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minimal, obvious, graphical web application interface

release: cicd

master: cicd

mogwai is a view library for creating GUI applications. It is written in Rust and runs in your browser and has enough functionality server-side to do rendering. It is an alternative to React, Backbone, Ember, Elm, Purescript, etc.



  • provide a declarative approach to creating and managing DOM nodes
  • encapsulate component state and compose components easily
  • explicate DOM updates
  • be small and fast (aka keep it snappy)

If mogwai achieves these goals, which I think it does, then maintaining application state, composing widgets and reasoning about your program will be easy. Furthermore, your users will be happy because their UI is snappy!


The main concepts behind mogwai are

  • channels instead of callbacks - view events like clicks, blurs, etc are transmitted into a channel instead of invoking a callback. Receiving ends of channels can be branched and may have their output messages be mapped, filtered and folded.

  • views are dumb - a View is just a bit of DOM that receives and transmits messages. When a View goes out of scope and is dropped in Rust, it is also dropped from the DOM. Views may be constructed and nested using plain Rust functions or an RSX macro.

  • widgets are folds over input messages - the user interface widget in mogwai is a ViewBuilder with a logic loop.


Here is an example of a button that counts the number of times it has been clicked:

use mogwai::prelude::*;

async fn logic(
  mut rx_click: broadcast::Receiver<()>,
  tx_text: broadcast::Sender<String>,
) {
    let mut clicks = 0;
    loop {
        match {
            Some(()) => {
                clicks += 1;
                let text = if clicks == 1 {
                    "Clicked 1 time".to_string()
                } else {
                    format!("Clicked {} times", clicks)
            None => break,

fn view(
    tx_click: broadcast::Sender<()>,
    rx_text: broadcast::Receiver<String>
) -> ViewBuilder<Dom> {
    let tx_event = tx_click.sink().contra_map(|_:DomEvent| ());

        // Create a button that transmits a message of `()` into tx_event on click.
        <button on:click=tx_event>
            // Using braces we can embed rust values in our DOM.
            // Here we're creating a text node that starts with the
            // string "Clicked 0 times" and then updates every time a
            // message is received on rx_text.
            {("Clicked 0 times", rx_text)}

let (tx_click, rx_click) = broadcast::bounded(2);
let (tx_text, rx_text) = broadcast::bounded(1);
let component: Component<Dom> = Component::from(view(tx_click.clone(), rx_text))
    .with_logic(logic(rx_click, tx_text));

let view: View<Dom> = component

// Spawn asyncronous actions on any target with `mogwai::spawn`.
mogwai::spawn(async move {
    // Queue some messages for the view as if the button had been clicked:

    // view's html is now "<button>Clicked 2 times</button>"


If you're interested in learning more - please read the introduction and documentation.


Rust is beginning to have a good number of frontend libraries. Many encorporate a virtual DOM with a magical update phase. Even in a language that has performance to spare this step can cause unwanted slowness and can be hard to reason about what is updating, exactly.

In mogwai, streams, sinks and a declarative view builder are used to define components and how they change over time.

DOM mutation is explicit and happens as a result of views receiving messages, so there is no performance overhead from vdom diffing.

If you prefer a functional style of programming with lots of maps and folds - or if you're looking to go vroom! then maybe mogwai is right for you :)

Please do keep in mind that mogwai is still in alpha and the API is actively changing - PRs, issues and questions are welcomed. As of the 0.5 release we expect that the API will be relatively backwards compatible.

made for rustaceans, by a rustacean

mogwai is a Rust first library. There is no requirement that you have npm or node. Getting your project up and running without writing any javascript is easy enough.


mogwai is snappy! Here are some very handwavey and sketchy todomvc metrics:

mogwai performance benchmarking

ok - where do i start?

First you'll need new(ish) version of the rust toolchain. For that you can visit and follow the installation instructions.

Then you'll need wasm-pack.

For starting a new mogwai project we'll use the wonderful cargo-generate, which can be installed using cargo install cargo-generate.

Then run

cargo generate --git

and give the command line a project name. Then cd into your sparkling new project and

wasm-pack build --target web

Then, if you don't already have it, cargo install basic-http-server or use your favorite alternative to serve your app:

basic-http-server -a

Happy hacking!

more examples please

Examples can be found in the examples folder.

To build the examples use:

wasm-pack build --target web examples/{the example}

Additional external examples include:


📗 Cooking with Mogwai is a series of example solutions to various UI problems. It aims to be a good reference doc but not a step-by-step tutorial.

group channel ☎️

Hang out and talk about mogwai in the support channel:


Please consider sponsoring the development of this library!


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