How can I force Mapserver to show ONLY the map extent?

[Daniele Margotti]

Hi,
I use MapServer 4.01 as CGI, with jBox.

When I pan the map (either dragging it with mouse, or using javascript pan
buttons), I'm able to go out of the original extent and I see... nothing!

I'd like, if possible, that a user couldn't show maps (or portions of
maps) if these are beyond the maximum extent of my shape files.

Can MapServer - by itself - limit visualization to visible shapes if the
request exceed established coordinates?
How can I set this "maximum extent" in the .map file?

Or should I hardcode the maximum extent in my template file and use
javascript to see if I "go out"?

I hope the question is enough clear...

Thank you,
  Daniele