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ITB Rust-Lua bridge

Lua bindings of various utilities used in development of mods for the game Into the Breach.

Modules

This repository incorporates projects that were previously standalone, as a way to reduce maintenance burden, and lower the total size of libraries included in each Mod Loader release (mostly due to each of them including the mlua library).

Currently, bindings for the following modules are exposed:

ITB-IO

Lua-interfacing library of helper functions related to dealing with basic IO and file system navigation, in a way that prevents Lua from touching files it is not allowed to.

Previously housed at https://github.com/itb-community/itb-io-rs, now fully incorporated into this project.

FTLDat

Rust implementation of FTLDat - a simple library for unpacking and repacking of .dat files, which are used by the games Into the Breach and Faster than Light.

Included as a crate dependency. Maintained at https://github.com/itb-community/ftldat-rs.

Building

This section assumes you have Rust set up with MSVC. If not, see here: https://www.rust-lang.org/learn/get-started.

Building for release mode with MINGW should also be possible, and potentially a bit simpler, but I didn't want to try getting MINGW set up yet.

Development

For development, the build process is very simple:

  1. Open a terminal in the project's root directory.
  2. Run cargo build.

Release

For release (as in, getting a .dll that Lua can interface with), the build process is quite a bit more involved.

  1. Change configuration to build the library in module mode.
    1. Go to Cargo.toml.
    2. Find the [dependencies] section.
    3. Find the entry for mlua and replace "vendored" with "module".
      • Or just comment/uncomment the prepared entries.
    • For explanation why this is needed, see the Troubleshooting section below.
  2. Open a terminal in the project's root directory.
  3. (First time only) Add i686-pc-windows-msvc target with the command rustup target add i686-pc-windows-msvc.
  4. Specify environment variables:
    • LUA_INC=lua/include - path to Lua headers
    • LUA_LIB=lua/lua5.1 - path to Lua .lib file
    • LUA_LIB_NAME=lua/lua5.1 - same path as in LUA_LIB
  5. Run cargo build --lib --release --target=i686-pc-windows-msvc

Steps 4 and 5 are automated in the form of build.sh script.

Compiled .dll will be available in ./target/i686-pc-windows-msvc/release/itb_rs_lua.dll.

Usage

Load the library in your Lua script:

-- load the dll - this exposes `itb_rs_lua` global variable,
-- with functions `new_package` and `read_package`
package.loadlib("itb_rs_lua.dll", "luaopen_itb_rs_lua")()

-- access exported fields or functions
local ftldat_module = itb_rs_lua.ftldat;
local io_module = itb_rs_lua.io;

Troubleshooting

The build process for getting a .dll that can interface with Lua is a little finicky.

Into the Breach runs as a 32-bit application, so the library has to be compiled with 32-bit target.

Also, the library has to be built in mlua's module mode, otherwise the game crashes during exit. The crash doesn't actually cause any issues, as far as I could tell, but it does leave sort of a sour aftertaste after getting everything else to work. It also has the advantage of producing a smaller binary.

Building in module mode under Windows requires linking to a Lua dll (as mentioned in the link). This is what the lua directory and build.sh script are for - if you don't want to run the script file, you'll need to set the variables from the script in your desired environment.

Attributions

Project setup, as well as linking the compiled .dll file and loading it in Lua was based off of https://github.com/voidshine/renoise_tools.