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[otlLib] Refactor chained contextual builders (#2007)

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* Introduce a new subclass for chained contextual (sub and pos)

* Rename .substitutions to .rules in subst builders to allow for code reuse

* Make format of subtable break marker tuple common between sub/pos

Note that prior to this patch, add_subtable_break in a Subst builder adds:

(self.SUBTABLE_BREAK_, self.SUBTABLE_BREAK_, self.SUBTABLE_BREAK_, self.SUBTABLE_BREAK_)

while add_subtable_break in a Pos builder adds:

(self.SUBTABLE_BREAK_, self.SUBTABLE_BREAK_, self.SUBTABLE_BREAK_, [self.SUBTABLE_BREAK_])

This is messy. If we read the first element from the tuple instead of the last one to test if a rule is a subtable break, we can make the marker tuple the same.

* And now the subtable break code can be hoisted into superclass

* These helper methods will make the build routine common

* Hoist common build method to superclass

The diff doesn’t show it very clearly because it’s being too clever, but all I’ve done is moved one method. Everything works apart from the error message, which comes next.

* Fix the error message
This commit is contained in:
Simon Cozens 2020-07-02 18:40:20 +01:00 committed by GitHub
parent ebfa4ba1fe
commit 6364d36633
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 58 additions and 68 deletions
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12
Lib/fontTools/feaLib/builder.py
View File

@ -868,7 +868,7 @@ class Builder(object):
def add_chain_context_subst(self, location,
prefix, glyphs, suffix, lookups):
lookup = self.get_lookup_(location, ChainContextSubstBuilder)
lookup.substitutions.append((prefix, glyphs, suffix,
lookup.rules.append((prefix, glyphs, suffix,
self.find_lookup_builders_(lookups)))
def add_alternate_subst(self, location,
@ -880,7 +880,7 @@ class Builder(object):
if prefix or suffix:
chain = self.get_lookup_(location, ChainContextSubstBuilder)
lookup = self.get_chained_lookup_(location, AlternateSubstBuilder)
chain.substitutions.append((prefix, [{glyph}], suffix, [lookup]))
chain.rules.append((prefix, [{glyph}], suffix, [lookup]))
else:
lookup = self.get_lookup_(location, AlternateSubstBuilder)
if glyph in lookup.alternates:
@ -935,7 +935,7 @@ class Builder(object):
if prefix or suffix or forceChain:
chain = self.get_lookup_(location, ChainContextSubstBuilder)
lookup = self.get_chained_lookup_(location, LigatureSubstBuilder)
chain.substitutions.append((prefix, glyphs, suffix, [lookup]))
chain.rules.append((prefix, glyphs, suffix, [lookup]))
else:
lookup = self.get_lookup_(location, LigatureSubstBuilder)
@ -953,7 +953,7 @@ class Builder(object):
chain = self.get_lookup_(location, ChainContextSubstBuilder)
sub = self.get_chained_lookup_(location, MultipleSubstBuilder)
sub.mapping[glyph] = replacements
chain.substitutions.append((prefix, [{glyph}], suffix, [sub]))
chain.rules.append((prefix, [{glyph}], suffix, [sub]))
return
lookup = self.get_lookup_(location, MultipleSubstBuilder)
if glyph in lookup.mapping:
@ -973,7 +973,7 @@ class Builder(object):
def add_reverse_chain_single_subst(self, location, old_prefix,
old_suffix, mapping):
lookup = self.get_lookup_(location, ReverseChainSingleSubstBuilder)
lookup.substitutions.append((old_prefix, old_suffix, mapping))
lookup.rules.append((old_prefix, old_suffix, mapping))
def add_single_subst(self, location, prefix, suffix, mapping, forceChain):
if self.cur_feature_name_ == "aalt":
@ -1007,7 +1007,7 @@ class Builder(object):
if sub is None:
sub = self.get_chained_lookup_(location, SingleSubstBuilder)
sub.mapping.update(mapping)
chain.substitutions.append((prefix, [mapping.keys()], suffix, [sub]))
chain.rules.append((prefix, [mapping.keys()], suffix, [sub]))
def add_cursive_pos(self, location, glyphclass, entryAnchor, exitAnchor):
lookup = self.get_lookup_(location, CursivePosBuilder)

