[Groff] Odd ms Macro Page Offset Register Behavior

[Andrew J. Piziali]

   This morning I spent a few hours trying to figure out why the page
offset of the second and subsequent pages of an ms document was
different than the first.  Rereading the ms documentation (Kollar's and
Lesk's), I discovered that the PO register is not intended to take
effect until the next page.

   However, the odd behavior I uncovered in the process is that the page
offset only appears to apply to subsequent pages if a preceding .if
directive succeeds.  Invoking groff as:

        groff -ms -Tps MyDocument.ms >MyDocument.ps

and using the following text as an example:

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
.if 1 \{
.  nr xy 12
.\}
.nr PO 1.875i
.NH 1
Xxxx Xxxxxxxx
.PP
Xx xxxx xxxxxxx X xxxxxxx xxx xxxxxxx xx xxxx xxxxxxxx \- xxxxxxxxx
xxxxxxxx xx
xx xxxxxxxxxx xxxxxxxx, xxx xxxxxxx xxxxxxx xxx xxx xxxxxxxxx xxx xxxxx.
.PP
Xxxx xxxxxxxx, xx xxx'xx xxxxxx xxxx xxxxxxx x, Xxxxxxxxx Xxxxxxxxxxxx
Xxxxxxxx, xxxxxxx xx xxxxxxxx xxxxxxxxxxxxxx xxxxxxxx xxxxx.
Xx xxxxxxxx xxxxxxxxxxxxxx xxxxxxxx xxxxx xx xxx xx xxxxx xxx xxxxxxxx
xxxxxxx
xxx xxxxxxx xx xxx xxxxxx xx xxx xxxxxxxxx xxx xxxxxxxxx xxxx xxx xxxxxx
xxxxxxxxxxxxxx.
'\"
'\" Add a sufficient number of paragraphs of text to fill several pages.
'\"
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

the second and subsequent pages of this document have a page offset of
1.875 inches.  However, if the ".if 1" is changed to ".if 0" the page
offset remains the default value of 26/27 inches.

   What might be the explanation for this bizarre behavior?

   Thanks.


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