[feaLib] Support compact syntax for chaining to alternate substitutions
https://github.com/behdad/fonttools/issues/445 Not sure whether it makes much sense to define a contextual chain that points to a GSUB type 3, but the OpenType feature file syntax does not explicitly forbid it. Adobe's `makeotf` tool rejects this kind of input with "Contextual alternate rule not yet supported"; this implies that the construct is valid (albeit definitely exotic).
This commit is contained in:
Sascha Brawer
parent
e19d5a8cbe
commit
db49f20d6b
@ -159,12 +159,20 @@ class MarkClassDefinition(Statement):
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class AlternateSubstStatement(Statement):
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def __init__(self, location, glyph, from_class):
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def __init__(self, location, prefix, glyph, suffix, replacement):
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Statement.__init__(self, location)
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self.glyph, self.from_class = (glyph, from_class)
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self.prefix, self.glyph, self.suffix = (prefix, glyph, suffix)
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self.replacement = replacement
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def build(self, builder):
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builder.add_alternate_subst(self.location, self.glyph, self.from_class)
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glyph = self.glyph.glyphSet()
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assert len(glyph) == 1, glyph
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glyph = list(glyph)[0]
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prefix = [p.glyphSet() for p in self.prefix]
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suffix = [s.glyphSet() for s in self.suffix]
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replacement = self.replacement.glyphSet()
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builder.add_alternate_subst(self.location, prefix, glyph, suffix,
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replacement)
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class Anchor(Expression):
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@ -403,13 +403,19 @@ class Builder(object):
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lookup.substitutions.append((prefix, glyphs, suffix,
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self.find_lookup_builders_(lookups)))
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def add_alternate_subst(self, location, glyph, from_class):
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lookup = self.get_lookup_(location, AlternateSubstBuilder)
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def add_alternate_subst(self, location,
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prefix, glyph, suffix, replacement):
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if prefix or suffix:
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lookup = self.get_chained_lookup_(location, AlternateSubstBuilder)
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chain = self.get_lookup_(location, ChainContextSubstBuilder)
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chain.substitutions.append((prefix, [glyph], suffix, [lookup]))
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else:
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lookup = self.get_lookup_(location, AlternateSubstBuilder)
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if glyph in lookup.alternates:
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raise FeatureLibError(
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'Already defined alternates for glyph "%s"' % glyph,
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location)
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lookup.alternates[glyph] = from_class
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lookup.alternates[glyph] = replacement
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def add_ligature_subst(self, location,
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prefix, glyphs, suffix, replacement):
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@ -473,9 +473,8 @@ class Parser(object):
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raise FeatureLibError(
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'Expected a single glyphclass after "from"',
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location)
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return ast.AlternateSubstStatement(location,
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list(old[0].glyphSet())[0],
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new[0].glyphSet())
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return ast.AlternateSubstStatement(
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location, old_prefix, old[0], old_suffix, new[0])
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num_lookups = len([l for l in lookups if l is not None])
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@ -819,9 +819,22 @@ class ParserTest(unittest.TestCase):
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" substitute a from [a.1 a.2 a.3];"
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"} test;")
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sub = doc.statements[0].statements[0]
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self.assertEqual(type(sub), ast.AlternateSubstStatement)
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self.assertEqual(sub.glyph, "a")
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self.assertEqual(sub.from_class, {"a.1", "a.2", "a.3"})
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self.assertIsInstance(sub, ast.AlternateSubstStatement)
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self.assertEqual(glyphstr(sub.prefix), "")
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self.assertEqual(glyphstr([sub.glyph]), "a")
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self.assertEqual(glyphstr(sub.suffix), "")
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self.assertEqual(glyphstr([sub.replacement]), "[a.1 a.2 a.3]")
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def test_substitute_from_chained(self): # chain to GSUB LookupType 3
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doc = self.parse("feature test {"
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" substitute A B a' [Y y] Z from [a.1 a.2 a.3];"
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"} test;")
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sub = doc.statements[0].statements[0]
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self.assertIsInstance(sub, ast.AlternateSubstStatement)
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self.assertEqual(glyphstr(sub.prefix), "A B")
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self.assertEqual(glyphstr([sub.glyph]), "a")
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self.assertEqual(glyphstr(sub.suffix), "[Y y] Z")
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self.assertEqual(glyphstr([sub.replacement]), "[a.1 a.2 a.3]")
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def test_substitute_from_glyphclass(self): # GSUB LookupType 3
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doc = self.parse("feature test {"
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@ -829,9 +842,12 @@ class ParserTest(unittest.TestCase):
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" substitute ampersand from @Ampersands;"
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"} test;")
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[glyphclass, sub] = doc.statements[0].statements
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self.assertEqual(type(sub), ast.AlternateSubstStatement)
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self.assertEqual(sub.glyph, "ampersand")
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self.assertEqual(sub.from_class, {"ampersand.1", "ampersand.2"})
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self.assertIsInstance(sub, ast.AlternateSubstStatement)
