08Lightbox With a Thumbnail Strip That Follows Along

<main class="stage">
<div class="scene is-demo" id="scene">
  <ul class="grid" id="grid">
    <li><button class="thumb" id="thumb0" type="button" aria-haspopup="dialog"><span class="thumbImg thumbImg--a"></span></button></li>
  </ul>
  <div class="backdrop" id="backdrop"></div>
  <div class="lightbox" id="lightbox" role="dialog" aria-modal="true" aria-hidden="true" aria-label="View with thumbnail strip">
    <span class="fullImg" id="fullImg"></span>
    <div class="strip" id="strip">
      <div class="stripTrack" id="stripTrack">
        <button class="stripThumb" id="stripThumb0" type="button" aria-label="Photo 1"><span class="thumbImg thumbImg--a"></span></button>
        <button class="stripThumb" id="stripThumb1" type="button" aria-label="Photo 2"><span class="thumbImg thumbImg--b"></span></button>
        <button class="stripThumb" id="stripThumb2" type="button" aria-label="Photo 3"><span class="thumbImg thumbImg--c"></span></button>
        <button class="stripThumb" id="stripThumb3" type="button" aria-label="Photo 4"><span class="thumbImg thumbImg--d"></span></button>
        <button class="stripThumb" id="stripThumb4" type="button" aria-label="Photo 5"><span class="thumbImg thumbImg--e"></span></button>
      </div>
    </div>
    <button class="closeBtn" id="closeBtn" type="button">Close</button>
  </div>
</div>
</main>

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

// 변수 3개
$duration: $dur-base;
$easing: $ease-out;
$color: $subject-blue-deep;

// 계산 겹: index.html 의 centerOffsetFor() 가 활성 썸네일의 실측 offsetLeft·offsetWidth 와
// 스트립의 실측 clientWidth 로 "가운데로 오는 이동량"을 매 전환마다 다시 계산한다(index*고정폭 아님).
@include stage($stage-paper);

.scene {
  position: relative;
  width: 320px;
  height: 180px;
  border-radius: $r-card;
  overflow: hidden;
  box-shadow: $shadow-raised;
  background: linear-gradient(160deg, #f3f1ea, $stage-paper 70%);
}

.grid {
  position: absolute;
  inset: 0;
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: center;
}

.thumb {
  appearance: none;
  border: none;
  background: none;
  padding: 0;
  cursor: pointer;

  &:focus-visible .thumbImg { outline: 2px solid $color; outline-offset: 2px; }
}

.thumbImg {
  display: block;
  width: 72px;
  height: 72px;
  border-radius: $r-sm;
  box-shadow: $shadow-press;

  &--a { background: linear-gradient(135deg, $subject-blue, $subject-lilac); }
  &--b { background: linear-gradient(135deg, $subject-mint, $subject-sky); }
  &--c { background: linear-gradient(135deg, $subject-pink, $subject-lilac); }
  &--d { background: linear-gradient(135deg, $subject-sky, $subject-mint); }
  &--e { background: linear-gradient(135deg, $subject-lilac, $subject-blue); }
}

.backdrop {
  position: absolute;
  inset: 0;
  background: $subject-ink;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

.lightbox {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: $sp-3;
  visibility: hidden;
}

.fullImg {
  display: block;
  width: 210px;
  height: 108px;
  border-radius: $r-card;

  &--a { background: linear-gradient(135deg, $subject-blue, $subject-lilac); }
  &--b { background: linear-gradient(135deg, $subject-mint, $subject-sky); }
  &--c { background: linear-gradient(135deg, $subject-pink, $subject-lilac); }
  &--d { background: linear-gradient(135deg, $subject-sky, $subject-mint); }
  &--e { background: linear-gradient(135deg, $subject-lilac, $subject-blue); }
}

.strip {
  position: relative;
  width: 240px;
  overflow: hidden;
}

.stripTrack {
  display: flex;
  gap: $sp-2;
  width: max-content;
  will-change: transform;
}

.stripThumb {
  appearance: none;
  border: none;
  background: none;
  padding: 0;
  cursor: pointer;
  flex: 0 0 auto;
  border-radius: $r-sm;

  .thumbImg { width: 40px; height: 40px; opacity: .55; }

  &.is-active .thumbImg {
    opacity: 1;
    outline: 2px solid $color;
    outline-offset: 2px;
  }
  &:focus-visible .thumbImg { outline: 2px solid $color; outline-offset: 2px; }
}

