rdjakovic/listening-to-tauri-events

Listening to Tauri Events in the Frontend

This skill covers how to subscribe to events emitted from Rust in a Tauri v2 application using the @tauri-apps/api/event module.

Core Concepts

Tauri provides two event scopes:

1. Global events - Broadcast to all listeners across all webviews
2. Webview-specific events - Targeted to specific webview windows

Important: Webview-specific events are NOT received by global listeners. Use the appropriate listener type based on how events are emitted from Rust.

Installation

The event API is part of the core Tauri API package:

npm install @tauri-apps/api
# or
pnpm add @tauri-apps/api
# or
yarn add @tauri-apps/api

Global Event Listening

Basic Listen Pattern

import { listen } from '@tauri-apps/api/event';

// Listen for a global event
const unlisten = await listen('download-started', (event) => {
  console.log('Event received:', event.payload);
});

// Clean up when done
unlisten();

Typed Event Payloads

Define TypeScript interfaces matching your Rust payload structures:

import { listen } from '@tauri-apps/api/event';

// Define the payload type (matches Rust struct with camelCase)
interface DownloadStarted {
  url: string;
  downloadId: number;
  contentLength: number;
}

// Use generic type parameter for type safety
const unlisten = await listen<DownloadStarted>('download-started', (event) => {
  console.log(`Downloading from ${event.payload.url}`);
  console.log(`Content length: ${event.payload.contentLength} bytes`);
  console.log(`Download ID: ${event.payload.downloadId}`);
});

Event Object Structure

The event callback receives an Event<T> object:

interface Event<T> {
  /** Event name */
  event: string;
  /** Event identifier */
  id: number;
  /** Event payload (your custom type) */
  payload: T;
}

Webview-Specific Event Listening

For events emitted with emit_to or emit_filter targeting specific webviews:

import { getCurrentWebviewWindow } from '@tauri-apps/api/webviewWindow';

const appWebview = getCurrentWebviewWindow();

// Listen for events targeted to this specific webview
const unlisten = await appWebview.listen<string>('login-result', (event) => {
  if (event.payload === 'loggedIn') {
    localStorage.setItem('authenticated', 'true');
  } else {
    console.error('Login failed:', event.payload);
  }
});

One-Time Event Listeners

Use once for events that should only be handled a single time:

import { once } from '@tauri-apps/api/event';
import { getCurrentWebviewWindow } from '@tauri-apps/api/webviewWindow';

// Global one-time listener
await once('app-ready', (event) => {
  console.log('Application is ready');
});

// Webview-specific one-time listener
const appWebview = getCurrentWebviewWindow();
await appWebview.once('initialized', (event) => {
  console.log('Webview initialized');
});

Cleanup and Unsubscription

Manual Cleanup

Always unsubscribe listeners when they are no longer needed:

import { listen } from '@tauri-apps/api/event';

const unlisten = await listen('my-event', (event) => {
  // Handle event
});

// Later, when done listening
unlisten();

React Component Cleanup

import { useEffect } from 'react';
import { listen } from '@tauri-apps/api/event';

interface ProgressPayload {
  percent: number;
  message: string;
}

function DownloadProgress() {
  useEffect(() => {
    let unlisten: (() => void) | undefined;

    const setupListener = async () => {
      unlisten = await listen<ProgressPayload>('download-progress', (event) => {
        console.log(`Progress: ${event.payload.percent}%`);
      });
    };

    setupListener();

    // Cleanup when component unmounts
    return () => {
      if (unlisten) {
        unlisten();
      }
    };
  }, []);

  return <div>Listening for progress...</div>;
}

Vue Composition API Cleanup

import { onMounted, onUnmounted } from 'vue';
import { listen } from '@tauri-apps/api/event';

interface NotificationPayload {
  title: string;
  body: string;
}

export default {
  setup() {
    let unlisten: (() => void) | undefined;

    onMounted(async () => {
      unlisten = await listen<NotificationPayload>('notification', (event) => {
        console.log(`${event.payload.title}: ${event.payload.body}`);
      });
    });

    onUnmounted(() => {
      if (unlisten) {
        unlisten();
      }
    });
  }
};

Svelte Cleanup

<script lang="ts">
  import { onMount, onDestroy } from 'svelte';
  import { listen } from '@tauri-apps/api/event';

  interface StatusPayload {
    status: 'idle' | 'loading' | 'complete';
  }

  let unlisten: (() => void) | undefined;

  onMount(async () => {
    unlisten = await listen<StatusPayload>('status-change', (event) => {
      console.log('Status:', event.payload.status);
    });
  });

  onDestroy(() => {
    if (unlisten) {
      unlisten();
    }
  });
</script>

Automatic Listener Cleanup

Tauri automatically clears listeners in these scenarios:

• Page reload - All listeners are cleared
• URL navigation - Listeners are cleared (except in SPA routers)

Warning: Single Page Application routers that do not trigger full page reloads will NOT automatically clean up listeners. You must manually unsubscribe.

