ttc fonts: crash resulting from unexpected OpenType features #597
Description
I found this by accident – it seems that DrawBot’s warning OpenType feature 'xxxx' not available for xxx does not reliably work for ttc fonts.
I get
Traceback (most recent call last):
File "<untitled>", line 10, in <module>
File "/Applications/DrawBot.app/Contents/Resources/lib/python3.12/drawBot/context/baseContext.py", line 1277, in __init__
File "/Applications/DrawBot.app/Contents/Resources/lib/python3.12/drawBot/context/baseContext.py", line 1402, in append
File "/Applications/DrawBot.app/Contents/Resources/lib/python3.12/drawBot/misc.py", line 402, in wrapper
File "/Applications/DrawBot.app/Contents/Resources/lib/python3.12/drawBot/context/tools/openType.py", line 65, in getFeatureTagsForFont
File "/Applications/DrawBot.app/Contents/Resources/lib/python3.12/fontTools/ttLib/tables/otBase.py", line 890, in __getattr__
File "/Applications/DrawBot.app/Contents/Resources/lib/python3.12/fontTools/ttLib/tables/otBase.py", line 987, in decompile
File "/Applications/DrawBot.app/Contents/Resources/lib/python3.12/fontTools/ttLib/tables/otConverters.py", line 157, in readArray
File "/Applications/DrawBot.app/Contents/Resources/lib/python3.12/fontTools/ttLib/tables/otConverters.py", line 603, in read
File "/Applications/DrawBot.app/Contents/Resources/lib/python3.12/fontTools/ttLib/tables/otBase.py", line 991, in decompile
File "/Applications/DrawBot.app/Contents/Resources/lib/python3.12/fontTools/ttLib/tables/otConverters.py", line 316, in read
File "/Applications/DrawBot.app/Contents/Resources/lib/python3.12/fontTools/ttLib/tables/otBase.py", line 329, in readUShort
File "/Applications/DrawBot.app/Contents/Resources/lib/python3.12/fontTools/ttLib/tables/otBase.py", line 291, in readValue
struct.error: ('unpack requires a buffer of 2 bytes', 'SettingValue', 'Setting')to reproduce:
from fontTools.ttLib import TTCollection
from pathlib import Path
fonts = list(Path('/System/Library/Fonts/Supplemental').rglob('*.ttc'))
for font_path in fonts:
tt_collection = TTCollection(font_path)
for font_number, font_obj in enumerate(tt_collection.fonts):
try:
fs = FormattedString(
'123',
font=str(font_path),
fontNumber=font_number,
openTypeFeatures=dict(onum=True),
)
except Exception:
print(f'bad font: {font_path}')