02가운데 글자 폭에 맞춰 양쪽 선이 나뉘는 구분선

<main class="stage">
<div class="dv is-demo" id="dvRoot">
  <div class="dv__card" id="dvCard">
    <div class="dv__row" id="dvRow" role="separator">
      <span class="dv__side" id="dvLeft"></span>
      <span class="dv__label" id="dvLabel">또는</span>
      <span class="dv__side dv__side--right" id="dvRight"></span>
    </div>
  </div>
  <div class="dv__bar">
  <button class="dv__btn" id="dvBtn" type="button">글자 바꾸기</button>
  <p class="dv__meta"><span class="dv__tag">LINE</span> <b id="dvPx">0</b><span>px</span></p>
  </div>
</div>
</main>

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

// 핵심: 가운데 글자 폭을 재서 양쪽 선 폭을 (줄 폭 - 글자 폭 - 간격 * 2) / 2 로 직접 계산한다.

$line-h: 6px;
$label-gap: 12px;
$line-color: $subject-sky;

@include stage($stage-ink);

.dv {
  width: min(100%, 440px);
  display: grid;
  gap: $sp-2;
  justify-items: center;
}

.dv__card {
  box-sizing: border-box;
  width: 420px;
  max-width: 100%;
  padding: $sp-8 $sp-4;
  border-radius: $r-card;
  background: $tick-panel;
}

.dv__row {
  display: flex;
  align-items: center;
  gap: $label-gap;
}

.dv__side {
  display: block;
  flex: none;
  height: $line-h;
  border-radius: $r-pill;
  background: linear-gradient(90deg, rgba($line-color, 0), $line-color 70%);
}
.dv__side--right { background: linear-gradient(270deg, rgba($line-color, 0), $line-color 70%); }

.dv__label {
  flex: none;
  color: $stage-paper;
  font-size: 14px;
  font-weight: 700;
  line-height: 20px;
  white-space: nowrap;
}

.dv__btn {
  box-sizing: border-box;
  height: 40px;
  padding: 0 $sp-5;
  border: 0;
  border-radius: $r-control;
  background: $subject-lilac;
  color: $subject-ink;
  font-family: inherit;
  font-size: 14px;
  font-weight: 700;
  line-height: 20px;
  cursor: pointer;
}
.dv__btn:focus-visible { outline: 3px solid $stage-paper; outline-offset: 3px; }

.dv__meta {
  margin: 0;
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: $sp-2;
  font-size: 12px;
  line-height: 16px;
  color: rgba($stage-paper, .78);
}
.dv__tag { font-weight: 700; letter-spacing: .08em; }
.dv__meta b { min-width: 3ch; text-align: right; font-variant-numeric: tabular-nums; color: $stage-paper; }

@media (prefers-reduced-motion: reduce) {
  .dv__btn { transition: none; }
}

.dv__bar { box-sizing: border-box; width: 100%; display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: $sp-2 $sp-3; }

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);
}

.dv {
  width: min(100%, 440px);
  display: grid;
  gap: 8px;
  justify-items: center;
}

.dv__card {
  box-sizing: border-box;
  width: 420px;
  max-width: 100%;
  padding: 32px 16px;
  border-radius: 16px;
  background: #231f28;
}

.dv__row {
  display: flex;
  align-items: center;
  gap: 12px;
}

.dv__side {
  display: block;
  flex: none;
  height: 6px;
  border-radius: 999px;
  background: linear-gradient(90deg, rgba(110, 200, 255, 0), #6ec8ff 70%);
}

.dv__side--right {
  background: linear-gradient(270deg, rgba(110, 200, 255, 0), #6ec8ff 70%);
}

.dv__label {
  flex: none;
  color: #ffffff;
  font-size: 14px;
  font-weight: 700;
  line-height: 20px;
  white-space: nowrap;
}

.dv__btn {
  box-sizing: border-box;
  height: 40px;
  padding: 0 20px;
  border: 0;
  border-radius: 12px;
  background: #b9a0ff;
  color: #17141a;
  font-family: inherit;
  font-size: 14px;
  font-weight: 700;
  line-height: 20px;
  cursor: pointer;
}

.dv__btn:focus-visible {
  outline: 3px solid #ffffff;
  outline-offset: 3px;
}

.dv__meta {
  margin: 0;
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 8px;
  font-size: 12px;
  line-height: 16px;
  color: rgba(255, 255, 255, 0.78);
}

.dv__tag {
  font-weight: 700;
  letter-spacing: 0.08em;
}

.dv__meta b {
  min-width: 3ch;
  text-align: right;
  font-variant-numeric: tabular-nums;
  color: #ffffff;
}

@media (prefers-reduced-motion: reduce) {
  .dv__btn {
    transition: none;
  }
}
.dv__bar {
  box-sizing: border-box;
  width: 100%;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 8px 12px;
}

(function () {
  // 기법: 글자 폭을 getBoundingClientRect 로 재고, 양쪽 선 폭 = (줄 폭 - 글자 폭 - LABEL_GAP * 2) / 2 를 직접 계산해 width 로 준다.
  // 데모는 카드 폭을 시간에 따라 줄였다 늘리고 글자를 돌려 가며 매 프레임 다시 계산한다.
  var LABEL_GAP = 12;
  var LINE_H_PX = 6;
  var CYCLE_MS = 2000;
  var NARROW_PX = 180;
  var WIDE_PX = 420;
  var LABELS = ['또는', '다른 방법으로 계속', '여기까지 읽은 내용'];

  var root = document.getElementById('dvRoot');
  var card = document.getElementById('dvCard');
  var row = document.getElementById('dvRow');
  var left = document.getElementById('dvLeft');
  var right = document.getElementById('dvRight');
  var label = document.getElementById('dvLabel');
  var btn = document.getElementById('dvBtn');
  var pxEl = document.getElementById('dvPx');
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var labelIndex = 0;

