A set of Unreal Engine 4 plugins that will allow users to write game-play code in C# (and eventually other CLI languages such as F#), in game projects targeting the Windows platform. If you're looking for a cross-platform alternative Xamarin has developed a plugin that provides Mono integration, however a commercial Mono license is not cheap. The primary aim of this project is to make it possible to do anything that can currently be done in Blueprints in C# scripts, in order to eliminate the need for complex Blueprint spaghetti.

The current development focus is on script components (see UKlawrScriptComponent), these are actor components whose functionality is implemented in a C# class. The C# class attached to a script component can access any Blueprint accessible property or function exposed by the actor it is attached to or any of its sibling components (this is still limited at present). Eventually the properties and methods defined in a C# script component will also be exposed to Blueprints.

Some time was also spent developing script objects, which allow for "subclassing" in C# of almost any UObject-derived class, actors included, but that's currently on the back-burner.

NOTE: This project is still highly experimental, and not very useful (though it's getting there).

Check the Wiki for additional details.

• Unreal Engine 4.4.0 or later (you'll need the source from GitHub)
• Visual Studio 2013
• .NET Framework 4.5 or later

The core of the CLR hosting code is located in the Klawr.ClrHost libraries, there is a C++ library that bootstraps the CLR, and a couple of C# libraries that handle hosting related tasks and provide some core classes for use by the auto-generated UE4 C# API as well as user scripts. The C++ library is linked against KlawrRuntimePlugin.

KlawrCodeGeneratorPlugin generates C# wrappers for UObject subclasses from the reflection information gathered by Unreal Header Tool from UFUNCTION and UPROPERTY decorators in the engine/game source. This is the same reflection information that underpins much of the functionality provided by Blueprints.

KlawrRuntimePlugin executes user scripts written in C#, scripts have access to the wrapped UE4 API generated by KlawrCodeGeneratorPlugin.

This is a two phase process, in the first phase the CLR hosting libraries must be built, in the second phase the plugins themselves.

The directory hierarchy of this repository matches that of the UE4 source repository, once you check out this project you can just copy the Engine directory into your UE4 source checkout and everything should end up in the right place. However, if you plan on making any changes to the source you'll probably want create a couple of directory junctions instead of copy/pasting files back and forth. To that end I've provided CreateLinks.bat, which you can right-click on and Run as administrator directly from the checkout root. The batch file will prompt you to enter the path to the UE4 source checkout that you'd like to use to build Klawr, and will then create the necessary directory junctions.

Now everything should be in the right place, from here on any paths are relative to the UE4 source checkout.

The UE4 source contains some built-in Script plugins, these are mostly meant as a reference for plugin developers, but they get in the way because the Unreal Build Tool (UBT) wastes time building and running them. So, before building the Klawr plugins you'll need to make a couple of one-line changes to the UE4 source to get the built-in Script plugins out of the way, you can either make the changes by hand or apply the two patch files that I've provided (ScriptPluginPatch.diff and UnrealHeaderToolPatch.diff). If you're making the changes by hand comment out the following line in Engine/Plugins/ScriptPlugin/Source/ScriptPlugin/Private/ScriptPlugin.cpp

#include "GeneratedScriptLibraries.inl"

and replace the following line in Engine/Source/Programs/UnrealHeaderTool/UnrealHeaderTool.Target.cs

AdditionalPlugins.Add("ScriptGeneratorPlugin");

with

AdditionalPlugins.Add("KlawrCodeGeneratorPlugin");

Now UBT won't waste time building the ScriptGeneratorPlugin, the ScriptGeneratorPlugin won't waste time generating wrapper functions that aren't used by anything, and ScriptPlugin won't fail to build because ScriptGeneratorPlugin didn't produce GeneratedScriptLibraries.inl.

1. Open Engine\Source\ThirdParty\Klawr\Klawr.ClrHost.sln in VS2013.
2. Set the Solution Configuration to either Release or Debug.
3. Set the Solution Platform to x64 (this is very important, Win32 builds are not supported yet).
4. Select Build Solution to build all the libraries.

Assuming that the build finished with no errors you can move on to phase two.

1. Configure Unreal Header Tool to use the KlawrCodeGeneratorPlugin, to do so add/edit the Plugins section in Engine\Programs\UnrealHeaderTool\Saved\Config\Windows\Engine.ini:

   [Plugins]
   ProgramEnabledPlugins=KlawrCodeGeneratorPlugin
   ScriptExcludedModules=ScriptPlugin
   ScriptExcludedModules=ScriptEditorPlugin
   ScriptExcludedModules=ScriptGeneratorPlugin
   

2. Run GenerateProjectFiles.bat in your UE4 source checkout.

3. Open UE4.sln in VS2013.

4. Set the Solution Configuration to Debug Editor or Development Editor.

5. Set the Solution Platform to Win64 (this is very important, Win32 builds are not supported yet).

6. Select Build Solution to build everything.

During the build you may see a bunch of console windows popup briefly, don't panic, this is just KlawrCodeGeneratorPlugin building the UE4 C# wrappers assembly.

First of all make sure you've got a project open that you don't mind obliterating in case something goes wrong, next enable KlawrRuntimePlugin and KlawrEditorPlugin in UnrealEd, restart as requested.

Now you can create a script component Blueprint.

Klawr is licensed under the MIT license.

Klawr uses the pugixml library to parse XML, it was written by Arseny Kapoulkine and is licensed under the MIT license.