alt-tab interface

[Owen Williams]

I've been hacking the donut[1] under Marco's supervision
(http://dev.laptop.org/ticket/554), and one of the things I'm doing is
writing an alt-tab UI.  When using alt tab, the act of releasing the alt
key is what selects an activity.  I need to know not only when alt+tab
has been pressed, but also when tab is being held or not held.  Looking
at the code for sugar-key-grabber I don't think this will work.  What's
the best way to watch for MOD1 press events?

thanks,
owen

[1] this is a more modest goal; a prelude to one day hacking a
_whole_planet_.