clipping stuff

Hi,

i want to create an application using bttv/video4linux
for my MiroPCTV, but one problem bothers me:
each time i move/resize the window containing the overlay
window, i must apply clipping. This creates some trash on the
screen. By reading the source of some other applications
(xawtv, kwintv), i've understood that by mapping/unmapping
a window i can remove this trash. This solution makes the handling
of X11 events quite complicated, and i am really clueless about
the "algorithm" to use for handling all the events (ConfigureNotify,
Expose, Visibility ...).

I believe that many developers encountered this problem, and i wanted to
know how they solved it (maybe simply by throwing away the overlay stuff
and using Xvideo :).

Thanks in advance,

Thomas