Add tests that optimize block matrices
This commit is contained in:
Jany Belluz
parent
ef67839fdb
commit
7860dd5fe8
@ -128,7 +128,9 @@ def _getClassRanges(glyphIDs: Iterable[int]):
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# Adapted from https://github.com/fonttools/fonttools/blob/f64f0b42f2d1163b2d85194e0979def539f5dca3/Lib/fontTools/ttLib/tables/otTables.py#L960-L989
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def _classDef_bytes(
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class_data: List[Tuple[List[Tuple[int, int]], int, int]], class_ids: List[int], coverage=False
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class_data: List[Tuple[List[Tuple[int, int]], int, int]],
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class_ids: List[int],
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coverage=False,
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):
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if not class_ids:
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return 0
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@ -152,6 +154,10 @@ def cluster_pairs_by_class2_coverage_custom_cost(
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pairs: Pairs,
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compression: int = 5,
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) -> List[Pairs]:
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if not pairs:
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# The subtable was actually empty?
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return [pairs]
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# Sorted for reproducibility/determinism
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all_class1 = sorted(set(pair[0] for pair in pairs))
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all_class2 = sorted(set(pair[1] for pair in pairs))
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@ -229,10 +235,13 @@ def cluster_pairs_by_class2_coverage_custom_cost(
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@property
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def cost(self):
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if self._cost is None:
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# From: https://docs.microsoft.com/en-us/typography/opentype/spec/gpos#pair-adjustment-positioning-format-2-class-pair-adjustment
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self._cost = (
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# uint16 posFormat Format identifier: format = 2
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# 2 bytes to store the offset to this subtable in the Lookup table above
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2
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# Contents of the subtable
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# From: https://docs.microsoft.com/en-us/typography/opentype/spec/gpos#pair-adjustment-positioning-format-2-class-pair-adjustment
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# uint16 posFormat Format identifier: format = 2
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+ 2
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# Offset16 coverageOffset Offset to Coverage table, from beginning of PairPos subtable.
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+ 2
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+ self.coverage_bytes
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@ -267,7 +276,9 @@ def cluster_pairs_by_class2_coverage_custom_cost(
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# uint16 glyphArray[glyphCount] Array of glyph IDs — in numerical order
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+ sum(len(all_class1[i]) for i in self.indices) * 2
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)
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ranges = sorted(chain.from_iterable(all_class1_data[i][0] for i in self.indices))
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ranges = sorted(
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chain.from_iterable(all_class1_data[i][0] for i in self.indices)
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)
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merged_range_count = 0
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last = None
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for (start, end) in ranges:
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@ -1,9 +1,18 @@
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import logging
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from pathlib import Path
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from subprocess import run
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import contextlib
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import os
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from typing import List, Optional, Tuple
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from fontTools.ttLib import TTFont
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import pytest
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from fontTools.feaLib.builder import addOpenTypeFeaturesFromString
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from fontTools.fontBuilder import FontBuilder
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from fontTools.ttLib.tables.otBase import OTTableWriter, ValueRecord
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def test_main(tmpdir: Path):
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"""Check that calling the main function on an input TTF works."""
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@ -36,19 +45,128 @@ def test_main(tmpdir: Path):
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assert output.exists()
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def test_off_by_default(tmpdir: Path):
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"""Check that calling the main function on an input TTF works."""
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glyphs = ".notdef space A B".split()
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features = """
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feature kern {
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pos A B -50;
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} kern;
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# Copy-pasted from https://stackoverflow.com/questions/2059482/python-temporarily-modify-the-current-processs-environment
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# TODO: remove when moving to the Config class
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@contextlib.contextmanager
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def set_env(**environ):
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"""
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fb = FontBuilder(1000)
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fb.setupGlyphOrder(glyphs)
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addOpenTypeFeaturesFromString(fb.font, features)
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input = tmpdir / "in.ttf"
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fb.save(str(input))
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output = tmpdir / "out.ttf"
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run(["fonttools", "otlLib.optimize", str(input), "-o", str(output)], check=True)
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assert output.exists()
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Temporarily set the process environment variables.
