// ==UserScript==
// @name         LaTeX for LIHKG
// @namespace    http://tampermonkey.net/
// @version      0.6
// @description  This is to convert LaTeX to image in LIHKG posts
// @author       CY Fung
// @match        https://lihkg.com/*
// @icon         https://avatars.githubusercontent.com/u/431808?s=48&v=4
// @grant        none
// @run-at       document-body
// @license      Apache 2.0
// ==/UserScript==
'use strict';
(function() {
'use strict';
/*
* Copyright (C) 2023 culefa.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
// Check if the current hostname ends with 'lihkg.com'
if (!location.hostname.endsWith('lihkg.com')) return;
const MAX_QUERY_LENGTH = 800; // 2000 for encoded
// Create an image element for LaTeX rendering
const createLatexNode = (t) => {
if (typeof t != 'string') return null;
const img = document.createElement('img');
img.className = 'lihkg-userscript-latex';
img.loading = 'lazy';
let s = t.length > MAX_QUERY_LENGTH ? t.substring(0, MAX_QUERY_LENGTH) : t;
img.src = `https://math.now.sh?bgcolor=auto&from=${encodeURIComponent(s)}`;
let title = `[latex]${t}[/latex]`;
img.setAttribute('alt', title);
img.setAttribute('title', title);
return img;
};
const validatedMap = new Map();
const validateLaTeX = (t) => {
let r = validatedMap.get(t);
if (typeof r == 'boolean') return r;
r = true;
if (/\:\/\/|\:\\\\|\<(script|h5|h4|h3|h2|h1|span|div|br|pre|quote|img|table|tr|td)\>|\b(javascript)\b|\`\`\`/i.test(t)) r = false;
validatedMap.set(t, r);
return r;
}
// Process a text node to replace LaTeX tags with image elements
const processTextNode = (textNode) => {
if (!textNode) return;
let textContent = textNode.textContent;
if (typeof textContent === 'string' && textContent.length > 15) {} else {
return;
}
textContent = textContent.trim();
// Check if the text content is long enough and has LaTeX tags
if (textContent.length > 15) {} else {
return;
}
if (textContent.indexOf('[latex]') < 0) return;
const split = textContent.split(/\[latex\]((?:(?!\[latex\]|\[\/latex\]).)*)\[\/latex\]/g);
// Check if the split array has an odd length (latex tags are found)
if (split.length >= 3 && (split.length % 2) === 1) {
const newNodes = split.map((t, j) => ((((j % 2) === 0) || !validateLaTeX(t)) ? document.createTextNode(t) : createLatexNode(t)));
textNode.replaceWith(...newNodes);
}
};
// Check a div element and process its text nodes
const checkDivDOM = (div) => {
let textNode = div.firstChild;
while (textNode) {
if (textNode.nodeType === Node.TEXT_NODE) {
processTextNode(textNode);
}
textNode = textNode.nextSibling;
}
}
// Check a post div for LaTeX tags and process its children divs
const checkPostDiv = (postDiv) => {
const html = postDiv.innerHTML;
if (html.indexOf('[latex]') >= 0) {
const divs = postDiv.querySelectorAll('div[class]:not(:empty), div[data-ast-root]:not(:empty)');
if (divs.length >= 1) {
for (const div of divs) {
checkDivDOM(div);
}
} else {
checkDivDOM(postDiv);
}
}
};
// Delayed check for processing post divs
function delayedCheck(arr) {
window.requestAnimationFrame(() => {
for (const s of arr) {
checkPostDiv(s);
}
});
}
// Create an observer to check for new posts and previews
const observer = new MutationObserver((mutations) => {
if (!location.pathname.startsWith('/thread/')) return;
let arr = [];
for (const s of document.querySelectorAll('[data-post-id]:not(.y24Yt), ._3rEWfQ3U63bl18JSaUvRX7 .GAagiRXJU88Nul1M7Ai0H:not(.y24Yt)')) {
s.classList.add('y24Yt');
arr.push(s);
}
if (arr.length >= 1) delayedCheck(arr);
});
// Start observing the body element for changes
observer.observe(document.body, {
subtree: true,
childList: true
});
})();