typeface.getVariationDesignPosition() not working as expected about skia-python

[justvanrossum]

I managed to rewrite my code so it doesn't rely on typeface.getVariationDesignPosition() anymore, and fontargs.setVariationDesignPosition() works perfectly, so this is no longer a blocking issue for me. Feel free to close or reclassify as feature request.

[kyamagu]

Thanks for reproducing this, let's keep this issue open since the fundamental issue isn't yet resolved

[kyamagu]

This is likely due to an internal fontconfig issue. Need to check if fontconfig version matters.

[justvanrossum]

FWIW: as of 87.1, this issue persists on Linux, but seems to have been resolved on Win and Mac.

[HinTak]

Not a fontconfig issue but a freetype issue. According to Skia's c++ source code, this routine has at least 3 different implementations - directwrite, coretext, freetype, being 3 of them... likely freetype too old on the wheel.

[HinTak]

I think I know exactly why this is broken - if you get the wheel prebuilt skia-python binary from pip, it uses the "locked" freetype version bundled with m87. So until and unless you build skia-python entirely from source, and make it depends on your system's up-to-date freetype (I have such an option in my private fork), or you switch to a much later skia (with a much later Locked freetype version), you are stuck with this bug.

[HinTak]

The line to change is around

skia-python/scripts/build_Linux.sh

Line 57 in 5d92743

skia_use_system_harfbuzz=false

, and also additional linker flags in the main setup.py. I see the pip-installed skia-python m87 has a private copy of very old freetype (2.8, i think - I dug it up properly and commented elsewhere) rpath'ed in its own private directory under pythonlib.

[HinTak]

Actually you might be able to fix it in the pip wheel, by patching skia's DEP file, to bundle a different freetype version.

[HinTak]

Those are relatively new routines in freetype so the version of freetype definitely matters.

[HinTak]

My system's freetype is up to date but I ended up having to make such a change to make m116 build in CI 8cf897f - this might give you some idea what to do if you want to fix m87.

[HinTak]

This seems to be fixed with 117bx (and possibly with 116b2) .