Does Qt Widgets has SOftware OVERLAY support.

[aashish.lg]

I am building my application using QWebView that intern derives from QWIdget only.
I would like to add software overlay suppport for my application, so that I can specify some colorkey , so that while drawing wherever be that colorkey matches on the screen my widget window will be drawn and in case of colorkey mismatch window will be clipped.

Please provide some details wheather is it possible using qt?

Regards
Ashish