09モーション低減値を検知して展開なしで即表示されるパネル

<main class="stage">
<div class="rp is-demo" id="rp">
  <button class="rp__trigger" id="rpTrigger" type="button" aria-haspopup="true" aria-expanded="false">設定</button>
  <div class="rp__panel" id="rpPanel" role="menu" hidden>
    <div class="rp__row" role="menuitem">背景模様</div>
    <div class="rp__row" role="menuitem">通知音</div>
    <div class="rp__row" role="menuitem">文字サイズ</div>
  </div>
  <p class="rp__badge" id="rpBadge">動作の軽減 オフ</p>
  <p class="rp__sr" role="status" aria-live="polite" id="rpLive"></p>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 계산 겹: index.html applyMotionPref() 가 matchMedia(prefers-reduced-motion).matches 값과
// 데모용 강제 값을 합쳐 지속시간(ms) 숫자를 계산해 패널에 인라인으로 놓는다.
@include stage($stage-ink);

.rp { display: flex; flex-direction: column; align-items: center; gap: $sp-2; position: relative; }

.rp__trigger {
  padding: $sp-2 $sp-3; border: none; border-radius: $r-pill;
  background: rgba($subject-cream, .92); color: $subject-ink; font-size: 13px; font-weight: 600;
  cursor: pointer; box-shadow: $shadow-raised;
}

.rp__panel {
  position: absolute; top: 100%; margin-top: $sp-2; left: 50%; min-width: 140px;
  display: flex; flex-direction: column; gap: $sp-1; padding: $sp-2; border-radius: $r-card;
  background: rgba($subject-cream, .97); box-shadow: $shadow-raised;
  // 붙는 지점(트리거 아래)이 있는 요소라 원점을 위쪽 중앙에 둔다
  transform-origin: top center;
  transform: translateX(-50%) scale(.9); opacity: 0; pointer-events: none;
  transition: transform $dur-base $ease-spring, opacity $dur-quick $ease-out;
}
// [hidden] 은 UA 스타일이 author .rp__panel 과 같은 특이도라 밀린다 — 명시로 되살린다
.rp__panel[hidden] { display: none; }
.rp__panel--open { transform: translateX(-50%) scale(1); opacity: 1; pointer-events: auto; }

.rp__row { padding: $sp-1 $sp-2; border-radius: $r-xs; color: $subject-ink; font-size: 12px; }

.rp__badge { font-size: 11px; color: rgba($subject-cream, .72); }

.rp__sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); margin: -1px; padding: 0; border: 0; }

@media (max-width: 340px) {
  .rp__panel { min-width: 116px; }
  .rp__trigger { font-size: 12px; padding: $sp-1 $sp-2; }
}

@media (prefers-reduced-motion: reduce) {
  .rp__panel { transition: none !important; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.rp {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  position: relative;
}

.rp__trigger {
  padding: 8px 12px;
  border: none;
  border-radius: 999px;
  background: rgba(255, 247, 230, 0.92);
  color: #17141a;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
}

.rp__panel {
  position: absolute;
  top: 100%;
  margin-top: 8px;
  left: 50%;
  min-width: 140px;
  display: flex;
  flex-direction: column;
  gap: 4px;
  padding: 8px;
  border-radius: 16px;
  background: rgba(255, 247, 230, 0.97);
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  transform-origin: top center;
  transform: translateX(-50%) scale(0.9);
  opacity: 0;
  pointer-events: none;
  transition: transform 300ms cubic-bezier(0.2, 0.8, 0.2, 1), opacity 220ms ease-out;
}

.rp__panel[hidden] {
  display: none;
}

.rp__panel--open {
  transform: translateX(-50%) scale(1);
  opacity: 1;
  pointer-events: auto;
}

.rp__row {
  padding: 4px 8px;
  border-radius: 4px;
  color: #17141a;
  font-size: 12px;
}

.rp__badge {
  font-size: 11px;
  color: rgba(255, 247, 230, 0.72);
}

.rp__sr {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  margin: -1px;
  padding: 0;
  border: 0;
}

