394 lines
17 KiB
Markdown
394 lines
17 KiB
Markdown
# PlaydateKit
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Swift bindings to the [Playdate](https://play.date) C API.
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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, `OptionSet` and `enum` types instead of raw constants, and typed `throws` for fallible calls.
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All ten C subsystems are covered:
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| Namespace | Wraps | Highlights |
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|---|---|---|
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| `System` | `playdate->system` | input, time, menu items, logging |
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| `Display` | `playdate->display` | refresh rate, scale, mosaic, flip |
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| `Graphics` | `playdate->graphics` | drawing, `Bitmap`, `Font`, `TileMap`, video |
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| `Sprite` | `playdate->sprite` | display list, collisions, custom draw |
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| `Sound` | `playdate->sound` | players, synths, sequences, effects |
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| `File` | `playdate->file` | `Handle`, directory operations |
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| `JSON` | `playdate->json` | `Value` tree decode/encode |
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| `Lua` | `playdate->lua` | C functions, classes, stack access |
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| `Scoreboards` | `playdate->scoreboards` | online leaderboards |
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| `Network` | `playdate->network` | wifi, `HTTPConnection`, `TCPConnection` |
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## Requirements
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- The [Playdate SDK](https://play.date/dev/) (3.1.1 or later). The SDK is not vendored into this repository.
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- Swift 6.3 tools or later.
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Device builds additionally need:
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- A [swift.org development snapshot toolchain](https://www.swift.org/install/macos/) — Xcode's toolchain does not ship the Embedded Swift stdlib for the device target (`armv7em-none-none-eabi`). The easiest way to get one is to install [Swiftly](https://www.swift.org/swiftly/), Swift's toolchain manager, and install the `main-snapshot` toolchain with it:
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```sh
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swiftly install main-snapshot
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```
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- The [Arm GNU toolchain](https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads) (`arm-none-eabi-gcc`) on your `PATH`, which the Playdate SDK's build support uses to compile and link the device binary.
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### One-time SDK setup
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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:
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```sh
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make setup
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```
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The target 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`). If you prefer another location on your `PKG_CONFIG_PATH`, run the underlying script directly with the destination as an argument: `Scripts/install-pkgconfig.sh <directory>`.
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If Xcode had the package open before you ran the setup, 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.
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## Adding the dependency
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```swift
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// Package.swift of your game
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dependencies: [
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.package(
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url: "https://github.com/rock-n-code/playdate-kit.git",
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from: "0.1.0"
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),
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],
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targets: [
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.target(
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name: "MyGame",
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dependencies: [
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.product(
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name: "PlaydateKit",
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package: "playdate-kit"
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)
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]
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),
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]
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```
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## Getting started
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A Playdate application or game has a single C entry point, `eventHandler`. Export it with `@_cdecl`, initialize the binding on the first event, and install an update callback:
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```swift
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import CPlaydate
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import PlaydateKit
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@_cdecl("eventHandler")
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func eventHandler(
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pointer: UnsafeMutableRawPointer,
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event: PDSystemEvent,
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argument: UInt32
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) -> Int32 {
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switch SystemEvent(event: event, argument: argument) {
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case .initialize:
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Playdate.initialize(with: pointer) // must happen before anything else
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Game.shared.start()
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case .pause:
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Game.shared.pause()
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default:
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break
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}
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return 0
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}
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final class Game {
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nonisolated(unsafe) static let shared = Game()
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var player = Sprite()
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func start() {
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Display.refreshRate = 50
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System.setUpdateCallback {
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self.update()
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return true // true = redraw the display this frame
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}
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}
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func update() {
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let (_, pushed, _) = System.buttonState
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if pushed.contains(.a) {
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System.log("A pressed at \(System.currentTimeMilliseconds)ms")
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}
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Sprite.updateAndDrawAll()
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System.drawFPS()
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}
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}
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```
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`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.
