02Bubble morph — three dots merging into one bubble's size

<main class="stage">
<section class="panel">
  <div class="row">
    <span class="avatar" aria-hidden="true"></span>
    <div class="bubble" id="bubble" role="status" aria-live="polite">
      <span class="dots" id="dots">
        <span class="dot"></span><span class="dot"></span><span class="dot"></span>
      </span>
      <span class="msg" id="msg">Message received</span>
    </div>
  </div>
</section>
</main>

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

@include stage($stage-yellow);

.panel { display: flex; flex-direction: column; align-items: center; gap: $sp-4; }
.row { display: flex; align-items: center; gap: $sp-3; }

.avatar { width: 32px; height: 32px; border-radius: $r-pill; background: $subject-ink; flex: none; }

// --w 는 점 3개의 합산 폭에서 메시지 폭까지 JS 가 매 프레임 재계산해 넣는 값(px, 단위 없이 저장)
.bubble {
  position: relative;
  height: 44px;
  width: calc(var(--w, 56) * 1px);
  border-radius: $r-card;
  background: $subject-ink;
  overflow: hidden;
}

.dots, .msg {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: $sp-2;
}

.dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: $subject-cream;
}

.msg {
  color: $subject-cream;
  font-size: 13px;
  white-space: nowrap;
  padding: 0 $sp-3;
  opacity: 0;
}

@media (max-width: 340px) {
  .bubble { height: 38px; }
  .avatar { width: 26px; height: 26px; }
  .msg { font-size: 12px; }
}

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

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  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: 16px;
}

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

.avatar {
  width: 32px;
  height: 32px;
  border-radius: 999px;
  background: #17141a;
  flex: none;
}

.bubble {
  position: relative;
  height: 44px;
  width: calc(var(--w, 56) * 1px);
  border-radius: 16px;
  background: #17141a;
  overflow: hidden;
}

.dots, .msg {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
}

.dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #fff7e6;
}

.msg {
  color: #fff7e6;
  font-size: 13px;
  white-space: nowrap;
  padding: 0 12px;
  opacity: 0;
}

@media (max-width: 340px) {
  .bubble {
    height: 38px;
  }
  .avatar {
    width: 26px;
    height: 26px;
  }
  .msg {
    font-size: 12px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .dots, .msg {
    transition: none;
  }
}

// 말풍선 모핑 — 점 세 개의 합산 너비 값을 말풍선 하나의 너비 값으로 보간한다.
// 계산 겹: 경과 비율 → 너비 값(px) 재계산 → CSS 커스텀 프로퍼티(--w)에 반영. 자동 재생만, 실사용자 리스너 없음.
(function () {
  var bubble = document.getElementById('bubble');
  var dots = document.getElementById('dots');
  var msg = document.getElementById('msg');
  if (!bubble || !dots || !msg) return;

  var DOT_W = 56;
  var MSG_W = 168;
  var CYCLE_MS = 2000;
  var MORPH_START = 0.10 * CYCLE_MS;
  var MORPH_MS = 640;
  var REVERT_AT = 0.62 * CYCLE_MS;

  function easeOut(p) { return 1 - Math.pow(1 - p, 3); }

  function apply(t) {
    var inMorph = t >= MORPH_START && t < REVERT_AT;
    var p = Math.min(Math.max((t - MORPH_START) / MORPH_MS, 0), 1);
    var eased = easeOut(p);
    var w = inMorph ? DOT_W + (MSG_W - DOT_W) * eased : DOT_W;
    bubble.style.setProperty('--w', w.toFixed(1));
    var done = inMorph && p >= 1;
    dots.style.opacity = done ? '0' : '1';
    msg.style.opacity = done ? '1' : '0';
  }

  apply(0);
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (reduce) { bubble.style.setProperty('--w', DOT_W); 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 "./TypingBubbleMorphIn.module.scss";

// 말풍선 모핑 — 점 세 개의 합산 너비 값을 말풍선 하나의 너비 값으로 보간한다.
// 계산 겹: 경과 비율 → 너비 값(px) 재계산 → CSS 커스텀 프로퍼티(--w)에 반영. 자동 재생만, 실사용자 리스너 없음.
const DOT_W = 56;
const MSG_W = 168;
const CYCLE_MS = 2000;
const MORPH_START = 0.10 * CYCLE_MS;
const MORPH_MS = 640;
const REVERT_AT = 0.62 * CYCLE_MS;

function easeOut(p: number) {
  return 1 - Math.pow(1 - p, 3);
}

export default function TypingBubbleMorphIn() {
  const bubbleRef = useRef<HTMLDivElement>(null);
  const dotsRef = useRef<HTMLSpanElement>(null);
  const msgRef = useRef<HTMLSpanElement>(null);

  useEffect(() => {
    const bubble = bubbleRef.current;
    const dots = dotsRef.current;
    const msg = msgRef.current;
    if (!bubble || !dots || !msg) return;

    function apply(t: number) {
      const inMorph = t >= MORPH_START && t < REVERT_AT;
      const p = Math.min(Math.max((t - MORPH_START) / MORPH_MS, 0), 1);
      const eased = easeOut(p);
      const w = inMorph ? DOT_W + (MSG_W - DOT_W) * eased : DOT_W;
      bubble!.style.setProperty("--w", w.toFixed(1));
      const done = inMorph && p >= 1;
      dots!.style.opacity = done ? "0" : "1";
      msg!.style.opacity = done ? "1" : "0";
    }

    apply(0);
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (reduce) {
      bubble.style.setProperty("--w", String(DOT_W));
      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}>
          <span className={styles.avatar} aria-hidden="true" />
          <div ref={bubbleRef} className={styles.bubble} role="status" aria-live="polite">
            <span ref={dotsRef} className={styles.dots}>
              <span className={styles.dot} />
              <span className={styles.dot} />
              <span className={styles.dot} />
            </span>
            <span ref={msgRef} className={styles.msg}>메시지 도착</span>
          </div>
        </div>
      </section>
    </div>
  );
}