04スクロール値で折りたたまれる下部固定ミニバー

<svg width="0" height="0" style="position:absolute" aria-hidden="true">
  <defs>
    <symbol id="ico-play" viewBox="0 0 256 256"><g fill="currentColor"><path d="M228.23 134.69L84.15 222.81A8 8 0 0 1 72 216.12V39.88a8 8 0 0 1 12.15-6.69l144.08 88.12a7.82 7.82 0 0 1 0 13.38" opacity=".2"/><path d="M232.4 114.49L88.32 26.35a16 16 0 0 0-16.2-.3A15.86 15.86 0 0 0 64 39.87v176.26A15.94 15.94 0 0 0 80 232a16.07 16.07 0 0 0 8.36-2.35l144.04-88.14a15.81 15.81 0 0 0 0-27ZM80 215.94V40l143.83 88Z"/></g></symbol>
  </defs>
</svg>
<main class="stage">
<div class="mb is-demo" id="mb">
  <p class="mb__hint"><span>下にスクロールすると値が計算されプレイヤーが下部のミニバーに折りたたまれます</span></p>
  <div class="mb__viewport" id="viewport">
    <div class="mb__scroll" id="scroll" tabindex="0" role="group" aria-label="スクロールデモ領域">
      <div class="mb__full" id="full">
        <div class="mb__art"></div>
        <div class="mb__meta">
          <div class="mb__title">Untitled Session</div>
          <div class="mb__sub">Track 01</div>
        </div>
      </div>
      <div class="mb__filler" aria-hidden="true">
        <div class="mb__line"></div>
        <div class="mb__line"></div>
        <div class="mb__line"></div>
        <div class="mb__line"></div>
        <div class="mb__line"></div>
        <div class="mb__line"></div>
      </div>
    </div>
    <button class="mb__mini" id="mini" type="button" aria-label="フルプレイヤーに戻る">
      <div class="mb__mini-art"></div>
      <div class="mb__mini-title">Untitled Session</div>
      <svg class="mb__mini-ico" aria-hidden="true"><use href="#ico-play"></use></svg>
    </button>
  </div>
</div>
</main>

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

// 계산 겹(스크롤 값 → 전환 진행률)은 index.html 의 recompute() 에 있다. 여기는 무대·레이아웃만.
$duration: $dur-base;
$easing:   $ease-out;
$color:    $subject-blue;

@include stage($stage-paper);

.mb {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-2;
  width: min(400px, 92vw);
}

.mb__hint {
  margin: 0;
  color: rgba($subject-ink, .72);
  font-size: 12px;
  font-weight: 500;
  line-height: 1.35;
  text-align: center;
}

.mb__viewport {
  position: relative;
  width: 100%;
  height: 120px;
  border-radius: $r-card;
  overflow: hidden;
  box-shadow: 0 0 0 1px rgba($subject-ink, .12);
  background: $subject-cream;
}

.mb__scroll {
  height: 100%;
  overflow-y: auto;
  overscroll-behavior: contain;
}

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

.mb__full {
  display: flex;
  align-items: center;
  gap: $sp-4;
  padding: $sp-5;
}

.mb__art {
  flex: 0 0 auto;
  width: 52px;
  height: 52px;
  border-radius: $r-control;
  background: $color;
}

.mb__meta { min-width: 0; }

.mb__title {
  color: $subject-ink;
  font-size: 13px;
  font-weight: 700;
}

.mb__sub {
  color: rgba($subject-ink, .6);
  font-size: 11px;
  font-weight: 500;
  margin-top: $sp-1;
}

.mb__filler {
  padding: 0 $sp-5 $sp-6;
  display: flex;
  flex-direction: column;
  gap: $sp-4;
}

.mb__line {
  height: 12px;
  border-radius: $r-xs;
  background: rgba($subject-ink, .08);
}

