05Progress bar attached to header

<main class="stage">
  <header class="head">
    <span class="head__logo">GODRICH</span>
    <span class="head__bar is-demo" aria-hidden="true"></span>
  </header>
  <div class="page">
    <p class="page__line"></p>
    <p class="page__line"></p>
    <p class="page__line short"></p>
  </div>
</main>

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

// ── 변수 3개 ──────────────────────────────────────────
$thickness: 3px;                                   // 바 두께. 굵게 6px
$color: $subject-blue;                              // 바 색
$track: rgba(255, 255, 255, .14);                    // 안 읽은 구간

// ── 데모 무대 ──────────────────────────────────────────
html, body { margin: 0; overflow: hidden; }
.stage {
  min-height: 100vh;
  margin: 0;
  background: $stage-ink;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

.head {
  position: sticky;
  top: 0;
  height: 56px;
  display: flex;
  align-items: center;
  padding: 0 clamp(16px, 5vw, 24px);
  background: $stage-ink;
  border-bottom: 1px solid $track;

  &__logo { color: $subject-cream; font-weight: 800; font-size: 18px; line-height: 1; font-family: inherit; letter-spacing: .04em; }

  // 진행 바는 헤더의 자식 요소라 헤더와 한 덩어리로 스크롤을 따라간다
  &__bar {
    position: absolute;
    left: 0; bottom: -$thickness;
    width: 100%;
    height: $thickness;
    background: $color;
    transform: scaleX(0);
    transform-origin: left; // 규칙8: 스크롤 진행띠 좌측 채움

    // 실제 사용: 문서 전체 스크롤 진행률이 곧 바 길이다
    @supports (animation-timeline: scroll()) {
      animation: fill-bar linear both;
      animation-timeline: scroll(root);
    }
  }
}

@keyframes fill-bar {
  from { transform: scaleX(0); }
  to   { transform: scaleX(1); }
}

// ── 데모(.is-demo): 2초 루프로 흉내 ────────────────────
.head__bar.is-demo {
  animation: fill-loop $dur-loop linear infinite;
}
@keyframes fill-loop {
  0%   { transform: scaleX(0); }
  90%  { transform: scaleX(1); }
  100% { transform: scaleX(1); }
}

// ── 배경: 문서처럼 보이는 자리 ─────────────────────────
.page { padding: 28px 24px 0; }
.page__line {
  height: 12px;
  margin: 0 0 14px;
  border-radius: 4px;
  background: rgba(255, 255, 255, .12);
  &.short { width: 60%; }
}

@media (prefers-reduced-motion: reduce) {
  .head__bar, .head__bar.is-demo { animation: none !important; transform: scaleX(1); }
}

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

.stage {
  min-height: 100vh;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
}

.head {
  position: sticky;
  top: 0;
  height: 56px;
  display: flex;
  align-items: center;
  padding: 0 clamp(16px, 5vw, 24px);
  background: #17141a;
  border-bottom: 1px solid rgba(255, 255, 255, 0.14);
}
.head__logo {
  color: #fff7e6;
  font-weight: 800;
  font-size: 18px;
  line-height: 1;
  font-family: inherit;
  letter-spacing: 0.04em;
}
.head__bar {
  position: absolute;
  left: 0;
  bottom: -3px;
  width: 100%;
  height: 3px;
  background: #2f6df6;
  transform: scaleX(0);
  transform-origin: left;
}
@supports (animation-timeline: scroll()) {
  .head__bar {
    animation: fill-bar linear both;
    animation-timeline: scroll(root);
  }
}

@keyframes fill-bar {
  from {
    transform: scaleX(0);
  }
  to {
    transform: scaleX(1);
  }
}
.head__bar.is-demo {
  animation: fill-loop 2s linear infinite;
}

@keyframes fill-loop {
  0% {
    transform: scaleX(0);
  }
  90% {
    transform: scaleX(1);
  }
  100% {
    transform: scaleX(1);
  }
}
.page {
  padding: 28px 24px 0;
}

.page__line {
  height: 12px;
  margin: 0 0 14px;
  border-radius: 4px;
  background: rgba(255, 255, 255, 0.12);
}
.page__line.short {
  width: 60%;
}

@media (prefers-reduced-motion: reduce) {
  .head__bar, .head__bar.is-demo {
    animation: none !important;
    transform: scaleX(1);
  }
}

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

export type HeaderProgressBarProps = {
  logo: string;
  /** 바 두께 (기본 3px) */
  thickness?: number;
  color?: string;
  track?: string;
};

type Vars = CSSProperties & { "--thickness"?: string; "--color"?: string; "--track"?: string };

export default function HeaderProgressBar({
  logo,
  thickness = 3,
  color = "#2f6df6",
  track = "rgba(255,255,255,.14)",
}: HeaderProgressBarProps) {
  const vars: Vars = { "--thickness": `${thickness}px`, "--color": color, "--track": track };

  return (
    <header className={styles.head} style={vars}>
      <span className={styles.logo}>{logo}</span>
      {/* scroll() 타임라인만으로 채워진다 — JS 없이 */}
      <span className={styles.bar} aria-hidden="true" />
    </header>
  );
}