where can I change the default font in the source topic

Hi,

I'm new with android ROM cooking. The compile from PC-Man and CM sources is working fine. I was able to change some little things (default wallpaper / bootanimation). But now I want change the default font.
Does any one knows, where it is defined ? I know, I can change it after the rom is flashed, but I want change it in the sources.

Thanks,
Harvey