04メディア基本比率固定 — 画像と動画が親要素の幅を超えないよう合わせる枠

<main class="stage">
<div class="wrap is-demo" id="wrap">
  <div class="row">
    <span class="rowLabel">そのままの画像</span>
    <div class="frame rawFrame" id="rawFrame">
      <img class="rawImg" id="rawImg" alt="風景サンプル画像" src="data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='220' height='64'><rect width='220' height='64' fill='%23ffd23f'/><circle cx='186' cy='16' r='11' fill='%23ff9ebb'/><polygon points='0,64 52,22 104,64' fill='%23c93000'/><polygon points='62,64 138,16 214,64' fill='%2317141a'/><rect y='56' width='220' height='8' fill='%232f6df6'/></svg>">
    </div>
  </div>
  <div class="row">
    <span class="rowLabel">調整後の画像</span>
    <div class="frame fitFrame" id="fitFrame">
      <img class="fitImg" id="fitImg" alt="風景サンプル画像" src="data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='220' height='64'><rect width='220' height='64' fill='%23ffd23f'/><circle cx='186' cy='16' r='11' fill='%23ff9ebb'/><polygon points='0,64 52,22 104,64' fill='%23c93000'/><polygon points='62,64 138,16 16,64' fill='%234cd4a6'/><rect y='56' width='220' height='8' fill='%232f6df6'/></svg>">
      <div class="handle" id="handle" role="separator" aria-label="枠幅を調整"></div>
    </div>
  </div>
  <div class="readout" id="readout">枠 —px</div>
</div>
</main>

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

// 계산 겹은 index.html 의 apply() 에 있다 — 틀 너비가 실시간으로 줄어들 때 그대로 이미지는
// 자연 폭(220px)을 지키다 틀 밖으로 삐져나가고(초과 px 를 문구로 세준다), 맞춤 이미지는
// max-width: 100% 로 틀 안으로 줄어든다. 실측은 getBoundingClientRect 로 매 프레임 다시.
@include stage($stage-paper);

.wrap {
  width: 300px;
  display: flex;
  flex-direction: column;
  gap: $sp-3;
}

.row {
  display: flex;
  align-items: center;
  gap: $sp-2;
}

.rowLabel {
  width: 72px;
  flex: 0 0 auto;
  color: $subject-ink;
  font-size: 11px;
  font-weight: 700;
}

.frame {
  position: relative;
  border: 2px solid $subject-ink;
  border-radius: $r-xs;
  overflow: hidden;
  transition: width $dur-base $ease-out;
}

.fitFrame { border-color: $subject-blue-deep; }

// 리셋 항목의 주인공 — img { max-width: 100%; } 를 .fitImg 에만 걸어 나란히 비교한다
.fitImg {
  display: block;
  max-width: 100%;
  height: auto;
}

.rawImg {
  display: block;
}

.handle {
  position: absolute;
  top: -2px;
  right: -9px;
  width: 14px;
  height: calc(100% + 4px);
  border-radius: $r-xs;
  background: $subject-blue-deep;
  cursor: ew-resize;
  opacity: .85;
  transition: opacity $dur-instant $ease-out;

  &::after {
    content: "";
    position: absolute;
    top: 50%;
    left: 50%;
    width: 2px;
    height: 14px;
    border-radius: $r-xs;
    background: $subject-cream;
    transform: translate(-50%, -50%);
  }

  &:hover { opacity: 1; }
}

.readout {
  color: $subject-ink;
  font-size: 11px;
  text-align: center;
}

@media (max-width: 340px) {
  .wrap { width: 260px; }
  .rowLabel { width: 60px; font-size: 10px; }
}

@media (prefers-reduced-motion: reduce) {
  // reduce: 자동 루프의 사인 진동만 멈춘다(핸들로 하는 실사용 조절은 즉시 반영)
  .frame { 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);
}

.wrap {
  width: 300px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.row {
  display: flex;
  align-items: center;
  gap: 8px;
}