.mb__mini {
  position: absolute;
  left: $sp-3;
  right: $sp-3;
  bottom: $sp-3;
  display: flex;
  align-items: center;
  gap: $sp-3;
  padding: $sp-2 $sp-3;
  border: none;
  border-radius: $r-pill;
  background: $subject-ink;
  box-shadow: 0 8px 20px rgba($subject-ink, .28);
  cursor: pointer;
  text-align: left;
  opacity: 0;
  transform: translateY(16px) scale(.94);
  transform-origin: bottom center; // 미니 바는 화면 아래에 붙는 것이 기준점 — 중심 기준이 아니다
}

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

.mb__mini-art {
  flex: 0 0 auto;
  width: 26px;
  height: 26px;
  border-radius: $r-sm;
  background: $color;
}

.mb__mini-title {
  flex: 1 1 auto;
  min-width: 0;
  color: $subject-cream;
  font-size: 12px;
  font-weight: 700;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.mb__mini-ico {
  flex: 0 0 auto;
  width: 14px;
  height: 14px;
  color: $subject-cream;
}

@media (max-width: 340px) {
  .mb__viewport { height: 108px; }
  .mb__art { width: 42px; height: 42px; }
  .mb__full { padding: $sp-3; }
}

@media (prefers-reduced-motion: reduce) {
  .mb__mini { 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);
}

.mb {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  width: min(400px, 92vw);
}

.mb__hint {
  margin: 0;
  color: rgba(23, 20, 26, 0.72);
  font-size: 12px;
  font-weight: 500;
  line-height: 1.35;
  text-align: center;
}

.mb__viewport {
  position: relative;
  width: 100%;
  height: 120px;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 0 0 1px rgba(23, 20, 26, 0.12);
  background: #fff7e6;
}

.mb__scroll {
  height: 100%;
  overflow-y: auto;
  overscroll-behavior: contain;
}

.mb__scroll:focus-visible {
  outline: 2px solid #2f6df6;
  outline-offset: -2px;
}

.mb__full {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 20px;
}

.mb__art {
  flex: 0 0 auto;
  width: 52px;
  height: 52px;
  border-radius: 12px;
  background: #2f6df6;
}

.mb__meta {
  min-width: 0;
}

.mb__title {
  color: #17141a;
  font-size: 13px;
  font-weight: 700;
}

.mb__sub {
  color: rgba(23, 20, 26, 0.6);
  font-size: 11px;
  font-weight: 500;
  margin-top: 4px;
}

.mb__filler {
  padding: 0 20px 24px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.mb__line {
  height: 12px;
  border-radius: 4px;
  background: rgba(23, 20, 26, 0.08);
}

.mb__mini {
  position: absolute;
  left: 12px;
  right: 12px;
  bottom: 12px;
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 8px 12px;
  border: none;
  border-radius: 999px;
  background: #17141a;
  box-shadow: 0 8px 20px rgba(23, 20, 26, 0.28);
  cursor: pointer;
  text-align: left;
  opacity: 0;
  transform: translateY(16px) scale(0.94);
  transform-origin: bottom center;
}

.mb__mini:focus-visible {
  outline: 2px solid #2f6df6;
  outline-offset: 2px;
}

.mb__mini-art {
  flex: 0 0 auto;
  width: 26px;
  height: 26px;
  border-radius: 8px;
  background: #2f6df6;
}

.mb__mini-title {
  flex: 1 1 auto;
  min-width: 0;
  color: #fff7e6;
  font-size: 12px;
  font-weight: 700;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.mb__mini-ico {
  flex: 0 0 auto;
  width: 14px;
  height: 14px;
  color: #fff7e6;
}

@media (max-width: 340px) {
  .mb__viewport {
    height: 108px;
  }
  .mb__art {
    width: 42px;
    height: 42px;
  }
  .mb__full {
    padding: 12px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .mb__mini {
    transition: none;
  }
}

