[SDL] SDL and Win32 processes

[Roger]

Hi,

I want to create an application where a piece of code associated with the SDL
window runs continually, drawing the frame and processing input, whether it is
the top window or not.  (Kind of like the way a game or emulator will continue
running in the background, but in this I want it to be part of the same
application.)

I have a console window that I want to still be able to type into and debug the
program with while it runs.  I'd like to be able to treat the background process
like a callback that is executed once each new frame.  

Does anyone have any advice on how it might be possible to do this?