transparent window even for events

[Eugen]

Hi,
I am using the composite extension (not Xdamage) to get transparent windows.
I need to create a transparent window (might be 100% transparent and maxsized) which can leave the X events to go through it. The other windows below the transparent window should get the keyboard and mouse events (even if the transparent window is above of them).

I have tried to get the answer myself, I am sorry if it's something obvious or allready available in the mailinglist archive.
Please help me to look into the right direction.
Thanks,
Eugen