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## Tour of the API
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### System: input, time, menu
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```swift
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// Buttons are an OptionSet: current (held), pushed and released this frame.
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let (current, pushed, released) = System.buttonState
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if current.contains([.b, .down]) { /* charge shot */ }
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// Crank.
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if !System.isCrankDocked {
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aim(degrees: System.crankAngle)
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spin(by: System.crankChange)
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}
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// Accelerometer is a peripheral you enable first.
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System.setPeripheralsEnabled(.accelerometer)
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let (x, y, z) = System.accelerometer
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// System menu items take closures; the binding keeps them alive until removed.
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System.addCheckmarkMenuItem(title: "music", isChecked: true) { item in
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Audio.musicEnabled = item.isChecked
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}
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System.addOptionsMenuItem(title: "mode", options: ["easy", "hard"]) { item in
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Game.shared.difficulty = item.value
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}
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// Logging goes to the simulator console or device serial.
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System.log("spawned \(count) enemies")
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System.error("unrecoverable") // stops execution
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```
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### Graphics: drawing, bitmaps, fonts
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Fallible loads (`Bitmap(path:)`, `Font(path:)`, …) throw `PlaydateError`,
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which carries the message produced by the OS:
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```swift
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let font = try Graphics.Font(path: "fonts/Asheville-Sans-14-Bold.pft")
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Graphics.setFont(font)
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Graphics.clear(color: .white)
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Graphics.fillRect(x: 0, y: 0, width: 400, height: 32, color: .black)
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Graphics.drawText("Hëllo, Playdate", x: 8, y: 8)
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// Colors are solid or 8×8 patterns.
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let checker = Graphics.Pattern(rows: (0xAA, 0x55, 0xAA, 0x55,
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0xAA, 0x55, 0xAA, 0x55))
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Graphics.fillEllipse(x: 100, y: 100, width: 64, height: 64,
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color: .pattern(checker))
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// Bitmaps draw themselves; draw into one by pushing it as the context.
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let logo = try Graphics.Bitmap(path: "images/logo")
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logo.draw(x: 168, y: 88)
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let canvas = Graphics.Bitmap(width: 64, height: 64)
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Graphics.pushContext(canvas)
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Graphics.drawLine(x1: 0, y1: 0, x2: 63, y2: 63, width: 2, color: .black)
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Graphics.popContext()
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```
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### Sprites and collisions
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```swift
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let ball = Sprite()
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ball.setImage(try Graphics.Bitmap(path: "images/ball"))
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ball.moveTo(x: 200, y: 120)
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ball.collideRect = Rect(x: 0, y: 0, width: 16, height: 16)
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ball.setCollisionResponseFunction { _, _ in .bounce }
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ball.add() // adds to the display list; the binding keeps it alive while added
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// In the update callback:
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let (actual, collisions) = ball.moveWithCollisions(goalX: goalX, goalY: goalY)
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for collision in collisions where collision.other.tag == Tags.brick {
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collision.other.remove()
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}
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// Every collision/query API also has a visitor form that iterates the
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// results in place instead of building an array — useful in hot loops:
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ball.moveWithCollisions(goalX: goalX, goalY: goalY) { collision in
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if collision.other.tag == Tags.brick { collision.other.remove() }
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}
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```
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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.
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### Sound
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```swift
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// Stream music from disk.
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let music = try Sound.FilePlayer(path: "audio/theme")
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music.play(repeat: 0) // 0 = loop forever
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// Play short effects from memory.
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let blip = try Sound.SamplePlayer(path: "audio/blip")
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blip.play()
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// Synthesis.
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let synth = Sound.Synth(waveform: .square)
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synth.setAttackTime(0.01)
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synth.setReleaseTime(0.2)
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synth.playMIDINote(Sound.noteC4, velocity: 0.8, length: 0.5)
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// Channels mix sources and effects.
