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Merge pull request #1802 from fonttools/subset-optimize-single-pos

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[subset] Optimize SinglePos lookup format when all values are same
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Cosimo Lupo 2020-01-17 11:18:11 -08:00 committed by GitHub
commit a37dab3824
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2 changed files with 72 additions and 0 deletions
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5
Lib/fontTools/subset/__init__.py
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@ -546,6 +546,11 @@ def prune_post_subset(self, font, options):
if not options.hinting: if not options.hinting:
# Drop device tables # Drop device tables
self.ValueFormat &= ~0x00F0 self.ValueFormat &= ~0x00F0
# Downgrade to Format 1 if all ValueRecords are the same
if self.Format == 2 and all(v == self.Value[0] for v in self.Value):
self.Format = 1
self.Value = self.Value[0] if self.ValueFormat != 0 else None
del self.ValueCount
return True return True
@_add_method(otTables.PairPos) @_add_method(otTables.PairPos)

67
Tests/subset/subset_test.py
View File

@ -1,5 +1,6 @@
import io import io
from fontTools.misc.py23 import * from fontTools.misc.py23 import *
from fontTools.misc.testTools import getXML
from fontTools import subset from fontTools import subset
from fontTools.fontBuilder import FontBuilder from fontTools.fontBuilder import FontBuilder
from fontTools.ttLib import TTFont, newTable from fontTools.ttLib import TTFont, newTable
@ -768,5 +769,71 @@ def test_subset_feature_variations():
assert "dollar.rvrn" in font.getGlyphOrder() assert "dollar.rvrn" in font.getGlyphOrder()
def test_subset_single_pos_format():
fb = FontBuilder(unitsPerEm=1000)
fb.setupGlyphOrder([".notdef", "a", "b", "c"])
fb.setupCharacterMap({ord("a"): "a", ord("b"): "b", ord("c"): "c"})
fb.setupNameTable({"familyName": "TestSingePosFormat", "styleName": "Regular"})
fb.setupPost()
fb.addOpenTypeFeatures("""
feature kern {
pos a -50;
pos b -40;
pos c -50;
} kern;
""")
buf = io.BytesIO()
fb.save(buf)
buf.seek(0)
font = TTFont(buf)
# The input font has a SinglePos Format 2 subtable where each glyph has
# different ValueRecords
assert getXML(font["GPOS"].table.LookupList.Lookup[0].toXML, font) == [
'<Lookup>',
' <LookupType value="1"/>',
' <LookupFlag value="0"/>',
' <!-- SubTableCount=1 -->',
' <SinglePos index="0" Format="2">',
' <Coverage Format="1">',
' <Glyph value="a"/>',
' <Glyph value="b"/>',
' <Glyph value="c"/>',
' </Coverage>',
' <ValueFormat value="4"/>',
' <!-- ValueCount=3 -->',
' <Value index="0" XAdvance="-50"/>',
' <Value index="1" XAdvance="-40"/>',
' <Value index="2" XAdvance="-50"/>',
' </SinglePos>',
'</Lookup>',
]
options = subset.Options()
subsetter = subset.Subsetter(options)
subsetter.populate(unicodes=[ord("a"), ord("c")])
subsetter.subset(font)
# All the subsetted glyphs from the original SinglePos Format2 subtable
# now have the same ValueRecord, so we use a more compact Format 1 subtable.
assert getXML(font["GPOS"].table.LookupList.Lookup[0].toXML, font) == [
'<Lookup>',
' <LookupType value="1"/>',
' <LookupFlag value="0"/>',
' <!-- SubTableCount=1 -->',
' <SinglePos index="0" Format="1">',
' <Coverage Format="1">',
' <Glyph value="a"/>',
' <Glyph value="c"/>',
' </Coverage>',
' <ValueFormat value="4"/>',
' <Value XAdvance="-50"/>',
' </SinglePos>',
'</Lookup>',
]
if __name__ == "__main__": if __name__ == "__main__":
sys.exit(unittest.main()) sys.exit(unittest.main())