01Tab Container a Measured Height Gap Stretches

<main class="stage">
<div class="tp is-demo" id="tp">
  <div class="tp__tabs" role="tablist" aria-label="Settings tabs">
    <button type="button" class="tp__tab is-active" role="tab" id="tp-tab-0" aria-selected="true" aria-controls="tp-panel-0" data-idx="0">Summary</button>
    <button type="button" class="tp__tab" role="tab" id="tp-tab-1" aria-selected="false" aria-controls="tp-panel-1" data-idx="1" tabindex="-1">Details</button>
    <button type="button" class="tp__tab" role="tab" id="tp-tab-2" aria-selected="false" aria-controls="tp-panel-2" data-idx="2" tabindex="-1">History</button>
  </div>
  <div class="tp__wrap" id="tpWrap">
    <div class="tp__panel" id="tp-panel-0" role="tabpanel" aria-labelledby="tp-tab-0" tabindex="0">
      <p class="tp__line tp__line--a"></p>
      <p class="tp__line tp__line--b"></p>
    </div>
    <div class="tp__panel" id="tp-panel-1" role="tabpanel" aria-labelledby="tp-tab-1" tabindex="0" hidden>
      <p class="tp__line tp__line--a"></p>
      <p class="tp__line tp__line--b"></p>
      <p class="tp__line tp__line--c"></p>
      <div class="tp__bars"><span></span><span></span><span></span><span></span></div>
    </div>
    <div class="tp__panel" id="tp-panel-2" role="tabpanel" aria-labelledby="tp-tab-2" tabindex="0" hidden>
      <p class="tp__line tp__line--a"></p>
      <ul class="tp__list">
        <li></li><li></li><li></li><li></li><li></li>
      </ul>
    </div>
  </div>
  <p class="tp__meta" id="tpMeta">Height diff <b id="tpDiff">0</b>px · transition <b id="tpDur">0</b>ms</p>
</div>
</main>

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

// 계산 겹: index.html select() 가 getBoundingClientRect 로 숨은/보이는 패널의 실측 높이를 재
// 그 차이(px)를 BASE_MS + diff*MS_PER_PX 식에 넣어 전환 시간을 정하고, wrap 의 height 를 그 시간 동안
// 이전 값에서 다음 패널 높이로 트랜지션한다 — 차이가 클수록 천천히, 작으면 짧게 늘어난다.
@include stage($stage-ink);

.tp { width: min(100%, 300px); display: flex; flex-direction: column; gap: $sp-3; }
.tp__tabs { display: flex; gap: $sp-1; background: rgba($subject-cream, .12); padding: $sp-1; border-radius: $r-pill; }
.tp__tab {
  flex: 1 1 0; border: none; background: transparent; border-radius: $r-pill; cursor: pointer;
  padding: $sp-2 $sp-3; font-size: 12px; font-weight: 700; color: rgba($subject-cream, .72);
}
.tp__tab.is-active { background: $subject-blue-deep; color: $subject-cream; }
.tp__tab:focus-visible { outline: 2px solid $subject-cream; outline-offset: 2px; }

.tp__wrap {
  position: relative; overflow: hidden; border-radius: $r-card; background: $subject-cream;
  transition: height var(--tp-dur, #{$dur-base}) $ease-out;
}
.tp__panel { padding: $sp-4; box-sizing: border-box; }
.tp__line { height: 10px; border-radius: $r-xs; background: rgba($subject-ink, .16); margin: 0 0 $sp-2; }
.tp__line--a { width: 82%; }
.tp__line--b { width: 58%; }
.tp__line--c { width: 68%; }
.tp__bars { display: flex; gap: $sp-2; margin-top: $sp-3; align-items: flex-end; height: 44px; }
.tp__bars span { flex: 1 1 0; border-radius: $r-xs $r-xs 0 0; background: $subject-blue; }
.tp__bars span:nth-child(1) { height: 60%; }
.tp__bars span:nth-child(2) { height: 100%; }
.tp__bars span:nth-child(3) { height: 40%; }
.tp__bars span:nth-child(4) { height: 78%; }
.tp__list { list-style: none; margin: $sp-3 0 0; padding: 0; display: flex; flex-direction: column; gap: $sp-2; }
.tp__list li { height: 14px; border-radius: $r-xs; background: rgba($subject-ink, .12); }
.tp__list li:nth-child(2n) { width: 88%; }
.tp__meta { margin: 0; font-size: 11px; color: rgba($subject-cream, .78); text-align: center; }
.tp__meta b { color: $subject-cream; font-weight: 700; }