@media (max-width: 340px) {
  .rp__panel {
    min-width: 116px;
  }
  .rp__trigger {
    font-size: 12px;
    padding: 4px 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .rp__panel {
    transition: none !important;
  }
}

(function () {
  var root = document.getElementById('rp');
  var trigger = document.getElementById('rpTrigger');
  var panel = document.getElementById('rpPanel');
  var badge = document.getElementById('rpBadge');
  var live = document.getElementById('rpLive');
  var synthetic = false;
  function human() { if (synthetic) return; if (root.classList.contains('is-demo')) root.classList.remove('is-demo'); }

  var REDUCE_MOTION_DURATION_MS = 0;
  var NORMAL_MOTION_DURATION_MS = 240;
  var reduceMQ = window.matchMedia('(prefers-reduced-motion: reduce)');
  var forcedReduce = false;

  // 계산 겹: 시스템의 動作の軽減 값(matchMedia.matches)과 데모용 강제 값(forcedReduce)을 합쳐
  // 실제로 쓸 지속시간 값을 계산해 패널에 직접 놓는다 — 미디어쿼리 블록이 있고 없고가 아니라
  // 그 값 자체를 읽어 duration 숫자를 정하고, 그 숫자를 배지·안내문에도 그대로 노출한다.
  function applyMotionPref() {
    var reduce = reduceMQ.matches || forcedReduce;
    var ms = reduce ? REDUCE_MOTION_DURATION_MS : NORMAL_MOTION_DURATION_MS;
    panel.style.transitionDuration = ms + 'ms';
    badge.textContent = '動作の軽減 ' + (reduce ? 'オン' : 'オフ');
    return { reduce: reduce, ms: ms };
  }
  applyMotionPref();

  function openPanel() {
    var pref = applyMotionPref();
    panel.hidden = false;
    requestAnimationFrame(function () { panel.classList.add('rp__panel--open'); });
    trigger.setAttribute('aria-expanded', 'true');
    live.textContent = pref.ms + 'ms の値で ' + (pref.reduce ? '即座に表示' : '展開');
  }
  function closePanel() {
    panel.classList.remove('rp__panel--open');
    trigger.setAttribute('aria-expanded', 'false');
    var pref = applyMotionPref();
    window.setTimeout(function () { if (!panel.classList.contains('rp__panel--open')) panel.hidden = true; }, pref.ms + 20);
  }
  trigger.addEventListener('click', function () {
    human();
    if (panel.hidden) openPanel(); else closePanel();
  });

  if (typeof reduceMQ.addEventListener === 'function') {
    reduceMQ.addEventListener('change', function () { forcedReduce = false; applyMotionPref(); });
  }

  var reduce = reduceMQ.matches;
  var phase = 0, loopTimer = 0;
  function runStep() {
    if (!root.classList.contains('is-demo')) return;
    synthetic = true;
    if (phase % 4 === 0) { forcedReduce = false; applyMotionPref(); }
    else if (phase % 4 === 2) { forcedReduce = true; applyMotionPref(); }
    trigger.dispatchEvent(new MouseEvent('click', { bubbles: true }));
    synthetic = false;
    phase++;
    loopTimer = window.setTimeout(runStep, 350);
  }
  if (!reduce) { loopTimer = window.setTimeout(runStep, 420); }
  else { root.classList.remove('is-demo'); }
})();

// EmojiPickerReducedMotionInstantPanel — vanilla 판(run/402/demo/09-.../index.html) 의 React 포트.
// 계산 겹: matchMedia(prefers-reduced-motion).matches 값과 데모용 강제 값을 합쳐 지속시간(ms)
// 숫자를 계산해 패널에 인라인으로 놓는다 — 미디어쿼리 블록의 존재 여부가 아니라 그 값 자체를 쓴다.
import { useEffect, useRef, useState } from "react";
import styles from "./EmojiPickerReducedMotionInstantPanel.module.scss";

type Box<T> = { current: T };

const REDUCE_MOTION_DURATION_MS = 0;
const NORMAL_MOTION_DURATION_MS = 240;
const ROWS = ["배경 무늬", "알림음", "글자 크기"];

