Drawing Transparent Plane with holes in GDI+

Answer 1

This is a way to do it: (although it doesnt sound fast, it uses pure blitfunctions so potentially it could be fast enough)

1. Create an offscreen bitmap the size of your window. (you only need to do this once, you could keep it for subsequent paints)
2. Fill it with the solid color.
3. Cookiecut holes in the offscreen bitmap with a distinct color (purple for instance)
4. bitblt the entire bitmap onto your window, half opaque and with purple as the colorkey. (so purple is not copied).