@media (max-width: 340px) {
  .tp { width: 100%; }
  .tp__tab { font-size: 11px; padding: $sp-1 $sp-2; }
}

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

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);
}

.tp {
  width: min(100%, 300px);
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.tp__tabs {
  display: flex;
  gap: 4px;
  background: rgba(255, 247, 230, 0.12);
  padding: 4px;
  border-radius: 999px;
}

.tp__tab {
  flex: 1 1 0;
  border: none;
  background: transparent;
  border-radius: 999px;
  cursor: pointer;
  padding: 8px 12px;
  font-size: 12px;
  font-weight: 700;
  color: rgba(255, 247, 230, 0.72);
}

.tp__tab.is-active {
  background: #0a4fe8;
  color: #fff7e6;
}

.tp__tab:focus-visible {
  outline: 2px solid #fff7e6;
  outline-offset: 2px;
}

.tp__wrap {
  position: relative;
  overflow: hidden;
  border-radius: 16px;
  background: #fff7e6;
  transition: height var(--tp-dur, 300ms) ease-out;
}

.tp__panel {
  padding: 16px;
  box-sizing: border-box;
}

.tp__line {
  height: 10px;
  border-radius: 4px;
  background: rgba(23, 20, 26, 0.16);
  margin: 0 0 8px;
}

.tp__line--a {
  width: 82%;
}

.tp__line--b {
  width: 58%;
}

.tp__line--c {
  width: 68%;
}

.tp__bars {
  display: flex;
  gap: 8px;
  margin-top: 12px;
  align-items: flex-end;
  height: 44px;
}

.tp__bars span {
  flex: 1 1 0;
  border-radius: 4px 4px 0 0;
  background: #2f6df6;
}

.tp__bars span:nth-child(1) {
  height: 60%;
}

.tp__bars span:nth-child(2) {
  height: 100%;
}

.tp__bars span:nth-child(3) {
  height: 40%;
}

.tp__bars span:nth-child(4) {
  height: 78%;
}

.tp__list {
  list-style: none;
  margin: 12px 0 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.tp__list li {
  height: 14px;
  border-radius: 4px;
  background: rgba(23, 20, 26, 0.12);
}

.tp__list li:nth-child(2n) {
  width: 88%;
}

.tp__meta {
  margin: 0;
  font-size: 11px;
  color: rgba(255, 247, 230, 0.78);
  text-align: center;
}

.tp__meta b {
  color: #fff7e6;
  font-weight: 700;
}

@media (max-width: 340px) {
  .tp {
    width: 100%;
  }
  .tp__tab {
    font-size: 11px;
    padding: 4px 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .tp__wrap {
    transition: none;
  }
}

