How to use the config system?

[simoncozens]

I need to turn off Harfbuzz repacking when compiling a troublesome font. I know there's a config option for this, but I don't really understand how to access the fonttools config system.

[anthrotype]

you'd set the relevant option in the TTFont.cfg dict-like object. E.g.

fonttools/Lib/fontTools/subset/__init__.py

Line 9 in bf6078a

from fontTools.ttLib.tables.otBase import USE_HARFBUZZ_REPACKER

and

fonttools/Lib/fontTools/subset/__init__.py

Line 3072 in bf6078a

font.cfg[USE_HARFBUZZ_REPACKER] = options.harfbuzz_repacker

You don't have to actually import the option from the module that use it, you can alternatively use the option's qualified name, in this case it's "fontTools.ttLib.tables.otBase:USE_HARFBUZZ_REPACKER"

fonttools/Lib/fontTools/ttLib/tables/otBase.py

Line 24 in bf6078a

USE_HARFBUZZ_REPACKER = OPTIONS[f"{__name__}:USE_HARFBUZZ_REPACKER"]

[anthrotype]

All the options are globally defined in https://github.com/fonttools/fonttools/blob/main/Lib/fontTools/config/__init__.py

[anthrotype]

So to answer your direct question, to force disable using harfbuzz repacker (even when uharfbuzz can be imported), you want to set your font's cfg like this:

font.cfg["fontTools.ttLib.tables.otBase:USE_HARFBUZZ_REPACKER"] = False

[belluzj]

I think what's missing is a way to pass these options on the command line or using a config file like Behdad was suggesting at some point?

[anthrotype]

yeah. I started adding support for that in ufo2ft in googlefonts/ufo2ft#607 a few months ago. Once that in place, fontmake could configure TTFont.cfg through ufo2ft API to set any relevant options, including that one.