I have the following

Buildin navigation system with 7inch 400x234 pix touchscreen.
Now lets assume that I add a carpc with the xp installed so minimum resolutin I can use is lets say 800x600. So there should be a way to map touchscreen touch coordinates into pc coordinates. How it is usually done? On what level? Yeah, I understand that I can do that on an application level but I dont think it is a good idea so most probably there are other solutions.

ps Let's assume also that I transform signals from the touchscreen into mouse clicks (so I simulate pc mouse)

Thanks for any tips