Merge pull request #3429 from fonttools/fealib-liga-order
[feaLib] keep declaration order of ligatures within ligature set
This commit is contained in:
Cosimo Lupo
GitHub
commit
a1cb14d3ec
@ -1338,7 +1338,7 @@ class Builder(object):
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# substitutions to be specified on target sequences that contain
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# glyph classes, the implementation software will enumerate
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# all specific glyph sequences if glyph classes are detected"
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for g in sorted(itertools.product(*glyphs)):
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for g in itertools.product(*glyphs):
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lookup.ligatures[g] = replacement
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# GSUB 5/6
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@ -1567,19 +1567,6 @@ def buildAlternateSubstSubtable(mapping):
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return self
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def _getLigatureKey(components):
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# Computes a key for ordering ligatures in a GSUB Type-4 lookup.
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# When building the OpenType lookup, we need to make sure that
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# the longest sequence of components is listed first, so we
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# use the negative length as the primary key for sorting.
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# To make buildLigatureSubstSubtable() deterministic, we use the
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# component sequence as the secondary key.
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# For example, this will sort (f,f,f) < (f,f,i) < (f,f) < (f,i) < (f,l).
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return (-len(components), components)
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def buildLigatureSubstSubtable(mapping):
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"""Builds a ligature substitution (GSUB4) subtable.
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@ -1613,7 +1600,7 @@ def buildLigatureSubstSubtable(mapping):
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# with fontTools >= 3.1:
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# self.ligatures = dict(mapping)
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self.ligatures = {}
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for components in sorted(mapping.keys(), key=_getLigatureKey):
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for components in sorted(mapping.keys(), key=self._getLigatureSortKey):
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ligature = ot.Ligature()
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ligature.Component = components[1:]
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ligature.CompCount = len(ligature.Component) + 1
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@ -1123,6 +1123,35 @@ class LigatureSubst(FormatSwitchingBaseTable):
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self.ligatures = ligatures
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del self.Format # Don't need this anymore
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@staticmethod
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def _getLigatureSortKey(components):
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# Computes a key for ordering ligatures in a GSUB Type-4 lookup.
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# When building the OpenType lookup, we need to make sure that
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# the longest sequence of components is listed first, so we
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# use the negative length as the key for sorting.
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# Note, we no longer need to worry about deterministic order because the
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# ligature mapping `dict` remembers the insertion order, and this in
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# turn depends on the order in which the ligatures are written in the FEA.
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# Since python sort algorithm is stable, the ligatures of equal length
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# will keep the relative order in which they appear in the feature file.
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# For example, given the following ligatures (all starting with 'f' and
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# thus belonging to the same LigatureSet):
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#
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# feature liga {
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# sub f i by f_i;
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# sub f f f by f_f_f;
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# sub f f by f_f;
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# sub f f i by f_f_i;
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# } liga;
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#
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# this should sort to: f_f_f, f_f_i, f_i, f_f
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# This is also what fea-rs does, see:
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# https://github.com/adobe-type-tools/afdko/issues/1727
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# https://github.com/fonttools/fonttools/issues/3428
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# https://github.com/googlefonts/fontc/pull/680
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return -len(components)
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def preWrite(self, font):
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self.Format = 1
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ligatures = getattr(self, "ligatures", None)
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@ -1135,13 +1164,11 @@ class LigatureSubst(FormatSwitchingBaseTable):
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# ligatures is map from components-sequence to lig-glyph
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newLigatures = dict()
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for comps, lig in sorted(
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ligatures.items(), key=lambda item: (-len(item[0]), item[0])
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):
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for comps in sorted(ligatures.keys(), key=self._getLigatureSortKey):
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ligature = Ligature()
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ligature.Component = comps[1:]
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ligature.CompCount = len(comps)
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ligature.LigGlyph = lig
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ligature.LigGlyph = ligatures[comps]
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newLigatures.setdefault(comps[0], []).append(ligature)
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ligatures = newLigatures
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@ -147,8 +147,8 @@
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<!-- SubTableCount=1 -->
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<LigatureSubst index="0">
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<LigatureSet glyph="c">
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<Ligature components="s" glyph="c_s"/>
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<Ligature components="t" glyph="c_t"/>
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<Ligature components="s" glyph="c_s"/>
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</LigatureSet>
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</LigatureSubst>
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</Lookup>
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@ -11,6 +11,16 @@ feature F1 {
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# if glyph classes are detected in <glyph sequence>. Thus, the above
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# example produces an identical representation in the font as if all
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# the sequences were manually enumerated by the font editor:
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#
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# NOTE(anthrotype): The previous sentence is no longer entirely true, since we
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# now preserve the order in which the ligatures (with same length and first glyph)
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# were specified in the feature file and do not sort them alphabetically
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# by the ligature component names. Therefore, the way this particular example from
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# the FEA spec is written will produce two slightly different representations
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# in the font in which the ligatures are enumerated differently, however the two
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# lookups are functionally equivalent.
