Embedding Lua in the Source Engine

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Andrew C. P. McWatters (me@andrewmcwatters.com), 2010
Software Development Engineer

SourceSource

What is Lua?

Lua is a powerful, fast, lightweight, embeddable scripting language.

Lua combines simple procedural syntax with powerful data description constructs based on associative arrays and extensible semantics. Lua is dynamically typed, runs by interpreting bytecode for a register-based virtual machine, and has automatic memory management with incremental garbage collection, making it ideal for configuration, scripting, and rapid prototyping.

You can find out more about Lua on their website, here.

Overview

Lua is currently the leading scripting language in games, and for Steam users, is synonymous with Garry's Mod. Unfortunately, Garry's Mod isn't open source, and as a result, we cannot use Team Garry's implementation of Lua for our and others' benefit. However, my project, <Half-Life 2> Half-Life 2: Sandbox is currently the leading open source project dedicated to bringing the developer community a method for embedding Lua into their mod nearly seamlessly, and in this article I'll explain how.

Half-Life 2: Sandbox uses a pure variant of Lua, different than Garry's implementation of the language, which has restrictions on many libraries, and modified syntax for C++ styled comments. Half-Life 2: Sandbox's goal is to provide a neutral, clean, standardized and well documented code base for interfacing with Lua, unlike articles seen within the Valve Developer Community such as the LuaBind oriented Lua tutorial or Adding Lua article.

Implementation

Files

Installation

The Lua manager scripts found in the Half-Life 2: Sandbox source code were written generically so they could be added to any mod.

  • If you're working with a mod's source code, rather than a plugin, the files above should be placed within src/game/shared
  • In your project files, place both the luamanager.cpp and luamanager.h in the Source Files filter
  • Compile your binaries
  • Simply add the precompiled lua51.dll to your mod's bin folder, and now your mod has integrated Lua!

Update: Half-Life 2: Sandbox has went through several revisions extending its Lua API greatly including many classes and libraries for real-world usage with Source. As a result of these expansions, you'll now find that to be able to use these classes, you'll need to add the individual class .cpp and .h files, which are all listed in luamanager.cpp by headers that correspond to .cpp files.

External links