roff escaped space character

roff escaped space character

[Ingo Schwarze]

Hi Kristaps,

on September 23, 2009, you have put the following descriptions
into mandoc_char(7):

  .It \e~ Ta non-breaking, non-collapsing space
  .It \e  Ta breaking, non-collapsing n-width space

However, chars.in has this:

  CHAR(" ", ascii_nbrsp, 160)
  CHAR("~", ascii_nbrsp, 160)

So the two are the same, which is correct behaviour for -Tascii.
I have just added a few lines to

  http://www.openbsd.org/cgi-bin/cvsweb/src/regress/usr.bin/mandoc/char/space/nobreak.in

showing that the code is indeed correct.

So, groff actually handles "\\ " as non-breaking as well.

Checking the current version of groff_char(7), i find this:

  160  the ISO latin1 no-break space is mapped to `\~', the stretchable
       space character.

However, i fail to find anything regarding "\\ ".

Apparently, the difference is that "\\~" is stretchable,
while "\\ " is fixed-width 1n?

Do you still remember where you got the idea from that "\\ "
is breaking (and 1n), or am i missing something?

The following would have to be changed if it turns out
that's actually a documentation error:

 * mandoc_char(7), subsection "Spaces":
   Part of that would have to be rewritten.

 * mandoc_char(7), SPECIAL CHARACTERS section:
   \   non-breaking, non-collapsing n-width space
   \~  non-breaking, non-collapsing strechable space

 * att.in, lib.in, st.in, mdoc_html.c, man_html.c:
   We might keep "\\~" there in case we ever implement
   variable width fonts in -Tps to get nicer spacing;
   or should we use "\\ " to give a better example
   regarding portability?  I tend to leave that as it is.

I tought i might ask first before spending time cooking up
actual patches...

Yours,
  Ingo
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