02배경 페이드 + 이미지 스케일업 전환

<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" data-w="280" data-h="210"><span class="thumbImg thumbImg--a"></span><span class="thumbLabel">사진 1</span></button></li>
    <li><button class="thumb" id="thumb1" type="button" aria-haspopup="dialog" data-w="200" data-h="200"><span class="thumbImg thumbImg--b"></span><span class="thumbLabel">사진 2</span></button></li>
    <li><button class="thumb" id="thumb2" type="button" aria-haspopup="dialog" data-w="180" data-h="240"><span class="thumbImg thumbImg--c"></span><span class="thumbLabel">사진 3</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="사진 확대 보기">
    <span class="fullImg" id="fullImg"></span>
    <p class="ratioNote" id="ratioNote"></p>
    <button class="closeBtn" id="closeBtn" type="button">닫기</button>
  </div>
</div>
</main>

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

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

// 계산 겹: index.html 의 fromAspect() 가 이미지 자신의 가로세로 비율을 0~1 로 정규화해
// 시작 스케일과 배경 어둡기(dim)를 같은 지점에서 함께 산출한다 — 세 사진마다 값이 다르다.
@include stage($stage-yellow);

.scene {
  position: relative;
  width: 320px;
  height: 180px;
  border-radius: $r-card;
  overflow: hidden;
  box-shadow: $shadow-raised;
  background: linear-gradient(160deg, #fff1c2, $stage-yellow 75%);
}

.grid {
  position: absolute;
  inset: 0;
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: $sp-4;
}

.thumb {
  appearance: none;
  border: none;
  background: none;
  padding: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-1;
  cursor: pointer;

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

.thumbImg {
  display: block;
  width: 64px;
  height: 48px;
  border-radius: $r-sm;
  box-shadow: $shadow-press;

  &--a { background: linear-gradient(135deg, $subject-blue, $subject-mint); height: 48px; }
  &--b { background: linear-gradient(135deg, $subject-pink, $subject-lilac); width: 56px; height: 56px; }
  &--c { background: linear-gradient(135deg, $subject-sky, $subject-lilac); width: 48px; height: 64px; }
}

.thumbLabel {
  font-size: 10px;
  font-weight: 600;
  color: $subject-ink;
}

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

.lightbox {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  gap: $sp-2;
  visibility: hidden;
}

.fullImg {
  display: block;
  width: 200px;
  height: 150px;
  border-radius: $r-card;
  box-shadow: $shadow-raised;
  transform-origin: center;

  &--a { background: linear-gradient(135deg, $subject-blue, $subject-mint); }
  &--b { background: linear-gradient(135deg, $subject-pink, $subject-lilac); width: 172px; height: 172px; }
  &--c { background: linear-gradient(135deg, $subject-sky, $subject-lilac); width: 138px; height: 184px; }
}

.ratioNote {
  position: absolute;
  bottom: $sp-2;
  left: 50%;
  transform: translateX(-50%);
  margin: 0;
  font-size: 10px;
  font-weight: 600;
  color: $subject-cream;
  background: rgba(#000, .4);
  padding: $sp-1 $sp-2;
  border-radius: $r-sm;
}

.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: $subject-ink;
  background: rgba($subject-cream, .95);
  cursor: pointer;

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

@media (max-width: 340px) {
  .scene { width: 220px; height: 124px; }
  .fullImg { width: 140px; height: 104px; &--b { width: 118px; height: 118px; } &--c { width: 96px; height: 128px; } }
  .ratioNote { font-size: 9px; }
}

@media (prefers-reduced-motion: reduce) {
  // 실사용 경로 적용 — 스케일업·페이드 트윈은 index.html 의 animate() 가 reduce 시 즉시 최종 상태로 처리한다.
  .closeBtn, .thumb { transition: none; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  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, #fff1c2, #ffd23f 75%);
}

.grid {
  position: absolute;
  inset: 0;
  margin: 0;
  padding: 0;
  list-style: none;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
}

.thumb {
  appearance: none;
  border: none;
  background: none;
  padding: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  cursor: pointer;
}
.thumb:focus-visible .thumbImg {
  outline: 2px solid #c93000;
  outline-offset: 2px;
}

