45 lines
2.7 KiB
JavaScript
45 lines
2.7 KiB
JavaScript
/** Visible content is the baseline. Enhance only when it enters the viewport. */
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export function initMotion(doc = document) {
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const view = doc.defaultView;
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const preference = view.matchMedia('(prefers-reduced-motion: reduce)');
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const animations = new Set();
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const seen = new WeakSet();
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const start = {
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fade: { opacity: .2 }, rise: { transform: 'translateY(28px)' }, sink: { transform: 'translateY(-28px)' },
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left: { transform: 'translateX(-36px)' }, right: { transform: 'translateX(36px)' },
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zoom: { transform: 'scale(.92)' }, flip: { transform: 'perspective(800px) rotateX(-16deg)' }, blur: { filter: 'blur(6px)' },
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};
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const nodes = [...doc.querySelectorAll('[class*="fx-entrance-"]')].filter(node => Object.keys(start).some(name => node.classList.contains(`fx-entrance-${name}`)));
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const show = node => {
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if (seen.has(node) || preference.matches) return;
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seen.add(node);
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const name = Object.keys(start).find(name => node.classList.contains(`fx-entrance-${name}`));
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const delay = node.classList.contains('fx-delay-long') ? 600 : node.classList.contains('fx-delay-medium') ? 300 : node.classList.contains('fx-delay-short') ? 150 : 0;
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// Fade itself is optional; direction, zoom and flip keep text at full contrast.
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const style = view.getComputedStyle(node);
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const finish = { opacity: style.opacity, transform: style.transform, filter: style.filter };
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const first = { ...start[name] };
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if (first.transform && finish.transform !== 'none') first.transform += ' ' + finish.transform;
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const animation = node.animate([first, finish], { duration: 650, delay, easing: 'cubic-bezier(.2,.7,.2,1)', fill: 'none' });
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animations.add(animation); animation.finished.then(() => animations.delete(animation), () => animations.delete(animation));
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};
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const observer = new view.IntersectionObserver(entries => {
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for (const entry of entries) if (entry.isIntersecting) { show(entry.target); observer.unobserve(entry.target); }
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}, { threshold: 0, rootMargin: '0px 0px -24px 0px' });
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const syncPreference = () => {
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if (preference.matches) {
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observer.disconnect();
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animations.forEach(animation => animation.cancel());
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} else {
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// Reduction may have been active at startup or enabled during this visit.
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// Resume observing unseen content when movement is allowed again.
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nodes.forEach(node => { if (!seen.has(node)) observer.observe(node); });
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}
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};
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preference.addEventListener('change', syncPreference);
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syncPreference();
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return () => { observer.disconnect(); animations.forEach(animation => animation.cancel()); preference.removeEventListener('change', syncPreference); };
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}
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if (!document.querySelector('#editor')) initMotion();
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