mogwai

minimalist, obvious, graphical web application interface

release:

master:

mogwai is a frontend DOM library for creating web 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.

goals

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

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!

concepts

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. mogwai's channels are many-producer, many-consumer and are immediate - they do not perform buffering and do not require polling.
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 - a Gizmo is mogwai's controller. Gizmos maintain state and communicate messages to views. The Gizmo's update function is a fold over messages sent on its Transmitter that mutate the state variable and send output messages to the View, which in turn update the DOM.
communication is easy - just gizmo.send(&my_message) to send a message into a gizmo and the gizmo will update its view accordingly.

example

Here is an example of a "dumb view" button that counts its own clicks.

extern crate mogwai;
use mogwai::prelude::*;

let (tx, rx) =
  txrx_fold(
    0,
    |n:&mut i32, _:&Event| -> String {
      *n += 1;
      if *n == 1 {
        "Clicked 1 time".to_string()
      } else {
        format!("Clicked {} times", *n)
      }
    }
  );

let view = view!(
    <button on:click=tx>
        {("Clicked 0 times", rx)}
    </button>
);

if cfg!(target_arch = "wasm32") {
  view.run().unwrap_throw()
}

Here's that same example using the elm-like Component trait:

use mogwai::prelude::*;

pub struct Button {
    pub clicks: i32
}

#[derive(Clone)]
pub enum ButtonIn {
    Click
}

#[derive(Clone)]
pub enum ButtonOut {
    Clicks(String)
}

impl Component for Button {
    type ModelMsg = ButtonIn;
    type ViewMsg = ButtonOut;
    type DomNode = HtmlElement;

    fn update(
        &mut self,
        msg: &ButtonIn,
        tx_view: &Transmitter<ButtonOut>,
        _subscriber: &Subscriber<ButtonIn>
    ) {
        match msg {
            ButtonIn::Click => {
                self.clicks += 1;
                let text = if self.clicks == 1 {
                    "Clicked 1 time".to_string()
                } else {
                    format!("Clicked {} times", self.clicks)
                };
                tx_view.send(&ButtonOut::Clicks(text))
            }
        }
    }

    // Notice that the `Component::view` function returns a `ViewBuilder<T>` and not
    // a `View<T`.
    fn view(
        &self,
        tx: &Transmitter<ButtonIn>,
        rx: &Receiver<ButtonOut>
    ) -> ViewBuilder<HtmlElement> {
        let tx_event = tx.contra_map(|_:&Event| ButtonIn::Click);
        let rx_text = rx.branch_map(|ButtonOut::Clicks(text)| text.clone());

        builder!(
            <button on:click=tx_event>
                {("Clicked 0 times", rx_text)}
            </button>
        )
    }
}

let gizmo = Gizmo::from(Button{ clicks: 0 });
let view = View::from(gizmo.view_builder());
// Queue some messages for the component, as if the button had been clicked:
gizmo.send(&ButtonIn::Click);
gizmo.send(&ButtonIn::Click);

assert_eq!(&view.html_string(), "<button>Clicked 2 times</button>");

if cfg!(target_arch = "wasm32") {
    // running a view adds its DOM to document.body and ownership is passed to the window
    // this only works in the browser
    view.run().unwrap_throw()
}

// After handing off the view the gizmo itself may fall out of scope and be dropped. The
// view is all that is needed for your app to run.

introduction

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

why

Rust is beginning to have a good number of frontend libraries. Most however, encorporate a virtual DOM with a magical update phase. Even in a languague that has performance to spare this step can cause unwanted slowness.

mogwai lives in a happy space just above "bare metal". It does this by providing the tools needed to declare exactly which parts of the DOM change and when. These same tools encourage functional progamming patterns like encapsulation over inheritance.

Channel-like primitives and a declarative view are used to define components and then wire them together. Once the interface is defined and built, the channels are effectively erased and it's functions all the way down. There's no performance overhead from vdom, shadow dom, polling or patching. So 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 and your team :)

Please do keep in mind that mogwai is still in alpha and the API is actively changing.

made for rustaceans, by a rustacean

Another benefit of mogwai is that it is Rust-first. There is no requirement that you have npm or node. Getting your project up and running without writing any javascript is easy enough.

performance

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

ok - where do i start?

First you'll need new(ish) version of the rust toolchain. For that you can visit https://rustup.rs/ 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 https://github.com/schell/mogwai-template.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 127.0.0.1:8888

Happy hacking! ☕ ☕ ☕

more examples please

For more examples, check out

the sandbox

the todomvc app

the benchmark suite

To build the examples use:

cd examples/whatever && wasm-pack build --target web

external examples

mogwai-realworld A "real world" app implementation (WIP)

support channel ☎️

There is an experimental realtime support channel at https://matrix.to/#/!iABugogSTxJNzlrcMW:matrix.org?via=matrix.org. YMMV

sponsorship

Please consider sponsoring the development of this library!

sponsor me on github

stoically/mogwai