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"""GSUBUnparser: Convert binary GSUB lookups to fontFeatures objects."""
from .GTableUnparser import GTableUnparser
import fontFeatures
# These are silly little functions which help to document the intent
def glyph(x):
"""Wraps a glyph name in an array, to document the fact that it occupies a slot."""
assert isinstance(x, str)
return [x]
def singleglyph(x):
"""Wraps a glyph name in two arrays, to document the fact that it is the only occupant of a slot."""
return [glyph(x)]
class GSUBUnparser(GTableUnparser):
"""Unparse a GSUB table into a fontFeatures object. See :py:class:`fontFeatures.ttLib.GTableUnparser`."""
_table = "GSUB"
lookupTypes = {
1: "SingleSubstitution",
2: "MultipleSubstitution",
3: "AlternateSubstitution",
4: "LigatureSubstitution",
5: "Contextual",
6: "ChainedContextual",
7: "Extension",
8: "ReverseContextualSubstitution",
}
_attrs = {
"lookup": "SubstLookupRecord",
"format1_ruleset": "SubRuleSet",
"format1_rule": "SubRule",
"format2_classset": "SubClassSet",
"format2_rule": "SubClassRule",
"chain_format1_ruleset": "ChainSubRuleSet",
"chain_format1_rule": "ChainSubRule",
"chain_format2_classset": "ChainSubClassSet",
"chain_format2_rule": "ChainSubClassRule",
}
def isChaining(self, lookupType):
"""Returns true if the given lookup type is a chaining lookup."""
return lookupType >= 5
def unparseReverseContextualSubstitution(self, lookup):
"""Turn a GPOS8 (reverse contextual substitution) subtable into a fontFeatures Routine."""
b = fontFeatures.Routine(
name=self.getname("ReverseContextualSubstitution" + self.gensym())
)
self._fix_flags(b, lookup)
for sub in lookup.SubTable:
prefix = []
outputs = []
suffix = []
if hasattr(sub, "BacktrackCoverage"):
for coverage in reversed(sub.BacktrackCoverage):
prefix.append(coverage.glyphs)
if hasattr(sub, "LookAheadCoverage"):
for i, coverage in enumerate(sub.LookAheadCoverage):
suffix.append(coverage.glyphs)
outputs = [sub.Substitute]
inputs = [sub.Coverage.glyphs]
b.addRule(
fontFeatures.Substitution(
inputs,
outputs,
prefix,
suffix,
flags=lookup.LookupFlag,
reverse=True,
)
)
return b, []
def unparseLigatureSubstitution(self, lookup):
"""Turn a GPOS4 (ligature substitution) subtable into a fontFeatures Routine."""
b = fontFeatures.Routine(
name=self.getname("LigatureSubstitution" + self.gensym())
)
self._fix_flags(b, lookup)
for sub in lookup.SubTable:
for first, ligatures in sub.ligatures.items():
for lig in ligatures:
substarray = [glyph(first)]
for x in lig.Component:
substarray.append(glyph(x))
b.addRule(
fontFeatures.Substitution(
substarray,
singleglyph(lig.LigGlyph),
address=self.currentLookup,
flags=lookup.LookupFlag,
)
)
return b, []
def unparseMultipleSubstitution(self, lookup):
"""Turn a GPOS2 (multiple substitution) subtable into a fontFeatures Routine."""
b = fontFeatures.Routine(
name=self.getname("MultipleSubstitution" + self.gensym())
)
self._fix_flags(b, lookup)
for sub in lookup.SubTable:
for in_glyph, out_glyphs in sub.mapping.items():
b.addRule(
fontFeatures.Substitution(
singleglyph(in_glyph),
[glyph(x) for x in out_glyphs],
address=self.currentLookup,
flags=lookup.LookupFlag,
)
)
return b, []
def unparseAlternateSubstitution(self, lookup):
"""Turn a GPOS3 (alternate substitution) subtable into a fontFeatures Routine."""
b = fontFeatures.Routine(
name=self.getname("AlternateSubstitution" + self.gensym())
)
self._fix_flags(b, lookup)
for sub in lookup.SubTable:
for in_glyph, out_glyphs in sub.alternates.items():
b.addRule(
fontFeatures.Substitution(
singleglyph(in_glyph),
[out_glyphs],
address=self.currentLookup,
flags=lookup.LookupFlag,
force_alt=True,
)
)
return b, []
def unparseSingleSubstitution(self, lookup):
"""Turn a GPOS1 (single substitution) subtable into a fontFeatures Routine."""
b = fontFeatures.Routine(
name=self.getname("SingleSubstitution" + self.gensym())
)
self._fix_flags(b, lookup)
for sub in lookup.SubTable:
for k, v in sub.mapping.items():
b.addRule(
fontFeatures.Substitution(
[[k]],
[[v]],
address=self.currentLookup,
flags=lookup.LookupFlag,
)
)
return b, []
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