  function layout() {
    var rowW = row.getBoundingClientRect().width;
    var labelW = label.getBoundingClientRect().width;
    var side = Math.max(0, (rowW - labelW - LABEL_GAP * 2) / 2);
    left.style.width = side.toFixed(1) + 'px';
    right.style.width = side.toFixed(1) + 'px';
    pxEl.textContent = String(Math.round(side));
  }
  function setLabel(i) {
    labelIndex = i;
    label.textContent = LABELS[i];
  }
  function stopDemo() { root.classList.remove('is-demo'); }

  btn.addEventListener('click', function () {
    stopDemo();
    setLabel((labelIndex + 1) % LABELS.length);
    layout();
  });

  var t0 = null;
  function tick(ts) {
    if (t0 === null) t0 = ts;
    if (root.classList.contains('is-demo')) {
      var now = ts - t0;
      var phase = (now % CYCLE_MS) / CYCLE_MS;
      var wave = 0.5 - 0.5 * Math.cos(phase * Math.PI * 2);
      card.style.width = (NARROW_PX + (WIDE_PX - NARROW_PX) * wave).toFixed(1) + 'px';
      var i = Math.floor(now / CYCLE_MS * 3) % LABELS.length;
      if (i !== labelIndex) setLabel(i);
      layout();
    }
    requestAnimationFrame(tick);
  }

  left.style.height = LINE_H_PX + 'px';
  right.style.height = LINE_H_PX + 'px';
  layout();
  if (reduce) {
    stopDemo();
  } else {
    requestAnimationFrame(tick);
  }
})();

// LabelDivider — vanilla 판(02-divl-centered-label-flex-lines) 의 React 포트.
// 가운데 글자 폭을 재서 양쪽 선 폭을 (줄 폭 - 글자 폭 - LABEL_GAP * 2) / 2 로 직접 계산한다.
import { useEffect, useRef } from "react";
import styles from "./LabelDivider.module.scss";

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

const LABEL_GAP = 12;
const LINE_H_PX = 6;
const CYCLE_MS = 2000;
const NARROW_PX = 180;
const WIDE_PX = 420;
const LABELS: string[] = ["또는", "다른 방법으로 계속", "여기까지 읽은 내용"];

export default function LabelDivider() {
  const cardRef = useRef<HTMLDivElement | null>(null) as Box<HTMLDivElement | null>;
  const rowRef = useRef<HTMLDivElement | null>(null) as Box<HTMLDivElement | null>;
  const leftRef = useRef<HTMLSpanElement | null>(null) as Box<HTMLSpanElement | null>;
  const rightRef = useRef<HTMLSpanElement | null>(null) as Box<HTMLSpanElement | null>;
  const labelRef = useRef<HTMLSpanElement | null>(null) as Box<HTMLSpanElement | null>;
  const btnRef = useRef<HTMLButtonElement | null>(null) as Box<HTMLButtonElement | null>;
  const pxRef = useRef<HTMLElement | null>(null) as Box<HTMLElement | null>;

  useEffect(() => {
    const card = cardRef.current;
    const row = rowRef.current;
    const left = leftRef.current;
    const right = rightRef.current;
    const label = labelRef.current;
    const btn = btnRef.current;
    const pxEl = pxRef.current;
    if (!card || !row || !left || !right || !label || !btn || !pxEl) return;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let demo = !reduce;
    let labelIndex = 0;
    let t0: number | null = null;
    let raf = 0;

    const layout = (): void => {
      const rowW = row.getBoundingClientRect().width;
      const labelW = label.getBoundingClientRect().width;
      const side = Math.max(0, (rowW - labelW - LABEL_GAP * 2) / 2);
      left.style.width = side.toFixed(1) + "px";
      right.style.width = side.toFixed(1) + "px";
      pxEl.textContent = String(Math.round(side));
    };
    const setLabel = (i: number): void => {
      labelIndex = i;
      label.textContent = LABELS[i];
    };
    const onClick = (): void => {
      demo = false;
      setLabel((labelIndex + 1) % LABELS.length);
      layout();
    };
    btn.addEventListener("click", onClick);

    const tick = (ts: number): void => {
      if (t0 === null) t0 = ts;
      if (demo) {
        const now = ts - t0;
        const phase = (now % CYCLE_MS) / CYCLE_MS;
        const wave = 0.5 - 0.5 * Math.cos(phase * Math.PI * 2);
        card.style.width = (NARROW_PX + (WIDE_PX - NARROW_PX) * wave).toFixed(1) + "px";
        const i = Math.floor((now / CYCLE_MS) * 3) % LABELS.length;
        if (i !== labelIndex) setLabel(i);
        layout();
      }
      raf = requestAnimationFrame(tick);
    };

    left.style.height = LINE_H_PX + "px";
    right.style.height = LINE_H_PX + "px";
    layout();
    if (!reduce) raf = requestAnimationFrame(tick);
    return () => {
      cancelAnimationFrame(raf);
      btn.removeEventListener("click", onClick);
    };
  }, []);

  return (
    <div className={styles.dv}>
      <div className={styles.card} ref={cardRef}>
        <div className={styles.row} ref={rowRef} role="separator">
          <span className={styles.side} ref={leftRef} />
          <span className={styles.label} ref={labelRef}>또는</span>
          <span className={styles.sideRight} ref={rightRef} />
        </div>
      </div>
      <div className={styles.bar}>
      <button className={styles.btn} ref={btnRef} type="button">글자 바꾸기</button>
      <p className={styles.meta}>
        <span className={styles.tag}>LINE</span> <b ref={pxRef}>0</b>
        <span>px</span>
      </p>
      </div>
    </div>
  );
}