05격자 위치 값이 순서를 계산하는 갤러리 지연 로딩

<main class="stage">
<div class="lgs is-demo" id="lgs">
  <div class="lgs__badge" id="lgsBadge">불러오는 중</div>
  <div class="lgs__grid" id="lgsGrid"></div>
  <p class="lgs__hint">클릭하면 다시 불러옵니다</p>
</div>
</main>

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

// 격자 위치(행+열) 값으로 지연 시간을 계산하는 맨해튼 거리 스태거.
// 왼쪽 위 칸이 가장 먼저, 오른쪽 아래로 갈수록 늦게 실제 사진으로 바뀐다.

$duration: $dur-enter;
$easing: $ease-elastic;
$color: $subject-lilac;

@include stage($stage-ink);

.lgs {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-3;
  outline: none;
  cursor: pointer;
}

.lgs__badge {
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(185, 160, 255, .18);
  color: $color;
  font-weight: 700;
  font-size: 11px;
}

.lgs__grid {
  display: grid;
  grid-template-columns: repeat(3, 70px);
  grid-template-rows: repeat(2, 70px);
  gap: $sp-2;
}

.lgs__cell {
  position: relative;
  border-radius: $r-sm;
  overflow: hidden;
}

.lgs__placeholder {
  position: absolute;
  inset: 0;
  background: rgba(255, 255, 255, .1);
  transition: opacity $dur-quick $ease-out;
}

.lgs__photo {
  position: absolute;
  inset: 0;
  opacity: 0;
  transform: scale(.7);
  transform-origin: center;
  transition: transform $duration $easing, opacity $dur-base $ease-out;
}

.lgs__photo--0 { background: linear-gradient(135deg, $subject-lilac, $subject-blue); }
.lgs__photo--1 { background: linear-gradient(135deg, $subject-pink, $subject-lilac); }
.lgs__photo--2 { background: linear-gradient(135deg, $subject-mint, $subject-sky); }
.lgs__photo--3 { background: linear-gradient(135deg, $subject-sky, $subject-blue-light); }

.lgs__cell--loaded .lgs__placeholder { opacity: 0; }
.lgs__cell--loaded .lgs__photo { opacity: 1; transform: scale(1); }

.lgs__hint {
  margin: 0;
  color: rgba(255, 255, 255, .5);
  font-size: 11px;
}

@media (max-width: 340px) {
  .lgs { gap: $sp-2; }
  .lgs__grid { grid-template-columns: repeat(3, 48px); grid-template-rows: repeat(2, 48px); gap: $sp-1; }
}

@media (prefers-reduced-motion: reduce) {
  .lgs__placeholder, .lgs__photo { 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);
}

.lgs {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  outline: none;
  cursor: pointer;
}

.lgs__badge {
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(185, 160, 255, 0.18);
  color: #b9a0ff;
  font-weight: 700;
  font-size: 11px;
}

.lgs__grid {
  display: grid;
  grid-template-columns: repeat(3, 70px);
  grid-template-rows: repeat(2, 70px);
  gap: 8px;
}

.lgs__cell {
  position: relative;
  border-radius: 8px;
  overflow: hidden;
}

.lgs__placeholder {
  position: absolute;
  inset: 0;
  background: rgba(255, 255, 255, 0.1);
  transition: opacity 220ms ease-out;
}

.lgs__photo {
  position: absolute;
  inset: 0;
  opacity: 0;
  transform: scale(0.7);
  transform-origin: center;
  transition: transform 600ms cubic-bezier(0.34, 1.56, 0.64, 1), opacity 300ms ease-out;
}

