Files
siftlode/frontend/src/components/BackToTop.tsx
T
peter 205f18a2e1 fix(a11y): address R9 code-review findings (glass shadow, focus dedup)
- #1: remove the 9 dead `shadow-*` from glass surfaces instead of letting them override the tuned glass
  box-shadow. The @layer components move made a JSX shadow-* win AND atomically drop the glass inset
  top-edge highlight; deleting the (always-dead) utilities keeps the intended glass depth incl. the
  inset sheen. Verified in-browser: a .glass box-shadow again includes its inset segment.
- #3: drop the per-element focus-visible outlines from the rail chrome buttons and SavedViews action
  buttons — the global button:focus-visible fallback already draws the identical 2px accent ring, so
  they were redundant. Verified: the pin button rings from the global rule alone.
- #5: unify the focus-within outline offset (offset-2) on the SearchBar and ShareDialog pills.
- #2 (double outline on the pill when an inner button is focused): NOT fixed — the clean fix
  (has-[input:focus] so only the input rings the pill) does not generate under Tailwind v4 (measured:
  no rule emitted). Kept the working focus-within, which is a11y-correct (every element still shows a
  focus indicator); the overlapping ring is an accepted cosmetic edge-case.
- #4 (weak ring on solid-fill selected items): deferred to R10 with the selected-paint tokenisation.

Gate green (tsc/eslint/prettier/knip/vitest 79).
2026-08-08 09:28:23 +02:00

64 lines
3.2 KiB
TypeScript

import { useEffect, useRef, useState } from "react";
import { createPortal } from "react-dom";
import { ArrowUp } from "lucide-react";
import { useTranslation } from "react-i18next";
// A floating "back to top" button that fades in once the current page's scroll container is
// scrolled past a threshold, and smooth-scrolls it back to the top. Every page scrolls inside a
// <main class="overflow-y-auto"> — the normal pages share App's, the channel page renders its own
// — so this follows whichever one is mounted. Portaled to <body> so its fixed position is
// viewport-relative regardless of transformed ancestors.
export default function BackToTop({ dep, threshold = 600 }: { dep?: unknown; threshold?: number }) {
const { t } = useTranslation();
const [show, setShow] = useState(false);
const scrollerRef = useRef<HTMLElement | null>(null);
// Listen on the document in the CAPTURE phase and read the scroller off the event, rather than
// looking <main> up when this binds. Scroll events don't bubble, but they do capture — and the
// lookup was a race the lazy pages lost: on the FIRST visit to the channel page its chunk is
// still loading, so the Suspense fallback is on screen, there is no <main> to find, and the
// effect gave up for good (its dep never changes again). The button then stayed dead for that
// whole visit and came back only once the chunk was cached. Nothing to find, nothing to race.
useEffect(() => {
const onScroll = (e: Event) => {
const el = e.target as HTMLElement | null;
if (!el || el.tagName !== "MAIN") return;
scrollerRef.current = el;
setShow(el.scrollTop > threshold);
};
document.addEventListener("scroll", onScroll, { passive: true, capture: true });
return () => document.removeEventListener("scroll", onScroll, { capture: true });
}, [threshold]);
// On navigation, re-read where the new page sits: usually the top (so hide), but some pages
// restore their scroll position. Missing <main> here is now harmless — a page that hasn't
// rendered hasn't scrolled either, and the listener above picks it up the moment it does.
useEffect(() => {
const el = document.querySelector("main");
scrollerRef.current = el;
setShow(!!el && el.scrollTop > threshold);
}, [dep, threshold]);
const toTop = () =>
(scrollerRef.current ?? document.querySelector("main"))?.scrollTo({
top: 0,
behavior: "smooth",
});
// No aria-label/title attributes: ad-block "annoyance" cosmetic filters (e.g. Brave Shields)
// commonly hide floating corner buttons via attribute selectors like [aria-label="Back to top"].
// The accessible name comes from a visually-hidden child instead, which those selectors can't match.
return createPortal(
<button
onClick={toTop}
className={`fixed bottom-5 right-5 z-chrome inline-flex items-center justify-center w-16 h-16 rounded-full glass-card glass-hover text-fg hover:text-accent transition-all duration-200 ${
show ? "opacity-100 translate-y-0" : "opacity-0 translate-y-3 pointer-events-none"
}`}
>
<ArrowUp className="w-7 h-7" aria-hidden="true" />
<span className="sr-only">{t("common.backToTop")}</span>
</button>,
document.body,
);
}