Ah, great, thanks. I've actually ran into it just before I saw your
posting, purely by accident, when I happened to look at the source for
panel.xyplot while looking for something else, and noticed the "type"
argument, and in particular the handling of type='h'... I didn't
realize plot(type='h'...) makes use of plot.xy(), otherwise the
plot.xy(graphics)->xyplot(lattice) move would have been obvious...