[bug #64866] [troff] throws useless warning about `bd` request in nroff mode

[G. Branden Robinson]

URL:
  <https://savannah.gnu.org/bugs/?64866>

                 Summary: [troff] throws useless warning about `bd` request in
nroff mode
                   Group: GNU roff
               Submitter: gbranden
               Submitted: Mon 06 Nov 2023 03:21:04 PM UTC
                Category: Core
                Severity: 2 - Minor
              Item Group: Warning/Suspicious behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None


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Follow-up Comments:


-------------------------------------------------------
Date: Mon 06 Nov 2023 03:21:04 PM UTC By: G. Branden Robinson <gbranden>
Observed when building NetHack.


cat Guidebook.dated.mn | ../util/makedefs --grep --input - --output - \
| tbl tmac.n - | nroff -c -Tascii  | col -bx > Guidebook.txt
troff:tmac.n:762: error: cannot load font 'S' for emboldening


Terminals are unlikely to support an `S` font, so my first instinct was just
to modify _tmac.n_ to prefix the `bd` request with `.if n`.  But technically
that might not be allowed by its license
([https://github.com/NetHack/NetHack/blob/NetHack-3.7/doc/tmac.n#L17 "please
do not distribute this package if you make any changes"]).

But that was okay, because it made me stop and think longer.

Terminals can't do what `bd` is defined to do in the first place.  Some of
them can overstrike, but not with tiny (and reliable) offsets.

So, in nroff mode, GNU troff should ignore the `bd` request like it does, say,
`ps`.







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