nodejs

Run doomkit from Node.js

Node can drive doomkit three ways. This example uses koffi, the modern Node FFI ("ctypes for Node") — it loads the prebuilt libdoomgeneric and registers the six callbacks with no native compilation. The other two options are noted at the bottom.

The one rule

Keep the registered callbacks alive. koffi.register(...) returns a pointer the engine stores and calls later; if the JS functions/pointers get garbage-collected, the engine calls freed memory. We keep them in the module-level callbacks object for the whole run.

Build & run

1. Build libdoomgeneric (see bindings/README.md):

   make lib ENGINE=/path/to/doomgeneric/doomgeneric   # from the project root

2. Install the FFI dependency and place the library where the script looks:

   cd examples/languages/nodejs
   npm install
   mkdir -p lib && cp /path/to/libdoomgeneric.* lib/   # or set DOOMKIT_LIB=/abs/path

3. Run:

   node doom.js -iwad /path/to/doom1.wad               # writes frame.ppm at frame 100

How it maps

koffi piece	Role
koffi.load(...)	open the shared library
koffi.struct('dg_callbacks', {...})	the 6-function-pointer struct
koffi.proto(...) + koffi.register(fn, ptr)	turn JS functions into C callbacks
lib.func('void dg_create(int, const char **)')	declare an exported function
koffi.decode(ptr, koffi.array('uint32_t', w*h))	read the framebuffer (0x00RRGGBB)

Notes

• onSleepMs busy-waits to keep this a single synchronous file. A real app would drive dg_tick() from a timer (setInterval/setImmediate) and never block the event loop.
• Real input: return 1 from onGetKey and write the DOOM key code / pressed flag into the pointer args with koffi.encode(...).

Other ways to use doomkit from Node

• Native N-API addon (node-gyp + node-addon-api): compile a .node that links the engine and exposes JS methods. More setup, but the most "official" native path and lets C call JS via thread-safe functions.
• Run the WebAssembly build in Node: make wasm output (doom.js) runs under Node's WebAssembly too — headless, so you'd save frames to disk instead of a <canvas>. See examples/platforms/wasm/.