GDExtension for Scala

State: Amoeba

Complete API breakeage should be expected

AI allowed.

Using the project

On the root folder of your Godot project, add a build.mill.yaml file that should look like this:

mill-version: 1.1.2
mill-build:
  mvnDeps:
  - net.julian-avar::gdext-mill-plugin::0.1.0
extends: net.julian-avar.gdext.godotscalanativelib.GodotScalaNativeModule
godotVersion: 4.7.0
scalaVersion: 3.8.4
scalaNativeVersion: 0.5.11
mvnDeps:
- net.julian-avar::gdext::0.1.0

Building the project

Edit flake.nix to match the godot version you're trying to use.

Make sure you have Nix installed, then run nix develop to enter the development environment. .envrc is included in case direnv is available. That should take care of the environment which includes:

• Mill
  • Scala 3.8.4
• JDK 21
• GraalVM dependencies
• LLVM
• Godot 4.5/4.6/4.7

The project's infra uses GraalVM, but the actual user code runs on Scala Native (which is pulled using Coursier). Garbage collection strategies have not been fully tested yet.

gdext is built as a real Mill plugin: gdext.ffi/gdext.core/gdext.api are cross-built once per supported Godot version (4.5.0, 4.6.1, 4.7.0), and codegen runs automatically as part of compiling those modules — there's no separate "generate" step to invoke. Each examples/* directory is its own standalone Mill build that consumes gdext/gdext-mill-plugin from ~/.ivy2/local, so publish locally before building an example.

Once you're in the nix shell:

just publishLocal        # publish gdext + gdext-mill-plugin to ~/.ivy2/local (godot=4.7.0 by default)
just run rigid_body      # publishLocal, then build + launch examples/rigid_body against Godot 4.7.0
just run rigid_body 4.5.0

just lint
# ./mill mill.scalalib.scalafmt