/**
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* A plugin which enables rendering of math equations inside
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* of reveal.js slides. Essentially a thin wrapper for KaTeX.
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*
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* @author Hakim El Hattab
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* @author Gerhard Burger
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*/
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export const KaTeX = () => {
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let deck;
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let defaultOptions = {
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version: 'latest',
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delimiters: [
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{left: '$$', right: '$$', display: true}, // Note: $$ has to come before $
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{left: '$', right: '$', display: false},
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{left: '\\(', right: '\\)', display: false},
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{left: '\\[', right: '\\]', display: true}
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],
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ignoredTags: ['script', 'noscript', 'style', 'textarea', 'pre']
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}
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const loadCss = src => {
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let link = document.createElement('link');
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link.rel = 'stylesheet';
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link.href = src;
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document.head.appendChild(link);
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};
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/**
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* Loads a JavaScript file and returns a Promise for when it is loaded
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* Credits: https://aaronsmith.online/easily-load-an-external-script-using-javascript/
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*/
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const loadScript = src => {
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return new Promise((resolve, reject) => {
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const script = document.createElement('script')
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script.type = 'text/javascript'
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script.onload = resolve
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script.onerror = reject
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script.src = src
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document.head.append(script)
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})
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};
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async function loadScripts(urls) {
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for(const url of urls) {
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await loadScript(url);
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}
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}
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return {
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id: 'katex',
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init: function (reveal) {
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deck = reveal;
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let revealOptions = deck.getConfig().katex || {};
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let options = {...defaultOptions, ...revealOptions};
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const {local, version, extensions, ...katexOptions} = options;
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let baseUrl = options.local || 'https://cdn.jsdelivr.net/npm/katex';
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let versionString = options.local ? '' : '@' + options.version;
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let cssUrl = baseUrl + versionString + '/dist/katex.min.css';
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let katexUrl = baseUrl + versionString + '/dist/katex.min.js';
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let mhchemUrl = baseUrl + versionString + '/dist/contrib/mhchem.min.js'
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let karUrl = baseUrl + versionString + '/dist/contrib/auto-render.min.js';
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let katexScripts = [katexUrl];
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if(options.extensions && options.extensions.includes("mhchem")) {
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katexScripts.push(mhchemUrl);
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}
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katexScripts.push(karUrl);
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const renderMath = () => {
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renderMathInElement(reveal.getSlidesElement(), katexOptions);
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deck.layout();
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}
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loadCss(cssUrl);
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// For some reason dynamically loading with defer attribute doesn't result in the expected behavior, the below code does
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loadScripts(katexScripts).then(() => {
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if( deck.isReady() ) {
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renderMath();
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}
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else {
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deck.on( 'ready', renderMath.bind( this ) );
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}
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});
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}
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}
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};
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