.thumbImg {
  display: block;
  width: 64px;
  height: 48px;
  border-radius: 8px;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
}
.thumbImg--a {
  background: linear-gradient(135deg, #2f6df6, #4cd4a6);
  height: 48px;
}
.thumbImg--b {
  background: linear-gradient(135deg, #ff9ebb, #b9a0ff);
  width: 56px;
  height: 56px;
}
.thumbImg--c {
  background: linear-gradient(135deg, #6ec8ff, #b9a0ff);
  width: 48px;
  height: 64px;
}

.thumbLabel {
  font-size: 10px;
  font-weight: 600;
  color: #17141a;
}

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

.lightbox {
  position: absolute;
  inset: 0;
  display: grid;
  place-items: center;
  gap: 8px;
  visibility: hidden;
}

.fullImg {
  display: block;
  width: 200px;
  height: 150px;
  border-radius: 16px;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  transform-origin: center;
}
.fullImg--a {
  background: linear-gradient(135deg, #2f6df6, #4cd4a6);
}
.fullImg--b {
  background: linear-gradient(135deg, #ff9ebb, #b9a0ff);
  width: 172px;
  height: 172px;
}
.fullImg--c {
  background: linear-gradient(135deg, #6ec8ff, #b9a0ff);
  width: 138px;
  height: 184px;
}

.ratioNote {
  position: absolute;
  bottom: 8px;
  left: 50%;
  transform: translateX(-50%);
  margin: 0;
  font-size: 10px;
  font-weight: 600;
  color: #fff7e6;
  background: rgba(0, 0, 0, 0.4);
  padding: 4px 8px;
  border-radius: 8px;
}

.closeBtn {
  position: absolute;
  top: 8px;
  right: 8px;
  appearance: none;
  border: none;
  border-radius: 999px;
  padding: 4px 12px;
  font-size: 11px;
  font-weight: 600;
  color: #17141a;
  background: rgba(255, 247, 230, 0.95);
  cursor: pointer;
}
.closeBtn:focus-visible {
  outline: 2px solid #c93000;
  outline-offset: 2px;
}

@media (max-width: 340px) {
  .scene {
    width: 220px;
    height: 124px;
  }
  .fullImg {
    width: 140px;
    height: 104px;
  }
  .fullImg--b {
    width: 118px;
    height: 118px;
  }
  .fullImg--c {
    width: 96px;
    height: 128px;
  }
  .ratioNote {
    font-size: 9px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .closeBtn, .thumb {
    transition: none;
  }
}

(function () {
  var OPEN_MS = 600;
  var CLOSE_MS = 420;
  var LOOP_MS = 2000;
  var HOLD_OPEN_MS = 620;
  var ASPECT_NORM_LO = 0.6;
  var ASPECT_NORM_HI = 1.6;
  var SCALE_FROM_MIN = 0.7;
  var SCALE_FROM_MAX = 0.92;
  var DIM_MAX = 0.82;
  var DIM_MIN = 0.58;

  var scene = document.getElementById('scene');
  var backdrop = document.getElementById('backdrop');
  var lightbox = document.getElementById('lightbox');
  var fullImg = document.getElementById('fullImg');
  var ratioNote = document.getElementById('ratioNote');
  var closeBtn = document.getElementById('closeBtn');
  var thumbs = [].slice.call(document.querySelectorAll('.thumb'));
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var imgClassByIdx = ['thumbImg--a', 'thumbImg--b', 'thumbImg--c'];

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

  // 이미지 자신의 가로세로 비율에서 시작 스케일과 배경 어둡기를 함께 계산한다 — 두 값이 같은 정규화 지점에서 나온다
  function fromAspect(w, h) {
    var aspect = w / h;
    var norm = clamp((aspect - ASPECT_NORM_LO) / (ASPECT_NORM_HI - ASPECT_NORM_LO), 0, 1);
    var scaleFrom = SCALE_FROM_MIN + (SCALE_FROM_MAX - SCALE_FROM_MIN) * norm;
    var dim = DIM_MAX - (DIM_MAX - DIM_MIN) * norm;
    return { aspect: aspect, scaleFrom: scaleFrom, dim: dim };
  }

  var open = false;
  var activeIdx = 1;
  var timers = [];

