Re: [Groff] Vertical position not affected by .sp request

[Tadziu Hoffmann]

> So it looks like -me and -ms break the .sp request in this context.

Well "break" is probably not the right word, since it implies
that this behavior is "not correct", whereas the behavior is
actually intended.  The macro packages set up a top margin
and skip this margin when outputting text.  Additionally,
they might set the "no space" flag, to disable vertical space
from being output at the top of the page (e.g., you might want
a small space between paragraphs, but not before a paragraph
that begins on a new page).

I think that the vertical position is initialized to -1 before
any text has been output is also by design, to be able to set
page margins on the first page with a ".wh 0 xx" trap.
To quote the Troff User's Manual:

  A pseudo-page transition onto the first page occurs either
  when the first break occurs or when the first nondiverted
  text processing occurs. Arrangements for a trap to occur
  at the top of the first page must be completed before
  this transition.