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let channel = Sound.Channel()
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channel.add()
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channel.addSource(synth)
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let filter = Sound.TwoPoleFilter(kind: .lowPass)
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filter.setFrequency(800)
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channel.addEffect(filter)
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// Anything that takes a modulator accepts any SignalValue (LFO, Envelope, …).
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let wobble = Sound.LFO(shape: .sine)
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wobble.setRate(2)
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synth.frequencyModulator = wobble
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```
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### Files and JSON
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```swift
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// Paths resolve against the game's Data directory and pdx per the open mode.
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let save = try File.Handle(path: "save.json", mode: .write)
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try save.write(JSON.encode(.table([
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"level": .int(3),
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"name": .string("Röck"),
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])))
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try save.close()
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let loaded = try JSON.decodeFile(path: "save.json")
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if case .table(let entries) = loaded, case .int(let level)? = entries["level"] {
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Game.shared.level = level
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}
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try File.listFiles(at: "replays") { name in
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System.log("found \(name)")
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}
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```
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### Network
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Network access requires user permission per server:
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```swift
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let reply = Network.HTTPConnection.requestAccess(
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server: "example.com", purpose: "Fetching daily puzzles") { allowed in
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guard allowed else { return }
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Puzzles.fetch()
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}
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func fetch() {
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guard let connection = Network.HTTPConnection(server: "example.com") else { return }
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connection.setRequestCompleteCallback { connection in
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let body = try? connection.read(length: connection.bytesAvailable)
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// … keep `connection` referenced somewhere until this fires …
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}
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try? connection.get(path: "/daily.json")
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}
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```
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### Lua interop
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Lua callbacks are C function pointers with no context, so they must be
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`@convention(c)` functions rather than capturing closures:
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```swift
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let double: Lua.CFunction = { _ in
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Lua.push(Lua.intArgument(at: 1) * 2)
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return 1 // number of return values pushed
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}
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try Lua.addFunction(double, name: "mylib.double")
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```
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## Conventions
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- **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: `PlaydateKit.System`.
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- **Properties vs. methods.** State the OS can report back is a property: read-write where the C API has a get/set pair (`Display.refreshRate`, `Source.volume`), get-only where it only has a getter (`Display.fps`). A `set…` method means the C API is write-only there (`Display.setScale`, `Synth.setAttackTime`) or setting takes extra arguments — a property getter never invents a value the OS can't return. Callbacks are installed with `set…Callback`/`set…Function` methods.
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- **Paths.** APIs that load a single file label the argument `path:` (`Bitmap(path:)`, `JSON.decodeFile(path:)`); directory operations use `at:` (`File.listFiles(at:)`). The POSIX-named `File.stat`, `File.mkdir`, and `File.unlink` take their path unlabeled, like their C namesakes.
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- **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.
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- **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.
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- **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
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completions, `getServerTime`); those track one Swift closure at a time, as noted in their documentation.
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- **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.
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## Building for the simulator and device
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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).
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Shipping a `.pdx` needs the Playdate toolchain on top:
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- **Simulator** builds compile your game as a host dylib placed in the pdx (`Examples/HelloPlaydate/build.sh` shows the SwiftPM-based flow).
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- **Device** builds cross-compile with Embedded Swift for ARM Cortex-M7 (`-enable-experimental-feature Embedded`, triple `armv7em-none-none-eabi`, `-fshort-enums` to match the firmware ABI) and link through the SDK's own make infrastructure.
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[`Examples/swift.mk`](Examples/swift.mk) packages the device pipeline: it locates the SDK and a Swift snapshot toolchain, compiles the `PlaydateKit` wrapper as a module-aliased Embedded Swift module, and hooks the game objects into the SDK's `common.mk`. A game needs only a short Makefile on top — [`Examples/HelloPlaydate/Makefile`](Examples/HelloPlaydate/Makefile) is the template, and `make` in that directory produces a `.pdx` containing both the device binary and the simulator dylib. Swift code is compiled `-Osize` by default (measured ~15% smaller than `-O` on the example); override with `make SWIFT_OPT=-O`. The setup follows Apple's [swift-playdate-examples](https://github.com/apple/swift-playdate-examples), adapted to this package.
