Porting DOOM (1993) to WebAssembly

Stahlstadt.js #25 on April 23, 2020
https://manu.ninja/
https://github.com/Lorti/sdldoom.wasm
https://www.twitch.tv/videos/600357768?t=01h29m15s
https://www.youtube.com/watch?v=lZnz46a58_Y

Transcript

1. Manuel Wieser, 2020-04-23 Porting DOOM (1993) to WebAssembl y StahlstadT.js https://manu.ninja, @manuelwieser
5. Which DOOM source port should I use?
7. Attempt #1 Chocolate Doom
8. Chocolate Doom Attempt #1 • Chocolate Doom has a separate repository for its build system • git clone https://github.com/chocolate-doom/chocpkg.git • cd chocpkg
 ./chocpkg/chocpkg build chocolate-doom • It fetches and compiles all of its dependencies • chocolate-doom-3.0.0 • SDL2_mixer-2.0.4 • SDL2_net-2.0.1 • SDL2-2.0.12
9. Where do I get DOOM.wad?
10. S egmentation F ault
11. Attempt #2 GZDoom
12. GZDoom Attempt #2 • brew install 
 jpeg-turbo fluid-synth openal-soft libsndfile mpg123 • git clone https://github.com/coelckers/gzdoom
13. GZDoom Attempt #2
14. Problem #1 How the hell does make work?
15. make C/C++ build automation • ./configure
 make • make reads a Makefile on how to build a program. • This is easy, if you stay on the same platform … if not, there’s other tools like Autoconf and CMake … they build a build script. To do this they have their own configuration files … http://www.c-howto.de/tutorial/makefiles/
16. CMake A cross-platform build system generator • mkdir build
 cd build
 cmake ..
 # cmake --build . • I was told there’s a GUI? • cmake-gui • ccmake • If you [C] Configure often enough, you will be able to [G] Generate …
17. Problem #2 ZMusic
19. ZMusic F ighting the monolith, I guess? • cmake .. throws a Could NOT find ZMusic (missing: ZMUSIC_LIBRARIES ZMUSIC_INCLUDE_DIR) error. • I was able to build ZMusic on the first try • cmake --build . finally compiles GZDoom, which takes ages on my MacBook Air (13-inch, Mid 2013). • ./gzdoom.app/Contents/MacOS/gzdoom
20. Emscripten Getting Started
23. Emscripten C/C++ to asm.js/WebAssembl y • “Using Emscripten is, at a base level, fairly simple.”
 – Emscripten Tutorial • “Building large projects with Emscripten is very easy. Emscripten provides two simple scripts that configure your makefiles to use emcc as a drop-in replacement for gcc — in most cases the rest of your project’s current build system remains unchanged.”
 – Building Projects
24. Emscripten C/C++ to asm.js/WebAssembl y • emcc -v • emconfigure ./configure
 emmake make • emcc project.bc -o project.html • emcc compiles the bytecode generated by make to JavaScript, 
 builds a project.html file as an output, 
 as well as an accompanying project.js launcher file, 
 and a project.wasm WebAssembly file.
25. Problem #3 What the hell is this thing building? It's not simple C code anymore ...
26. Attempt #2,5 Chocolate Doom and Emscripten?
28. All of this fluff is nested and complicated ...
29. Attempt #3 SDLDoom
31. SDLDoom Attempt #3 • SDLDoom is a minimalistic port of Doom by Sam Lantinga • Released in 1998, its based on the code released by id Software in 1997 • Simple DirectMedia Layer? • Sam Lantinga? • It’s a single folder with C code and a configure then make build process
32. SDLDoom Attempt #3 Fix compiler errors
33. SDLDoom Attempt #3 Live codinG
34. SDLDoom Attempt #3 1. Fixing compilation errors • You should hack this file for your BSD sockets layer • SDL_byteorder.h file not found • implicitly declaring library function alloca 2. Fixing runtime errors • failure to dynamicAlloc • Game mode indeterminate. • Uncaught CopyOnLock is not supported for SDL_LockSurface • The game shows a black screen, then halts at the closing credits • wasm streaming compile failed 3. Profit
37. What I've learned Key takeaways • Stay humble, new stuff is always daunting • Stuff you wrote may not run in a couple of years/months • Front-End Developers are not the only people … • … dealing with platform-specific problems • … creating overly complex, nested build systems • Don’t try to tackle the complex problem first, start small
38. What I've learned Key takeaways • Doom is still fun after 27 years • Porting C code to the web platform is not a one-click solution, 
 even with tools like Emscripten • Ports can be impressive work on their own • Sh*t about the Doom engine (not part of this talk)
40. Manuel Wieser, 2020-04-23 Porting DOOM (1993) to WebAssembl y Questions? StahlstadT.js https://manu.ninja, @manuelwieser