blog

28th September 2022

Build a cross platform app with Tauri


Tauri proves that building fast, lightweight, and portable desktop applications using web technology doesn’t have to come at a cost. Developers traditionally reach for tools like Electron, which powers some of the most popular desktop apps around such as VSCode, Spotify, and Discord. However, newer tools such as Tauri are changing how we think about bringing the Web to our desktops. Tauri is powered by Rust which is a big reason why it’s so fast and lightweight.

In this post, I will create a simple file reading app with Svelte and Tauri, and explain how Tauri works along the way. I chose Svelte for the frontend here as it’s my favourite framework, but you can use whatever web stack you like!

Prerequisites

If you want to follow along with this post in your IDE, you might need to install some tools. It won’t take long, and you can find Tauri’s official guide on their website.

For those of you who haven’t written any Rust before, don’t be scared. Rust is one of the best programming languages ever made. If you aren’t convinced, then five minutes of watching No Boilerplate on YouTube will make you fall in love. For those yet to learn rust, there are so many free YouTube tutorials. There is also an amazing paid course called Rust for JavaScript developers.

Create our project

Fortunately, we don’t need to do any work here, as create-tauri-app will do all the heavy lifting. Open your terminal and run:

npm create tauri-app

Once we’ve answered a couple questions, open your code editor and run npm run tauri dev. The first time this runs, Rust will need to compile some dependancies, but don’t worry; they’re cached on subsequent runs.

Project Structure

Every project will have the same core structure. It doesn’t include any framework specific files:

package.json
src/                    # The frontend app code
src-tauri/              # The backend app code
    tauri.conf.json     # Tauri configuration
    src/                # Our tauri/custom rust code

Tauri API

Tauri provides many powerful built in APIs for interacting with the system. This includes fs, path, clipboard, os, and much more. You can use this api with the @tauri-apps/api package, which you will soon become very familiar with. We will even be using some of these APIs later! Let’s show an example of how you might use the clipboard API:

// Import from @tauri-apps/api/ followed by the name of the API you want
import { readText, writeText } from '@tauri-apps/api/clipboard';

// Get the text from the clipboard
const text = await readText();

// Lets truncate the text to 50 characters
const newText = `${text.slice(0, 50)}...`;

// Finally write the text back
await writeText(newText)

Tauri Commands

Tauri has a system called commands which allow you to call Rust code from the frontend. You can write as many commands as you like, and they’re a superpower when writing Tauri apps. For those of you curious about the shape of a Tauri command, let’s write an example command that takes in a name parameter and returns Hello <name>!.

#[tauri::command] // This macro marks this as a command
fn greet(name: &str) -> String {
    return format!("Hello, {}!", name) // Return a string 
}

We should also add this command to our Tauri handler:

fn main() {
  tauri::Builder::default()
    // This is where you pass in your commands
    .invoke_handler(tauri::generate_handler![greet])
    .run(tauri::generate_context!())
    .expect("Failed to run app");
}

We can then call this from the frontend:

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

async function run() {
    const result = await invoke('greet', {
        // Because of how powerful Rust's macros are, Tauri can workout that the parameter our greet command takes is called "name"
        name: 'Willow'
    });

    console.log(result); // Hello Willow!
}

run()

File Reading app

As promised, we can now cover our file reading app. Using what we have learned about Tauri, we can hit the ground running.

We’re going to use the built-in dialog and fs APIs. The dialog api’s open function is used to prompt the user to select a path. There are a lot of options you can use here to control what the user can select. The fs library provides a few options for reading files, but we’re going to use the readTextFile api.

<script>
    import { readTextFile } from '@tauri-apps/api/fs';
    import { open } from '@tauri-apps/api/dialog';

    let contents;

    async function openFile() {
        const file = await open({
            multiple: false,
            directory: false,
        });

        contents = await readTextFile(file);
    }
</script>

<button on:click={openFile}> Open File </button>

{#if contents}
    <pre>{contents}</pre>
{/if}

The code for this app is available on GitHub if you want to check it out.

Building

You can build your app as a Windows Installer, MacOS Bundle, Debian Package, or an App Image. All the build decisions are managed through your tauri.conf.json, so you don’t have to use an external tool or mess around with cli flags.

Tauri doesn’t fully support cross-platform compliation (i.e. building for Windows on Linux). The recommended workflow is to use CI/CD such as GitHub actions.

Building your Tauri app is as simple as npm run tauri build!

Conclusion

Tauri is great for building cross platform applications. It’s light weight, comes with all kinds of APIs and features for powering your app, and supports using web technology, making it super easy to use. If you want to get started, check out the official guides, and for support you can join the Tauri Discord, or my Discord The Dev Lounge.