I've just revised the documentation of .em -- maybe you haven't known
these limitations...
Werner
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-- Request: .em macro
Set a trap at the end of input. MACRO is executed after the last
line of the input file has been processed.
For example, if the document had to have a section at the bottom
of the last page for someone to approve it, the `em' request could
be used.
.de approval
\c
. ne 3v
. sp (\\n[.t]u - 3v)
. in +4i
. lc _
. br
Approved:\t\a
. sp
Date:\t\t\a
..
.
.em approval
The `\c' in the above example needs explanation. For historical
reasons (and for compatibility with AT&T `troff'), the end macro
exits as soon as it causes a page break and no remaining data is
in the partially collected line.
Let us assume that there is no `\c' in the above `approval' macro,
and that the page is full and has been ended with, say, a `br'
request. The `ne' request now causes the start of a new page,
which in turn makes `troff' exit immediately for the reasons just
described. In most situations this is not intended.
To always force processing the whole end macro independently of
this behaviour it is thus advisable to insert something which
starts an empty partially filled line (`\c') whenever there is a
chance that a page break can happen. In the above example, the
call of the `ne' request assures that the remaining code stays on
the same page, so we have to insert `\c' only once.
The next example shows how to append three lines, then starting a
new page unconditionally. Since `.ne 1' doesn't give the desired
effect - there is always one line available or we are already at
the beginning of the next page - we temporarily increase the page
length by one line so that we can use `.ne 2'.
.de EM
.pl +1v
\c
.ne 2
line one
.br
\c
.ne 2
line two
.br
\c
.ne 2
line three
.br
.pl -1v
\c
'bp
..
.em EM
Note that this specific feature affects only the first potential
page break caused by the end macro; further page breaks emitted by
the end macro are handled normally.
