quakespasm-entire-engine

Quakespasm is a heavily retooled version of glquake

    Glquake is a port of DosQuake (if that is it's name) to OpenGL made by Id Software 
  (probably programmer John Carmack).

    This means that Quakespasm doesn't use SVGA anymore. Secondly Quakespasm is glquake 
  only which means it doesn't carry over the software render. It also has multiple 
  improvements and speedups to the quake engine and refactors alot of code such as the 
  function GL_Blend (if that is the name of it).

    It also probably fixes that bug where the internal loop uses the same loop iterator 
  variable as the one it is nested in, could probably figure out where that is. 

Quakespasm is written in C (like all original quake)

    Id Software did not accept C++ until Id Tech 4 or Doom3 (doom3 engine was not called 
  id tech 4 until later). Quakespasm uses SDL 1, and it has some info in there for SDL2 
  usage some #includes or #ifdefs or #ifndefs. "CRC" appears to be a quick hashing 
  algorithm like MD5 or SHA256 or 512 "for verifying maps of some kind".

1. Main function

    the main function is located in main_sdl.c. Original quake presumably doesn't have
  main_sdl so perhaps this was derived from sdl quake or created by  quakespasm developer 
  itself. Also quakespasm is derived from fitzquake, so it has "fitzquake emulation" mode 
  if that is the name. (figure out what version this is specifically documentating for)

    So the file "renderer.doc" will "focus first on the renderer", because that's what you 
  see on the screen. So then "How it gets to the renderer from main"