[HarfBuzz] Horizontal positions for vertical text?

[Khaled Hosny]

Hi,

It seems that almost every HarfBuzz client doing vertical text that I
checked will reverse the positions returned by HarfBuzz for vertical
text to use them as if they were horizontal. May be we should have a
buffer option to do this in HarfBuzz since it seems to be the most
common use? (this is mainly because every time I do it I get it wrong
the first few iterations :)

Regards,
Khaled