.rowLabel {
  width: 72px;
  flex: 0 0 auto;
  color: #17141a;
  font-size: 11px;
  font-weight: 700;
}

.frame {
  position: relative;
  border: 2px solid #17141a;
  border-radius: 4px;
  overflow: hidden;
  transition: width 300ms ease-out;
}

.fitFrame {
  border-color: #0a4fe8;
}

.fitImg {
  display: block;
  max-width: 100%;
  height: auto;
}

.rawImg {
  display: block;
}

.handle {
  position: absolute;
  top: -2px;
  right: -9px;
  width: 14px;
  height: calc(100% + 4px);
  border-radius: 4px;
  background: #0a4fe8;
  cursor: ew-resize;
  opacity: 0.85;
  transition: opacity 140ms ease-out;
}
.handle::after {
  content: "";
  position: absolute;
  top: 50%;
  left: 50%;
  width: 2px;
  height: 14px;
  border-radius: 4px;
  background: #fff7e6;
  transform: translate(-50%, -50%);
}
.handle:hover {
  opacity: 1;
}

.readout {
  color: #17141a;
  font-size: 11px;
  text-align: center;
}

@media (max-width: 340px) {
  .wrap {
    width: 260px;
  }
  .rowLabel {
    width: 60px;
    font-size: 10px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .frame {
    transition: none;
  }
}

(function () {
  var MIN_FRAME_PX = 130;
  var MAX_FRAME_PX = 230;
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var wrap = document.getElementById('wrap');
  var rawFrame = document.getElementById('rawFrame');
  var rawImg = document.getElementById('rawImg');
  var fitFrame = document.getElementById('fitFrame');
  var fitImg = document.getElementById('fitImg');
  var handle = document.getElementById('handle');
  var readout = document.getElementById('readout');
  var isDemo = true;
  var frameW = 180;

  function apply() {
    rawFrame.style.width = frameW + 'px';
    fitFrame.style.width = frameW + 'px';
    // 실측 — 두 이미지의 실제 렌더 폭을 매 프레임 다시 잰다 (자연 폭 220px 는 svg width 에서 온다)
    var fitW = fitImg.getBoundingClientRect().width;
    var rawW = rawImg.getBoundingClientRect().width;
    var over = Math.max(0, Math.round(rawW - frameW));
    readout.textContent = '枠 ' + Math.round(frameW) + 'px・そのまま ' + Math.round(rawW) +
      'px（超過 ' + over + 'px）・調整後 ' + Math.round(fitW) + 'px';
  }

  var start = 0;
  function loop(ts) {
    if (!start) start = ts;
    if (isDemo && !reduce) { frameW = 180 + 50 * Math.sin((ts - start) / 900); }
    apply();
    requestAnimationFrame(loop);
  }

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

  function onMove(e) {
    var rect = fitFrame.getBoundingClientRect();
    frameW = Math.min(MAX_FRAME_PX, Math.max(MIN_FRAME_PX, e.clientX - rect.left));
  }
  function onUp() {
    window.removeEventListener('pointermove', onMove);
    window.removeEventListener('pointerup', onUp);
  }
  handle.addEventListener('pointerdown', function (e) {
    human();
    e.preventDefault();
    onMove(e);
    window.addEventListener('pointermove', onMove);
    window.addEventListener('pointerup', onUp);
  });

  requestAnimationFrame(loop);
})();

// MediaBlock — vanilla 판(run/376/demo/04-media-block/index.html) 의 React 포트.
// 틀 너비를 핸들로 끌면 두 이미지의 실제 렌더 폭(getBoundingClientRect)을 다시 재
// "그대로 이미지" 는 자연 폭을 지키다 넘치고 "맞춤 이미지" 는 max-width:100% 로 줄어드는
// 차이를 초과 px 문구로 보여준다.
import { useEffect, useRef } from "react";
import styles from "./MediaBlock.module.scss";

