05スクロール端のフェード

<main class="stage">
  <div class="sf-viewport">
    <div class="sf-track is-demo">
      <div class="sf-msg">Here's the summary you asked for.</div>
      <div class="sf-msg">Let me check the docs first.</div>
      <div class="sf-msg">Found three matching results.</div>
      <div class="sf-msg">Comparing the two approaches now.</div>
      <div class="sf-msg">Here's the summary you asked for.</div>
      <div class="sf-msg">Let me check the docs first.</div>
      <div class="sf-msg">Found three matching results.</div>
      <div class="sf-msg">Comparing the two approaches now.</div>
    </div>
  </div>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$duration: 6s;
$easing: linear;
$color: $subject-ink;

@include stage($stage-ink);

.sf-viewport {
  width: min(300px, 88vw);
  height: 170px;
  overflow: hidden;
  box-sizing: border-box;
  border-radius: $r-card;
  background: $stage-paper;
  box-shadow: $shadow-raised;
  // 가장자리 페이드 — 이 마스크는 고정. 움직이는 건 안의 트랙뿐
  -webkit-mask-image: linear-gradient(to bottom, transparent 0, #000 $sp-8, #000 calc(100% - #{$sp-8}), transparent 100%);
  mask-image: linear-gradient(to bottom, transparent 0, #000 $sp-8, #000 calc(100% - #{$sp-8}), transparent 100%);
  padding: $sp-4 0;
}

.sf-track {
  display: flex;
  flex-direction: column;
}

.sf-msg {
  padding: $sp-2 $sp-4;
  margin: 0 $sp-4 $sp-2;
  border-radius: $r-sm;
  background: rgba(23, 20, 26, .06);
  color: $color;
  font: 500 12px/1.4 -apple-system, "Segoe UI", sans-serif;
}

// 실사용: 새 메시지가 올 때마다 scrollTop 을 내린다. 데모는 같은 목록 두 벌을 이어 -50% 루프로 흉내낸다
@keyframes sf-scroll {
  from { transform: translateY(0); }
  to   { transform: translateY(-50%); }
}
.sf-track.is-demo {
  animation: sf-scroll $duration $easing infinite;
}

@media (prefers-reduced-motion: reduce) {
  .sf-track.is-demo {
    animation: none !important;
    transform: none !important;
  }
}

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);
}

.sf-viewport {
  width: min(300px, 88vw);
  height: 170px;
  overflow: hidden;
  box-sizing: border-box;
  border-radius: 16px;
  background: #ffffff;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  -webkit-mask-image: linear-gradient(to bottom, transparent 0, #000 32px, #000 calc(100% - 32px), transparent 100%);
  mask-image: linear-gradient(to bottom, transparent 0, #000 32px, #000 calc(100% - 32px), transparent 100%);
  padding: 16px 0;
}

.sf-track {
  display: flex;
  flex-direction: column;
}

.sf-msg {
  padding: 8px 16px;
  margin: 0 16px 8px;
  border-radius: 8px;
  background: rgba(23, 20, 26, 0.06);
  color: #17141a;
  font: 500 12px/1.4 -apple-system, "Segoe UI", sans-serif;
}

@keyframes sf-scroll {
  from {
    transform: translateY(0);
  }
  to {
    transform: translateY(-50%);
  }
}
.sf-track.is-demo {
  animation: sf-scroll 6s linear infinite;
}

@media (prefers-reduced-motion: reduce) {
  .sf-track.is-demo {
    animation: none !important;
    transform: none !important;
  }
}

import { CSSProperties } from "react";
import styles from "./ScrollFadeEdges.module.scss";

type Vars = CSSProperties & {
  "--duration"?: string;
  "--easing"?: string;
  "--color"?: string;
};

export interface ScrollFadeEdgesProps {
  duration?: string;
  easing?: string;
  color?: string;
  messages?: string[];
}

const DEFAULT_MESSAGES = [
  "Here's the summary you asked for.",
  "Let me check the docs first.",
  "Found three matching results.",
  "Comparing the two approaches now.",
];

export default function ScrollFadeEdges({
  duration = "6s",
  easing = "linear",
  color = "#17141a",
  messages = DEFAULT_MESSAGES,
}: ScrollFadeEdgesProps) {
  const style: Vars = {
    "--duration": duration,
    "--easing": easing,
    "--color": color,
  };
  const doubled = [...messages, ...messages];
  return (
    <div className={styles.viewport} style={style}>
      <div className={styles.track}>
        {doubled.map((m, i) => (
          <div className={styles.msg} key={i}>{m}</div>
        ))}
      </div>
    </div>
  );
}