(function () {
  var BASE_MS = 180; // 계산 겹 상수: 높이 차이가 0px 이어도 최소한의 스무딩을 준다
  var MS_PER_PX = 1.1; // 계산 겹 상수: Height diff 1px 마다 전환 시간이 이만큼 늘어난다
  var MIN_MS = 180, MAX_MS = 620;
  var HOLD_MS = 760; // 자동 순환이 탭 하나에 머무는 시간
  var COUNT = 3;
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var root = document.getElementById('tp');
  var wrap = document.getElementById('tpWrap');
  var diffEl = document.getElementById('tpDiff');
  var durEl = document.getElementById('tpDur');
  var tabs = [0, 1, 2].map(function (i) { return document.getElementById('tp-tab-' + i); });
  var panels = [0, 1, 2].map(function (i) { return document.getElementById('tp-panel-' + i); });

  var isDemo = true;
  var active = 0;
  var busy = false;

  function rectHeight(idx) {
    // 계산 겹: 숨은 패널도 잠깐 측정 가능한 상태로 만들어 getBoundingClientRect 로 실측한다 — 짐작값을 쓰지 않는다
    var p = panels[idx];
    var wasHidden = p.hasAttribute('hidden');
    if (wasHidden) {
      p.style.visibility = 'hidden';
      p.style.position = 'absolute';
      p.style.width = wrap.clientWidth + 'px';
      p.removeAttribute('hidden');
    }
    var h = p.getBoundingClientRect().height;
    if (wasHidden) {
      p.setAttribute('hidden', '');
      p.style.visibility = '';
      p.style.position = '';
      p.style.width = '';
    }
    return h;
  }

  function human() {
    if (isDemo) { root.classList.remove('is-demo'); isDemo = false; }
  }

  function select(idx) {
    if (idx === active || busy) return;
    busy = true;
    var fromH = rectHeight(active);
    var toH = rectHeight(idx);
    var diff = Math.abs(toH - fromH); // 계산 겹: 두 패널의 실측 Height diff(px)
    var dur = Math.min(MAX_MS, Math.max(MIN_MS, BASE_MS + diff * MS_PER_PX)); // 계산 겹: 차이가 클수록 전환이 길다

    wrap.style.setProperty('--tp-dur', dur.toFixed(0) + 'ms');
    wrap.style.height = fromH.toFixed(2) + 'px';
    wrap.getBoundingClientRect(); // 강제 리플로우 — 시작 높이를 확정한 뒤에 목표 높이를 건다

    tabs[active].classList.remove('is-active');
    tabs[active].setAttribute('aria-selected', 'false');
    tabs[active].setAttribute('tabindex', '-1');
    panels[active].setAttribute('hidden', '');

    tabs[idx].classList.add('is-active');
    tabs[idx].setAttribute('aria-selected', 'true');
    tabs[idx].setAttribute('tabindex', '0');
    panels[idx].removeAttribute('hidden');

    requestAnimationFrame(function () {
      wrap.style.height = toH.toFixed(2) + 'px';
    });

    diffEl.textContent = Math.round(diff);
    durEl.textContent = Math.round(dur);
    active = idx;
    window.setTimeout(function () {
      busy = false;
      wrap.style.height = panels[active].getBoundingClientRect().height + 'px';
    }, dur + 40);
  }

  tabs.forEach(function (t, i) {
    t.addEventListener('click', function () { human(); select(i); });
  });

  root.addEventListener('keydown', function (e) {
    var idx = tabs.indexOf(document.activeElement);
    if (idx === -1) return;
    var next = null;
    if (e.key === 'ArrowRight') next = (idx + 1) % COUNT;
    else if (e.key === 'ArrowLeft') next = (idx - 1 + COUNT) % COUNT;
    else if (e.key === 'Home') next = 0;
    else if (e.key === 'End') next = COUNT - 1;
    if (next === null) return;
    e.preventDefault();
    human();
    tabs[next].focus({ preventScroll: true });
    select(next);
  });

  function loop() {
    if (!isDemo) return;
    select((active + 1) % COUNT);
    window.setTimeout(loop, HOLD_MS);
  }

  wrap.style.height = rectHeight(0) + 'px';
  if (!reduce) {
    window.setTimeout(loop, HOLD_MS);
  } else {
    root.classList.remove('is-demo');
  }
})();

