid is already remapped to a different
					# gid, because of another Unicode character.
					# TODO: Try harder to do something about these.
					log.warning("Dropped mapping from codepoint %#06X to glyphId '%s'", uni, gid)

	cmapBmpOnly = {uni: gid for uni,gid in cmap.items() if uni <= 0xFFFF}
	self.tables = []
	module = ttLib.getTableModule('cmap')
	if len(cmapBmpOnly) != len(cmap):
		# format-12 required.
		cmapTable = module.cmap_classes[12](12)
		cmapTable.platformID = 3
		cmapTable.platEncID = 10
		cmapTable.language = 0
		cmapTable.cmap = cmap
		self.tables.append(cmapTable)
	# always create format-4
	cmapTable = module.cmap_classes[4](4)
	cmapTable.platformID = 3
	cmapTable.platEncID = 1
	cmapTable.language = 0
	cmapTable.cmap = cmapBmpOnly
	# ordered by platform then encoding
	self.tables.insert(0, cmapTable)
	self.tableVersion = 0
	self.numSubTables = len(self.tables)
	return self


def mergeLookupLists(lst):
	# TODO Do smarter merge.
	return sumLists(lst)

def mergeFeatures(lst):
	assert lst
	self = otTables.Feature()
	self.FeatureParams = None
	self.LookupListIndex = mergeLookupLists([l.LookupListIndex for l in lst if l.LookupListIndex])
	self.LookupCount = len(self.LookupListIndex)
	return self

def mergeFeatureLists(lst):
	d = {}
	for l in lst:
		for f in l:
			tag = f.FeatureTag
			if tag not in d:
				d[tag] = []
			d[tag].append(f.Feature)
	ret = []
	for tag in sorted(d.keys()):
		rec = otTables.FeatureRecord()
		rec.FeatureTag = tag
		rec.Feature = mergeFeatures(d[tag])
		ret.append(rec)
	return ret

def mergeLangSyses(lst):
	assert lst

	# TODO Support merging ReqFeatureIndex
	assert all(l.ReqFeatureIndex == 0xFFFF for l in lst)

	self = otTables.LangSys()
	self.LookupOrder = None
	self.ReqFeatureIndex = 0xFFFF
	self.FeatureIndex = mergeFeatureLists([l.FeatureIndex for l in lst if l.FeatureIndex])
	self.FeatureCount = len(self.FeatureIndex)
	return self

def mergeScripts(lst):
	assert lst

	if len(lst) == 1:
		return lst[0]
	langSyses = {}
	for sr in lst:
		for lsr in sr.LangSysRecord:
			if lsr.LangSysTag not in langSyses:
				langSyses[lsr.LangSysTag] = []
			langSyses[lsr.LangSysTag].append(lsr.LangSys)
	lsrecords = []
	for tag, langSys_list in sorted(langSyses.items()):
		lsr = otTables.LangSysRecord()
		lsr.LangSys = mergeLangSyses(langSys_list)
		lsr.LangSysTag = tag
		lsrecords.append(lsr)

	self = otTables.Script()
	self.LangSysRecord = lsrecords
	self.LangSysCount = len(lsrecords)
	dfltLangSyses = [s.DefaultLangSys for s in lst if s.DefaultLangSys]
	if dfltLangSyses:
		self.DefaultLangSys = mergeLangSyses(dfltLangSyses)
	else:
		self.DefaultLangSys = None
	return self

def mergeScriptRecords(lst):
	d = {}
	for l in lst:
		for s in l:
			tag = s.ScriptTag
			if tag not in d:
				d[tag] = []
			d[tag].append(s.Script)
	ret = []
	for tag in sorted(d.keys()):
		rec = otTables.ScriptRecord()
		rec.ScriptTag = tag
		rec.Script = mergeScripts(d[tag])
		ret.append(rec)
	return ret

