[luatex] \predisplaydirection from etex in luatex has no effect

[Taco Hoekwater]

Vafa Khalighi wrote:
> 
> Hi Taco
> 
> Thanks a lot for this fix.
> 
> The good news is that the bug that exist with pdftex and xetex, does not
> exist with luatex.
> 
> The bad news is that, this fix introduces two new bugs shown in the
> attached.

This stuff is trickier then one would expect, because of interactions
between \mathdir, \pardir, and \leqno / \eqno. So let's forget about
the ability to set \predisplaydirection manually for a moment, and
focus on the core functionality first.

The big question is this: should \eqno and \leqno adhere to \pardir,
to \mathdir, or simply be physical right and left without regard to
direction specifiers at all? I don't know the answer to that, so
somebody has to enlighten me.


Best wishes,
Taco