graphical output on win xp with gnavi-package

[duke_luke@gmx.de (Duke Luke)]

Hello,

now most things are working as they're supposed to.
i programmed a nice tetris with the gnavi package and everything is
great.

i have only one problem left: 
when i create a window (canvas) and paint in it, it works as long as i
dont change its focus.
any time i change its focus, the whole window becomes blank and
nothing can be drawn on it further.
=> this means, one cant even click on the window to activize it,
because that would make it blank!

why does this happen and what can i do about it?
do i have to use another package? which?

Greetings,

Lukas