[HarfBuzz] Fallback vertical shaping?

[Khaled Hosny]

Hi,

I was looking into Firefox’s code to check how they handle vertical text
(to see why they get better results for the same font than my code), and
noticed that they try to use vertical presentation forms [1] when the
font lacks ‘vert’ feature [2]. I was wondering if this is something
HarfBuzz should be doing instead?

Regards,
Khaled

1. https://dxr.mozilla.org/mozilla-central/source/gfx/thebes/gfxHarfBuzzShaper.cpp#208-279
2. https://dxr.mozilla.org/mozilla-central/source/gfx/thebes/gfxHarfBuzzShaper.cpp#1438