[bug #60228] [ms]: should support footnote marker brackets for nroff mode

[G. Branden Robinson]

URL:
  <https://savannah.gnu.org/bugs/?60228>

                 Summary: [ms]: should support footnote marker brackets for
nroff mode
                 Project: GNU troff
            Submitted by: gbranden
            Submitted on: Sun 14 Mar 2021 03:10:50 AM UTC
                Category: Macro - ms
                Severity: 1 - Wish
              Item Group: New feature
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None

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Details:

When Berkeley added support for automatically numbered footnotes to ms in
4.2BSD, they placed square brackets around the numbers in nroff mode as an
alternative to superscripting them.

groff ms does not do this, and the output is ugly.

Input:

$ cat footnote-markers.ms 
.LP
This is my\** paragraph*.
.
.FS
numeric footnote
.FE
.
.FS
* symbolic footnote
.FE


groff Git HEAD output:

$ ./build/test-groff -Tutf8 -ms footnote-markers.ms | sed '/^$/d'
This is my1 paragraph*.
───────────
  1 numeric footnote
* symbolic footnote


Heirloom Doctools (191015) ms output:


$ ./bin/nroff -ms footnote-markers.ms | sed '/^$/d'
This is my[1] paragraph*.
_________________________
   [1] numeric footnote
   [1] * symbolic footnote
                       March 14, 2021


For historical interest, here's V7 Unix ms output (via SIMH):


$ nroff -ms foot* | sed '/^$/d'
This is my paragraph*.
__________________________
numeric footnote
* symbolic footnote
                     September 23, 1988


The undefined string * was ignored.  In V7, ms took no responsibility for
marking footnotes.

Here's Berkeley's implementation, extracted from 4.2BSD tmac.s.


.       \" \** - numbered footnote
.ds * \\*([.\\n+*\\*(.]

.if \n(.V>19 .ds [. \f1[
.if \n(.V>19 .ds .] ]\fP
.if \n(.V<20 .ds [. \f1\s-2\v'-.4m'
.if \n(.V<20 .ds .] \v'.4m'\s+2\fP


The above is inadequate for groff's purposes.  The footnote marker-bracketing
strings are conditioned on the number of basic units per vertical unit of
device output resolution, which seems to me to be a heuristic guess about
whether the device supports superscripting or not.  I would be interested to
know why the conditionals weren't simply '.if n' and '.if t'.

For groff ms I suggest we can do exactly that.

Here's our implementation:

.ds * \E*[par@sup-start]\En+[fn*text-num]\E*[par@sup-end]


I propose indirecting these par@sup-{start,end} strings through
user-configuration footnote marker bracketing strings, named perhaps FMO and
FMC (yes, three letters since groff ms doesn't work in compatibility mode
anyway).  The default would be to use square brackets as Berkeley ms does.

So something like this:


.ie n \{\
.        ds FMO [
.        ds FMC ]
.\}
.el \{\
.        als FMO par@sup-start
.        als FMC par@sup-end
.\}
.ds * \E*[FMO]\En+[fn*text-num]\E*[FMC]


Thoughts?




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