export default function EmojiPickerReducedMotionInstantPanel() {
  const [isDemo, setIsDemo] = useState(true);
  const [open, setOpen] = useState(false);
  const [hidden, setHidden] = useState(true);
  const [reduceOn, setReduceOn] = useState(false);
  const [live, setLive] = useState("");
  const [durationMs, setDurationMs] = useState(NORMAL_MOTION_DURATION_MS);

  const isDemoRef = useRef(true) as unknown as Box<boolean>;
  const synthRef = useRef(false) as unknown as Box<boolean>;
  const openRef = useRef(false) as unknown as Box<boolean>;
  const forcedReduceRef = useRef(false) as unknown as Box<boolean>;
  const hideTimerRef = useRef(0) as unknown as Box<number>;
  const loopTimerRef = useRef(0) as unknown as Box<number>;

  function human() {
    if (synthRef.current) return;
    if (isDemoRef.current) { isDemoRef.current = false; setIsDemo(false); }
  }

  function applyMotionPref(): { reduce: boolean; ms: number } {
    const mq = window.matchMedia("(prefers-reduced-motion: reduce)");
    const reduce = mq.matches || forcedReduceRef.current;
    const ms = reduce ? REDUCE_MOTION_DURATION_MS : NORMAL_MOTION_DURATION_MS;
    setDurationMs(ms);
    setReduceOn(reduce);
    return { reduce: reduce, ms: ms };
  }

  function openPanel() {
    const pref = applyMotionPref();
    setHidden(false);
    window.setTimeout(() => setOpen(true), 0);
    setLive(pref.ms + "ms 값으로 " + (pref.reduce ? "즉시 표시" : "펼쳐짐"));
  }

  function closePanel() {
    setOpen(false);
    const pref = applyMotionPref();
    window.clearTimeout(hideTimerRef.current);
    hideTimerRef.current = window.setTimeout(() => setHidden(true), pref.ms + 20);
  }

  function toggle() {
    human();
    if (!openRef.current) { openRef.current = true; openPanel(); }
    else { openRef.current = false; closePanel(); }
  }

  useEffect(() => {
    const mq = window.matchMedia("(prefers-reduced-motion: reduce)");
    function onChange() { forcedReduceRef.current = false; applyMotionPref(); }
    if (typeof mq.addEventListener === "function") mq.addEventListener("change", onChange);

    const reduce = mq.matches;
    let phase = 0;
    function runStep() {
      if (!isDemoRef.current) return;
      synthRef.current = true;
      if (phase % 4 === 0) { forcedReduceRef.current = false; applyMotionPref(); }
      else if (phase % 4 === 2) { forcedReduceRef.current = true; applyMotionPref(); }
      toggle();
      synthRef.current = false;
      phase++;
      loopTimerRef.current = window.setTimeout(runStep, 350);
    }
    if (!reduce) { loopTimerRef.current = window.setTimeout(runStep, 420); }
    else { isDemoRef.current = false; setIsDemo(false); }
    return () => {
      window.clearTimeout(loopTimerRef.current);
      window.clearTimeout(hideTimerRef.current);
      if (typeof mq.removeEventListener === "function") mq.removeEventListener("change", onChange);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  const panelStyle = { transitionDuration: durationMs + "ms" } as any;

  return (
    <main className={styles.stage}>
      <div className={styles.rp + " " + (isDemo ? styles.isDemo : "")}>
        <button
          className={styles.trigger}
          type="button"
          aria-haspopup="true"
          aria-expanded={open}
          onClick={toggle}
        >
          설정
        </button>
        <div
          className={styles.panel + " " + (open ? styles.panelOpen : "")}
          role="menu"
          hidden={hidden}
          style={panelStyle}
        >
          {ROWS.map((r, i) => (
            <div key={i} className={styles.row} role="menuitem">{r}</div>
          ))}
        </div>
        <p className={styles.badge}>{"동작 줄임 " + (reduceOn ? "켜짐" : "꺼짐")}</p>
        <p className={styles.sr} role="status" aria-live="polite">{live}</p>
      </div>
    </main>
  );
}