25 lines
757 B
JavaScript
25 lines
757 B
JavaScript
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/*
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* Top bar scroll state — shared with the main site's behaviour.
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* Transparent while parked; past the first 80px the bar earns the
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* translucent ground, hairline and blur. Toggles `is-scrolled`.
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*/
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const SCROLL_START = 80;
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export function startNavScroll(bar = document.querySelector("[data-topbar]")) {
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if (!bar) return () => {};
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let frame = 0;
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const apply = () => {
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frame = 0;
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bar.classList.toggle("is-scrolled", window.scrollY > SCROLL_START);
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};
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const onScroll = () => {
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if (!frame) frame = requestAnimationFrame(apply);
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};
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apply();
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window.addEventListener("scroll", onScroll, { passive: true });
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return () => {
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window.removeEventListener("scroll", onScroll);
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if (frame) cancelAnimationFrame(frame);
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};
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}
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