otTables.ScriptList.mergeMap = {
	'ScriptCount': lambda lst: None, # TODO
	'ScriptRecord': mergeScriptRecords,
}
otTables.BaseScriptList.mergeMap = {
	'BaseScriptCount': lambda lst: None, # TODO
	# TODO: Merge duplicate entries
	'BaseScriptRecord': lambda lst: sorted(sumLists(lst), key=lambda s: s.BaseScriptTag),
}

otTables.FeatureList.mergeMap = {
	'FeatureCount': sum,
	'FeatureRecord': lambda lst: sorted(sumLists(lst), key=lambda s: s.FeatureTag),
}

otTables.LookupList.mergeMap = {
	'LookupCount': sum,
	'Lookup': sumLists,
}

otTables.Coverage.mergeMap = {
	'Format': min,
	'glyphs': sumLists,
}

otTables.ClassDef.mergeMap = {
	'Format': min,
	'classDefs': sumDicts,
}

otTables.LigCaretList.mergeMap = {
	'Coverage': mergeObjects,
	'LigGlyphCount': sum,
	'LigGlyph': sumLists,
}

otTables.AttachList.mergeMap = {
	'Coverage': mergeObjects,
	'GlyphCount': sum,
	'AttachPoint': sumLists,
}

# XXX Renumber MarkFilterSets of lookups
otTables.MarkGlyphSetsDef.mergeMap = {
	'MarkSetTableFormat': equal,
	'MarkSetCount': sum,
	'Coverage': sumLists,
}

otTables.Axis.mergeMap = {
	'*': mergeObjects,
}

# XXX Fix BASE table merging
otTables.BaseTagList.mergeMap = {
	'BaseTagCount': sum,
	'BaselineTag': sumLists,
}

otTables.GDEF.mergeMap = \
otTables.GSUB.mergeMap = \
otTables.GPOS.mergeMap = \
otTables.BASE.mergeMap = \
otTables.JSTF.mergeMap = \
otTables.MATH.mergeMap = \
{
	'*': mergeObjects,
	'Version': max,
}

ttLib.getTableClass('GDEF').mergeMap = \
ttLib.getTableClass('GSUB').mergeMap = \
ttLib.getTableClass('GPOS').mergeMap = \
ttLib.getTableClass('BASE').mergeMap = \
ttLib.getTableClass('JSTF').mergeMap = \
ttLib.getTableClass('MATH').mergeMap = \
{
	'tableTag': onlyExisting(equal), # XXX clean me up
	'table': mergeObjects,
}

@_add_method(ttLib.getTableClass('GSUB'))
def merge(self, m, tables):

	assert len(tables) == len(m.duplicateGlyphsPerFont)
	for i,(table,dups) in enumerate(zip(tables, m.duplicateGlyphsPerFont)):
		if not dups: continue
		assert (table is not None and table is not NotImplemented), "Have duplicates to resolve for font %d but no GSUB: %s" % (i + 1, dups)
		synthFeature = None
		synthLookup = None
		for script in table.table.ScriptList.ScriptRecord:
			if script.ScriptTag == 'DFLT': continue # XXX
			for langsys in [script.Script.DefaultLangSys] + [l.LangSys for l in script.Script.LangSysRecord]:
				if langsys is None: continue # XXX Create!
				feature = [v for v in langsys.FeatureIndex if v.FeatureTag == 'locl']
				assert len(feature) <= 1
				if feature:
					feature = feature[0]
				else:
					if not synthFeature:
						synthFeature = otTables.FeatureRecord()
						synthFeature.FeatureTag = 'locl'
						f = synthFeature.Feature = otTables.Feature()
						f.FeatureParams = None
						f.LookupCount = 0
						f.LookupListIndex = []
						langsys.FeatureIndex.append(synthFeature)
						langsys.FeatureIndex.sort(key=lambda v: v.FeatureTag)
						table.table.FeatureList.FeatureRecord.append(synthFeature)
						table.table.FeatureList.FeatureCount += 1
					feature = synthFeature

