noticing focus loss for a popup widnow

[Stefan Kost <ensonic hora-obscura de>]

hi,

I use popup window (such as the one from the volume applet). When I
click my items on the scren I show the volume popup (a window containing
+/- buttons + a scale). I looks good and the buttons can be used. Now
the problem is that I want to hide it when one clicks somewhere else
(outside the popup).
I've seen Ronald Bultje asking this in may 2005 for the volume applet
and I've also looked at the code, but can't figure it out :(
I've monitored focus, focus-out, move-focus events for the widnow to no
avail. Any idea?

Stefan