// TabHeightAutoMorph — vanilla 판(run/394/demo/01-tab-panel-height-auto-morph/index.html) 의 React 포트.
// select() 가 getBoundingClientRect 로 숨은/보이는 패널의 실측 높이를 재 그 차이(px)를
// BASE_MS + diff*MS_PER_PX 식에 넣어 전환 시간을 정하고, wrap 의 height 를 그 시간 동안 트랜지션한다.
import { useEffect, useRef } from "react";
import styles from "./TabHeightAutoMorph.module.scss";

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

const BASE_MS = 180; // 계산 겹 상수: 높이 차이가 0px 이어도 최소한의 스무딩을 준다
const MS_PER_PX = 1.1; // 계산 겹 상수: 높이 차이 1px 마다 전환 시간이 이만큼 늘어난다
const MIN_MS = 180, MAX_MS = 620;
const HOLD_MS = 760; // 자동 순환이 탭 하나에 머무는 시간
const COUNT = 3;

export default function TabHeightAutoMorph() {
  const rootRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const wrapRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const diffRef = useRef(null) as unknown as Box<HTMLElement>;
  const durRef = useRef(null) as unknown as Box<HTMLElement>;
  const tabRefs = useRef([null, null, null]) as unknown as Box<(HTMLButtonElement | null)[]>;
  const panelRefs = useRef([null, null, null]) as unknown as Box<(HTMLDivElement | null)[]>;
  const timerRef = useRef(0) as unknown as Box<number>;

  useEffect(() => {
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let isDemo = true;
    let active = 0;
    let busy = false;

    function rectHeight(idx: number): number {
      const p = panelRefs.current[idx];
      const wrap = wrapRef.current;
      if (!p || !wrap) return 0;
      const wasHidden = p.hasAttribute("hidden");
      if (wasHidden) {
        p.style.visibility = "hidden";
        p.style.position = "absolute";
        p.style.width = wrap.clientWidth + "px";
        p.removeAttribute("hidden");
      }
      const h = p.getBoundingClientRect().height;
      if (wasHidden) {
        p.setAttribute("hidden", "");
        p.style.visibility = "";
        p.style.position = "";
        p.style.width = "";
      }
      return h;
    }

    function human() {
      if (isDemo) { rootRef.current?.classList.remove(styles.isDemo); isDemo = false; }
    }

    function select(idx: number) {
      if (idx === active || busy) return;
      busy = true;
      const wrap = wrapRef.current;
      const fromH = rectHeight(active);
      const toH = rectHeight(idx);
      if (!wrap) return;
      const diff = Math.abs(toH - fromH); // 계산 겹: 두 패널의 실측 높이 차이(px)
      const dur = Math.min(MAX_MS, Math.max(MIN_MS, BASE_MS + diff * MS_PER_PX)); // 계산 겹: 차이가 클수록 전환이 길다

      wrap.style.setProperty("--tp-dur", dur.toFixed(0) + "ms");
      wrap.style.height = fromH.toFixed(2) + "px";
      wrap.getBoundingClientRect(); // 강제 리플로우

      const prevTab = tabRefs.current[active], nextTab = tabRefs.current[idx];
      const prevPanel = panelRefs.current[active], nextPanel = panelRefs.current[idx];
      prevTab?.classList.remove(styles.isActive);
      prevTab?.setAttribute("aria-selected", "false");
      prevTab?.setAttribute("tabindex", "-1");
      prevPanel?.setAttribute("hidden", "");
      nextTab?.classList.add(styles.isActive);
      nextTab?.setAttribute("aria-selected", "true");
      nextTab?.setAttribute("tabindex", "0");
      nextPanel?.removeAttribute("hidden");

      requestAnimationFrame(() => { wrap.style.height = toH.toFixed(2) + "px"; });

      if (diffRef.current) diffRef.current.textContent = String(Math.round(diff));
      if (durRef.current) durRef.current.textContent = String(Math.round(dur));
      active = idx;
      window.setTimeout(() => {
        busy = false;
        const p = panelRefs.current[active];
        if (wrap && p) wrap.style.height = p.getBoundingClientRect().height + "px";
      }, dur + 40);
    }

