cpm-libgsx
GSX functions library for CP/M (...and SDL2 with SDL2_gfx)
This library can be built for either CP/M or UNIX systems. On UNIX systems it depends on the SDL2 library (along with the SDL2_gfx).
For CP/M, this library should compile with LLVM's Clang patched for Z80 architecture support. To build test applications you need to link them against CP/M C library (see my other project, cpm-ulibc).