[Optimoz] Check if only one browser window is open?

[Mark Lengowski]

Hi. I'm new to this list and Mozilla programming.  I have managed to
hack together a few basic gestures but I'm stuck on a couple ideas.

How can I check to see if there is only one browser window open before
attempting to close it?

It may sound silly but I sometimes get carried away with my 'close
tab/window' gesture and end up closing my last window instance.

This would also have to account for windows that are open but aren't
really 'browser' windows (e.g. this Gmail - Compose Mail window I am
typing in).  Maybe I'm alone on this one, but it's no fun to be left
with a browser window that has no menus or toolbars. ;-)

Thanks for the help.

- Mark