Re: Should vertical motions be in vees or ems? Where does the baseline go?

[G. Branden Robinson]

At 2021-11-17T21:17:34-0600, Dave Kemper wrote:
> On 11/16/21, Tadziu Hoffmann <hoffmann@usm.uni-muenchen.de> wrote:
> > However, if we assume they were
> > intended as an easy way to get super- and subscripts (e.g., for
> > footnote markers, or as in "H\d2\uO"), then you definitely want
> > the motion to be in units of the current font size and not in
> > baseline spacings.  Otherwise, those super- and subscripts
> > would be ripped from the text lines they belong to if you
> > were to try setting the text double-spaced by requesting
> > (say) .vs 24 for a 10-point font.
> 
> A very good point, thank you.  That does rather scuttle my argument.
> I wonder if it's worth pointing this out in the documentation of these
> escapes.

Yes, I think it does, and this is exactly the kind of clarification I
was hoping for.

Circular arguments presuming the inerrancy of CSTR #54 illuminate
little.  Tadziu's explanation is perfectly clear, and to boot does not
require insider knowledge of the abbreviation practices of the AT&T
troff source code.  Does "v" stand for "vertical" or "vee" (the unit)?
Does "m" stand for "motion" or "em" (the unit)?  Or, for that matter,
should "makem()" be analyzed as "make-m(otion)" or "mak(e)-em"?

I'll adapt Tadziu's observation into the explanatory material for these
escapes, to motivate/justify the unusual choice of vertical unit for
them.  Some of this might appear only in our Texinfo manual, though
(which now needs to be corrected outright after 19 years of saying "v").

Thank you, Tadziu!

Anyone feel game to tackle the groff/Heirloom baseline rule discrepancy?
:D

Regards,
Branden

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