.closeBtn {
  position: absolute;
  top: $sp-2;
  right: $sp-2;
  appearance: none;
  border: none;
  border-radius: $r-pill;
  padding: $sp-1 $sp-3;
  font-size: 11px;
  font-weight: 600;
  color: $subject-cream;
  background: rgba($subject-ink, .82);
  cursor: pointer;

  &:focus-visible { outline: 2px solid $color; outline-offset: 2px; }
}

@media (max-width: 340px) {
  .scene { width: 220px; height: 124px; }
  .fullImg { width: 150px; height: 80px; }
  .strip { width: 170px; }
  .stripThumb .thumbImg { width: 30px; height: 30px; }
}

@media (prefers-reduced-motion: reduce) {
  // 실사용 경로 적용 — 스트립 중앙 정렬 이동은 index.html 의 animate() 가 reduce 시 즉시 최종 위치로 처리한다.
  .closeBtn, .thumb, .stripThumb { transition: none; }
}

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

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

.scene {
  position: relative;
  width: 320px;
  height: 180px;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  background: linear-gradient(160deg, #f3f1ea, #ffffff 70%);
}

.grid {
  position: absolute;
  inset: 0;
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: center;
}

.thumb {
  appearance: none;
  border: none;
  background: none;
  padding: 0;
  cursor: pointer;
}
.thumb:focus-visible .thumbImg {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}

.thumbImg {
  display: block;
  width: 72px;
  height: 72px;
  border-radius: 8px;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
}
.thumbImg--a {
  background: linear-gradient(135deg, #2f6df6, #b9a0ff);
}
.thumbImg--b {
  background: linear-gradient(135deg, #4cd4a6, #6ec8ff);
}
.thumbImg--c {
  background: linear-gradient(135deg, #ff9ebb, #b9a0ff);
}
.thumbImg--d {
  background: linear-gradient(135deg, #6ec8ff, #4cd4a6);
}
.thumbImg--e {
  background: linear-gradient(135deg, #b9a0ff, #2f6df6);
}

.backdrop {
  position: absolute;
  inset: 0;
  background: #17141a;
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

.lightbox {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 12px;
  visibility: hidden;
}

.fullImg {
  display: block;
  width: 210px;
  height: 108px;
  border-radius: 16px;
}
.fullImg--a {
  background: linear-gradient(135deg, #2f6df6, #b9a0ff);
}
.fullImg--b {
  background: linear-gradient(135deg, #4cd4a6, #6ec8ff);
}
.fullImg--c {
  background: linear-gradient(135deg, #ff9ebb, #b9a0ff);
}
.fullImg--d {
  background: linear-gradient(135deg, #6ec8ff, #4cd4a6);
}
.fullImg--e {
  background: linear-gradient(135deg, #b9a0ff, #2f6df6);
}

.strip {
  position: relative;
  width: 240px;
  overflow: hidden;
}

.stripTrack {
  display: flex;
  gap: 8px;
  width: max-content;
  will-change: transform;
}

.stripThumb {
  appearance: none;
  border: none;
  background: none;
  padding: 0;
  cursor: pointer;
  flex: 0 0 auto;
  border-radius: 8px;
}
.stripThumb .thumbImg {
  width: 40px;
  height: 40px;
  opacity: 0.55;
}
.stripThumb.is-active .thumbImg {
  opacity: 1;
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}
.stripThumb:focus-visible .thumbImg {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}

.closeBtn {
  position: absolute;
  top: 8px;
  right: 8px;
  appearance: none;
  border: none;
  border-radius: 999px;
  padding: 4px 12px;
  font-size: 11px;
  font-weight: 600;
  color: #fff7e6;
  background: rgba(23, 20, 26, 0.82);
  cursor: pointer;
}
.closeBtn:focus-visible {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}

@media (max-width: 340px) {
  .scene {
    width: 220px;
    height: 124px;
  }
  .fullImg {
    width: 150px;
    height: 80px;
  }
  .strip {
    width: 170px;
  }
  .stripThumb .thumbImg {
    width: 30px;
    height: 30px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .closeBtn, .thumb, .stripThumb {
    transition: none;
  }
}