  // reduce: 실사용 경로 적용 — 트윈 없이 최종 상태로 즉시 전환한다
  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);
  }

  function openFrom(idx) {
    if (open) return;
    open = true;
    var t = thumbs[idx];
    var calc = fromAspect(Number(t.dataset.w), Number(t.dataset.h));
    fullImg.className = 'fullImg ' + imgClassByIdx[idx];
    ratioNote.textContent = '비율 ' + calc.aspect.toFixed(2) + ' · 시작 배율 ' + calc.scaleFrom.toFixed(2);
    lightbox.style.visibility = 'visible';
    lightbox.setAttribute('aria-hidden', 'false');
    backdrop.style.visibility = 'visible';
    animate(OPEN_MS, function (e) {
      var s = calc.scaleFrom + (1 - calc.scaleFrom) * e;
      fullImg.style.transform = 'scale(' + s.toFixed(4) + ')';
      backdrop.style.opacity = (calc.dim * e).toFixed(3);
    }, function () {
      closeBtn.focus({ preventScroll: true });
    });
  }

  function closeLightbox(idx) {
    if (!open) return;
    var t = thumbs[idx];
    var calc = fromAspect(Number(t.dataset.w), Number(t.dataset.h));
    animate(CLOSE_MS, function (e) {
      var s = 1 + (calc.scaleFrom - 1) * e;
      fullImg.style.transform = 'scale(' + s.toFixed(4) + ')';
      backdrop.style.opacity = (calc.dim * (1 - e)).toFixed(3);
    }, function () {
      lightbox.style.visibility = 'hidden';
      lightbox.setAttribute('aria-hidden', 'true');
      backdrop.style.visibility = 'hidden';
      open = false;
      thumbs[idx].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 = [];
    }
  }

  thumbs.forEach(function (t, i) {
    t.addEventListener('click', function () {
      human();
      activeIdx = i;
      openFrom(i);
    });
  });
  closeBtn.addEventListener('click', function () { human(); closeLightbox(activeIdx); });
  backdrop.addEventListener('click', function () { human(); closeLightbox(activeIdx); });
  document.addEventListener('keydown', function (e) {
    if (e.key === 'Escape' && open) { human(); closeLightbox(activeIdx); }
  });

  function cycle() {
    activeIdx = 2;
    openFrom(2);
    timers.push(setTimeout(function () { closeLightbox(2); }, OPEN_MS + HOLD_OPEN_MS));
  }

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

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

const OPEN_MS = 600;
const CLOSE_MS = 420;
const LOOP_MS = 2000;
const HOLD_OPEN_MS = 620;
const ASPECT_NORM_LO = 0.6;
const ASPECT_NORM_HI = 1.6;
const SCALE_FROM_MIN = 0.7;
const SCALE_FROM_MAX = 0.92;
const DIM_MAX = 0.82;
const DIM_MIN = 0.58;

const THUMB_SIZES: { w: number; h: number }[] = [
  { w: 280, h: 210 },
  { w: 200, h: 200 },
  { w: 180, h: 240 },
];

export default function BackdropFadeScale() {
  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 ratioNote0 = scene0.querySelector<HTMLParagraphElement>('.' + styles.ratioNote);
    const closeBtn0 = scene0.querySelector<HTMLButtonElement>('.' + styles.closeBtn);
    const thumbs = Array.from(scene0.querySelectorAll<HTMLButtonElement>('.' + styles.thumb));
    if (!backdrop0 || !lightbox0 || !fullImg0 || !ratioNote0 || !closeBtn0 || thumbs.length === 0) return undefined;
    const scene = scene0;
    const backdrop = backdrop0;
    const lightbox = lightbox0;
    const fullImg = fullImg0;
    const ratioNote = ratioNote0;
    const closeBtn = closeBtn0;

    const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
    const imgClassByIdx = [styles['thumbImg--a'], styles['thumbImg--b'], styles['thumbImg--c']];