    function onKeydown(e: KeyboardEvent) {
      const idx = tabRefs.current.indexOf(document.activeElement as HTMLButtonElement);
      if (idx === -1) return;
      let next: number | null = null;
      if (e.key === "ArrowRight") next = (idx + 1) % COUNT;
      else if (e.key === "ArrowLeft") next = (idx - 1 + COUNT) % COUNT;
      else if (e.key === "Home") next = 0;
      else if (e.key === "End") next = COUNT - 1;
      if (next === null) return;
      e.preventDefault();
      human();
      tabRefs.current[next]?.focus({ preventScroll: true });
      select(next);
    }

    function onTabClick(i: number) { return () => { human(); select(i); }; }
    const clickHandlers = [0, 1, 2].map(onTabClick);
    tabRefs.current.forEach((t, i) => t?.addEventListener("click", clickHandlers[i]));
    rootRef.current?.addEventListener("keydown", onKeydown);

    function loop() {
      if (!isDemo) return;
      select((active + 1) % COUNT);
      timerRef.current = window.setTimeout(loop, HOLD_MS);
    }

    const wrap = wrapRef.current;
    if (wrap) wrap.style.height = rectHeight(0) + "px";
    if (!reduce) {
      timerRef.current = window.setTimeout(loop, HOLD_MS);
    } else {
      rootRef.current?.classList.remove(styles.isDemo);
    }

    return () => {
      window.clearTimeout(timerRef.current);
      tabRefs.current.forEach((t, i) => t?.removeEventListener("click", clickHandlers[i]));
      rootRef.current?.removeEventListener("keydown", onKeydown);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.tp + " " + styles.isDemo} ref={rootRef}>
        <div className={styles.tabs} role="tablist" aria-label="설정 탭">
          <button type="button" className={styles.tab + " " + styles.isActive} role="tab" aria-selected="true" aria-controls="rtp-panel-0" data-idx="0"
            ref={(el: HTMLButtonElement | null) => { tabRefs.current[0] = el; }}>요약</button>
          <button type="button" className={styles.tab} role="tab" aria-selected="false" aria-controls="rtp-panel-1" data-idx="1" tabIndex={-1}
            ref={(el: HTMLButtonElement | null) => { tabRefs.current[1] = el; }}>세부</button>
          <button type="button" className={styles.tab} role="tab" aria-selected="false" aria-controls="rtp-panel-2" data-idx="2" tabIndex={-1}
            ref={(el: HTMLButtonElement | null) => { tabRefs.current[2] = el; }}>이력</button>
        </div>
        <div className={styles.wrap} ref={wrapRef}>
          <div className={styles.panel} id="rtp-panel-0" role="tabpanel" tabIndex={0}
            ref={(el: HTMLDivElement | null) => { panelRefs.current[0] = el; }}>
            <p className={styles.lineA} />
            <p className={styles.lineB} />
          </div>
          <div className={styles.panel} id="rtp-panel-1" role="tabpanel" tabIndex={0} hidden
            ref={(el: HTMLDivElement | null) => { panelRefs.current[1] = el; }}>
            <p className={styles.lineA} />
            <p className={styles.lineB} />
            <p className={styles.lineC} />
            <div className={styles.bars}><span /><span /><span /><span /></div>
          </div>
          <div className={styles.panel} id="rtp-panel-2" role="tabpanel" tabIndex={0} hidden
            ref={(el: HTMLDivElement | null) => { panelRefs.current[2] = el; }}>
            <p className={styles.lineA} />
            <ul className={styles.list}>
              <li /><li /><li /><li /><li />
            </ul>
          </div>
        </div>
        <p className={styles.meta}>
          높이 차이 <b ref={diffRef}>0</b>px · 전환 <b ref={durRef}>0</b>ms
        </p>
      </div>
    </main>
  );
}