Multiple Event Listeners

Listening to Multiple Events

import { listen } from '@tauri-apps/api/event';

interface DownloadEvent {
  url: string;
}

interface ProgressEvent {
  percent: number;
}

interface CompleteEvent {
  path: string;
  size: number;
}

async function setupDownloadListeners() {
  const unlisteners: Array<() => void> = [];

  unlisteners.push(
    await listen<DownloadEvent>('download-started', (event) => {
      console.log(`Started downloading: ${event.payload.url}`);
    })
  );

  unlisteners.push(
    await listen<ProgressEvent>('download-progress', (event) => {
      console.log(`Progress: ${event.payload.percent}%`);
    })
  );

  unlisteners.push(
    await listen<CompleteEvent>('download-complete', (event) => {
      console.log(`Complete: ${event.payload.path} (${event.payload.size} bytes)`);
    })
  );

  // Return cleanup function
  return () => {
    unlisteners.forEach((unlisten) => unlisten());
  };
}

// Usage
const cleanup = await setupDownloadListeners();
// Later...
cleanup();

Type Definitions Reference

Creating Typed Event Helpers

import { listen, once, Event } from '@tauri-apps/api/event';

// Define all your event types in one place
export interface AppEvents {
  'download-started': { url: string; downloadId: number };
  'download-progress': { downloadId: number; percent: number };
  'download-complete': { downloadId: number; path: string };
  'download-error': { downloadId: number; error: string };
  'notification': { title: string; body: string };
}

// Type-safe listen helper
export async function listenTyped<K extends keyof AppEvents>(
  eventName: K,
  handler: (event: Event<AppEvents[K]>) => void
): Promise<() => void> {
  return listen<AppEvents[K]>(eventName, handler);
}

// Usage
const unlisten = await listenTyped('download-started', (event) => {
  // event.payload is typed as { url: string; downloadId: number }
  console.log(event.payload.url);
});

Corresponding Rust Emit Code

For reference, here is how events are emitted from Rust:

Global Emit

use tauri::{AppHandle, Emitter};
use serde::Serialize;

#[derive(Clone, Serialize)]
#[serde(rename_all = "camelCase")]
struct DownloadStarted {
    url: String,
    download_id: usize,
    content_length: usize,
}

#[tauri::command]
fn start_download(app: AppHandle, url: String) {
    app.emit("download-started", DownloadStarted {
        url,
        download_id: 1,
        content_length: 1024,
    }).unwrap();
}

Webview-Specific Emit

use tauri::{AppHandle, Emitter};

#[tauri::command]
fn notify_window(app: AppHandle, window_label: &str, message: String) {
    // Emit to a specific webview by label
    app.emit_to(window_label, "notification", message).unwrap();
}

Filtered Emit

use tauri::{AppHandle, Emitter, EventTarget};

#[tauri::command]
fn broadcast_to_editors(app: AppHandle, content: String) {
    app.emit_filter("content-update", content, |target| {
        match target {
            EventTarget::WebviewWindow { label } => {
                label.starts_with("editor-")
            }
            _ => false,
        }
    }).unwrap();
}

Best Practices

1. Always define TypeScript interfaces for event payloads to catch type mismatches at compile time

2. Use serde(rename_all = "camelCase") in Rust structs to match JavaScript naming conventions

3. Store unlisten functions and call them during cleanup to prevent memory leaks

4. Use once for initialization events that only fire a single time

5. Match listener scope to emit scope - use webview-specific listeners for emit_to events

6. Centralize event type definitions in a shared module for consistency

Common Patterns

Event Bus Pattern

import { listen, Event } from '@tauri-apps/api/event';

type EventHandler<T> = (payload: T) => void;

class TauriEventBus {
  private unlisteners: Map<string, () => void> = new Map();

  async subscribe<T>(event: string, handler: EventHandler<T>): Promise<void> {
    if (this.unlisteners.has(event)) {
      this.unlisteners.get(event)!();
    }

    const unlisten = await listen<T>(event, (e: Event<T>) => {
      handler(e.payload);
    });

    this.unlisteners.set(event, unlisten);
  }

  unsubscribe(event: string): void {
    const unlisten = this.unlisteners.get(event);
    if (unlisten) {
      unlisten();
      this.unlisteners.delete(event);
    }
  }

  unsubscribeAll(): void {
    this.unlisteners.forEach((unlisten) => unlisten());
    this.unlisteners.clear();
  }
}

export const eventBus = new TauriEventBus();

React Hook Pattern

import { useEffect, useState } from 'react';
import { listen, Event } from '@tauri-apps/api/event';

export function useTauriEvent<T>(eventName: string, initialValue: T): T {
  const [value, setValue] = useState<T>(initialValue);

  useEffect(() => {
    let unlisten: (() => void) | undefined;

    listen<T>(eventName, (event: Event<T>) => {
      setValue(event.payload);
    }).then((fn) => {
      unlisten = fn;
    });

    return () => {
      if (unlisten) {
        unlisten();
      }
    };
  }, [eventName]);

  return value;
}

// Usage
function StatusDisplay() {
  const status = useTauriEvent<string>('app-status', 'initializing');
  return <div>Status: {status}</div>;
}