> > Clearly Ghostview talks to Ghostscript in some fashion. Is the actual
> > communication protocol between the two documented in some fashion other
> > than the source code?
> It opens a pipe and talks postscript to it I'm sure.
Ah, I had hoped that you might actually know. There is an additional
protocol using X Client Events that runs between ghostscript and
ghostview. Also, the environment variable protocol you described seems
to be more complex; it's more like
setenv GHOSTVIEW "<window-id-1> <window-id-2>"
where <window-id-1> is the window on which ghostscript is supposed to
render, and <window-id-2> is the window to which ghostscript sends
events, in order to run this out-of-band additional protocol. I believe
setenv GHOSTVIEW "<window-id>"
will also work in some fashion, though I don't know to what extent the
protocol will be crippled.