A new plugin

The goal: a Rust plugin, built and loaded in a project where you can try it.

A plugin lives in a Rusteal project, which builds it with the engine and gives it a level to be tried in: the game it is for, or a project made for it.

rusteal new PluginLab
cd PluginLab
rusteal plugin new Inventory
rusteal plugin new LevelTools --template editor

rusteal plugin new writes the plugin into the project’s Plugins/, lists it in the .uproject and runs the build pipeline. The plugin’s name is also its C++ module’s: letters and digits, not the project’s own name.

Flag	What it does
`--template <name>`	The plugin template, `blank` by default.
`--project <path>`	The project to add it to, when not run from inside it.
`--no-build`	Writes the plugin and stops.

Plugin templates

Template	What it is
`blank`	A runtime plugin with a `HelloComponent` in Rust.
`editor`	An editor plugin: an editor subsystem, a Tools menu entry that counts the project’s assets on a background thread, a console command doing the same, and an asset validator.
`inventory`	A runtime gameplay plugin: items as data assets, an inventory component that stacks them and broadcasts its changes, a world subsystem, project settings for its limits, and console commands that give, take and list the player’s items. See An inventory.
`mannequin`	The `mannequin` feature, a mannequin that copies the player’s movement. See Adding features.

Layout

Plugins/Inventory/
├── Inventory.uplugin           # the plugin, depending on Rusteal
├── rusteal.toml                # the plugin's library: crate, kind, engine modules
├── Source/Inventory/           # its C++ module, which hands the library to Rusteal
│   └── Generated/              # generated C++ wrappers
├── Rust/
│   ├── Cargo.toml              # the plugin's own workspace
│   ├── inventory/              # its code
│   └── bindings/               # its generated bindings
├── Binaries/<Platform>/        # librusteal_Inventory.so, rusteal_Inventory.dll
└── Content/                    # the plugin's assets

The plugin carries everything it needs: the directory can be copied into another Rusteal project at the same version, or kept in a repository of its own. Its Rust/Cargo.toml pins the Rusteal crates as the project’s does, and rusteal upgrade moves both.

The plugin’s rusteal.toml

[plugin]
crate = "inventory"
kind = "runtime"

[codegen]
features = ["core", "engine", "input", "slate", "umg"]

kind is runtime or editor. The [codegen] section works as the game’s (see Binding more of the engine). A module far bigger than a plugin needs can be limited to some classes, and the ones they derive from:

UnrealEd = { module = "unreal_ed", feature = "editor", classes = ["EditorActorSubsystem", "EditorAssetSubsystem"] }

Building and reloading

rusteal build
rusteal build --plugin Inventory
rusteal watch --plugin Inventory

rusteal build builds every library of the project, the game’s and each plugin’s. --plugin <Name> limits the codegen, Cargo and deploy steps to one plugin, which is what working on it needs. In the editor, Rusteal.Reload Inventory reloads only that plugin’s library, and each build reloads it on its own (see Hot reload).

In the editor

The plugin shows in Edit > Plugins, under the project’s plugins, and its content folder in the Content Browser once Settings > Show Plugin Content is on.

Screenshot: the Plugins window listing the Rust plugin. (images/plugins/plugins_window.png)