[ REQ 6867]: `Pause until key is pressed'

[gartside at maths.ox.ac.uk]

I wish to use geomview (running on my laptop, which will be attached to
a data projector) to animate in real time some geometric objects, as part
of a conference talk.

I have written gcl files which perform the manipulations (using Stage
Manager).

My question: is there a gcl command which will pause execution until a key
is pressed (or a mouse button is clicked etc). I could not find such a
command in the manual. Can you suggest some devious method ?!

My computer is an Intel 686 running Linux and X windows.

With thanks,
Paul.