58 lines
1.6 KiB
HTML
58 lines
1.6 KiB
HTML
<script>
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const menuBarHeight = document.querySelector("nav.navbar").clientHeight;
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const mainTocMenuWidth = document.getElementById('main-toc-menu').clientWidth;
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const tocItems = document.querySelectorAll(".toc");
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const navSections = new Array(tocItems.length);
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// Page content
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/*
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Focus effect on current section anchor when user scrolls.
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*/
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tocItems.forEach((el, i) => {
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let id = el.getAttribute("id").substring(5);
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navSections[i] = document.getElementById(id);
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})
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function isVisible(tocIndex) {
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const current = navSections[tocIndex];
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const next = tocIndex < tocItems.length - 1 ? navSections[tocIndex + 1]
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: document.querySelectorAll("section.section").item(1);
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const c = current.getBoundingClientRect();
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if (next) {
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const n = next.getBoundingClientRect();
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const h = (window.innerHeight || document.documentElement.clientHeight);
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return (c.top <= h) && (n.top - menuBarHeight >= 0);
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} else {
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const h = (window.innerHeight || document.documentElement.clientHeight);
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return (c.top <= h);
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}
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}
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function activateIfVisible() {
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for (b = true, i = 0; i < tocItems.length; i++) {
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if (b && isVisible(i)) {
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tocItems[i].classList.add('is-active');
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b = false;
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} else
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tocItems[i].classList.remove('is-active');
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}
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}
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var isTicking = null;
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window.addEventListener('scroll', () => {
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if (!isTicking) {
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window.requestAnimationFrame(() => {
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activateIfVisible();
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isTicking = false;
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});
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isTicking = true;
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}
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}, false);
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</script>
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