    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); }

    // 이미지 자신의 가로세로 비율에서 시작 스케일과 배경 어둡기를 함께 계산한다 — 두 값이 같은 정규화 지점에서 나온다
    function fromAspect(w: number, h: number) {
      const aspect = w / h;
      const norm = clamp((aspect - ASPECT_NORM_LO) / (ASPECT_NORM_HI - ASPECT_NORM_LO), 0, 1);
      const scaleFrom = SCALE_FROM_MIN + (SCALE_FROM_MAX - SCALE_FROM_MIN) * norm;
      const dim = DIM_MAX - (DIM_MAX - DIM_MIN) * norm;
      return { aspect, scaleFrom, dim };
    }

    let open = false;
    let activeIdx = 1;
    let timers: number[] = [];

    // reduce: 실사용 경로 적용 — 트윈 없이 최종 상태로 즉시 전환한다
    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);
    }

    function openFrom(idx: number) {
      if (open) return;
      open = true;
      const calc = fromAspect(THUMB_SIZES[idx].w, THUMB_SIZES[idx].h);
      fullImg.className = styles.fullImg + ' ' + imgClassByIdx[idx];
      ratioNote.textContent = '비율 ' + calc.aspect.toFixed(2) + ' · 시작 배율 ' + calc.scaleFrom.toFixed(2);
      lightbox.style.visibility = 'visible';
      lightbox.setAttribute('aria-hidden', 'false');
      backdrop.style.visibility = 'visible';
      animate(OPEN_MS, (e) => {
        const s = calc.scaleFrom + (1 - calc.scaleFrom) * e;
        fullImg.style.transform = 'scale(' + s.toFixed(4) + ')';
        backdrop.style.opacity = (calc.dim * e).toFixed(3);
      }, () => {
        closeBtn.focus({ preventScroll: true });
      });
    }

    function closeLightbox(idx: number) {
      if (!open) return;
      const calc = fromAspect(THUMB_SIZES[idx].w, THUMB_SIZES[idx].h);
      animate(CLOSE_MS, (e) => {
        const s = 1 + (calc.scaleFrom - 1) * e;
        fullImg.style.transform = 'scale(' + s.toFixed(4) + ')';
        backdrop.style.opacity = (calc.dim * (1 - e)).toFixed(3);
      }, () => {
        lightbox.style.visibility = 'hidden';
        lightbox.setAttribute('aria-hidden', 'true');
        backdrop.style.visibility = 'hidden';
        open = false;
        thumbs[idx].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 = [];
      }
    }

    const thumbHandlers = thumbs.map((_, i) => () => { human(); activeIdx = i; openFrom(i); });
    thumbs.forEach((t, i) => t.addEventListener('click', thumbHandlers[i]));

    function onCloseClick() { human(); closeLightbox(activeIdx); }
    function onBackdropClick() { human(); closeLightbox(activeIdx); }
    function onKeydown(e: KeyboardEvent) {
      if (e.key === 'Escape' && open) { human(); closeLightbox(activeIdx); }
    }
    closeBtn.addEventListener('click', onCloseClick);
    backdrop.addEventListener('click', onBackdropClick);
    document.addEventListener('keydown', onKeydown);

    function cycle() {
      activeIdx = 2;
      openFrom(2);
      timers.push(window.setTimeout(() => { closeLightbox(2); }, OPEN_MS + HOLD_OPEN_MS));
    }

    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); });
      thumbs.forEach((t, i) => t.removeEventListener('click', thumbHandlers[i]));
      closeBtn.removeEventListener('click', onCloseClick);
      backdrop.removeEventListener('click', onBackdropClick);
      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} ${styles['thumbImg--a']}`} /><span className={styles.thumbLabel}>사진 1</span></button></li>
        <li><button className={styles.thumb} type="button" aria-haspopup="dialog"><span className={`${styles.thumbImg} ${styles['thumbImg--b']}`} /><span className={styles.thumbLabel}>사진 2</span></button></li>
        <li><button className={styles.thumb} type="button" aria-haspopup="dialog"><span className={`${styles.thumbImg} ${styles['thumbImg--c']}`} /><span className={styles.thumbLabel}>사진 3</span></button></li>
      </ul>
      <div className={styles.backdrop} />
      <div className={styles.lightbox} role="dialog" aria-modal="true" aria-hidden="true" aria-label="사진 확대 보기">
        <span className={styles.fullImg} />
        <p className={styles.ratioNote} />
        <button className={styles.closeBtn} type="button">닫기</button>
      </div>
    </div>
  );
}