(function () {
  var root = document.getElementById('mb');
  var viewport = document.getElementById('viewport');
  var scrollEl = document.getElementById('scroll');
  var full = document.getElementById('full');
  var mini = document.getElementById('mini');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var isDemo = true;

  var MORPH_RANGE_PX = 56; // 완전 전환까지 걸리는 스크롤 거리
  var SCROLL_STEP_PX = 48; // 방향키 한 번의 스크롤 단위
  var programmatic = false; // 시연 루프가 scrollTop 을 밀 때 뜨는 scroll 이벤트를 실사용 스크롤과 구분한다

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

  function recompute() {
    var threshold = full.offsetHeight; // 실제 카드 높이를 기준으로 전환 시점을 계산한다
    var y = scrollEl.scrollTop;
    var p = Math.min(1, Math.max(0, (y - threshold) / MORPH_RANGE_PX));
    mini.style.opacity = String(p);
    mini.style.transform = 'translateY(' + ((1 - p) * 16) + 'px) scale(' + (0.94 + p * 0.06) + ')';
    mini.style.pointerEvents = p > 0.5 ? 'auto' : 'none';
  }

  function onScroll() {
    if (programmatic) { programmatic = false; recompute(); return; }
    human(); recompute();
  }

  function onScrollKeydown(e) {
    if (e.key === 'ArrowDown' || e.key === 'ArrowUp') {
      e.preventDefault();
      human();
      scrollEl.scrollTop += (e.key === 'ArrowDown' ? SCROLL_STEP_PX : -SCROLL_STEP_PX);
      recompute();
    }
  }

  function onMiniClick() {
    human();
    scrollEl.scrollTop = 0;
    recompute();
  }

  var driveStart = 0;
  function triangle(frac) { return frac < 0.5 ? frac * 2 : 2 - frac * 2; }
  function driveTick(now) {
    if (!driveStart) driveStart = now;
    if (isDemo) {
      var DRIVE_PERIOD_MS = 2000; // 렌더 캐처 창(설정 초=2.0)과 같은 주기 — 시연 전용
      var frac = ((now - driveStart) % DRIVE_PERIOD_MS) / DRIVE_PERIOD_MS;
      var max = scrollEl.scrollHeight - scrollEl.clientHeight;
      programmatic = true;
      scrollEl.scrollTop = triangle(frac) * max;
      recompute();
    }
    requestAnimationFrame(driveTick);
  }

  window.addEventListener('resize', recompute);

  if (reduce) {
    root.classList.add('is-still');
    recompute();
    scrollEl.addEventListener('scroll', onScroll);
    scrollEl.addEventListener('keydown', onScrollKeydown);
    mini.addEventListener('click', onMiniClick);
  } else {
    scrollEl.addEventListener('scroll', onScroll);
    scrollEl.addEventListener('keydown', onScrollKeydown);
    mini.addEventListener('click', onMiniClick);
    recompute();
    requestAnimationFrame(driveTick);
  }
})();

import { useEffect, useRef } from "react";
import styles from "./MiniSticky.module.scss";

export default function MiniSticky() {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const scrollRef = useRef<HTMLDivElement | null>(null);
  const fullRef = useRef<HTMLDivElement | null>(null);
  const miniRef = useRef<HTMLButtonElement | null>(null);

  useEffect(() => {
    const root = rootRef.current;
    const scrollEl = scrollRef.current;
    const full = fullRef.current;
    const mini = miniRef.current;
    if (!root || !scrollEl || !full || !mini) return;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let isDemo = true;

    const MORPH_RANGE_PX = 56; // 완전 전환까지 걸리는 스크롤 거리
    const SCROLL_STEP_PX = 48; // 방향키 한 번의 스크롤 단위
    let programmatic = false; // 시연 루프가 scrollTop 을 밀 때 뜨는 scroll 이벤트를 실사용 스크롤과 구분한다

    function human() { if (isDemo) { root!.classList.remove(styles["is-demo"]); isDemo = false; } }