				if not synthLookup:
					subtable = otTables.SingleSubst()
					subtable.mapping = dups
					synthLookup = otTables.Lookup()
					synthLookup.LookupFlag = 0
					synthLookup.LookupType = 1
					synthLookup.SubTableCount = 1
					synthLookup.SubTable = [subtable]
					if table.table.LookupList is None:
						# mtiLib uses None as default value for LookupList,
						# while feaLib points to an empty array with count 0
						# TODO: make them do the same
						table.table.LookupList = otTables.LookupList()
						table.table.LookupList.Lookup = []
						table.table.LookupList.LookupCount = 0
					table.table.LookupList.Lookup.append(synthLookup)
					table.table.LookupList.LookupCount += 1

				feature.Feature.LookupListIndex[:0] = [synthLookup]
				feature.Feature.LookupCount += 1

	DefaultTable.merge(self, m, tables)
	return self

@_add_method(otTables.SingleSubst,
		otTables.MultipleSubst,
		otTables.AlternateSubst,
		otTables.LigatureSubst,
		otTables.ReverseChainSingleSubst,
		otTables.SinglePos,
		otTables.PairPos,
		otTables.CursivePos,
		otTables.MarkBasePos,
		otTables.MarkLigPos,
		otTables.MarkMarkPos)
def mapLookups(self, lookupMap):
	pass

# Copied and trimmed down from subset.py
@_add_method(otTables.ContextSubst,
		otTables.ChainContextSubst,
		otTables.ContextPos,
		otTables.ChainContextPos)
def __merge_classify_context(self):

	class ContextHelper(object):
		def __init__(self, klass, Format):
			if klass.__name__.endswith('Subst'):
				Typ = 'Sub'
				Type = 'Subst'
			else:
				Typ = 'Pos'
				Type = 'Pos'
			if klass.__name__.startswith('Chain'):
				Chain = 'Chain'
			else:
				Chain = ''
			ChainTyp = Chain+Typ

			self.Typ = Typ
			self.Type = Type
			self.Chain = Chain
			self.ChainTyp = ChainTyp

			self.LookupRecord = Type+'LookupRecord'

			if Format == 1:
				self.Rule = ChainTyp+'Rule'
				self.RuleSet = ChainTyp+'RuleSet'
			elif Format == 2:
				self.Rule = ChainTyp+'ClassRule'
				self.RuleSet = ChainTyp+'ClassSet'

	if self.Format not in [1, 2, 3]:
		return None  # Don't shoot the messenger; let it go
	if not hasattr(self.__class__, "__ContextHelpers"):
		self.__class__.__ContextHelpers = {}
	if self.Format not in self.__class__.__ContextHelpers:
		helper = ContextHelper(self.__class__, self.Format)
		self.__class__.__ContextHelpers[self.Format] = helper
	return self.__class__.__ContextHelpers[self.Format]


@_add_method(otTables.ContextSubst,
		otTables.ChainContextSubst,
		otTables.ContextPos,
		otTables.ChainContextPos)
def mapLookups(self, lookupMap):
	c = self.__merge_classify_context()

	if self.Format in [1, 2]:
		for rs in getattr(self, c.RuleSet):
			if not rs: continue
			for r in getattr(rs, c.Rule):
				if not r: continue
				for ll in getattr(r, c.LookupRecord):
					if not ll: continue
					ll.LookupListIndex = lookupMap[ll.LookupListIndex]
	elif self.Format == 3:
		for ll in getattr(self, c.LookupRecord):
			if not ll: continue
			ll.LookupListIndex = lookupMap[ll.LookupListIndex]
	else:
		assert 0, "unknown format: %s" % self.Format

@_add_method(otTables.ExtensionSubst,
		otTables.ExtensionPos)
def mapLookups(self, lookupMap):
	if self.Format == 1:
		self.ExtSubTable.mapLookups(lookupMap)
	else:
		assert 0, "unknown format: %s" % self.Format

