PlayDate

Swift bindings to the Playdate C API.

The Playdate C API is delivered as a PlaydateAPI* struct of function pointers that the firmware hands to your game at launch. This package wraps that surface in idiomatic Swift: namespaced APIs, wrapper types with ownership semantics, closures instead of function-pointer/userdata pairs, OptionSets and enums instead of raw constants, and typed throws for fallible calls.

All ten C subsystems are covered:

Namespace	Wraps	Highlights
System	playdate->system	input, time, menu items, logging
Display	playdate->display	refresh rate, scale, mosaic, flip
Graphics	playdate->graphics	drawing, Bitmap, Font, TileMap, video
Sprite	playdate->sprite	display list, collisions, custom draw
Sound	playdate->sound	players, synths, sequences, effects
File	playdate->file	Handle, directory operations
JSON	playdate->json	Value tree decode/encode
Lua	playdate->lua	C functions, classes, stack access
Scoreboards	playdate->scoreboards	online leaderboards
Network	playdate->network	wifi, HTTPConnection, TCPConnection

Requirements

• The Playdate SDK (3.1.1 or later). The SDK is not vendored into this repository.
• Swift 6.4 tools or later.

One-time SDK setup

The CPlaydate target resolves pd_api.h through a playdate pkg-config module, so the package works as a normal SwiftPM dependency without unsafe build flags. Generate the pkg-config file once per machine:

Scripts/install-pkgconfig.sh

The script locates the SDK via PLAYDATE_SDK_PATH (default ~/Developer/PlaydateSDK) and writes playdate.pc into a directory SwiftPM searches by default (/usr/local/lib/pkgconfig). Pass a custom destination as an argument if you prefer another location on your PKG_CONFIG_PATH.

If Xcode had the package open before you ran the script, make it re-read the manifest (File ▸ Packages ▸ Reset Package Caches) — Xcode caches package resolution and won't notice the new .pc file on its own.

Adding the dependency

// Package.swift of your game
dependencies: [
    .package(url: "https://github.com/<you>/play-date.git", from: "0.1.0"),
    // …or, while developing locally:
    // .package(path: "../play-date"),
],
targets: [
    .target(
        name: "MyGame",
        dependencies: [.product(name: "PlayDate", package: "play-date")]
    ),
]

Getting started

A Playdate game has a single C entry point, eventHandler. Export it with @_cdecl, initialize the binding on the first event, and install an update callback:

import CPlaydate
import PlayDate

@_cdecl("eventHandler")
func eventHandler(
    pointer: UnsafeMutableRawPointer,
    event: PDSystemEvent,
    argument: UInt32
) -> Int32 {
    switch SystemEvent(event: event, argument: argument) {
    case .initialize:
        Playdate.initialize(with: pointer)   // must happen before anything else
        Game.shared.start()
    case .pause:
        Game.shared.pause()
    default:
        break
    }

    return 0
}

final class Game {
    nonisolated(unsafe) static let shared = Game()

    var player = Sprite()

    func start() {
        Display.setRefreshRate(50)

        System.setUpdateCallback {
            self.update()
            return true   // true = redraw the display this frame
        }
    }

    func update() {
        let (_, pushed, _) = System.buttonState
        if pushed.contains(.a) {
            System.log("A pressed at \(System.currentTimeMilliseconds)ms")
        }

        Sprite.updateAndDrawAll()
        System.drawFPS()
    }
}

Playdate.initialize(with:) stores the API pointer once; every wrapper in the module uses it from then on. Calling any wrapper before initialize is a programmer error and will crash.

Tour of the API

System: input, time, menu

// Buttons are an OptionSet: current (held), pushed and released this frame.
let (current, pushed, released) = System.buttonState
if current.contains([.b, .down]) { /* charge shot */ }

// Crank.
if !System.isCrankDocked {
    aim(degrees: System.crankAngle)
    spin(by: System.crankChange)
}

// Accelerometer is a peripheral you enable first.
System.setPeripheralsEnabled(.accelerometer)
let (x, y, z) = System.accelerometer

// System menu items take closures; the binding keeps them alive until removed.
System.addCheckmarkMenuItem(title: "music", isChecked: true) { item in
    Audio.musicEnabled = item.isChecked
}
System.addOptionsMenuItem(title: "mode", options: ["easy", "hard"]) { item in
    Game.shared.difficulty = item.value
}

