Re: [Groff] Cross references

[Keith MARSHALL]

Meg McRoberts wrote:
> I believe Amber's question was not how to build a PDF or PS
> file, but how to create cross-references that become hot links
> in the build document.  I don't think raw groff has this
> capability...

I guess this *is* what Amber is asking, so Larry's and my replies
perhaps don't give the full story.

Amber wants to know how to create `hot links' in PDF or PostScript
documents; note that `hot links' implies that the document is to be
viewed on-screen.  For PDF documents, such links are implemented
using `pdfmarks';  the pdfmark.tmac macro package provides the
`pdfhref' macro, to facilitate the creation of such `pdfmarks'.
Specifically, `.pdfhref M ...' will create an anchor, to which a
link may refer, and `.pdfhref L ...' creates the `hot link'.
(There is also the `.pdfhref D ...' variation on `.pdfhref M ...',
which makes it possible to define an external anchor, to enable
`hot link' references across document boundaries).

Raw groff *does* make it possible to create such links -- after
all pdfmark.tmac must eventually resolve all its macro expansions
down to raw groff code.  However, using the macro package will
take a lot of pain out of the process, should you feel tempted
to try writing the raw groff code yourself; it is a far from
trivial exercise!

As a page description language, raw PostScript seems to me more
geared towards preparing documents for printing, rather than for
on-screen display.  Thus, its support for `hot links' probably
isn't fundamental to the language definition.  However, I'm no
PostScript expert, and I have no idea how PostScript viewers
handle such features -- perhaps they also rely on the `pdfmark'
mechanism, in which case, the `pdfmark' macros could also work
for raw PostScript intended to be viewed on-screen.

> Does ps2pdf no longer work?  It worked fine for version 17.1
> but I haven't been able to get it to work for ps files generated
> with 19.1.  I'll have to try it again with the new version.

`ps2pdf' is simply a wrapper around GhostScript, so there is no
reason why it shouldn't still work with current groff versions.
In `pdfroff', I chose to invoke GhostScript directly, rather than
to use yet another intermediate wrapper. `Pdfroff' also provides
a level of document pre-processing, through multiple groff passes,
to ensure that `.pdfhref' cross references are properly resolved;
`ps2pdf' doesn't have this capability, so if you use it instead of
`pdfroff', your `hot link' cross references are unlikely to work.

HTH.

Keith.