@_add_method(otTables.Lookup)
def mapLookups(self, lookupMap):
	for st in self.SubTable:
		if not st: continue
		st.mapLookups(lookupMap)

@_add_method(otTables.LookupList)
def mapLookups(self, lookupMap):
	for l in self.Lookup:
		if not l: continue
		l.mapLookups(lookupMap)

@_add_method(otTables.Feature)
def mapLookups(self, lookupMap):
	self.LookupListIndex = [lookupMap[i] for i in self.LookupListIndex]

@_add_method(otTables.FeatureList)
def mapLookups(self, lookupMap):
	for f in self.FeatureRecord:
		if not f or not f.Feature: continue
		f.Feature.mapLookups(lookupMap)

@_add_method(otTables.DefaultLangSys,
		otTables.LangSys)
def mapFeatures(self, featureMap):
	self.FeatureIndex = [featureMap[i] for i in self.FeatureIndex]
	if self.ReqFeatureIndex != 65535:
		self.ReqFeatureIndex = featureMap[self.ReqFeatureIndex]

@_add_method(otTables.Script)
def mapFeatures(self, featureMap):
	if self.DefaultLangSys:
		self.DefaultLangSys.mapFeatures(featureMap)
	for l in self.LangSysRecord:
		if not l or not l.LangSys: continue
		l.LangSys.mapFeatures(featureMap)

@_add_method(otTables.ScriptList)
def mapFeatures(self, featureMap):
	for s in self.ScriptRecord:
		if not s or not s.Script: continue
		s.Script.mapFeatures(featureMap)


class Options(object):

	class UnknownOptionError(Exception):
		pass

	def __init__(self, **kwargs):

		self.verbose = False
		self.timing = False

		self.set(**kwargs)

	def set(self, **kwargs):
		for k,v in kwargs.items():
			if not hasattr(self, k):
				raise self.UnknownOptionError("Unknown option '%s'" % k)
			setattr(self, k, v)

	def parse_opts(self, argv, ignore_unknown=[]):
		ret = []
		opts = {}
		for a in argv:
			orig_a = a
			if not a.startswith('--'):
				ret.append(a)
				continue
			a = a[2:]
			i = a.find('=')
			op = '='
			if i == -1:
				if a.startswith("no-"):
					k = a[3:]
					v = False
				else:
					k = a
					v = True
			else:
				k = a[:i]
				if k[-1] in "-+":
					op = k[-1]+'='  # Ops is '-=' or '+=' now.
					k = k[:-1]
				v = a[i+1:]
			k = k.replace('-', '_')
			if not hasattr(self, k):
				if ignore_unknown is True or k in ignore_unknown:
					ret.append(orig_a)
					continue
				else:
					raise self.UnknownOptionError("Unknown option '%s'" % a)

			ov = getattr(self, k)
			if isinstance(ov, bool):
				v = bool(v)
			elif isinstance(ov, int):
				v = int(v)
			elif isinstance(ov, list):
				vv = v.split(',')
				if vv == ['']:
					vv = []
				vv = [int(x, 0) if len(x) and x[0] in "0123456789" else x for x in vv]
				if op == '=':
					v = vv
				elif op == '+=':
					v = ov
					v.extend(vv)
				elif op == '-=':
					v = ov
					for x in vv:
						if x in v:
							v.remove(x)
				else:
					assert 0

			opts[k] = v
		self.set(**opts)

		return ret

class _AttendanceRecordingIdentityDict(object):
	"""A dictionary-like object that records indices of items actually accessed
	from a list."""

	def __init__(self, lst):
		self.l = lst
		self.d = {id(v):i for i,v in enumerate(lst)}
		self.s = set()

	def __getitem__(self, v):
		self.s.add(self.d[id(v)])
		return v

class _GregariousIdentityDict(object):
	"""A dictionary-like object that welcomes guests without reservations and
	adds them to the end of the guest list."""

