Embedding in Unity

Create Unity project then introduce SeedLang DLLs

First, create an empty 2D or 3D (Built-in, URP and HDRP pipelines are supported) project with Unity Hub.

Second, introduce SeedLang into your Unity game. There are several ways to add SeedLang DLLs to Unity project:

Method 1: Use a pre-built Unity package

Download the newest pre-built SeedLang .unitypackage file at SeedLang’s release page.

From Unity’s menu, select Assets / Import Package / Custom Package, open the downloaded .unitypackage file, then import everything in the package.

Method 2: Add SeedLang DLLs to the Plugins dir

In Unity, create a folder under the Assets folder: Assets/Plugins.

Build the SeedLang DLLs yourself from the SeedLang repo, or reuse the pre-built DLLs at SeedLangUnityCommon/Runtime/Plugins.

A SeedLang build include the main SeedLang DLL and its dependencies:

SeedLang.dll
Antlr4.Runtime.Standard.dll
System.Collections.Immutable.dll

Drag those DLL files into your Unity project’s Assets/Plugins folder.

Method 3: Import SeedLang via its NuGet package

SeedLang publishes its NuGet package at https://www.nuget.org/packages/SeedLang/.

Unity does not support importing NuGet packages directly, but you can use a third-party plug-in, NuGetForUnity, to achieve this.

See NuGetForUnity’s documentations for more details.

Use SeedLang in Unity

Create a source code folder in Unity, such as: Assets/Scripts.

Add a C# script in the Assets/Scripts folder, e.g.: SeedLangTest.cs.

Unlike console applications, Unity has no stdout pipe to support SeedPython’s print() function. For running a SeedLang script in Unity and capturing the script’s outputs, we need to redirect stdout to a custom C# class:

class ConsoleWriter : TextWriter {
  private readonly StringBuilder _buffer = new StringBuilder();
  public override System.Text.Encoding Encoding => Encoding.Default;
  public override void Write(char c) {
    if (c == '\n') {
      if (_buffer.Length > 0) {
        Debug.Log(_buffer.ToString());
        _buffer.Clear();
      }
    } else {
      _buffer.Append(c);
    }
  }
}

The full example code SeedLangTest.cs:

using System.IO;
using System.Text;
using UnityEngine;

using SeedLang;
using SeedLang.Common;

public class SeedLangTest : MonoBehaviour {
  class ConsoleWriter : TextWriter {
    private readonly StringBuilder _buffer = new StringBuilder();
    public override System.Text.Encoding Encoding => Encoding.Default;
    public override void Write(char c) {
      if (c == '\n') {
        if (_buffer.Length > 0) {
          Debug.Log(_buffer.ToString());
          _buffer.Clear();
        }
      } else {
        _buffer.Append(c);
      }
    }
  }

  const string _script = @"
msg = 'HelloWorld'
for i in range(len(msg)):
    print(msg[:i+1])
";

  void Start() {
    var engine = new Engine(SeedXLanguage.SeedPython, RunMode.Script);
    var consoleWriter = new ConsoleWriter();
    engine.RedirectStdout(consoleWriter);
    engine.Compile(_script, "main");
    engine.Run();
  }
}

In Unity, remember to drag SeedLangTest.cs onto an object (e.g., a 3D cube or an empty object such as GameManager in your scene), otherwise, Unity will never run your C# code.

Start the game and open Unity’s Console window, where you can find all the output lines of the “Hello, World” script.

Register visualizers and use them in Unity games

Once you have registered visualizers to a SeedLang engine, you can trigger or control Unity animations in your game scene. In order to do that, you can run the SeedLang engine either in a separate thread or in a Unity coroutine.

See SeedLangExample: XyzWaler’s CodeExecutor.cs for a detailed demo.