Re: .Bl -tag -width ".mdoc macro" not recognised sometimes(?)

[Ingo Schwarze <schwarze@usta.de>]

Hi Nab,

Nab wrote on Sun, Jun 05, 2022 at 08:28:24PM +0200:
> On Sun, Jun 05, 2022 at 07:55:39PM +0200, Jan Stary wrote:

>> On Jun 05 18:16:35, nabijaczleweli@nabijaczleweli.xyz wrote:
>> Quoting mdoc(7):
>> 
>> 	The -width and -offset arguments accept
>> 	macro names as described for Bd -offset,
>> 	scaling widths as described in roff(7),
>> 	or use the length of the given string.
>> 
>> Is your -width a macro name (such as Ds) as descibed for -offset? No.
>> Is it a scalinbg width as described in roff(7)? No.
>> Apparently, mandoc uses the length of the given string then.
>> AFAICT, that's what you told it to do.

> Ah, yeah, that's fair; this is, apparently, a groffism:
>   If ⟨string⟩ starts with a ‘.’ (dot) immediately followed by a valid
>   -mdoc macro name, interpret ⟨string⟩ and use the width of the result.

I think you are right that this is a groff extension.
I did quick testing with Cynthia's final version of the 4.4BSD mdoc(7)
macros and they don't appear to support a full macro line (including
the leading dot) as a -width argument, or rather, they just take the
string length of the line, like mandoc(1) does.

Then again, Cynthia's version of the macros is very old and mandoc(1)
mostly aims for groff compatibility.  So supporting this feature is
desirable.  But it looks seriously complicated given the existing
mandoc code structure.  So it's certainly not a short-term task and
maybe not even feasible in the medium term but rather a long-term
goal.  Besides, the priority is moderate at best because i don't
recall having seen this often in practice.

>   Almost all lists in this document use this option.

I must admit i share Jan's curiosity in which real-world document
this feature is used.

In general, if a feature is used in important, widely used manual
pages, that raises the priority of supporting it - even though in
this case, admittedly, even a very high priority would help little
to overcome the significant difficulty of implementing it.

Yours,
  Ingo
--
 To unsubscribe send an email to discuss+unsubscribe@mandoc.bsd.lv