GodotDart

An attempt to be able to use Dart as a scripting language for Godot.

Because I like Dart.

And I want to use it in Godot.

Current State

Currently, Dart can be initialized as a language usable as a GDExtension, but not as a scripting language. This means you can create Dart classes and Nodes and add them to you scene tree, and they will execute both in editor and in game.

Here's a list of planned features and work still to be done ( ✅ - Seems to be working, 🟨 - Partially working, ❌ - Not working)

Feature	Support	Note
Dart as a Godot Extension Language	🟨
Ref counted object support	❌
Dart Debugging Extension	✅	Attach to http://127.0.0.1:5858
Dart Available as a Scripting Language	❌
Hot Reload	❌
Simplified Binding using build_runner	❌
Dart native Variants	❌	Needed for performance reasons
Memory efficiency / Leak prevention	❌

Some notes about the current state:

• The binding is likely leaking both Dart objects and native allocations. I intend on making a pass through to make sure all of that is cleaned up at some point and correctly utilize native finalizers.
• Right now Godot will crash on exit because the binding isn't cleaning up after itself and it tried to free Dart objects after Dart has aready been shut down.

Using

I have only tested this on Windows. I know for certain it will only work on 'float_64' builds of Godot.

Things you will need

• A clone of this repo.
• Dart (2.19 Current Stable, not tested with 3.0)
• Godot 4.0.2 or a custom build compatible with 4.0.2
• A build of the Dart Shared Library. Windows x64 .dlls for Dart 2.19 are provided in src/dart_dll/bin/win64.
• A way to build src/cpp. A Visual Studio solution is provided if you have Visual Studio. If not, use your favorite tool to build the provided files.

Current Setup

To use the extension, you need to:

• Copy both your dart_dll dynamic library and the godot_dart dynamic library to your project directory.
• Copy simple/example.gdextension to your project directory (note this is only configured for windows.64 builds and will need to be modified for any other OS).
• Create a src directory in your project directory to hold your Dart code. This should be a proper Dart package, complete with a pubspec.yaml file. Add a main.dart to this directory.
• Run the Binding Generator

# From tools/binding_generator
dart ./bin/binding_generator.dart

• Add a reference to the godot_dart package that is defined in src/dart. You will need to use a path dependency for this for now.
• Add a main function to your main.dart. This is where you will register your Godot classes

You should now be able to write Dart code for Godot! But, there are some requirements for any Godot accessible Dart class. Here's the Simple example class in simple/src/simple.dart

class Simple extends Sprite2D {
  // typeInfo is required. Make sure that your class name
  // and the inheritted name are both correct.
  static late TypeInfo typeInfo;
  static void initTypeInfo() => typeInfo = TypeInfo(
        StringName.fromString('Simple'),
        parentClass: StringName.fromString('Sprite2D'),
      );
  // a vTable getter is also required. If you are not adding any
  // virtual functions, just return the base class's vTable
  static Map<String, Pointer<GodotVirtualFunction>> get vTable =>
      Sprite2D.vTable;

  // An override of [staticTypeInfo] is ALSO required. This is how
  // the bindings understand the what types it's looking at.
  @override
  TypeInfo get staticTypeInfo => typeInfo;

  double _timePassed = 0.0;

  // Constructor is required and MUST call [postInitialize]
  Simple() : super() {
    postInitialize();
  }

  // All virtual functions from Godot should be available, and start
  // with a v instead of an underscore.
  @override
  void vProcess(double delta) {
    _timePassed += delta;

    final x = 10.0 + (10.0 * sin(_timePassed * 2.0));
    final y = 10.0 + (10.0 * cos(_timePassed * 2.0));
    final newPosition = Vector2.fromXY(x, y);
    print('vProcess - $x, $y, ${newPosition.x}, ${newPosition.y}');
    setPosition(newPosition);
  }
}

Classes also need to be registered to Godot in main.dart:

void main() {
  Simple.initTypeInfo();

  gde.dartBindings.bindClass(Simple, Simple.typeInfo);
}

I know this is a very complicated setup. I'll be looking to simplify it in the future once more features are working.

More Info

This utilizes my custom built Dart shared library for embedding Dart, the source for which is available here. I've included the win64 prebuilt binaries in this repo for simplicity.