pdfroff and tables of contents

[T. Kurt Bond]

The pdfroff man page says:

It transparently handles the mechanics of multiple pass groff  processing,
 when  applied to suitably marked up groff source files, such that tables
of contents and body text are formatted separately, and are subsequently
 combined  in  the  correct order, for final publication as a single PDF
document.


What does "suitably marked up" mean?  Looking at pdfmark.ms I see that it
is marked up with the .XN macro,which it says is to used to addressed ms's
"standard mechanism for generating a table of contents entry based on the
text of the section heading; neither is there any recognised standard
method for establishing a cross reference link to the section."  (This
seems to ignore the .TC macro entirely, which does output a table of
contents built from the text of the section headings, just at the end of
the document, not at the beginning.)   Other than its use in pdfmark.ms
there seem to be no documentation for .XN.  The section in pdfmark.ms about
.XN has no contents, alas.

Would it be worth mentioning the existence of pdfmark.pdf (and pdfmark.ms,
since its use of .XN is the only example) in pdfroff(1)?
-- 
T. Kurt Bond, tkurtbond@gmail.com, https://tkurtbond.github.io