// Logging goes to the simulator console or device serial.
System.log("spawned \(count) enemies")
System.error("unrecoverable")   // stops execution

Graphics: drawing, bitmaps, fonts

Fallible loads (Bitmap(path:), Font(path:), …) throw PlaydateError, which carries the message produced by the OS:

let font = try Graphics.Font(path: "fonts/Asheville-Sans-14-Bold.pft")
Graphics.setFont(font)

Graphics.clear(color: .white)
Graphics.fillRect(x: 0, y: 0, width: 400, height: 32, color: .black)
Graphics.drawText("Hëllo, Playdate", x: 8, y: 8)

// Colors are solid or 8×8 patterns.
let checker = Graphics.Pattern(rows: (0xAA, 0x55, 0xAA, 0x55,
                                      0xAA, 0x55, 0xAA, 0x55))
Graphics.fillEllipse(x: 100, y: 100, width: 64, height: 64,
                     color: .pattern(checker))

// Bitmaps draw themselves; draw into one by pushing it as the context.
let logo = try Graphics.Bitmap(path: "images/logo")
logo.draw(x: 168, y: 88)

let canvas = Graphics.Bitmap(width: 64, height: 64)
Graphics.pushContext(canvas)
Graphics.drawLine(x1: 0, y1: 0, x2: 63, y2: 63, width: 2, color: .black)
Graphics.popContext()

Sprites and collisions

let ball = Sprite()
ball.setImage(try Graphics.Bitmap(path: "images/ball"))
ball.moveTo(x: 200, y: 120)
ball.collideRect = Rect(x: 0, y: 0, width: 16, height: 16)
ball.setCollisionResponseFunction { _, _ in .bounce }
ball.add()   // adds to the display list; the binding keeps it alive while added

// In the update callback:
let (actual, collisions) = ball.moveWithCollisions(goalX: goalX, goalY: goalY)
for collision in collisions where collision.other.tag == Tags.brick {
    collision.other.remove()
}

Sprite callbacks (setUpdateFunction, setDrawFunction, setCollisionResponseFunction) receive the Swift wrapper back. The C-level sprite userdata slot is reserved by the binding for that recovery — use the userdata property on Sprite for your own per-sprite storage instead.

Sound

// Stream music from disk.
let music = try Sound.FilePlayer(path: "audio/theme")
music.play(repeat: 0)   // 0 = loop forever

// Play short effects from memory.
let blip = try Sound.SamplePlayer(path: "audio/blip")
blip.play()

// Synthesis.
let synth = Sound.Synth(waveform: .square)
synth.setAttackTime(0.01)
synth.setReleaseTime(0.2)
synth.playMIDINote(Sound.noteC4, velocity: 0.8, length: 0.5)

// Channels mix sources and effects.
let channel = Sound.Channel()
channel.add()
channel.addSource(synth)
let filter = Sound.TwoPoleFilter(kind: .lowPass)
filter.setFrequency(800)
channel.addEffect(filter)

// Anything that takes a modulator accepts any SignalValue (LFO, Envelope, …).
let wobble = Sound.LFO(shape: .sine)
wobble.setRate(2)
synth.frequencyModulator = wobble

Files and JSON

// Paths resolve against the game's Data directory and pdx per the open mode.
let save = try File.Handle(path: "save.json", mode: .write)
try save.write(JSON.encode(.table([
    "level": .int(3),
    "name": .string("Röck"),
])))
try save.close()

let loaded = try JSON.decodeFile(at: "save.json")
if case .table(let entries) = loaded, case .int(let level)? = entries["level"] {
    Game.shared.level = level
}

try File.listFiles(at: "replays") { name in
    System.log("found \(name)")
}

Network

Network access requires user permission per server:

let reply = Network.HTTPConnection.requestAccess(
    server: "example.com", purpose: "Fetching daily puzzles") { allowed in
    guard allowed else { return }
    Puzzles.fetch()
}

func fetch() {
    guard let connection = Network.HTTPConnection(server: "example.com") else { return }
    connection.setRequestCompleteCallback { connection in
        let body = try? connection.read(length: connection.bytesAvailable)
        // … keep `connection` referenced somewhere until this fires …
    }
    try? connection.get(path: "/daily.json")
}

