Leaflet

SUSI being an interactive personal assistant, answers questions in a variety of formats. This includes maps, RSS, table, and pie-chart. SUSI MagicMirror Module earlier provided support for only Answer Action Type. So, if you were to ask about a location, it could not show you a map for that location. Support for a variety of formats was added to SUSI Module for MagicMirror so that users can benefit from rich responses by SUSI.AI.

One problem that was faced while adding UI components is that in the MagicMirror Module structure, each module needs to supply its DOM by overriding the getDom() method. Therefore, you need to manage all the UI programmatically. Managing UI programmatically in Javascript is a cumbersome task since you need to create DOM nodes, manually apply styling to them, and add them to parent DOM object which is needed to be returned. We need to write UI for each element like below:

getDom: function () {
        .... 
        ....
        const moduleDiv = document.createElement("div");

        const visualizerCanvas = document.createElement("canvas");
        moduleDiv.appendChild(visualizerCanvas);

        const mapDiv = document.createElement("div");
        loadMap(mapDiv,lat, long);
        moduleDiv.appendChild(mapDiv);
        ...
        ...
}

As you can see, manually managing the DOM is neither that easy nor a recommended practice. It can be done in a more efficient way using the React Library by Facebook.  React is an open source UI library by Facebook. It works on the concept of Virtual DOM i.e. the whole DOM object gets created in the memory and only the changed components are reflected on the document.

Since the SUSI MagicMirror Module is primarily written in open-source TypeScript Lang (a typed superset of JavaScript), we also need to write React in TypeScript. To add React to a Typescript Project, we need to add some dependencies. They can be added using:

$ yarn add react react-dom @types/react @types/react

Now, we need to change our Webpack config to build .tsx files for React. TSX like JSX can contain HTML like syntax for representing DOM object in a syntactic sugar form. This can be done by changing resolve extensions and loaders config so that awesome typescript loaded compiles that TSX files. It is needed to be modified like below

resolve: {
   extensions: [".js", ".ts", ".tsx", ".jsx"],
},

module: {
   loaders: [{
       test: /\.tsx?$/,
       loaders: ["awesome-typescript-loader"],
   },
       {
           test: /\.json$/,
           loaders: ["json-loader"],
       }],
},

This will allow webpack to build and load both .tsx and .ts files. Now that project is setup properly, we need to add UI for Map and RSS Action Type.

The UI for Map is added with the help of React-Leaflet library. React-Leaflet module is a module build on top of Leaflet Map library for loading maps in Browser. We add the React-Leaflet library using

$ yarn add react-leaflet

Now, we declare a MapView Component in React and render Map in it using the React-Leaflet Library. Custom styling can be applied to it. The render function for MapView React Component is defined as follows.

import * as React from "react";
import {Map, Marker, Popup, TileLayer} from "react-leaflet";
interface IMapProps {
   latitude: number;
   longitude: number;
   zoom: number;
}

export class MapView extends React.Component<IMapProps, any> {

   public constructor(props: IMapProps) {
       super(props);
   }

   public render(): JSX.Element | any | any {
       const center = [this.props.latitude, this.props.longitude];
       console.log(center);
       return <Map center={center} zoom={this.props.zoom} style={{height: "300px"}}>
           <TileLayer url="http://{s}.tile.osm.org/{z}/{x}/{y}.png"/>
           <Marker position={center}>
               <Popup>
                   <span> Here </span>
               </Popup>
           </Marker>
       </Map>;
   }
}

For making the UI for RSS Action Type, we define an RSS Card Component. An RSS feed is constituted by various RSS Cards. An RSS Card is defined as follows.

import * as React from "react";

export interface IRssProps {
   title: string;
   description: string;
   link: string;
}

export class RSSCard extends React.Component <IRssProps, any> {

   constructor(props: IRssProps) {
       super(props);
   }

   public render(): JSX.Element | any | any {
       return <div className="card">
           <div className="card-title">{this.props.title}</div>
           <div className="card-description">{this.props.description}</div>
       </div>;
   }
}

Now, we define an RSS feed which is constituted by various RSS Information Cards. Since screen size is limited and there is no option available to the user to scroll, we limit the number of cards displayed to 5 with slice operation on data array.

import * as React from "react";
import {IRssProps, RSSCard} from "./rss-card";

export interface IRSSFeedProps {
   feeds: Array<IRssProps>;
}

export class RSSFeed extends React.Component <IRSSFeedProps, any> {

   public constructor(props: IRSSFeedProps) {
       super(props);
   }

   public render(): JSX.Element | any | any {
       return <div className="rss-div">
           {this.props.feeds.map((feed: IRssProps) => {
                   return <RSSCard key={feed.title} title={feed.title} description={feed.description} link={feed.link}/>;
               }
           ).slice(0, 5)}
       </div>;
   }
}

Now, we can add these components to UI easily and render it with ReactDOM like:

ReactDOM.render(<TableView data={tableData} columns={action.columns}/>, tableDiv);

Below is an example screenshot of RSS and Map View in SUSI MagicMirror.

Resources:

• Using React with Typescript and Webpack article on Medium.
• React and Typescript usage documentation on Typescript Website.
• React Leaflet Library for adding Maps.