Re: luatex problems with texinfo.tex

[Karl Berry]

    I agree it should be skipped. 

In some ideal world, but in this world, I think doing so would lead to
huge problems.  For the present, it seems far more feasible to me to
keep using the UTF-8 code in texinfo.tex for the immediate problem than
refactor all the font stuff, all the character support, all the engine
support, etc., to take account of native UTF-8.

    The only drawback is that documents may look slightly different
    between tex/pdftex and luatex/xetex due to different glyphs being
    used, 

There are other drawbacks.  you have to switch to a UTF-encoded font,
and nothing in texinfo.tex is ready to do that now.  Nor is it easy to
do.  Furthermore, even if it were done, any character not present in the
font would simply be lost.

Also, clearly the native UTF-8 support in xe/luatex must be disabled for
Texinfo documents that are *not* in UTF-8, so there needs to be a way to
disable the UTF-8 interpretation anyway.

    Does anyone know how to check whether luatex or xetex is being used
    in TeX?

\luatexversion
\XeTeXrevision
See, e.g., ifxetex.sty, ifluatex.sty, ifplatform.sty.

You also want to know if (for luatex) the output is PDF (ifpdf.sty, good
luck reading that one), which gets more complicated.  And upcoming
incompatibilities in luatex will make the situation worse, as I wrote
you before, Gavin.

    Is there a simple correspondence between
    naming of 8-bit Computer Modern and the super fonts?

I wouldn't call it "simple".  There is code in texinfo.tex now
(\etcfont) to use cm-super, via the ec* and tc* tfms, for various
characters not present in CM, such as eth, thorn, ogoneks (@DH{}, @TH{},
etc.).  Switching to it for everything does not seem like a good idea to
me, since it is certainly possible to have a usable TeX installation
without cm-super at all.  And, I fail to see how cm-super solves
anything about UTF-8.

    Do you know of any way to go back to byte-wise input instead
    of input by UTF-8 characters?

Of course it's possible (and I think it is the right thing to do),
otherwise the millions of TeX documents not written in (not to mention
predating) UTF-8 and Unicode could not be processed by those engines.
However, I'm afraid I don't have simple chunks at hand for the job.  I
wish I did.  But you can look up the documentation and figure it out at
least as well as I can.  -k