    function recompute() {
      const threshold = full!.offsetHeight; // 실제 카드 높이를 기준으로 전환 시점을 계산한다
      const y = scrollEl!.scrollTop;
      const p = Math.min(1, Math.max(0, (y - threshold) / MORPH_RANGE_PX));
      mini!.style.opacity = String(p);
      mini!.style.transform = "translateY(" + (1 - p) * 16 + "px) scale(" + (0.94 + p * 0.06) + ")";
      mini!.style.pointerEvents = p > 0.5 ? "auto" : "none";
    }

    function onScroll() {
      if (programmatic) { programmatic = false; recompute(); return; }
      human(); recompute();
    }

    function onScrollKeydown(e: KeyboardEvent) {
      if (e.key === "ArrowDown" || e.key === "ArrowUp") {
        e.preventDefault();
        human();
        scrollEl!.scrollTop += e.key === "ArrowDown" ? SCROLL_STEP_PX : -SCROLL_STEP_PX;
        recompute();
      }
    }

    function onMiniClick() {
      human();
      scrollEl!.scrollTop = 0;
      recompute();
    }

    let driveStart = 0;
    function triangle(frac: number) { return frac < 0.5 ? frac * 2 : 2 - frac * 2; }
    let rafDrive = 0;
    function driveTick(now: number) {
      if (!driveStart) driveStart = now;
      if (isDemo) {
        const DRIVE_PERIOD_MS = 2000; // 렌더 캐처 창(설정 초=2.0)과 같은 주기 — 시연 전용
        const frac = ((now - driveStart) % DRIVE_PERIOD_MS) / DRIVE_PERIOD_MS;
        const max = scrollEl!.scrollHeight - scrollEl!.clientHeight;
        programmatic = true;
        scrollEl!.scrollTop = triangle(frac) * max;
        recompute();
      }
      rafDrive = requestAnimationFrame(driveTick);
    }

    window.addEventListener("resize", recompute);

    if (reduce) {
      root.classList.add(styles["is-still"]);
      recompute();
      scrollEl.addEventListener("scroll", onScroll);
      scrollEl.addEventListener("keydown", onScrollKeydown);
      mini.addEventListener("click", onMiniClick);
    } else {
      scrollEl.addEventListener("scroll", onScroll);
      scrollEl.addEventListener("keydown", onScrollKeydown);
      mini.addEventListener("click", onMiniClick);
      recompute();
      rafDrive = requestAnimationFrame(driveTick);
    }

    return () => {
      window.removeEventListener("resize", recompute);
      cancelAnimationFrame(rafDrive);
      scrollEl.removeEventListener("scroll", onScroll);
      scrollEl.removeEventListener("keydown", onScrollKeydown);
      mini.removeEventListener("click", onMiniClick);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.mb + " " + styles["is-demo"]} ref={rootRef}>
        <p className={styles.hint}><span>아래로 스크롤하면 값이 계산되어 플레이어가 하단 미니 바로 접힙니다</span></p>
        <div className={styles.viewport}>
          <div className={styles.scroll} ref={scrollRef} tabIndex={0} role="group" aria-label="스크롤 데모 영역">
            <div className={styles.full} ref={fullRef}>
              <div className={styles.art} />
              <div className={styles.meta}>
                <div className={styles.title}>Untitled Session</div>
                <div className={styles.sub}>Track 01</div>
              </div>
            </div>
            <div className={styles.filler} aria-hidden="true">
              <div className={styles.line} />
              <div className={styles.line} />
              <div className={styles.line} />
              <div className={styles.line} />
              <div className={styles.line} />
              <div className={styles.line} />
            </div>
          </div>
          <button className={styles.mini} ref={miniRef} type="button" aria-label="전체 플레이어로 돌아가기">
            <div className={styles.miniArt} />
            <div className={styles.miniTitle}>Untitled Session</div>
            <svg className={styles.miniIco} aria-hidden="true"><use href="#ico-play" /></svg>
          </button>
        </div>
      </div>
    </main>
  );
}