Scala Native bindings for SDL2 covering 2D rendering and input, with optional antialiased primitives from SDL2_gfx.

The binding has two layers:

• io.github.edadma.sdl2.extern — raw @extern declarations. The only place Scala Native FFI types (Ptr, CInt, UByte, …) appear.
• io.github.edadma.sdl2 — a pure-Scala layer. This is the only package you import. It speaks in Int, Boolean, String, and Color; native pointers are wrapped in zero-cost AnyVal value classes (Window, Renderer, Texture); memory and C strings are managed for you.

This is a Scala Native–only artifact. You need SDL2 (and SDL2_gfx for the antialiased primitives) installed and on the linker path:

brew install sdl2 sdl2_gfx        # macOS
# apt-get install libsdl2-dev libsdl2-gfx-dev   # Debian/Ubuntu

libraryDependencies += "io.github.edadma" %%% "sdl2" % "0.0.3"

import io.github.edadma.sdl2.*

@main def run(): Unit =
  setMainReady()
  if !init(INIT_VIDEO) then sys.error(s"SDL_Init failed: $error")

  val window   = createWindow("hello", 800, 600)
  val renderer = window.createRenderer()

  var running = true
  while running do
    var ev = pollEvent()
    while ev.isDefined do
      val e = ev.get
      if e.kind == QUIT then running = false
      else if e.kind == KEYDOWN && e.keyScancode == Scancode.Escape then running = false
      ev = pollEvent()

    renderer.clear(Color.fromRGB(0x0a0a18))
    renderer.fillCircle(400, 300, 80, Color.fromRGB(0x4dabf7)) // antialiased
    renderer.present()

  renderer.destroy(); window.destroy(); quit()

Run the bundled demo (bouncing antialiased balls) with sbt run.

SDL invokes a C function pointer per event. The binding registers a single trampoline and keeps your Scala closures in a map, so you pass ordinary functions. Watches fire while events are pumped, on the calling thread.

val id = addEventWatch { e =>
  if e.kind == KEYDOWN && !e.keyRepeat then println(s"key ${e.keyScancode}")
}
// ...later
removeEventWatch(id)

fillCircle/aaLine/drawCircle use SDL2_gfx for smooth edges. For a fully antialiased scene (including straight drawLine calls), render into a supersampled target texture and downscale it with linear filtering:

setHint(HINT_RENDER_SCALE_QUALITY, "1")
val target = renderer.createTexture(window.pixelFormat, TEXTUREACCESS_TARGET, w * 2, h * 2)
target.setScaleMode(SCALEMODE_LINEAR)
// each frame:
renderer.setTarget(target);  /* draw at 2x */  renderer.resetTarget()
renderer.copy(target); renderer.present()

Lifecycle, hints, window, renderer (draw colour/blend, clear, point/line/rect, render targets, full and positioned copy, present), textures (create, create from surface, scale mode, size), surfaces (width/height/free), SDL2_gfx primitives (aaLine, line, drawCircle, fillCircle, fillBox), event polling with field accessors, event watches, and keyboard/mouse state with a Scancode table. The surface/texture bridge supports companion libraries such as SDL2_ttf. Contributions to widen the surface are welcome.