Optimizing polygon clipping in QGraphicsScene drawing

Hi,

I have a custom foreground implementation for my QGraphicsScene.
I draw a lot of polygon; Polygon clipping is yet very slow( I know that it will be working much faster in Qt4.5). I am looking for a solution for faster polygon drawing;
I draw a part of a map, coords in(-180,-90,180,90) build of polygons without borders;
I am thinking about this kind of a solution:
I would like to first paint my polygons on a image/pixmap, then paint the pixmap/image in the scene foreground; Maybe it will work faster?

I would like to consult this idea.

Thank you for any comment.

Kacper

It will work faster only if you won't redraw the contents of that pixmap in every paint event. Otherwise you will be doubling the work, since every widget already has a backing store.