114
Lib/fontTools/otlLib/builder.py
View File

@ -156,11 +156,7 @@ class AlternateSubstBuilder(LookupBuilder):
self.alternates[(self.SUBTABLE_BREAK_, location)] = self.SUBTABLE_BREAK_
class ChainContextPosBuilder(LookupBuilder):
def __init__(self, font, location):
LookupBuilder.__init__(self, font, location, 'GPOS', 8)
self.rules = [] # (prefix, input, suffix, lookups)
class ChainContextualBuilder(LookupBuilder):
def equals(self, other):
return (LookupBuilder.equals(self, other) and
self.rules == other.rules)
@ -170,32 +166,56 @@ class ChainContextPosBuilder(LookupBuilder):
for (prefix, glyphs, suffix, lookups) in self.rules:
if prefix == self.SUBTABLE_BREAK_:
continue
st = ot.ChainContextPos()
st = self.newSubtable_()
subtables.append(st)
st.Format = 3
self.setBacktrackCoverage_(prefix, st)
self.setLookAheadCoverage_(suffix, st)
self.setInputCoverage_(glyphs, st)
st.PosCount = 0
st.PosLookupRecord = []
for sequenceIndex, lookupList in enumerate(lookups):
if lookupList is not None:
if not isinstance(lookupList, list):
# Can happen with synthesised lookups
lookupList = [ lookupList ]
for l in lookupList:
st.PosCount += 1
if l.lookup_index is None:
if isinstance(self, ChainContextPosBuilder):
other = "substitution"
else:
other = "positioning"
raise OpenTypeLibError('Missing index of the specified '
'lookup, might be a substitution lookup',
f'lookup, might be a {other} lookup',
self.location)
rec = ot.PosLookupRecord()
rec = self.newLookupRecord_()
rec.SequenceIndex = sequenceIndex
rec.LookupListIndex = l.lookup_index
st.PosLookupRecord.append(rec)
self.addLookupRecordToSubtable_(st, rec)
return self.buildLookup_(subtables)
def add_subtable_break(self, location):
self.rules.append((self.SUBTABLE_BREAK_, self.SUBTABLE_BREAK_,
self.SUBTABLE_BREAK_, [self.SUBTABLE_BREAK_]))
class ChainContextPosBuilder(ChainContextualBuilder):
def __init__(self, font, location):
LookupBuilder.__init__(self, font, location, 'GPOS', 8)
self.rules = [] # (prefix, input, suffix, lookups)
def newSubtable_(self):
st = ot.ChainContextPos()
st.PosCount = 0
st.PosLookupRecord = []
return st
def newLookupRecord_(self):
return ot.PosLookupRecord()
def addLookupRecordToSubtable_(self, st, rec):
st.PosCount += 1
st.PosLookupRecord.append(rec)
def find_chainable_single_pos(self, lookups, glyphs, value):
"""Helper for add_single_pos_chained_()"""
res = None
@ -207,55 +227,29 @@ class ChainContextPosBuilder(LookupBuilder):
res = lookup
return res
def add_subtable_break(self, location):
self.rules.append((self.SUBTABLE_BREAK_, self.SUBTABLE_BREAK_,
self.SUBTABLE_BREAK_, [self.SUBTABLE_BREAK_]))
class ChainContextSubstBuilder(LookupBuilder):
class ChainContextSubstBuilder(ChainContextualBuilder):
def __init__(self, font, location):
LookupBuilder.__init__(self, font, location, 'GSUB', 6)
self.substitutions = [] # (prefix, input, suffix, lookups)
self.rules = [] # (prefix, input, suffix, lookups)
def equals(self, other):
return (LookupBuilder.equals(self, other) and
self.substitutions == other.substitutions)
def newSubtable_(self):
st = ot.ChainContextSubst()
st.SubstCount = 0
st.SubstLookupRecord = []
return st
def build(self):
subtables = []
for (prefix, input, suffix, lookups) in self.substitutions:
if prefix == self.SUBTABLE_BREAK_:
continue
st = ot.ChainContextSubst()
subtables.append(st)
st.Format = 3
self.setBacktrackCoverage_(prefix, st)
self.setLookAheadCoverage_(suffix, st)
self.setInputCoverage_(input, st)
def newLookupRecord_(self):
return ot.SubstLookupRecord()
st.SubstCount = 0
st.SubstLookupRecord = []
for sequenceIndex, lookupList in enumerate(lookups):
if lookupList is not None:
if not isinstance(lookupList, list):
# Can happen with synthesised lookups
lookupList = [ lookupList ]
for l in lookupList:
st.SubstCount += 1
if l.lookup_index is None:
raise OpenTypeLibError('Missing index of the specified '
'lookup, might be a positioning lookup',
self.location)
rec = ot.SubstLookupRecord()
rec.SequenceIndex = sequenceIndex
rec.LookupListIndex = l.lookup_index
st.SubstLookupRecord.append(rec)
return self.buildLookup_(subtables)
def addLookupRecordToSubtable_(self, st, rec):
st.SubstCount += 1
st.SubstLookupRecord.append(rec)
def getAlternateGlyphs(self):
result = {}
for (_, _, _, lookuplist) in self.substitutions:
if lookuplist == self.SUBTABLE_BREAK_:
for (prefix, _, _, lookuplist) in self.rules:
if prefix == self.SUBTABLE_BREAK_:
continue
for lookups in lookuplist:
if not isinstance(lookups, list):
@ -270,19 +264,15 @@ class ChainContextSubstBuilder(LookupBuilder):
def find_chainable_single_subst(self, glyphs):
"""Helper for add_single_subst_chained_()"""
res = None
for _, _, _, substitutions in self.substitutions[::-1]:
if substitutions == self.SUBTABLE_BREAK_:
for prefix, _, _, rules in self.rules[::-1]:
if prefix == self.SUBTABLE_BREAK_:
return res
for sub in substitutions:
for sub in rules:
if (isinstance(sub, SingleSubstBuilder) and
not any(g in glyphs for g in sub.mapping.keys())):
res = sub
return res
def add_subtable_break(self, location):
self.substitutions.append((self.SUBTABLE_BREAK_, self.SUBTABLE_BREAK_,
self.SUBTABLE_BREAK_, self.SUBTABLE_BREAK_))
class LigatureSubstBuilder(LookupBuilder):
def __init__(self, font, location):
@ -435,15 +425,15 @@ class MarkMarkPosBuilder(LookupBuilder):
class ReverseChainSingleSubstBuilder(LookupBuilder):
def __init__(self, font, location):
LookupBuilder.__init__(self, font, location, 'GSUB', 8)
self.substitutions = [] # (prefix, suffix, mapping)
self.rules = [] # (prefix, suffix, mapping)
def equals(self, other):
return (LookupBuilder.equals(self, other) and
self.substitutions == other.substitutions)
self.rules == other.rules)
def build(self):
subtables = []
for prefix, suffix, mapping in self.substitutions:
for prefix, suffix, mapping in self.rules:
st = ot.ReverseChainSingleSubst()
st.Format = 1
self.setBacktrackCoverage_(prefix, st)