What is Linux’s native GUI API?

Question

Both Windows (Win32 API) and OS X (Cocoa) have their own APIs to handle windows, events and other OS stuff. I have never really got a clear answer as to what Linux’s equival

Answer 1

The linux kernel graphical operations are in /include/linux/fb.h as struct fb_ops. Eventually this is what add-ons like X11, Wayland, or DRM appear to reference. As these operations are only for video cards, not vector or raster hardcopy or tty oriented terminal devices, their usefulness as a GUI is limited; it's just not entirely true you need those add-ons to get graphical output if you don't mind using some assembler to bypass syscall as necessary.