.lgs__photo--0 {
  background: linear-gradient(135deg, #b9a0ff, #2f6df6);
}

.lgs__photo--1 {
  background: linear-gradient(135deg, #ff9ebb, #b9a0ff);
}

.lgs__photo--2 {
  background: linear-gradient(135deg, #4cd4a6, #6ec8ff);
}

.lgs__photo--3 {
  background: linear-gradient(135deg, #6ec8ff, #5b8cf8);
}

.lgs__cell--loaded .lgs__placeholder {
  opacity: 0;
}

.lgs__cell--loaded .lgs__photo {
  opacity: 1;
  transform: scale(1);
}

.lgs__hint {
  margin: 0;
  color: rgba(255, 255, 255, 0.5);
  font-size: 11px;
}

@media (max-width: 340px) {
  .lgs {
    gap: 8px;
  }
  .lgs__grid {
    grid-template-columns: repeat(3, 48px);
    grid-template-rows: repeat(2, 48px);
    gap: 4px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .lgs__placeholder, .lgs__photo {
    transition: none !important;
  }
}

(function () {
  var root = document.getElementById('lgs');
  var grid = document.getElementById('lgsGrid');
  var badge = document.getElementById('lgsBadge');
  var COLS = 3;
  var ROWS = 2;
  var STAGGER_STEP_MS = 90;
  var START_DELAY_MS = 200;
  var CYCLE_GAP_MS = 1600;

  var cells = [];
  for (var i = 0; i < COLS * ROWS; i += 1) {
    var cell = document.createElement('div');
    cell.className = 'lgs__cell';
    cell.innerHTML = '<div class="lgs__placeholder"></div><div class="lgs__photo lgs__photo--' + (i % 4) + '"></div>';
    grid.appendChild(cell);
    cells.push(cell);
  }

  // 계산 겹: 격자 위치(행 값 + 열 값)로 지연 시간을 계산한다 — 맨해튼 거리 스태거.
  // 왼쪽 위(행0·열0)가 가장 먼저, 오른쪽 아래로 갈수록 늦게 실제 사진으로 바뀐다.
  function delayFor(idx) {
    var row = Math.floor(idx / COLS);
    var col = idx % COLS;
    return START_DELAY_MS + (row + col) * STAGGER_STEP_MS;
  }

  var timers = [];
  function clearTimers() { timers.forEach(clearTimeout); timers = []; }

  function loadAll() {
    cells.forEach(function (cell) { cell.classList.remove('lgs__cell--loaded'); });
    badge.textContent = '불러오는 중';
    var maxDelay = 0;
    cells.forEach(function (cell, idx) {
      var d = delayFor(idx);
      maxDelay = Math.max(maxDelay, d);
      var t = setTimeout(function () { cell.classList.add('lgs__cell--loaded'); }, d);
      timers.push(t);
    });
    var t2 = setTimeout(function () { badge.textContent = '전부 불러옴'; }, maxDelay + 120);
    timers.push(t2);
    return maxDelay + 120;
  }

  root.addEventListener('click', function () {
    root.classList.remove('is-demo');
    clearTimers();
    loadAll();
  });
  root.addEventListener('keydown', function (e) {
    if (e.key === 'Enter' || e.key === ' ') { e.preventDefault(); root.click(); }
  });
  root.tabIndex = 0;

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (reduce) {
    root.classList.remove('is-demo');
    cells.forEach(function (cell) { cell.classList.add('lgs__cell--loaded'); });
    badge.textContent = '전부 불러옴';
  } else {
    (function loop() {
      clearTimers();
      var total = loadAll();
      setTimeout(function () {
        if (!root.classList.contains('is-demo')) { return; }
        setTimeout(function () {
          if (root.classList.contains('is-demo')) { loop(); }
        }, 500);
      }, total + CYCLE_GAP_MS);
    })();
  }
})();

import { useEffect, useRef, useState, useCallback } from "react";
import styles from "./GalleryGridStaggerReveal.module.scss";