Lua interop

Lua callbacks are C function pointers with no context, so they must be @convention(c) functions rather than capturing closures:

let double: Lua.CFunction = { _ in
    Lua.push(Lua.intArgument(at: 1) * 2)
    return 1   // number of return values pushed
}
try Lua.addFunction(double, name: "mylib.double")

Conventions

• Namespaces. The subsystem namespaces (System, Graphics, Sound, …) live at the top level of the module; only the raw C API bootstrap stays under Playdate (Playdate.initialize(with:), Playdate.api). On a name collision with another module, qualify with the module name: PlayDate.System.
• Errors. Fallible operations use typed throws — throws(PlaydateError) generally, throws(Network.NetError) for network I/O — so catch gives you a concrete type, and no any Error existentials are needed.
• Ownership. A wrapper that creates a C object frees it on deinit; keep the wrapper referenced for as long as you use it. Wrappers vending OS-owned objects (a Bitmap from a BitmapTable, a track from a Sequence, …) don't free them — keep the owner alive instead, as documented on each API. Resources a C object keeps referencing (a sprite's image, a synth's sample, modulators, menu-item option titles) are retained by the wrapper automatically.
• Callbacks. Where the C API provides a userdata slot, closures are supported everywhere and delivered back with the right wrapper. A few C callbacks have no userdata (serial messages, headphone changes, scoreboard completions, getServerTime); those track one Swift closure at a time, as noted in their documentation.
• Threading. The Playdate runtime is single-threaded (audio callbacks excepted); statics in the binding are nonisolated(unsafe) on that basis. Don't call the API from other threads.

Building for the simulator and device

This package builds as a plain Swift library, which is how you develop and unit-test game logic on the host (swift test works out of the box).

Shipping a .pdx needs the Playdate toolchain on top:

• Simulator builds compile your game as a host dylib placed in the pdx.
• Device builds require Embedded Swift for ARM Cortex-M7 (-enable-experimental-feature Embedded, triple armv7em-none-none-eabi).

The wrappers are written within the Embedded Swift subset for exactly this reason: no Foundation, no reflection, no untyped throws. That claim is enforced, not aspirational: Scripts/build-embedded.sh cross-compiles the whole module for armv7em-none-none-eabi with Embedded Swift enabled, and CI runs it on every push. Running it locally needs a swift.org development snapshot toolchain (Xcode's toolchain doesn't ship the bare-metal embedded stdlib) and the Arm GNU toolchain headers:

SWIFT_BIN=~/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-<date>.xctoolchain/usr/bin/swift \
    Scripts/build-embedded.sh

See Apple's swift-playdate-examples for a working Makefile/toolchain setup that this library slots into.

Example

Examples/HelloPlaydate is a complete minimal game — bouncing box, crank needle, button handling, a system menu item — that builds into a runnable simulator .pdx:

cd Examples/HelloPlaydate
./build.sh
open -a "$HOME/Developer/PlaydateSDK/bin/Playdate Simulator.app" HelloPlaydate.pdx

Documentation

The API reference is a DocC catalog. Generate it locally with:

swift package generate-documentation --target PlayDate

or browse it with Xcode's documentation viewer (Product ▸ Build Documentation). Pushes to main publish the rendered docs to GitHub Pages via .github/workflows/docs.yml (enable Pages ▸ Source: GitHub Actions in the repository settings once).

Layout

Examples/
  HelloPlaydate/    Minimal game buildable into a simulator .pdx
Scripts/
  install-pkgconfig.sh   One-time setup: points the "playdate" pkg-config
                         module at your SDK installation
  build-embedded.sh      Compile-only device check: Embedded Swift for
                         armv7em-none-none-eabi (run by CI)
  consumer-test.sh       Builds a scratch package depending on play-date
                         to prove settings propagate to consumers (CI)
Sources/
  CPlaydate/        System library target: module map + umbrella header
                    importing pd_api.h from the SDK, plus inline shims for
                    the variadic log/error functions
  PlayDate/         The Swift bindings, one file per subsystem
                    (Sound and Graphics are split across several files),
                    plus the PlayDate.docc documentation catalog
Tests/
  PlayDate/         Host-runnable tests for the pure value types

License

MIT — see LICENSE. The Playdate SDK itself is licensed separately by Panic, Inc. and is not distributed with this package.