Re: [Groff] .ss problem

[Tadziu Hoffmann]

> > > > Before fixing, a general question.  In Unix troff, .ss is ignored
> > > > if in nroff mode.  Shall GNU troff behave identically if
> > > > compatibility mode is on?  Does it really make sense to `cripple'
> > > > GNU troff for compatibility reasons?

The interesting thing is that the Troff User's Manual states
that (Unix) nroff has an option to ``produce equally-spaced
words in adjusted lines, using full terminal resolution.''
If this implies that there are typewriter-like devices with
better-than-character-cell horizontal positioning, it makes one
wonder why `.ss' should be ignored completely in nroff, instead
of the more natural notion that `.ss' should accept all
arguments compatible with the horizontal resolution of the
device.

Therefore, I would agree that source-level compatibility is
much more important than exactly mimicking seldom-used features
--- meaning, ``behaves as intended'' (whatever we choose to mean
by that) rather than ``behaving exactly as''.
(Did anybody ever rely on `.ss' being ignored in nroff, anyway?)

Remember, this issue is actually the largest ``philosophical''
difference between TeX and troff:  whereas TeX intends to give
the same formatting on all devices (which is then ``realized''
as best as possible by the DVI driver), troff attempts to give
the best formatting possible for the device.  On this premise,
it is permissible for ``my'' [g]troff to give different
formatting than ``your'' [g]troff for the same output device,
as long as macros and requests behave similarly in the sense
that they behave similarly when formatting for different output
devices.

With this in mind, I agree with everybody else in that it does
make sense to support `.ss' also in nroff mode.

> In that case I think it is more fair to say that we have a GNU troff
> but no GNU nroff.  Our troff just happens to be able to output to
> tty-like devices [...]

Well, actually that's really not too different from Unix troff:
According to The Manual,

  nroff necessarily cannot support all features of troff. Within
  that limitation, it is the same as troff, and in fact there is
  only a single program invoked by two different names.


Cheers,
Tadziu