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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: the check cross-compiles the whole module for `armv7em-none-none-eabi` with Embedded Swift enabled and the device's `-fshort-enums` ABI. Running it needs the same snapshot toolchain and Arm GNU toolchain headers:
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```sh
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make embedded
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```
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The target picks up a snapshot toolchain installed at `~/Library/Developer/Toolchains` automatically; point it at another one with `make embedded SWIFT_BIN=<path to swift>`.
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## Make targets
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A root Makefile fronts the development lifecycle; a bare `make` (or `make help`) lists the targets. `build`, `test`, `docs`, and `consumer-test` need only Xcode's toolchain (after the one-time `make setup`); `embedded` and the example targets additionally need the device toolchains above.
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| Target | Effect |
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| `make setup` | One-time: point the `playdate` pkg-config module at the SDK |
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| `make build` / `make test` | Build the bindings for the host / run the unit tests |
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| `make outdated` / `make upgrade` | Show / apply updates to the SwiftPM dependencies |
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| `make embedded` | Compile-only device check (Embedded Swift, `armv7em-none-none-eabi`) |
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| `make consumer-test` | Build and run a scratch package depending on playdate-kit |
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| `make check` | The full verification suite: build, test, embedded, consumer-test |
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| `make docs` / `make docs-preview` | Generate / preview the DocC documentation |
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| `make example` / `make example-run` | Build the HelloPlaydate example / open it in the Playdate Simulator |
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| `make clean` | Remove build products of the package and the example |
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## Example
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[`Examples/HelloPlaydate`](Examples/HelloPlaydate) is a complete minimal game — bouncing box, crank needle, button handling, a system menu item — that builds into a runnable `.pdx`:
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```sh
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cd Examples/HelloPlaydate
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# Simulator only (plain SwiftPM, no extra toolchains):
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./build.sh
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open -a "$HOME/Developer/PlaydateSDK/bin/Playdate Simulator.app" HelloPlaydate.pdx
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# Device + simulator (snapshot toolchain and arm-none-eabi-gcc required):
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make
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```
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Sideload the device build from the Playdate Simulator (Device ▸ Upload Game to Device) or with the SDK's `pdutil`.
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## Documentation
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The API reference is a DocC catalog. Generate it locally with:
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```sh
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make docs
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```
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serve it in a local web server with `make docs-preview`, or browse it with Xcode's documentation viewer (Product ▸ Build Documentation).
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## Layout
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```
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Examples/
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swift.mk Shared make rules for device builds: toolchain/SDK discovery and Embedded Swift compile flags
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HelloPlaydate/ Minimal game buildable into a .pdx for the simulator (build.sh) or simulator + device (make)
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Scripts/
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install-pkgconfig.sh One-time setup: points the "playdate" pkg-config module at your SDK installation
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build-embedded.sh Compile-only device check: Embedded Swift for armv7em-none-none-eabi with the device ABI
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consumer-test.sh Builds a scratch package depending on playdate-kit to prove settings propagate to consumers
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Sources/
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CPlaydate/ System library target: module map + umbrella header importing pd_api.h from the SDK, plus inline shims for the variadic log/error functions
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PlaydateKit/ The Swift bindings, one folder per subsystem (System, Graphics, Sound, ...) holding one type per file, grouped by kind (Classes, Structures, Enumerations, Aliases);
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Sound is further split into the Source, Signal, Effect, and Synth subdomains. Also holds the shared Support.swift helpers and the PlaydateKit.docc documentation catalog
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Tests/
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PlaydateKit/ Host-runnable tests for the pure value types
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```
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## License
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MIT — see [LICENSE](LICENSE). The Playdate SDK itself is licensed separately by Panic, Inc. and is not distributed with this package.
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