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