How to emit a Tauri window event from rocket request

Question

I hope this is not too obscure.

I am playing around with Tauri where I want to expose a web based control panel for the app. By going to a url on the local.network, eg http://192.168.1.101:8000/some-action , it will send a window message to the Tauri app running on that machine. Imagine a dashboard app in an office where users on the.network can control how the app behaves via a web url.

Here is my rust code so far:

// use rocket runtime
#[rocket::main]
async fn main() {
    tauri::Builder::default()
        .setup(|app| {

            let window = app.get_window("main").unwrap();

            #[get("/")]
            fn index() {
                // this is where I want to emit the window event if possible
                //window.emit("from-rust", format!("message")).expect("failed to emit");
            }
            
            // mount the rocket instance
            tauri::async_runtime::spawn(async move {
                let _rocket = rocket::build()
                    .mount("/", routes![index])
                    .launch().await;
                });
            
            Ok(())
        })
        .run(tauri::generate_context!())
        .expect("error while running tauri application");
}

I am able to run the rocket server, however, I can't work out how to send the window event from the rocket request handler function.

Any suggestions or insights would be very much appreciated.

Answer 1

fn items are not allowed to capture their environment. But since #[get(...)] is only allowed to be used on fn you can't use it.

You can just implement the required traits for a custom struct yourself though.

use async_trait::async_trait;
use rocket::http::Method;
use rocket::route::{Handler, Outcome};
use rocket::{Data, Request, Route};
use tauri::{Manager, generate_context};

#[derive(Clone)]
struct WindowHandler {
    window: tauri::Window,
}

impl WindowHandler {
    fn new(window: tauri::Window) -> Self {
        Self { window }
    }
}

#[async_trait]
impl Handler for WindowHandler {
    async fn handle<'r>(&self, request: &'r Request<'_>, data: Data<'r>) -> Outcome<'r> {
        self.window
            .emit("from-rust", format!("message"))
            .expect("failed to emit");
        todo!()
    }
}
impl From<WindowHandler> for Vec<Route> {
    fn from(value: WindowHandler) -> Self {
        vec![Route::new(Method::Get, "/", value)]
    }
}

#[rocket::main]
async fn main() {
    tauri::Builder::default()
        .setup(|app| {
            let window = app.get_window("main").unwrap();

            let index = WindowHandler::new(window);
            // mount the rocket instance
            tauri::async_runtime::spawn(async move {
                let _rocket = rocket::build().mount("/", index).launch().await;
            });
            Ok(())
        })
        .run(generate_context!())
        .expect("error while running tauri application");
}

---

Or another possibility is to use a global WINDOW: OnceLock<Window> like this:

#![feature(once_cell)]
use std::sync::OnceLock;

use rocket::{get, routes};
use tauri::{Manager, generate_context, Window};

static WINDOW: OnceLock<Window> = OnceLock::new();
#[rocket::main]
async fn main() {
    tauri::Builder::default()
        .setup(|app| {
            let window = app.get_window("main").unwrap();

            _ = WINDOW.set(window);

            #[get("/")]
            fn index() {
                WINDOW.get().expect("window is available").emit("from-rust", format!("message")).expect("failed to emit");
            }
            // mount the rocket instance
            tauri::async_runtime::spawn(async move {
                let _rocket = rocket::build().mount("/", routes![index]).launch().await;
            });
            Ok(())
        })
        .run(generate_context!())
        .expect("error while running tauri application");
}