(function () {
  var SYNC_MS = 320;
  var HOLD_MS = 340;
  var LOOP_MS = 2000;

  var scene = document.getElementById('scene');
  var backdrop = document.getElementById('backdrop');
  var lightbox = document.getElementById('lightbox');
  var fullImg = document.getElementById('fullImg');
  var strip = document.getElementById('strip');
  var stripTrack = document.getElementById('stripTrack');
  var closeBtn = document.getElementById('closeBtn');
  var thumb = document.getElementById('thumb0');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var stripThumbs = [].slice.call(document.querySelectorAll('.stripThumb'));
  var imgClassByIdx = ['a', 'b', 'c', 'd', 'e'];
  var COUNT = stripThumbs.length;

  var open = false;
  var idx = 0;
  var currentX = 0;
  var timers = [];

  function clamp(v, lo, hi) { return Math.min(hi, Math.max(lo, v)); }
  function easeOutCubic(t) { return 1 - Math.pow(1 - t, 3); }

  function animate(duration, onFrame, onDone) {
    if (reduce) { onFrame(1); if (onDone) onDone(); return; }
    var start = performance.now();
    function frame(now) {
      var p = clamp((now - start) / duration, 0, 1);
      onFrame(easeOutCubic(p));
      if (p < 1) requestAnimationFrame(frame);
      else if (onDone) onDone();
    }
    requestAnimationFrame(frame);
  }

  // 활성 썸네일을 줄 가운데로 오게 하는 이동량을 그때그때 실측한다 — index * 고정폭이 아니다.
  // (082/256 의 정적 배열형 스트립과 다른 지점: 여기는 화면 폭이 바뀌거나 썸네일 크기가 달라져도
  // offsetLeft·clientWidth 실측으로 다시 계산되므로 항상 정중앙에 맞는다.)
  function centerOffsetFor(el) {
    var thumbLeft = el.offsetLeft;
    var thumbW = el.offsetWidth;
    var stripW = strip.clientWidth;
    var trackW = stripTrack.scrollWidth;
    var target = stripW / 2 - thumbLeft - thumbW / 2;
    var minOffset = Math.min(0, stripW - trackW);
    return clamp(target, minOffset, 0);
  }

  function setStripX(px) { stripTrack.style.transform = 'translateX(' + px.toFixed(2) + 'px)'; }

  function goTo(nextIdx, onDone) {
    nextIdx = clamp(nextIdx, 0, COUNT - 1);
    idx = nextIdx;
    fullImg.className = 'fullImg fullImg--' + imgClassByIdx[idx];
    stripThumbs.forEach(function (t, i) { t.classList.toggle('is-active', i === idx); });
    var target = centerOffsetFor(stripThumbs[idx]);
    var fromX = currentX;
    animate(SYNC_MS, function (e) {
      var x = fromX + (target - fromX) * e;
      setStripX(x);
    }, function () {
      currentX = target;
      if (onDone) onDone();
    });
  }

  function openFrom() {
    if (open) return;
    open = true;
    idx = 0;
    currentX = 0;
    setStripX(0);
    fullImg.className = 'fullImg fullImg--a';
    stripThumbs.forEach(function (t, i) { t.classList.toggle('is-active', i === 0); });
    lightbox.style.visibility = 'visible';
    lightbox.setAttribute('aria-hidden', 'false');
    backdrop.style.visibility = 'visible';
    animate(220, function (e) { backdrop.style.opacity = (e * 0.78).toFixed(3); }, function () {
      closeBtn.focus({ preventScroll: true });
    });
  }

  function closeLightbox() {
    if (!open) return;
    animate(200, function (e) { backdrop.style.opacity = (0.78 * (1 - e)).toFixed(3); }, function () {
      lightbox.style.visibility = 'hidden';
      lightbox.setAttribute('aria-hidden', 'true');
      backdrop.style.visibility = 'hidden';
      open = false;
      thumb.focus({ preventScroll: true });
    });
  }

  function human() {
    if (scene.classList.contains('is-demo')) {
      scene.classList.remove('is-demo');
      timers.forEach(function (id) { clearTimeout(id); clearInterval(id); });
      timers = [];
    }
  }

  thumb.addEventListener('click', function () { human(); openFrom(); });
  closeBtn.addEventListener('click', function () { human(); closeLightbox(); });
  backdrop.addEventListener('click', function () { human(); closeLightbox(); });
  stripThumbs.forEach(function (t, i) {
    t.addEventListener('click', function () { human(); goTo(i); });
  });
  document.addEventListener('keydown', function (e) {
    if (!open) return;
    if (e.key === 'Escape') { human(); closeLightbox(); }
    else if (e.key === 'ArrowRight') { human(); goTo(idx + 1); }
    else if (e.key === 'ArrowLeft') { human(); goTo(idx - 1); }
  });

  function cycle() {
    openFrom();
    timers.push(setTimeout(function () { goTo(2); }, 300));
    timers.push(setTimeout(function () { goTo(4); }, 300 + SYNC_MS + HOLD_MS));
    timers.push(setTimeout(closeLightbox, 300 + (SYNC_MS + HOLD_MS) * 2));
  }