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

const MIN_FRAME_PX = 130;
const MAX_FRAME_PX = 230;
const SAMPLE_SVG =
  "data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='220' height='64'><rect width='220' height='64' fill='%23ffd23f'/><circle cx='186' cy='16' r='11' fill='%23ff9ebb'/><polygon points='0,64 52,22 104,64' fill='%23c93000'/><polygon points='62,64 138,16 214,64' fill='%2317141a'/><rect y='56' width='220' height='8' fill='%232f6df6'/></svg>";

export default function MediaBlock() {
  const wrapRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const rawFrameRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const rawImgRef = useRef(null) as unknown as Box<HTMLImageElement>;
  const fitFrameRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const fitImgRef = useRef(null) as unknown as Box<HTMLImageElement>;
  const handleRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const readoutRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const rafRef = useRef(0) as unknown as Box<number>;

  useEffect(() => {
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    const wrap = wrapRef.current;
    const rawFrame = rawFrameRef.current;
    const rawImg = rawImgRef.current;
    const fitFrame = fitFrameRef.current;
    const fitImg = fitImgRef.current;
    const handle = handleRef.current;
    const readout = readoutRef.current;
    if (!wrap || !rawFrame || !rawImg || !fitFrame || !fitImg || !handle || !readout) return;

    let isDemo = true;
    let frameW = 180;

    function apply() {
      rawFrame!.style.width = frameW + "px";
      fitFrame!.style.width = frameW + "px";
      const fitW = fitImg!.getBoundingClientRect().width;
      const rawW = rawImg!.getBoundingClientRect().width;
      const over = Math.max(0, Math.round(rawW - frameW));
      readout!.textContent = "틀 " + Math.round(frameW) + "px · 그대로 " + Math.round(rawW) +
        "px (초과 " + over + "px) · 맞춤 " + Math.round(fitW) + "px";
    }

    let start = 0;
    function loop(ts: number) {
      if (!start) start = ts;
      if (isDemo && !reduce) { frameW = 180 + 50 * Math.sin((ts - start) / 900); }
      apply();
      rafRef.current = requestAnimationFrame(loop);
    }

    function human() { if (isDemo) { wrap!.classList.remove(styles.isDemo); isDemo = false; } }

    function onMove(e: PointerEvent) {
      const rect = fitFrame!.getBoundingClientRect();
      frameW = Math.min(MAX_FRAME_PX, Math.max(MIN_FRAME_PX, e.clientX - rect.left));
    }
    function onUp() {
      window.removeEventListener("pointermove", onMove);
      window.removeEventListener("pointerup", onUp);
    }
    function onDown(e: PointerEvent) {
      human();
      e.preventDefault();
      onMove(e);
      window.addEventListener("pointermove", onMove);
      window.addEventListener("pointerup", onUp);
    }
    handle.addEventListener("pointerdown", onDown as unknown as EventListener);

    rafRef.current = requestAnimationFrame(loop);

    return () => {
      handle!.removeEventListener("pointerdown", onDown as unknown as EventListener);
      window.removeEventListener("pointermove", onMove);
      window.removeEventListener("pointerup", onUp);
      cancelAnimationFrame(rafRef.current);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.wrap + " " + styles.isDemo} ref={wrapRef}>
        <div className={styles.row}>
          <span className={styles.rowLabel}>그대로 이미지</span>
          <div className={styles.frame + " " + styles.rawFrame} ref={rawFrameRef}>
            <img className={styles.rawImg} ref={rawImgRef} alt="풍경 샘플 이미지" src={SAMPLE_SVG} />
          </div>
        </div>
        <div className={styles.row}>
          <span className={styles.rowLabel}>맞춤 이미지</span>
          <div className={styles.frame + " " + styles.fitFrame} ref={fitFrameRef}>
            <img className={styles.fitImg} ref={fitImgRef} alt="풍경 샘플 이미지" src={SAMPLE_SVG} />
            <div className={styles.handle} ref={handleRef} role="separator" aria-label="틀 너비 조절"></div>
          </div>
        </div>
        <div className={styles.readout} ref={readoutRef}>틀 —px</div>
      </div>
    </main>
  );
}