shadowfacts/fonttools
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Merge pull request #3337 from fonttools/instancer-sync-vmetrics

Browse Source 
[instancer] Ensure hhea vertical metrics stay in sync with OS/2 after MVAR instancing
This commit is contained in:
Cosimo Lupo 2023-11-15 15:02:10 +00:00 committed by GitHub
commit 64b2e5c968
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 84 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
Lib/fontTools/varLib/instancer/__init__.py
View File

@ -105,6 +105,7 @@ from fontTools.misc.cliTools import makeOutputFileName
from fontTools.varLib.instancer import solver
import collections
import dataclasses
from contextlib import contextmanager
from copy import deepcopy
from enum import IntEnum
import logging
@ -694,6 +695,43 @@ def setMvarDeltas(varfont, deltas):
)
@contextmanager
def verticalMetricsKeptInSync(varfont):
"""Ensure hhea vertical metrics stay in sync with OS/2 ones after instancing.
When applying MVAR deltas to the OS/2 table, if the ascender, descender and
line gap change but they were the same as the respective hhea metrics in the
original font, this context manager ensures that hhea metrcs also get updated
accordingly.
The MVAR spec only has tags for the OS/2 metrics, but it is common in fonts
to have the hhea metrics be equal to those for compat reasons.
https://learn.microsoft.com/en-us/typography/opentype/spec/mvar
https://googlefonts.github.io/gf-guide/metrics.html#7-hhea-and-typo-metrics-should-be-equal
https://github.com/fonttools/fonttools/issues/3297
"""
current_os2_vmetrics = [
getattr(varfont["OS/2"], attr)
for attr in ("sTypoAscender", "sTypoDescender", "sTypoLineGap")
]
metrics_are_synced = current_os2_vmetrics == [
getattr(varfont["hhea"], attr) for attr in ("ascender", "descender", "lineGap")
]
yield metrics_are_synced
if metrics_are_synced:
new_os2_vmetrics = [
getattr(varfont["OS/2"], attr)
for attr in ("sTypoAscender", "sTypoDescender", "sTypoLineGap")
]
if current_os2_vmetrics != new_os2_vmetrics:
for attr, value in zip(
("ascender", "descender", "lineGap"), new_os2_vmetrics
):
setattr(varfont["hhea"], attr, value)
def instantiateMVAR(varfont, axisLimits):
log.info("Instantiating MVAR table")
@ -701,6 +739,8 @@ def instantiateMVAR(varfont, axisLimits):
fvarAxes = varfont["fvar"].axes
varStore = mvar.VarStore
defaultDeltas = instantiateItemVariationStore(varStore, fvarAxes, axisLimits)
with verticalMetricsKeptInSync(varfont):
setMvarDeltas(varfont, defaultDeltas)
if varStore.VarRegionList.Region:

9
Tests/varLib/instancer/data/PartialInstancerTest-VF.ttx
View File

@ -108,9 +108,9 @@
<fsSelection value="00000000 01000000"/>
<usFirstCharIndex value="32"/>
<usLastCharIndex value="8722"/>
<sTypoAscender value="800"/>
<sTypoAscender value="1000"/>
<sTypoDescender value="-200"/>
<sTypoLineGap value="200"/>
<sTypoLineGap value="0"/>
<usWinAscent value="1000"/>
<usWinDescent value="200"/>
<ulCodePageRange1 value="00000000 00000000 00000000 00000001"/>
@ -687,6 +687,7 @@
<!-- VarRegionCount=1 -->
<VarRegionIndex index="0" value="0"/>
<Item index="0" value="[30]"/>
<Item index="1" value="[100]"/>
</VarData>
</VarStore>
<ValueRecord index="0">
@ -705,6 +706,10 @@
<ValueTag value="xhgt"/>
<VarIdx value="65536"/>
</ValueRecord>
<ValueRecord index="3">
<ValueTag value="hasc"/>
<VarIdx value="65537"/>
</ValueRecord>
</MVAR>
<STAT>

42
Tests/varLib/instancer/instancer_test.py
View File

@ -304,39 +304,69 @@ class InstantiateMVARTest(object):
assert len(mvar.VarStore.VarData) == 1
@pytest.mark.parametrize(
"location, expected",
"location, expected, sync_vmetrics",
[
pytest.param(
{"wght": 1.0, "wdth": 0.0},
{"strs": 100, "undo": -200, "unds": 150},
{"strs": 100, "undo": -200, "unds": 150, "hasc": 1100},
True,
id="wght=1.0,wdth=0.0",
),
pytest.param(
{"wght": 0.0, "wdth": -1.0},
{"strs": 20, "undo": -100, "unds": 50},
{"strs": 20, "undo": -100, "unds": 50, "hasc": 1000},
True,
id="wght=0.0,wdth=-1.0",
),
pytest.param(
{"wght": 0.5, "wdth": -0.5},
{"strs": 55, "undo": -145, "unds": 95},
{"strs": 55, "undo": -145, "unds": 95, "hasc": 1050},
True,
id="wght=0.5,wdth=-0.5",
),
pytest.param(
{"wght": 1.0, "wdth": -1.0},
{"strs": 50, "undo": -180, "unds": 130},
{"strs": 50, "undo": -180, "unds": 130, "hasc": 1100},
True,
id="wght=0.5,wdth=-0.5",
),
pytest.param(
{"wght": 1.0, "wdth": 0.0},
{"strs": 100, "undo": -200, "unds": 150, "hasc": 1100},
False,
id="wght=1.0,wdth=0.0,no_sync_vmetrics",
),
],
)
def test_full_instance(self, varfont, location, expected):
def test_full_instance(self, varfont, location, sync_vmetrics, expected):
location = instancer.NormalizedAxisLimits(location)
# check vertical metrics are in sync before...
if sync_vmetrics:
assert varfont["OS/2"].sTypoAscender == varfont["hhea"].ascender
assert varfont["OS/2"].sTypoDescender == varfont["hhea"].descender
assert varfont["OS/2"].sTypoLineGap == varfont["hhea"].lineGap
else:
# force them not to be in sync
varfont["OS/2"].sTypoDescender -= 100
varfont["OS/2"].sTypoLineGap += 200
instancer.instantiateMVAR(varfont, location)
for mvar_tag, expected_value in expected.items():
table_tag, item_name = MVAR_ENTRIES[mvar_tag]
assert getattr(varfont[table_tag], item_name) == expected_value
# ... as well as after instancing, but only if they were already
# https://github.com/fonttools/fonttools/issues/3297
if sync_vmetrics:
assert varfont["OS/2"].sTypoAscender == varfont["hhea"].ascender
assert varfont["OS/2"].sTypoDescender == varfont["hhea"].descender
assert varfont["OS/2"].sTypoLineGap == varfont["hhea"].lineGap
else:
assert varfont["OS/2"].sTypoDescender != varfont["hhea"].descender
assert varfont["OS/2"].sTypoLineGap != varfont["hhea"].lineGap
assert "MVAR" not in varfont