  if (!reduce) {
    cycle();
    timers.push(setInterval(function () {
      if (scene.classList.contains('is-demo')) cycle();
    }, LOOP_MS));
  }
})();

import { useEffect, useRef } from 'react';
import styles from './ThumbnailStripSync.module.scss';

const SYNC_MS = 320;
const HOLD_MS = 340;
const LOOP_MS = 2000;

export default function ThumbnailStripSync() {
  const sceneRef = useRef<HTMLDivElement>(null);

  useEffect(() => {
    const scene0 = sceneRef.current;
    if (!scene0) return undefined;
    const backdrop0 = scene0.querySelector<HTMLDivElement>('.' + styles.backdrop);
    const lightbox0 = scene0.querySelector<HTMLDivElement>('.' + styles.lightbox);
    const fullImg0 = scene0.querySelector<HTMLSpanElement>('.' + styles.fullImg);
    const strip0 = scene0.querySelector<HTMLDivElement>('.' + styles.strip);
    const stripTrack0 = scene0.querySelector<HTMLDivElement>('.' + styles.stripTrack);
    const closeBtn0 = scene0.querySelector<HTMLButtonElement>('.' + styles.closeBtn);
    const thumb0 = scene0.querySelector<HTMLButtonElement>('.' + styles.thumb);
    const stripThumbs = Array.from(scene0.querySelectorAll<HTMLButtonElement>('.' + styles.stripThumb));
    if (!backdrop0 || !lightbox0 || !fullImg0 || !strip0 || !stripTrack0 || !closeBtn0 || !thumb0 || stripThumbs.length === 0) return undefined;
    const scene = scene0;
    const backdrop = backdrop0;
    const lightbox = lightbox0;
    const fullImg = fullImg0;
    const strip = strip0;
    const stripTrack = stripTrack0;
    const closeBtn = closeBtn0;
    const thumb = thumb0;

    const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
    const imgClassByIdx = ['a', 'b', 'c', 'd', 'e'];
    const fullImgClassByIdx = [styles['fullImg--a'], styles['fullImg--b'], styles['fullImg--c'], styles['fullImg--d'], styles['fullImg--e']];
    const COUNT = stripThumbs.length;

    let open = false;
    let idx = 0;
    let currentX = 0;
    let timers: number[] = [];

    function clamp(v: number, lo: number, hi: number) { return Math.min(hi, Math.max(lo, v)); }
    function easeOutCubic(t: number) { return 1 - Math.pow(1 - t, 3); }

    function animate(duration: number, onFrame: (e: number) => void, onDone?: () => void) {
      if (reduce) { onFrame(1); if (onDone) onDone(); return; }
      const start = performance.now();
      function frame(now: number) {
        const p = clamp((now - start) / duration, 0, 1);
        onFrame(easeOutCubic(p));
        if (p < 1) requestAnimationFrame(frame);
        else if (onDone) onDone();
      }
      requestAnimationFrame(frame);
    }

    // 활성 썸네일을 줄 가운데로 오게 하는 이동량을 그때그때 실측한다 — index * 고정폭이 아니다.
    function centerOffsetFor(el: HTMLElement) {
      const thumbLeft = el.offsetLeft;
      const thumbW = el.offsetWidth;
      const stripW = strip.clientWidth;
      const trackW = stripTrack.scrollWidth;
      const target = stripW / 2 - thumbLeft - thumbW / 2;
      const minOffset = Math.min(0, stripW - trackW);
      return clamp(target, minOffset, 0);
    }

    function setStripX(px: number) { stripTrack.style.transform = 'translateX(' + px.toFixed(2) + 'px)'; }

    function goTo(nextIdxRaw: number, onDone?: () => void) {
      const nextIdx = clamp(nextIdxRaw, 0, COUNT - 1);
      idx = nextIdx;
      fullImg.className = styles.fullImg + ' ' + fullImgClassByIdx[idx];
      stripThumbs.forEach((t, i) => { t.classList.toggle(styles['is-active'], i === idx); });
      const target = centerOffsetFor(stripThumbs[idx]);
      const fromX = currentX;
      animate(SYNC_MS, (e) => {
        const x = fromX + (target - fromX) * e;
        setStripX(x);
      }, () => {
        currentX = target;
        if (onDone) onDone();
      });
    }