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>>> with set_env(PLUGINS_DIR=u'test/plugins'):
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... "PLUGINS_DIR" in os.environ
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True
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>>> "PLUGINS_DIR" in os.environ
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False
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:type environ: dict[str, unicode]
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:param environ: Environment variables to set
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"""
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old_environ = dict(os.environ)
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os.environ.update(environ)
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try:
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yield
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finally:
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os.environ.clear()
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os.environ.update(old_environ)
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def count_pairpos_subtables(font: TTFont) -> int:
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subtables = 0
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for lookup in font["GPOS"].table.LookupList.Lookup:
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if lookup.LookupType == 2:
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subtables += len(lookup.SubTable)
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elif lookup.LookupType == 9:
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for subtable in lookup.SubTable:
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if subtable.ExtensionLookupType == 2:
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subtables += 1
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return subtables
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def count_pairpos_bytes(font: TTFont) -> int:
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bytes = 0
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gpos = font["GPOS"]
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for lookup in font["GPOS"].table.LookupList.Lookup:
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if lookup.LookupType == 2:
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w = OTTableWriter(tableTag=gpos.tableTag)
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lookup.compile(w, font)
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bytes += len(w.getAllData())
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elif lookup.LookupType == 9:
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if any(subtable.ExtensionLookupType == 2 for subtable in lookup.SubTable):
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w = OTTableWriter(tableTag=gpos.tableTag)
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lookup.compile(w, font)
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bytes += len(w.getAllData())
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return bytes
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def get_kerning_by_blocks(blocks: List[Tuple[int, int]]) -> Tuple[List[str], str]:
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"""Generate a highly compressible font by generating a bunch of rectangular
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blocks on the diagonal that can easily be sliced into subtables.
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Returns the list of glyphs and feature code of the font.
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"""
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value = 0
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glyphs: List[str] = []
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rules = []
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# Each block is like a script in a multi-script font
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for script, (width, height) in enumerate(blocks):
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glyphs.extend(f"g_{script}_{i}" for i in range(max(width, height)))
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for l in range(height):
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for r in range(width):
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value += 1
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rules.append((f"g_{script}_{l}", f"g_{script}_{r}", value))
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classes = "\n".join([f"@{g} = [{g}];" for g in glyphs])
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statements = "\n".join([f"pos @{l} @{r} {v};" for (l, r, v) in rules])
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features = f"""
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{classes}
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feature kern {{
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{statements}
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}} kern;
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"""
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return glyphs, features
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@pytest.mark.parametrize(
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("blocks", "mode", "expected_subtables", "expected_bytes"),
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[
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# Mode = 0 = no optimization leads to 650 bytes of GPOS
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([(15, 3), (2, 10)], None, 1, 602),
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# Optimization level 1 recognizes the 2 blocks and splits into 2
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# subtables = adds 1 subtable leading to a size reduction of
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# (602-298)/602 = 50%
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([(15, 3), (2, 10)], 1, 2, 298),
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# On a bigger block configuration, we see that mode=5 doesn't create
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# as many subtables as it could, because of the stop criteria
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([(4, 4) for _ in range(20)], 5, 14, 2042),
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# while level=9 creates as many subtables as there were blocks on the
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# diagonal and yields a better saving
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([(4, 4) for _ in range(20)], 9, 20, 1886),
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# On a fully occupied kerning matrix, even the strategy 9 doesn't
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# split anything.
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([(10, 10)], 9, 1, 304)
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],
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)
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def test_optimization_mode(
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caplog,
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blocks: List[Tuple[int, int]],
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mode: Optional[int],
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expected_subtables: int,
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expected_bytes: int,
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):
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"""Check that the optimizations are off by default, and that increasing
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the optimization level creates more subtables and a smaller byte size.
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"""
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caplog.set_level(logging.DEBUG)
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glyphs, features = get_kerning_by_blocks(blocks)
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glyphs = [".notdef space"] + glyphs
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env = {}
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if mode is not None:
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env["FONTTOOLS_GPOS_COMPACT_MODE"] = str(mode)
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with set_env(**env):
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fb = FontBuilder(1000)
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fb.setupGlyphOrder(glyphs)
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addOpenTypeFeaturesFromString(fb.font, features)
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assert expected_subtables == count_pairpos_subtables(fb.font)
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assert expected_bytes == count_pairpos_bytes(fb.font)
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