[Groff] pointsize changes in .NH ms-macro

[joerg van den hoff]

dear groffers,

groff 1.19/MacOS 10.3.5 (this is _not_ the obsolete groff version 
distributed by Apple):

in the attached troff file there is a macro definition SHEAD which
essentially calls .NH including a NH-level dependent pointsize increase 
which immediately is resetted after the .NH call.
for the headings and the text body this works as expected, but there is
a problem with the footers (and headers, probably - I did not test this):

if a subsequent heading starts right at the top of a new page, the reset 
of the pointsize after the .NH call (which actually works for the text 
body) does not 'reach' text in the footer.

in the attached example: the headers should be in 16 pt, the body and 
footer in 13 pt. but the footer on page one is in 16 pt, _if_ the next 
section starts on a new page. by uncommenting the .ig-block in lines 
32-35 you get the desired result: all footers in 13 pt (because now the 
2. section does not start at the top of the second page.

it looks like the pointsize for the current footer is that which is in 
the PS register valid on the top of the *next* page (more precisely: the 
PS register itself behaves unexpectedly (at least for me)). did I miss 
something or is this a bug?

regards

joerg

.pl 29.7c  
.ll 21c-2i
.   nr PO 1.25i
.   po    1.25i       \"enforce PO on first page without additional .bp
.   nr HM 1.0i
.   nr FM 1.0i
.   if !rLL .nr LL \n[.l]u  
.   nr LT \n(LL
.   nr PS 13
.   nr VS \n(PS+4
.\"
.ds LF "pointsize: 
\\n(PS------------------------------------------------------------------
.\"
.de SHEAD
.\"inputs: $1: NH-level, $2: title
.\"------
.nr incps 4-\\$1
.if \\n[incps]<0 .nr incps 0  \"just in case ...
.nr PS \\n(PS+\\n[incps]
.nr VS \\n(VS+\\n[incps]
.NH \\$1
\\$2
.nr PS \\n(PS-\\n[incps]
.nr VS \\n(VS-\\n[incps]
.\"
..
.\"=============================================================================
.               SHEAD 1 "pointsize: \\n(PS
.\"=============================================================================
.LP
pointsize: \n(PS    test test test test test test test test test test test test 
test test test test
.ig
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.\"=============================================================================
.               SHEAD 1 "pointsize: \\n(PS
.\"=============================================================================
.LP
pointsize: \n(PS    test test test test test test test test test test test test 
test test test test
test test test test test test test test test test test test test test test test 
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