# sdl3-dos-port-pr

This is the combined work of @icculus @madebr @glebm @jayschwa @ccawley2011 and me rounding it off with stability fixes and missing features, thanks to everyone for pitching in.

<img width="690" height="567" alt="image" src="https://github.com/user-attachments/assets/1b3f0a62-d574-44aa-9aa0-4b8460c581a1" />

This is a fairly complete port to DOS with only minor features like audio recording missing. I have tested it extensively with DevilutionX in DOSBox. But no real hardware testing. The features I didn't add is mostly because I didn't have a good way to test that they worked correctly.

For threading I took some conceptual inspiration from the PS2 port.

## What's supported

- **Video:** VGA and VESA 1.2+ framebuffer, RGB, and 8-bit indexed color with VGA DAC palette programming, hardware page-flipping with vsync, VBE state save/restore on exit
- **Audio:** Sound Blaster 16 (16-bit stereo, up to 44.1 kHz), Sound Blaster Pro (8-bit stereo, up to 22 kHz), Sound Blaster 2.0/1.x (8-bit mono), all via IRQ-driven DMA with double-buffered auto-init
- **Input:** PS/2 keyboard with extended scancodes (0xE0 prefix), INT 33h mouse with queried sensitivity, gameport joystick via BIOS INT 15h with auto-calibration
- **Threading:** Cooperative scheduler using `setjmp`/`longjmp` with stack patching. Real mutexes, semaphores, TLS, and condition variables (generic fallback). Yield points in the event pump and delay functions keep audio and other threads responsive.
- **Timer:** Native PIT-based timer using DJGPP's `uclock()` at ~1.19 MHz resolution
- **Filesystem:** `GetBasePath` / `GetPrefPath` via DJGPP's `searchpath()`, POSIX filesystem ops fallback
- **Build:** CMake cross-compilation toolchain file, DJGPP CI job, preseed cache for faster configure

## What's NOT included

- **Audio recording** playback only
- **`SDL_TIME` native implementation** reuses Unix `gettimeofday` via DJGPP's POSIX layer (works fine)
- **Shared library** loading support (no `SDL_LoadObject`).

## How to build

```
cmake -S. -Bbuild-dos \
  -DCMAKE_TOOLCHAIN_FILE=build-scripts/i586-pc-msdosdjgpp.cmake \
  -DCMAKE_BUILD_TYPE=Release
cmake --build build-dos -j$(nproc)