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[feaLib] Emit SinglePos (GPOS type 1) in format 2 when this is more compact

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This commit is contained in:
Sascha Brawer 2015-12-07 11:39:14 +01:00
parent f129f658c9
commit 117683680e
3 changed files with 89 additions and 23 deletions
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44
Lib/fontTools/feaLib/builder.py
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@ -600,20 +600,56 @@ class SinglePosBuilder(LookupBuilder):
for glyphs in values.values():
glyphs.sort(key=self.font.getGlyphID)
# Make a list of (glyphs, (otBase.ValueRecord, int valueFormat)).
# Glyphs with the same otBase.ValueRecord are grouped into one item.
values = [(glyphs, makeOpenTypeValueRecord(valrec))
for valrec, glyphs in values.items()]
# Find out which glyphs should be encoded as SinglePos format 2.
# Format 2 is more compact than format 1 when multiple glyphs
# have different values but share the same integer valueFormat.
format2 = {} # valueFormat --> [(glyph, value), (glyph, value), ...]
for glyphs, (value, valueFormat) in values:
if len(glyphs) == 1:
glyph = glyphs[0]
format2.setdefault(valueFormat, []).append((glyph, value))
# Only use format 2 if multiple glyphs share the same valueFormat.
# Otherwise, format 1 is more compact.
format2 = [(valueFormat, valueList)
for valueFormat, valueList in format2.items()
if len(valueList) > 1]
format2.sort()
format2Glyphs = set() # {"A", "B", "C"}
for _, valueList in format2:
for (glyph, _) in valueList:
format2Glyphs.add(glyph)
for valueFormat, valueList in format2:
valueList.sort(key=lambda x: self.font.getGlyphID(x[0]))
st = otTables.SinglePos()
subtables.append(st)
st.Format = 2
st.ValueFormat = valueFormat
st.Coverage = otTables.Coverage()
st.Coverage.glyphs = [glyph for glyph, _value in valueList]
st.ValueCount = len(valueList)
st.Value = [value for _glyph, value in valueList]
# To make the ordering of our subtables deterministic,
# we sort subtables by the first glyph ID in their coverage.
# Not doing this would be OK for OpenType, but testing the
# compiler would be harder with non-deterministic output.
values = list(values.items())
values.sort(key=lambda x: self.font.getGlyphID(x[1][0]))
values.sort(key=lambda x: self.font.getGlyphID(x[0][0]))
for valrec, glyphs in values:
for glyphs, (value, valueFormat) in values:
if len(glyphs) == 1 and glyphs[0] in format2Glyphs:
continue # already emitted as part of a format 2 subtable
st = otTables.SinglePos()
subtables.append(st)
st.Format = 1
st.Coverage = otTables.Coverage()
st.Coverage.glyphs = glyphs
st.Value, st.ValueFormat = makeOpenTypeValueRecord(valrec)
st.Value, st.ValueFormat = value, valueFormat
lookup = otTables.Lookup()
lookup.SubTable = subtables

8
Lib/fontTools/feaLib/testdata/GPOS_1.fea vendored
View File

@ -20,10 +20,18 @@ feature kern {
<device 11 -8, 14 7> <device 13 8, 15 1>
>;
position four 400;
position four.oldstyle 401;
position five <-80 0 -160 0>;
position six -200;
position @sevenEightNine -100;
pos P <1 0 800 0>;
pos Q <1 0 801 0>;
pos R <1 0 802 0>;
pos S <1 1 803 0>;
pos T <1 1 804 0>;
pos U <1 1 805 0>;
# The AFDKO makeotf tool accepts re-definitions of previously defined
# single adjustment positionings, provided the re-definition is using
# the same value. We replicate this behavior.

60
Lib/fontTools/feaLib/testdata/GPOS_1.ttx vendored
View File

@ -53,8 +53,44 @@
<Lookup index="0">
<!-- LookupType=1 -->
<LookupFlag value="0"/>
<!-- SubTableCount=6 -->
<SinglePos index="0" Format="1">
<!-- SubTableCount=7 -->
<SinglePos index="0" Format="2">
<Coverage>
<Glyph value="four"/>
<Glyph value="six"/>
<Glyph value="four.oldstyle"/>
</Coverage>
<ValueFormat value="4"/>
<!-- ValueCount=3 -->
<Value index="0" XAdvance="400"/>
<Value index="1" XAdvance="-200"/>
<Value index="2" XAdvance="401"/>
</SinglePos>
<SinglePos index="1" Format="2">
<Coverage>
<Glyph value="P"/>
<Glyph value="Q"/>
<Glyph value="R"/>
</Coverage>
<ValueFormat value="5"/>
<!-- ValueCount=3 -->
<Value index="0" XPlacement="1" XAdvance="800"/>
<Value index="1" XPlacement="1" XAdvance="801"/>
<Value index="2" XPlacement="1" XAdvance="802"/>
</SinglePos>
<SinglePos index="2" Format="2">
<Coverage>
<Glyph value="S"/>
<Glyph value="T"/>
<Glyph value="U"/>
</Coverage>
<ValueFormat value="7"/>
<!-- ValueCount=3 -->
<Value index="0" XPlacement="1" YPlacement="1" XAdvance="803"/>
<Value index="1" XPlacement="1" YPlacement="1" XAdvance="804"/>
<Value index="2" XPlacement="1" YPlacement="1" XAdvance="805"/>
</SinglePos>
<SinglePos index="3" Format="1">
<Coverage>
<Glyph value="one"/>
<Glyph value="two"/>
@ -64,21 +100,7 @@
<ValueFormat value="5"/>
<Value XPlacement="-80" XAdvance="-160"/>
</SinglePos>
<SinglePos index="1" Format="1">
<Coverage>
<Glyph value="four"/>
</Coverage>
<ValueFormat value="4"/>
<Value XAdvance="400"/>
</SinglePos>
<SinglePos index="2" Format="1">
<Coverage>
<Glyph value="six"/>
</Coverage>
<ValueFormat value="4"/>
<Value XAdvance="-200"/>
</SinglePos>
<SinglePos index="3" Format="1">
<SinglePos index="4" Format="1">
<Coverage>
<Glyph value="seven"/>
<Glyph value="eight"/>
@ -87,7 +109,7 @@
<ValueFormat value="4"/>
<Value XAdvance="-100"/>
</SinglePos>
<SinglePos index="4" Format="1">
<SinglePos index="5" Format="1">
<Coverage>
<Glyph value="A"/>
<Glyph value="B"/>
@ -114,7 +136,7 @@
</XAdvDevice>
</Value>
</SinglePos>
<SinglePos index="5" Format="1">
<SinglePos index="6" Format="1">
<Coverage>
<Glyph value="C"/>
</Coverage>