Painting on overlay surfaces

Hi!

In AVS (Settings -> Display) you can check the button
"overlay" which directs the visualization onto the
windows background (which is very cool).

As I received no response from a graphics newsgroup,
I put my question to you: How can I program that stuff?
I don't have much knowledge of DirectX, so the more
detailed the answer is, the happier I am :-))

Merry christmas and "good slip into new year" (word-by-word
translation from German). 😁

stem