02Exit lúc unmount (allow-discrete)

<main class="stage">
  <div class="ue-wrap is-demo">
    <div class="ue-dialog">
      <span class="ue-dialog__title">Delete file?</span>
      <span class="ue-dialog__btn">Confirm</span>
    </div>
  </div>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: $dur-base;
$easing: $ease-out;
$color: $subject-ink;

@include stage($stage-yellow);

.ue-wrap {
  width: min(320px, 90vw);
  display: grid;
  place-items: center;
}

.ue-dialog {
  width: min(240px, 82vw);
  box-sizing: border-box;
  padding: $sp-5;
  border-radius: $r-card;
  background: $stage-paper;
  box-shadow: $shadow-raised;
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: $sp-4;
  font-family: -apple-system, "Segoe UI", sans-serif;
}

.ue-dialog__title { font-weight: 700; font-size: 15px; line-height: 1.3; font-family: inherit; color: $color; }

.ue-dialog__btn {
  padding: $sp-2 $sp-4;
  border-radius: $r-control;
  background: $stage-orange;
  color: $subject-ink;   // 주황 면 위 크림 글자는 3.11:1 — 잉크로 5.50:1
  font-weight: 600;
  font-size: 12px;
  line-height: 1;
  font-family: inherit;
}

// 실사용 원리: onClick 에서 바로 state 를 지우지 않고 class="is-exiting" 을 먼저 붙인 뒤
// transition-behavior: allow-discrete 로 display:none 전환을 트랜지션이 끝날 때까지 미룬다.
// 실제 언마운트(state 제거)는 onTransitionEnd 안에서 일어난다.
.ue-dialog {
  display: flex;
  opacity: 1;
  transform: scale(1);
  transition: opacity $duration $easing, transform $duration $easing, display $duration allow-discrete;
}
.ue-dialog.is-exiting {
  display: none;
  opacity: 0;
  transform: scale(.92) translateY(6px);
}

// 캡처용 루프: 대화상자가 열려 있다가(60%) 닫힘 트랜지션을 겪고(75%) 다시 열리는 순환
@keyframes ue-exit {
  0%, 45%  { opacity: 1; transform: scale(1); }
  90%, 100% { opacity: 0; transform: scale(.92) translateY(6px); }
}
.ue-wrap.is-demo .ue-dialog { animation: ue-exit $dur-loop $easing infinite; }

@media (prefers-reduced-motion: reduce) {
  .ue-dialog { transition: none; }
  .ue-wrap.is-demo .ue-dialog { animation: none !important; opacity: 1; transform: 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);
}

.ue-wrap {
  width: min(320px, 90vw);
  display: grid;
  place-items: center;
}

.ue-dialog {
  width: min(240px, 82vw);
  box-sizing: border-box;
  padding: 20px;
  border-radius: 16px;
  background: #ffffff;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 16px;
  font-family: -apple-system, "Segoe UI", sans-serif;
}

.ue-dialog__title {
  font-weight: 700;
  font-size: 15px;
  line-height: 1.3;
  font-family: inherit;
  color: #17141a;
}

.ue-dialog__btn {
  padding: 8px 16px;
  border-radius: 12px;
  background: #ff4d1f;
  color: #17141a;
  font-weight: 600;
  font-size: 12px;
  line-height: 1;
  font-family: inherit;
}

.ue-dialog {
  display: flex;
  opacity: 1;
  transform: scale(1);
  transition: opacity 300ms ease-out, transform 300ms ease-out, display 300ms allow-discrete;
}

.ue-dialog.is-exiting {
  display: none;
  opacity: 0;
  transform: scale(0.92) translateY(6px);
}

@keyframes ue-exit {
  0%, 45% {
    opacity: 1;
    transform: scale(1);
  }
  90%, 100% {
    opacity: 0;
    transform: scale(0.92) translateY(6px);
  }
}
.ue-wrap.is-demo .ue-dialog {
  animation: ue-exit 2s ease-out infinite;
}

@media (prefers-reduced-motion: reduce) {
  .ue-dialog {
    transition: none;
  }
  .ue-wrap.is-demo .ue-dialog {
    animation: none !important;
    opacity: 1;
    transform: none;
  }
}

import { CSSProperties, useState } from "react";
import styles from "./UnmountExitDiscrete.module.scss";

export interface UnmountExitDiscreteProps {
  duration?: string;
  easing?: string;
}

export default function UnmountExitDiscrete({
  duration = "300ms",
  easing = "ease-out",
}: UnmountExitDiscreteProps) {
  const [open, setOpen] = useState(true);
  const [exiting, setExiting] = useState(false);

  const close = () => {
    // Don't remove the dialog from state right away — add the exit class first.
    // transition-behavior: allow-discrete (in the CSS module) keeps display: flex
    // alive until the transition actually finishes; onTransitionEnd below does the
    // real unmount once the browser reports the animation is done.
    setExiting(true);
  };

  const style: CSSProperties & { "--duration"?: string; "--easing"?: string } = {
    "--duration": duration,
    "--easing": easing,
  };

  if (!open) return null;

  return (
    <div className={styles.wrap} style={style}>
      <div
        className={`${styles.dialog} ${exiting ? styles.exiting : ""}`}
        onTransitionEnd={() => {
          if (exiting) setOpen(false);
        }}
      >
        <span className={styles.title}>Delete file?</span>
        <button className={styles.btn} onClick={close}>Confirm</button>
      </div>
    </div>
  );
}