csharp

Run doomkit from C# (.NET / P/Invoke)

.NET's built-in interop is P/Invoke ([DllImport]). Delegates marshal to C function pointers automatically, so the six callbacks are just methods.

The one rule you must not forget

Keep the delegates alive. The library stores the function pointers and calls them later. If the managed delegate objects get garbage-collected, those pointers dangle and the engine crashes. Here we store the whole Callbacks struct (which holds the delegates) in a static field, which roots them for the program's lifetime.

Build & run

1. Build libdoomgeneric (see bindings/README.md).
2. Make the native library loadable. Easiest options:
   • copy it next to the built binary (bin/Release/net8.0/), or
   • macOS: export DYLD_LIBRARY_PATH=/path/to/lib
   • Linux: export LD_LIBRARY_PATH=/path/to/lib
3. Build and run:

   dotnet run -c Release -- -iwad /path/to/doom1.wad

   It writes frame.ppm at frame 100.

[DllImport("doomgeneric")] resolves to libdoomgeneric.so / .dylib / doomgeneric.dll per OS automatically.

Notes

• string[] argv marshals to C's char**, so engine flags like -iwad work. We prepend a fake argv[0] ("doomdemo") because C programs expect it.
• dg_screen_buffer() returns an IntPtr; Marshal.Copy pulls the pixels into an int[] (each 0x00RRGGBB) with no unsafe code.
• Real input: return 1 from OnGetKey and set pressed/doomKey (a DOOM key code) from events your UI framework delivers.