skia.Typeface.MakeFromFile() (ttc)index argument not working about skia-python

[justvanrossum]

Oh, I just ran this on GH Actions on Linux and Win and macOS: the problem only exists on macOS.

[HinTak]

Since it is just a direct call to a single upstream routine:

skia-python/src/skia/Font.cpp

Line 575 in f71fdee

return SkTypeface::MakeFromFile(&path[0], index);

, I think it is an upstream bug and you should report it upward. FWIW, I put a test through GH action with m117 and it is still failing, on mac os x, and only on mac os x. So you should file upstream against m117 / current.

[HinTak]

Just a heads-up: this API is being deprecated upstream in skia https://github.com/google/skia/blob/main/relnotes/typeface.md - so we'll have to either emulate it in skia-python for backward-compatibility, or just drop it, in m120+ .

Either way, you might consider using the FontMgr API as it says... I had an impression that there is no platform-specific APIs in skia-python (except the one I added a couple of months ago on COLRv1 fonts on freetype-based platforms), so it probably does not exist in skia-python yet. So here is a chance for you to influence how FontMgr_mac_ct should work in skia-python, for it to be added.

[HinTak]

Filed upstream https://issues.skia.org/issues/310510989

[HinTak]

See also #213 - that might workaround this issue when it lands. The tests already include a variant of this test set.

[HinTak]

I think skia.Typeface.MakeFromFile(p, N) is equivalent to invoking the default system font manager (CoreText) like this:
skia.FontMgr().makeFromFile(p, N) which does not work against CoreText. This is filed upstream
https://issues.skia.org/issues/310510989.

However, while looking for something else, I came across some info that Chrome on all platforms can use FreeType for font formats which the host font manager does not support - this include CBDT color fonts on Apple, variation fonts on old versions of windows, and etc. This is invoked via
skia.FontMgr.New_Custom_Empty() to get a "custom (ie based on freetype and non-host) Empty (have no access to system platform built-in fonts)" font manager, and load your font via this custom empty font manager:
skia.FontMgr.New_Custom_Empty().makeFromFile(p, N) .

And I have tested this in my playground pull HinTak/skia-m1xx-python#6 , and tidy up in #210 .

So if you really want it to work with the default CoreText based font manger, bug Google folks at the upstream URL; if you just like it to work "somehow" on mac OS, when m120 #210 get merged, you can do load via freetype on mac os with:
skia.FontMgr.New_Custom_Empty().makeFromFile(p, N) .

Of course I would like CoreText to work... close for now.