[Groff] Re: Disabling SGR in grotty(1): gory details

[Werner LEMBERG]

Please run the following small fragment with AT&T nroff:

  .pl 5v
  foo
  .sp 3
  foo
  .sp 3
  bar

I get the following:

  foo



  foo
  bar

and I want to know whether AT&T does the same -- just to be sure.

In groff, .sp first causes a break internally, then it does the
vertical move.  If this internal break springs a trap (either an
explicit one or the implicit new page trap which groff uses to eject
the current page) it doesn't do further vertical motion.

Two solutions:

  a) Disable vertical traps temporarily:

       .vpt 0
       .sp -2
       .vpt 1

     You need this if you move up with .sp.

  b) Explicitly use a break if no previous command has caused one:

       .br
       .sp 2

My new solution to Ruslan's problem triggered the bug -- I've just
fixed the man macros (and I will check the mdoc macros soon).

I don't think other macro packages are affected, but I invite you to
check this.


    Werner