03Multi-user overlap — a row computing name-tag width from concurrent typers

<main class="stage">
<section class="panel">
  <div class="row" role="status" aria-live="polite" aria-label="Multiple people typing">
    <div class="avatars">
      <span class="avatar avatar--1" aria-hidden="true"></span>
      <span class="avatar avatar--2" aria-hidden="true"></span>
      <span class="avatar avatar--3" aria-hidden="true"></span>
    </div>
    <span class="badge" id="badge">+2</span>
  </div>
  <span class="measure" id="measure" aria-hidden="true">+2</span>
</section>
</main>

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

@include stage($stage-orange);

.panel { display: flex; flex-direction: column; align-items: center; gap: $sp-3; }
.row { display: flex; align-items: center; gap: $sp-2; }

.avatars { display: flex; }
.avatar {
  width: 28px;
  height: 28px;
  border-radius: $r-pill;
  background: $subject-cream;
  border: 2px solid $stage-orange;
  margin-left: -$sp-2;
}
.avatar--1 { margin-left: 0; }

// --bw 는 배지 텍스트("+N")의 실측 너비(px, 단위 없이 저장)에서 다음 단계 너비로 보간되는 값
.badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 22px;
  width: calc((var(--bw, 20) * 1px) + #{$sp-3 * 2});
  border-radius: $r-pill;
  background: $subject-cream;
  color: $subject-ink;
  font-size: 12px;
  font-weight: 600;
}

.measure {
  position: absolute;
  visibility: hidden;
  pointer-events: none;
  white-space: nowrap;
  font-size: 12px;
  font-weight: 600;
}

@media (max-width: 340px) {
  .avatar { width: 22px; height: 22px; }
  .badge { height: 18px; font-size: 11px; }
}

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

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.panel {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}

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

.avatars {
  display: flex;
}

.avatar {
  width: 28px;
  height: 28px;
  border-radius: 999px;
  background: #fff7e6;
  border: 2px solid #ff4d1f;
  margin-left: -8px;
}

.avatar--1 {
  margin-left: 0;
}

.badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 22px;
  width: calc(var(--bw, 20) * 1px + 24px);
  border-radius: 999px;
  background: #fff7e6;
  color: #17141a;
  font-size: 12px;
  font-weight: 600;
}

.measure {
  position: absolute;
  visibility: hidden;
  pointer-events: none;
  white-space: nowrap;
  font-size: 12px;
  font-weight: 600;
}

@media (max-width: 340px) {
  .avatar {
    width: 22px;
    height: 22px;
  }
  .badge {
    height: 18px;
    font-size: 11px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .badge {
    transition: none;
  }
}

// 다중 사용자 겹침 — 동시 입력자 수가 바뀔 때마다 라벨 텍스트의 실제 렌더 너비를 재고 그 값으로 배지 너비를 다시 그린다.
// 계산 겹: 인원 수 → 라벨 텍스트 → getBoundingClientRect 실측 폭 → 배지 너비 보간. 자동 재생만, 실사용자 리스너 없음.
(function () {
  var badge = document.getElementById('badge');
  var measure = document.getElementById('measure');
  if (!badge || !measure) return;

  var COUNTS = [2, 3, 4];
  var HOLD_MS = 620;
  var MORPH_MS = 300;

  function widthFor(n) {
    measure.textContent = '+' + n;
    return measure.getBoundingClientRect().width;
  }

  var widths = COUNTS.map(widthFor);
  var CYCLE_MS = HOLD_MS * COUNTS.length;

  function apply(t) {
    var phase = Math.floor(t / HOLD_MS) % COUNTS.length;
    var next = (phase + 1) % COUNTS.length;
    var phaseT = t % HOLD_MS;
    var p = Math.min(phaseT / MORPH_MS, 1);
    var w = widths[phase] + (widths[next] - widths[phase]) * p;
    badge.style.setProperty('--bw', w.toFixed(1));
    badge.textContent = '+' + COUNTS[phase];
  }

  apply(0);
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (reduce) { badge.style.setProperty('--bw', widths[0]); badge.textContent = '+' + COUNTS[0]; return; }
  var start = null;
  function loop(ts) {
    if (start === null) start = ts;
    var t = (ts - start) % CYCLE_MS;
    apply(t);
    requestAnimationFrame(loop);
  }
  requestAnimationFrame(loop);
})();

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

// 다중 사용자 겹침 — 동시 입력자 수가 바뀔 때마다 라벨 텍스트의 실제 렌더 너비를 재고 그 값으로 배지 너비를 다시 그린다.
// 계산 겹: 인원 수 → 라벨 텍스트 → getBoundingClientRect 실측 폭 → 배지 너비 보간. 자동 재생만, 실사용자 리스너 없음.
const COUNTS = [2, 3, 4];
const HOLD_MS = 620;
const MORPH_MS = 300;

export default function TypingMultiUserStack() {
  const badgeRef = useRef<HTMLSpanElement>(null);
  const measureRef = useRef<HTMLSpanElement>(null);

  useEffect(() => {
    const badge = badgeRef.current;
    const measure = measureRef.current;
    if (!badge || !measure) return;

    function widthFor(n: number) {
      measure!.textContent = "+" + n;
      return measure!.getBoundingClientRect().width;
    }

    const widths = COUNTS.map(widthFor);
    const CYCLE_MS = HOLD_MS * COUNTS.length;

    function apply(t: number) {
      const phase = Math.floor(t / HOLD_MS) % COUNTS.length;
      const next = (phase + 1) % COUNTS.length;
      const phaseT = t % HOLD_MS;
      const p = Math.min(phaseT / MORPH_MS, 1);
      const w = widths[phase] + (widths[next] - widths[phase]) * p;
      badge!.style.setProperty("--bw", w.toFixed(1));
      badge!.textContent = "+" + COUNTS[phase];
    }

    apply(0);
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (reduce) {
      badge.style.setProperty("--bw", String(widths[0]));
      badge.textContent = "+" + COUNTS[0];
      return;
    }
    let start: number | null = null;
    let raf = 0;
    function loop(ts: number) {
      if (start === null) start = ts;
      const t = (ts - start) % CYCLE_MS;
      apply(t);
      raf = requestAnimationFrame(loop);
    }
    raf = requestAnimationFrame(loop);
    return () => cancelAnimationFrame(raf);
  }, []);

  return (
    <div className={styles.stage}>
      <section className={styles.panel}>
        <div className={styles.row} role="status" aria-live="polite" aria-label="동시 입력 중">
          <div className={styles.avatars}>
            <span className={`${styles.avatar} ${styles["avatar--1"]}`} aria-hidden="true" />
            <span className={`${styles.avatar} ${styles["avatar--2"]}`} aria-hidden="true" />
            <span className={`${styles.avatar} ${styles["avatar--3"]}`} aria-hidden="true" />
          </div>
          <span ref={badgeRef} className={styles.badge}>+2</span>
        </div>
        <span ref={measureRef} className={styles.measure} aria-hidden="true">+2</span>
      </section>
    </div>
  );
}