// 격자 위치(행+열) 값으로 지연 시간을 계산하는 맨해튼 거리 스태거.
const COLS = 3;
const ROWS = 2;
const STAGGER_STEP_MS = 90;
const START_DELAY_MS = 200;
const CYCLE_GAP_MS = 1600;
const CELL_COUNT = COLS * ROWS;

function delayFor(idx: number): number {
  const row = Math.floor(idx / COLS);
  const col = idx % COLS;
  return START_DELAY_MS + (row + col) * STAGGER_STEP_MS;
}

type Box<T> = { current: T };
function useBox<T>(initial: T): Box<T> {
  return useRef(initial) as unknown as Box<T>;
}

export default function GalleryGridStaggerReveal() {
  const rootRef = useRef<HTMLDivElement>(null);
  const [demo, setDemo] = useState(true);
  const [loaded, setLoaded] = useState<boolean[]>(Array(CELL_COUNT).fill(false));
  const [badge, setBadge] = useState("불러오는 중");
  const timersRef = useBox<number[]>([]);

  const clearTimers = useCallback(() => {
    timersRef.current.forEach((t) => window.clearTimeout(t));
    timersRef.current = [];
  }, [timersRef]);

  const loadAll = useCallback((): number => {
    setLoaded(Array(CELL_COUNT).fill(false));
    setBadge("불러오는 중");
    let maxDelay = 0;
    for (let idx = 0; idx < CELL_COUNT; idx += 1) {
      const d = delayFor(idx);
      maxDelay = Math.max(maxDelay, d);
      const t = window.setTimeout(() => {
        setLoaded((prev) => prev.map((v, j) => (j === idx ? true : v)));
      }, d);
      timersRef.current.push(t);
    }
    const t2 = window.setTimeout(() => setBadge("전부 불러옴"), maxDelay + 120);
    timersRef.current.push(t2);
    return maxDelay + 120;
  }, [timersRef]);

  const onActivate = useCallback(() => {
    setDemo(false);
    clearTimers();
    loadAll();
  }, [clearTimers, loadAll]);

  useEffect(() => {
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (reduce) {
      setDemo(false);
      setLoaded(Array(CELL_COUNT).fill(true));
      setBadge("전부 불러옴");
      return;
    }
    let cancelled = false;
    let outer: number | null = null;
    let inner: number | null = null;
    function loop() {
      if (cancelled) { return; }
      clearTimers();
      const total = loadAll();
      outer = window.setTimeout(() => {
        if (cancelled || !rootRef.current?.classList.contains(styles["is-demo"])) { return; }
        inner = window.setTimeout(() => {
          if (!cancelled && rootRef.current?.classList.contains(styles["is-demo"])) { loop(); }
        }, 500);
      }, total + CYCLE_GAP_MS);
    }
    loop();
    return () => {
      cancelled = true;
      clearTimers();
      if (outer !== null) { window.clearTimeout(outer); }
      if (inner !== null) { window.clearTimeout(inner); }
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  useEffect(() => {
    const root = rootRef.current;
    function onKeyDown(e: KeyboardEvent) {
      if (e.key === "Enter" || e.key === " ") { e.preventDefault(); onActivate(); }
    }
    root?.addEventListener("keydown", onKeyDown);
    return () => root?.removeEventListener("keydown", onKeyDown);
  }, [onActivate]);

  return (
    <main className={styles.stage}>
      <div
        ref={rootRef}
        className={`${styles.lgs} ${demo ? styles["is-demo"] : ""}`}
        tabIndex={0}
        onClick={onActivate}
      >
        <div className={styles["lgs__badge"]}>{badge}</div>
        <div className={styles["lgs__grid"]}>
          {Array.from({ length: CELL_COUNT }).map((_, idx) => (
            <div key={idx} className={`${styles["lgs__cell"]} ${loaded[idx] ? styles["lgs__cell--loaded"] : ""}`}>
              <div className={styles["lgs__placeholder"]} />
              <div className={`${styles["lgs__photo"]} ${styles["lgs__photo--" + (idx % 4)]}`} />
            </div>
          ))}
        </div>
        <p className={styles["lgs__hint"]}>클릭하면 다시 불러옵니다</p>
      </div>
    </main>
  );
}