Godot-D

D language bindings for the Godot Engine's GDNative C interface.

WIP: These bindings are still under development. Until v1.0.0, expect breaking changes, bugs, and missing documentation. Please report any issues and confusing or undocumented features on the GitHub page.

Usage

Dependencies

• D compiler:
  • DMD 2.082+ or
  • LDC 1.11.0+
• DUB package/build tool (usually included with both compilers)

Project setup

The easiest way to build your library is to use D's package/build manager, DUB. Create a DUB project in a file called dub.json in your Godot project folder:

{
	"name": "asteroids-demo",
	"sourcePaths": ["asteroids"],
	"importPaths": ["asteroids"],
	"targetType": "dynamicLibrary",
	"dependencies": {
		"godot-d": "~>0.1.4"
	},
	"preGenerateCommands": [
		"dub run godot-d:pregenerate"
	]
}

Your project will usually be organized like this:

asteroids-demo
├─ project.godot         Godot project
├─ <other Godot assets>
│
├─ addons
│  └─ godot-d-importer   D editor plugin
│
├─ dub.json              DUB project
├─ *.dll / .so           Compiled libraries for each platform
└─ asteroids
   ├─ *.d                D source files
   └─ entrypoint.d       Entry point (auto-generated)

The location of the D source files is up to you. In this example, we use a subfolder with the game's name to keep them neatly organized, since the file path is used as both the D module name and the Godot resource path.

D native scripts

In Godot, a "script" is an object that exposes methods, properties, and signals to the engine. It is always attached to one of the engine's own C++ classes, listed in the class reference.
To expose a D class to the engine as a native script, inherit from GodotScript with the Godot class the script should be attached to:

import godot, godot.button;

class TestButton : GodotScript!Button
{
	@Property(Property.Hint.range, "1,10") int number = 9;
	
	@Signal static void function(String message, int num) sendMessage;
	
	@Method void _pressed()
	{
		print("Button was pressed. `number` is currently ", number);
		emitSignal("send_message", "`number` is currently ", number);
	}
	
	...
}

Properties and methods can be exposed to Godot with the Property and Method UDAs. Exposed properties will be saved/loaded along with instances of the class and can be modified in the Godot editor. The optional hint parameter can specify how the editor should treat the property, for example limiting a number to the range 1-10.

Library initialization

Your library needs to expose an entry point through which Godot will load and initialize it:

1: Automatic entry point generator

Add godot-d:pregenerate to your DUB project's preGenerateCommands:

	"preGenerateCommands": [ "dub run godot-d:pregenerate" ],

The pregenerate tool will create the entry point entrypoint.d in your source directory and a list of script classes in your string import directory (views by default).

Your GDNativeLibrary's symbol_prefix will be the name of your DUB project, with symbols like - replaced by underscores.

2: Manual entry point mixin

Put the GodotNativeLibrary mixin into one of your files:

import godot.d.register;

mixin GodotNativeLibrary!
(
	// your GDNativeLibrary resource's symbol_prefix
	"platformer",
	
	// a list of all of your script classes
	Player,
	Enemy,
	Level,
	
	// functions to call at initialization and termination (both optional)
	(GodotInitOptions o){ writeln("Library initialized"); },
	(GodotTerminateOptions o){ writeln("Library terminated"); }
);

3: Both

You can manually create the GodotNativeLibrary mixin while still using the pregenerate tool. It will not create a new entrypoint.d if the mixin already exists. You no longer need to list your script classes, but can still use GodotNativeLibrary to configure your library.

Godot API

Godot's full script API can be used from D:

• godot.core submodules contain container, math, and engine structs like Vector3 and String.

• Other submodules of godot contain bindings to Godot classes, auto-generated from the engine's API. These are the C++ classes scripts can be attached to.

• These bindings use camelCase instead of snake_case.

  Change window to fullscreen example:

  # GDScript
  OS.set_window_fullscreen(false)

  Would be:

  // D
  OS.setWindowFullscreen(false);

• D code should use D naming conventions (PascalCase for classes, camelCase for properties and methods). Your method and property names will be converted to Godot's own snake_case style when registered into Godot, so refer to them in snake_case from inside the editor and GDScript. This behavior can be disabled with the GodotNoAutomaticNamingConvention version switch if you prefer to use camelCase even inside Godot/GDScript.

Building Godot-D manually

DUB package releases will contain pre-generated bindings for official releases of Godot, but you can generate your own bindings in a few cases:

• using the master branch of Godot
• using the master branch of Godot-D, which doesn't include pre-built bindings
• using a custom Godot build or custom C++ modules

Make a local clone of Godot-D and generate updated bindings using the API generator. In your game project, use this local clone's path as a dependency instead of a released version of godot-d:

	"dependencies":
	{
		"godot-d": { "path": "../godot-d-customized" },
	},

Versioning

The GDNative API is binary-compatible between Godot versions, so a D library can be used with a Godot build older or newer than the one used to generate the bindings. D bindings must still be generated with the most recent GDNative API (modules/gdnative/gdnative_api.json in the Godot repository) even if an older Godot binary will be used.

Extension version properties can be checked to prevent newer functions from being called with older Godot binaries. For example:

if(GDNativeVersion.hasNativescript!(1, 1)) useNewNativescriptFunctions();
else doNothing();

A D library can also specify minimum required extensions using a compiler flag or the versions property in their DUB project. The format of the version flag is GDNativeRequire<Extension name or "Core">_<major version>_<minor version>. For example, with "versions": [ "GDNativeRequireNativescript_1_1" ] in dub.json, runtime checks and non-1.1 code such as the example above can be safely optimized out in both library code and binding-internal code.

License

MIT - https://opensource.org/licenses/MIT

Links

GitHub repository - https://github.com/GodotNativeTools/godot-d
The C++ bindings these are based on - https://github.com/GodotNativeTools/godot-cpp
GDNative repository - https://github.com/GodotNativeTools/godot_headers

Godot Engine - https://godotengine.org
D programming language - https://dlang.org