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# See: https://github.com/fonttools/fonttools/issues/3428
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# https://github.com/adobe-type-tools/afdko/issues/1727
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feature F2 {
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sub one slash two by onehalf;
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sub one.oldstyle slash two by onehalf;
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@ -43,16 +43,16 @@
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<!-- SubTableCount=1 -->
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<LigatureSubst index="0">
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<LigatureSet glyph="one">
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<Ligature components="fraction,two" glyph="onehalf"/>
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<Ligature components="fraction,two.oldstyle" glyph="onehalf"/>
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<Ligature components="slash,two" glyph="onehalf"/>
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<Ligature components="slash,two.oldstyle" glyph="onehalf"/>
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<Ligature components="fraction,two" glyph="onehalf"/>
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<Ligature components="fraction,two.oldstyle" glyph="onehalf"/>
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</LigatureSet>
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<LigatureSet glyph="one.oldstyle">
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<Ligature components="fraction,two" glyph="onehalf"/>
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<Ligature components="fraction,two.oldstyle" glyph="onehalf"/>
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<Ligature components="slash,two" glyph="onehalf"/>
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<Ligature components="slash,two.oldstyle" glyph="onehalf"/>
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<Ligature components="fraction,two" glyph="onehalf"/>
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<Ligature components="fraction,two.oldstyle" glyph="onehalf"/>
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</LigatureSet>
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</LigatureSubst>
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</Lookup>
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@ -62,16 +62,16 @@
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<!-- SubTableCount=1 -->
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<LigatureSubst index="0">
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<LigatureSet glyph="one">
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<Ligature components="fraction,two" glyph="onehalf"/>
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<Ligature components="fraction,two.oldstyle" glyph="onehalf"/>
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<Ligature components="slash,two" glyph="onehalf"/>
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<Ligature components="fraction,two" glyph="onehalf"/>
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<Ligature components="slash,two.oldstyle" glyph="onehalf"/>
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<Ligature components="fraction,two.oldstyle" glyph="onehalf"/>
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</LigatureSet>
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<LigatureSet glyph="one.oldstyle">
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<Ligature components="fraction,two" glyph="onehalf"/>
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<Ligature components="fraction,two.oldstyle" glyph="onehalf"/>
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<Ligature components="slash,two" glyph="onehalf"/>
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<Ligature components="fraction,two" glyph="onehalf"/>
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<Ligature components="slash,two.oldstyle" glyph="onehalf"/>
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<Ligature components="fraction,two.oldstyle" glyph="onehalf"/>
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</LigatureSet>
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</LigatureSubst>
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</Lookup>
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@ -16,20 +16,20 @@
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<Ligature components="Jsmall" glyph="IJsmall"/>
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</LigatureSet>
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<LigatureSet glyph="f">
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<Ligature components="f,b" glyph="ffb"/>
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<Ligature components="f,h" glyph="ffh"/>
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<Ligature components="f,i" glyph="ffi"/>
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<Ligature components="f,k" glyph="ffk"/>
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<Ligature components="f,l" glyph="ffl"/>
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<Ligature components="f,t" glyph="fft"/>
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<Ligature components="b" glyph="fb"/>
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<Ligature components="f" glyph="ff"/>
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<Ligature components="h" glyph="fh"/>
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<Ligature components="f,b" glyph="ffb"/>
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<Ligature components="f,h" glyph="ffh"/>
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<Ligature components="f,k" glyph="ffk"/>
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<Ligature components="i" glyph="fi"/>
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<Ligature components="j" glyph="fj"/>
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<Ligature components="k" glyph="fk"/>
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<Ligature components="l" glyph="fl"/>
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<Ligature components="f" glyph="ff"/>
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<Ligature components="t" glyph="ft"/>
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<Ligature components="b" glyph="fb"/>
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<Ligature components="h" glyph="fh"/>
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<Ligature components="k" glyph="fk"/>
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<Ligature components="j" glyph="fj"/>
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</LigatureSet>
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<LigatureSet glyph="i">
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<Ligature components="j" glyph="ij"/>
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@ -1051,11 +1051,11 @@ class BuilderTest(object):
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func = lambda writer, font: value.toXML(writer, font, valueName="Val")
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assert getXML(func) == ['<Val XPlacement="7" YPlacement="23"/>']
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def test_getLigatureKey(self):
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def test_getLigatureSortKey(self):
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components = lambda s: [tuple(word) for word in s.split()]
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c = components("fi fl ff ffi fff")
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c.sort(key=builder._getLigatureKey)
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assert c == components("fff ffi ff fi fl")
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c.sort(key=otTables.LigatureSubst._getLigatureSortKey)
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assert c == components("ffi fff fi fl ff")
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def test_getSinglePosValueKey(self):
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device = builder.buildDevice({10: 1, 11: 3})
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