	def __init__(self, lst):
		self.l = lst
		self.s = set(id(v) for v in lst)

	def __getitem__(self, v):
		if id(v) not in self.s:
			self.s.add(id(v))
			self.l.append(v)
		return v

class _NonhashableDict(object):
	"""A dictionary-like object mapping objects to values."""

	def __init__(self, keys, values=None):
		if values is None:
			self.d = {id(v):i for i,v in enumerate(keys)}
		else:
			self.d = {id(k):v for k,v in zip(keys, values)}

	def __getitem__(self, k):
		return self.d[id(k)]

	def __setitem__(self, k, v):
		self.d[id(k)] = v

	def __delitem__(self, k):
		del self.d[id(k)]

class Merger(object):

	def __init__(self, options=None):

		if not options:
			options = Options()

		self.options = options

	def merge(self, fontfiles):

		mega = ttLib.TTFont()

		#
		# Settle on a mega glyph order.
		#
		fonts = [ttLib.TTFont(fontfile) for fontfile in fontfiles]
		glyphOrders = [font.getGlyphOrder() for font in fonts]
		megaGlyphOrder = self._mergeGlyphOrders(glyphOrders)
		# Reload fonts and set new glyph names on them.
		# TODO Is it necessary to reload font?  I think it is.  At least
		# it's safer, in case tables were loaded to provide glyph names.
		fonts = [ttLib.TTFont(fontfile) for fontfile in fontfiles]
		for font,glyphOrder in zip(fonts, glyphOrders):
			font.setGlyphOrder(glyphOrder)
		mega.setGlyphOrder(megaGlyphOrder)

		for font in fonts:
			self._preMerge(font)

		self.fonts = fonts
		self.duplicateGlyphsPerFont = [{} for f in fonts]

		allTags = reduce(set.union, (list(font.keys()) for font in fonts), set())
		allTags.remove('GlyphOrder')

		# Make sure we process cmap before GSUB as we have a dependency there.
		if 'GSUB' in allTags:
			allTags.remove('GSUB')
			allTags = ['GSUB'] + list(allTags)
		if 'cmap' in allTags:
			allTags.remove('cmap')
			allTags = ['cmap'] + list(allTags)

		for tag in allTags:
			with timer("merge '%s'" % tag):
				tables = [font.get(tag, NotImplemented) for font in fonts]

				log.info("Merging '%s'.", tag)
				clazz = ttLib.getTableClass(tag)
				table = clazz(tag).merge(self, tables)
				# XXX Clean this up and use:  table = mergeObjects(tables)

				if table is not NotImplemented and table is not False:
					mega[tag] = table
					log.info("Merged '%s'.", tag)
				else:
					log.info("Dropped '%s'.", tag)

		del self.duplicateGlyphsPerFont
		del self.fonts

		self._postMerge(mega)

		return mega

	def _mergeGlyphOrders(self, glyphOrders):
		"""Modifies passed-in glyphOrders to reflect new glyph names.
		Returns glyphOrder for the merged font."""
		# Simply append font index to the glyph name for now.
		# TODO Even this simplistic numbering can result in conflicts.
		# But then again, we have to improve this soon anyway.
		mega = []
		for n,glyphOrder in enumerate(glyphOrders):
			for i,glyphName in enumerate(glyphOrder):
				glyphName += "#" + repr(n)
				glyphOrder[i] = glyphName
				mega.append(glyphName)
		return mega

	def mergeObjects(self, returnTable, logic, tables):
		# Right now we don't use self at all.  Will use in the future
		# for options and logging.

		allKeys = set.union(set(), *(vars(table).keys() for table in tables if table is not NotImplemented))
		for key in allKeys:
			try:
				mergeLogic = logic[key]
			except KeyError:
				try:
					mergeLogic = logic['*']
				except KeyError:
					raise Exception("Don't know how to merge key %s of class %s" %
							(key, returnTable.__class__.__name__))
			if mergeLogic is NotImplemented:
				continue
			value = mergeLogic(getattr(table, key, NotImplemented) for table in tables)
			if value is not NotImplemented:
				setattr(returnTable, key, value)

		return returnTable

	def _preMerge(self, font):

