Swift for Playdate

Playdate is a cool gaming console with limited memory and CPU power. Swift is a cool language which can be compiled to run efficiently on a wide range of devices. This is a proof of concept of what it could be like to write Playdate apps using Swift, but there are currenly many limitations.

Most importantly, you can only run apps on the Playdate Simulator, on an Apple Silicon Mac.

This repo implements the "Hello World" app from the SDK's C_API examples.

Requirements

• On a Mac with Apple Silicon (i.e. M1)
• Install the Playdate SDK (version 1.9.2 works)
• Install swiftc, probably as part of Xcode (I used 13.1)

Build

Navigate to the directory containing one of the examples (or your own app) and run the build script:

$ cd Examples/SpriteGame
$ ../../build.sh

This script runs swift build to compile your app (along with the API wrappers, writing a .dylib and a bunch of other junk under .build/

Then it runs pdc to assemble any images, fonts, etc. from the directory Sources/Resources, into (for example) SpriteGame.pdx (which is actually a directory.)

Finally, it copies the app executable into the pdx and you should be ready to go.

Run

$ open SpriteGame.pdx

Or just double-click the .pdx icon.

If you want to see your Swift print() output (or anything else written to stdout), then run the simulator like this:

$ ~/"Developer/PlaydateSDK/bin/Playdate Simulator.app/Contents/MacOS/Playdate Simulator" HelloWorld.pdx

Or just use System.logToConsole() to send messages to the console window in the UI. Note: to format messages, use Swift's string interpolation, not Lua's, for example System.logToConsole("This is cool: \(awesomeness > 0.80)").

Starting an app from scratch

You just need a directory with these files:

./
  Package.swift
  Sources/
    MyApp/
      TheApp.swift
    Resources/
      pdxinfo

Take a look at Examples/HelloWorld/ for the bare minumum you need to get going.

Update the various target names and the relative path to the swift-pd package in your Package.swift. Then run build.sh from your directory.

Caveats

Your app built this way will not run on the Playdate hardware, only in the simulator. It would probably be possible to get something like this to work for building games to run on the device, but it looks like it will take a lot more effort and knowledge.

If anything goes wrong, the simulator might refuse to load the app, or give a confusing error, or just crash.

There are probably lots of Swift language/library features that won't work at all. And lots that will work in the Simulator but don't really make sense for the device.

Only a portion the the Playdate API is currently wrapped in nice Swift syntax, including basic input and drawing, and sprites. Additional APIs are often easy to add, but it can be tedious. With the current structure, you can't talk directly to the raw C APIs from your app, but you have the library source, so feel free to add what you need and submit a PR if you're feeling like sharing.

This might actually work on an Intel Mac, or on Linux or Windows, with some changes. If you try it and get somewhere, submit a PR.

I haven't tried to get Xcode to build the app. Imagine connecting the debugger to your Swift app running in the simulator. And keep imagining it, because it's definitely not happening at the moment.

Credit

@ericlewis worked out some details to get this off the ground. See this devforum thread for the full story.

This is only possible due to the amazing work of the Playdate and Swift teams. I don't know how either of them would feel about this being a real thing, but it's thanks to them that even an ugly hack like this can be done.