SDL_mixer reads loop information from WAV files if you use the Mix_Music
interface, but NOT the Mix_Chunk interface. So bgm now uses the
Mix_Music interface to get proper looping.
There's also some code here for reading bgi files (taken from xsystem35)
but it's not actually used. There doesn't seem to be a simple way to set
up custom loops with SDL_mixer.
- Create separate directories for source and header files.
- Build code shared between xsystem4 and aindump as a static library.
- Create header dirs gfx/ system4/ and vm/
- Make CG.c/h usable without a running VM