The Rust SDK

openomsi-plugin-sdk is the guest library for Rust plugins. A plugin is a cdylib built for wasm32-unknown-unknown.

use openomsi_plugin_sdk as omsi;

omsi::plugin!(|| {
    // Register handlers here; this closure runs once at start.
    omsi::on_vehicle(|name| {
        if let Some(name) = name {
            let _ = omsi::api::message(&format!("You drive the {name}"), Some(6.0));
        }
    });

    omsi::every(0.5, || {
        let kmh = omsi::api::speed().unwrap_or(0.0);
        // build a HUD panel, etc.
        let _ = kmh;
    });
});

What the SDK gives you

• plugin! defines the ABI exports the host calls - you never write extern "C" yourself.
• Events: on_start, on_frame, on_key, on_vehicle, and the generic on(event, ...).
• Timers and watches: after, every, watch, cancel.
• Typed API: everything in omsi::api, generated from the game's API manifest, so each call has real argument and return types.
• Escape hatch: omsi::call(name, json!([...])) reaches any function the manifest lists, even one newer than this SDK's generated wrappers.

Data crosses the boundary as JSON (serde_json::Value). The SDK and the oopc build take care of compiling to a stripped WebAssembly module.

Regenerating the typed API

When the game ships a bigger API manifest, regenerate the wrappers with one command:

cargo xtask gen-sdk path/to/api.json