    function openFrom() {
      if (open) return;
      open = true;
      idx = 0;
      currentX = 0;
      setStripX(0);
      fullImg.className = styles.fullImg + ' ' + styles['fullImg--a'];
      stripThumbs.forEach((t, i) => { t.classList.toggle(styles['is-active'], i === 0); });
      lightbox.style.visibility = 'visible';
      lightbox.setAttribute('aria-hidden', 'false');
      backdrop.style.visibility = 'visible';
      animate(220, (e) => { backdrop.style.opacity = (e * 0.78).toFixed(3); }, () => {
        closeBtn.focus({ preventScroll: true });
      });
    }

    function closeLightbox() {
      if (!open) return;
      animate(200, (e) => { backdrop.style.opacity = (0.78 * (1 - e)).toFixed(3); }, () => {
        lightbox.style.visibility = 'hidden';
        lightbox.setAttribute('aria-hidden', 'true');
        backdrop.style.visibility = 'hidden';
        open = false;
        thumb.focus({ preventScroll: true });
      });
    }

    function human() {
      if (scene.classList.contains(styles['is-demo'])) {
        scene.classList.remove(styles['is-demo']);
        timers.forEach((id) => { window.clearTimeout(id); window.clearInterval(id); });
        timers = [];
      }
    }

    function onThumbClick() { human(); openFrom(); }
    function onCloseClick() { human(); closeLightbox(); }
    function onBackdropClick() { human(); closeLightbox(); }
    thumb.addEventListener('click', onThumbClick);
    closeBtn.addEventListener('click', onCloseClick);
    backdrop.addEventListener('click', onBackdropClick);

    const stripHandlers = stripThumbs.map((_, i) => () => { human(); goTo(i); });
    stripThumbs.forEach((t, i) => t.addEventListener('click', stripHandlers[i]));

    function onKeydown(e: KeyboardEvent) {
      if (!open) return;
      if (e.key === 'Escape') { human(); closeLightbox(); }
      else if (e.key === 'ArrowRight') { human(); goTo(idx + 1); }
      else if (e.key === 'ArrowLeft') { human(); goTo(idx - 1); }
    }
    document.addEventListener('keydown', onKeydown);

    function cycle() {
      openFrom();
      timers.push(window.setTimeout(() => { goTo(2); }, 300));
      timers.push(window.setTimeout(() => { goTo(4); }, 300 + SYNC_MS + HOLD_MS));
      timers.push(window.setTimeout(closeLightbox, 300 + (SYNC_MS + HOLD_MS) * 2));
    }

    if (!reduce) {
      cycle();
      timers.push(window.setInterval(() => {
        if (scene.classList.contains(styles['is-demo'])) cycle();
      }, LOOP_MS));
    }

    return () => {
      timers.forEach((id) => { window.clearTimeout(id); window.clearInterval(id); });
      thumb.removeEventListener('click', onThumbClick);
      closeBtn.removeEventListener('click', onCloseClick);
      backdrop.removeEventListener('click', onBackdropClick);
      stripThumbs.forEach((t, i) => t.removeEventListener('click', stripHandlers[i]));
      document.removeEventListener('keydown', onKeydown);
    };
  }, []);

  return (
    <div className={`${styles.scene} ${styles['is-demo']}`} ref={sceneRef}>
      <ul className={styles.grid}>
        <li><button className={styles.thumb} type="button" aria-haspopup="dialog"><span className={`${styles.thumbImg} ${styles['thumbImg--a']}`} /></button></li>
      </ul>
      <div className={styles.backdrop} />
      <div className={styles.lightbox} role="dialog" aria-modal="true" aria-hidden="true" aria-label="썸네일 줄과 함께 보기">
        <span className={styles.fullImg} />
        <div className={styles.strip}>
          <div className={styles.stripTrack}>
            <button className={styles.stripThumb} type="button" aria-label="1번째 사진"><span className={`${styles.thumbImg} ${styles['thumbImg--a']}`} /></button>
            <button className={styles.stripThumb} type="button" aria-label="2번째 사진"><span className={`${styles.thumbImg} ${styles['thumbImg--b']}`} /></button>
            <button className={styles.stripThumb} type="button" aria-label="3번째 사진"><span className={`${styles.thumbImg} ${styles['thumbImg--c']}`} /></button>
            <button className={styles.stripThumb} type="button" aria-label="4번째 사진"><span className={`${styles.thumbImg} ${styles['thumbImg--d']}`} /></button>
            <button className={styles.stripThumb} type="button" aria-label="5번째 사진"><span className={`${styles.thumbImg} ${styles['thumbImg--e']}`} /></button>
          </div>
        </div>
        <button className={styles.closeBtn} type="button">닫기</button>
      </div>
    </div>
  );
}