		# Map indices to references

		GDEF = font.get('GDEF')
		GSUB = font.get('GSUB')
		GPOS = font.get('GPOS')

		for t in [GSUB, GPOS]:
			if not t: continue

			if t.table.LookupList:
				lookupMap = {i:v for i,v in enumerate(t.table.LookupList.Lookup)}
				t.table.LookupList.mapLookups(lookupMap)
				t.table.FeatureList.mapLookups(lookupMap)

			if t.table.FeatureList and t.table.ScriptList:
				featureMap = {i:v for i,v in enumerate(t.table.FeatureList.FeatureRecord)}
				t.table.ScriptList.mapFeatures(featureMap)

		# TODO GDEF/Lookup MarkFilteringSets
		# TODO FeatureParams nameIDs

	def _postMerge(self, font):

		# Map references back to indices

		GDEF = font.get('GDEF')
		GSUB = font.get('GSUB')
		GPOS = font.get('GPOS')

		for t in [GSUB, GPOS]:
			if not t: continue

			if t.table.FeatureList and t.table.ScriptList:

				# Collect unregistered (new) features.
				featureMap = _GregariousIdentityDict(t.table.FeatureList.FeatureRecord)
				t.table.ScriptList.mapFeatures(featureMap)

				# Record used features.
				featureMap = _AttendanceRecordingIdentityDict(t.table.FeatureList.FeatureRecord)
				t.table.ScriptList.mapFeatures(featureMap)
				usedIndices = featureMap.s

				# Remove unused features
				t.table.FeatureList.FeatureRecord = [f for i,f in enumerate(t.table.FeatureList.FeatureRecord) if i in usedIndices]

				# Map back to indices.
				featureMap = _NonhashableDict(t.table.FeatureList.FeatureRecord)
				t.table.ScriptList.mapFeatures(featureMap)

				t.table.FeatureList.FeatureCount = len(t.table.FeatureList.FeatureRecord)

			if t.table.LookupList:

				# Collect unregistered (new) lookups.
				lookupMap = _GregariousIdentityDict(t.table.LookupList.Lookup)
				t.table.FeatureList.mapLookups(lookupMap)
				t.table.LookupList.mapLookups(lookupMap)

				# Record used lookups.
				lookupMap = _AttendanceRecordingIdentityDict(t.table.LookupList.Lookup)
				t.table.FeatureList.mapLookups(lookupMap)
				t.table.LookupList.mapLookups(lookupMap)
				usedIndices = lookupMap.s

				# Remove unused lookups
				t.table.LookupList.Lookup = [l for i,l in enumerate(t.table.LookupList.Lookup) if i in usedIndices]

				# Map back to indices.
				lookupMap = _NonhashableDict(t.table.LookupList.Lookup)
				t.table.FeatureList.mapLookups(lookupMap)
				t.table.LookupList.mapLookups(lookupMap)

				t.table.LookupList.LookupCount = len(t.table.LookupList.Lookup)

		# TODO GDEF/Lookup MarkFilteringSets
		# TODO FeatureParams nameIDs


__all__ = [
	'Options',
	'Merger',
	'main'
]

@timer("make one with everything (TOTAL TIME)")
def main(args=None):
	from fontTools import configLogger

	if args is None:
		args = sys.argv[1:]

	options = Options()
	args = options.parse_opts(args)

	if len(args) < 1:
		print("usage: pyftmerge font...", file=sys.stderr)
		return 1

	configLogger(level=logging.INFO if options.verbose else logging.WARNING)
	if options.timing:
		timer.logger.setLevel(logging.DEBUG)
	else:
		timer.logger.disabled = True

	merger = Merger(options=options)
	font = merger.merge(args)
	outfile = 'merged.ttf'
	with timer("compile and save font"):
		font.save(outfile)


if __name__ == "__main__":
	sys.exit(main())