Re: [Groff] Nesting font macros in man pages

[Ingo Schwarze]

Hi,

Bjarni Ingi Gislason wrote on Thu, Apr 27, 2017 at 04:00:29AM +0000:
> On Mon, Apr 24, 2017 at 11:41:22AM -0400, G. Branden Robinson wrote:
> > At 2017-04-24T16:22:37+0100, Ralph Corderoy wrote:

>>> .SM affect the next input line as it uses an input trap, `.it'.  `\c'
>>> doesn't make an input line continue to the next as far as input traps
>>> are concerned;  groff has .itc for that.  So the .SM is over by the `)'.

>> That's exactly the hack I wanted to make to the TP macro.  I want to
>> change its .it to an itc, thus:

> One can use the transparent line indicator (\!) to use macros in a label,
> without changing the '.TP' macro:
> 
> .TH testman 1 2017-04-DD
> .TP
> \!.B \-scale \c 
> .IR xfac [, yfac ]
> Multiply the horizontal and vertical window size by

The \! escape seems at least as arcane as \c.  Besides, the
documentation for groff and Heirloom is noticeably different.
Groff talks about diversions only, while Heirloom says that diversions
are merely one example where this escape can be applied.

I'm not even sure anything requires that .TP must be implemented
in terms of diversions.  My impression is that this use of \! depends
on internal properties of the particular implementation in groff.

Please, when designing recommendations for how to write manual
pages, let's not digress into a cleverness contest trying to make
the end-user dig as deeply as possible into roff internals...

You don't really want to say that the above is in any way better
than using well-established, easy-to-understand, and certainly
portable font escapes, right?

Yours,
  Ingo