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self.assertEqual(glyphstr(sub.prefix), "")
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self.assertEqual(glyphstr([sub.glyph]), "ampersand")
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self.assertEqual(glyphstr(sub.suffix), "")
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self.assertEqual(glyphstr([sub.replacement]),
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"[ampersand.1 ampersand.2]")
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def test_substitute_ligature(self): # GSUB LookupType 4
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doc = self.parse("feature liga {substitute f f i by f_f_i;} liga;")
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5
Lib/fontTools/feaLib/testdata/GSUB_6.fea
vendored
5
Lib/fontTools/feaLib/testdata/GSUB_6.fea
vendored
@ -7,6 +7,10 @@ lookup ChainedMultipleSubst {
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substitute [A-C a-c] [D d] E c_t' V [W w] [X-Z x-z] by c t;
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} ChainedMultipleSubst;
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lookup ChainedAlternateSubst {
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substitute [space comma semicolon] e' from [e e.begin];
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} ChainedAlternateSubst;
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lookup ChainedLigatureSubst {
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substitute A [C c]' [T t]' Z by c_t;
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} ChainedLigatureSubst;
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@ -14,5 +18,6 @@ lookup ChainedLigatureSubst {
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feature test {
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lookup ChainedSingleSubst;
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lookup ChainedMultipleSubst;
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lookup ChainedAlternateSubst;
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lookup ChainedLigatureSubst;
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} test;
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43
Lib/fontTools/feaLib/testdata/GSUB_6.ttx
vendored
43
Lib/fontTools/feaLib/testdata/GSUB_6.ttx
vendored
@ -22,15 +22,16 @@
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<FeatureRecord index="0">
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<FeatureTag value="test"/>
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<Feature>
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<!-- LookupCount=3 -->
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<!-- LookupCount=4 -->
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<LookupListIndex index="0" value="1"/>
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<LookupListIndex index="1" value="4"/>
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<LookupListIndex index="2" value="6"/>
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<LookupListIndex index="3" value="8"/>
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</Feature>
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</FeatureRecord>
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</FeatureList>
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<LookupList>
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<!-- LookupCount=7 -->
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<!-- LookupCount=9 -->
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<Lookup index="0">
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<!-- LookupType=1 -->
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<LookupFlag value="0"/>
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@ -153,6 +154,40 @@
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</ChainContextSubst>
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</Lookup>
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<Lookup index="5">
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<!-- LookupType=3 -->
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<LookupFlag value="0"/>
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<!-- SubTableCount=1 -->
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<AlternateSubst index="0" Format="1">
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<AlternateSet glyph="e">
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<Alternate glyph="e"/>
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<Alternate glyph="e.begin"/>
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</AlternateSet>
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</AlternateSubst>
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</Lookup>
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<Lookup index="6">
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<!-- LookupType=6 -->
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<LookupFlag value="0"/>
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<!-- SubTableCount=1 -->
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<ChainContextSubst index="0" Format="3">
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<!-- BacktrackGlyphCount=1 -->
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<BacktrackCoverage index="0">
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<Glyph value="space"/>
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<Glyph value="semicolon"/>
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<Glyph value="comma"/>
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</BacktrackCoverage>
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<!-- InputGlyphCount=1 -->
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<InputCoverage index="0">
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<Glyph value="e"/>
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</InputCoverage>
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<!-- LookAheadGlyphCount=0 -->
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<!-- SubstCount=1 -->
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<SubstLookupRecord index="0">
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<SequenceIndex value="0"/>
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<LookupListIndex value="5"/>
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</SubstLookupRecord>
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</ChainContextSubst>
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</Lookup>
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<Lookup index="7">
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<!-- LookupType=4 -->
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<LookupFlag value="0"/>
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<!-- SubTableCount=1 -->
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@ -167,7 +202,7 @@
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</LigatureSet>
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</LigatureSubst>
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</Lookup>
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<Lookup index="6">
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<Lookup index="8">
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<!-- LookupType=6 -->
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<LookupFlag value="0"/>
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<!-- SubTableCount=1 -->
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@ -192,7 +227,7 @@
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<!-- SubstCount=1 -->
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<SubstLookupRecord index="0">
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<SequenceIndex value="0"/>
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<LookupListIndex value="5"/>
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<LookupListIndex value="7"/>
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</SubstLookupRecord>
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</ChainContextSubst>
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</Lookup>
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