06Range Slider That Picks a Span Over a Histogram Background

<main class="stage">
<div class="ds is-demo" id="ds">
  <div class="ds__hist" id="hist" aria-hidden="true"></div>
  <div class="ds__track" id="track">
    <div class="ds__fill" id="fill"></div>
    <button type="button" class="ds__thumb ds__thumb--lo" id="thumbLo" role="slider"
      aria-label="Minimum value" aria-valuemin="0" aria-valuemax="100" aria-valuenow="30" aria-valuetext="30" tabindex="0"></button>
    <button type="button" class="ds__thumb ds__thumb--hi" id="thumbHi" role="slider"
      aria-label="Maximum value" aria-valuemin="0" aria-valuemax="100" aria-valuenow="72" aria-valuetext="72" tabindex="0"></button>
  </div>
  <p class="ds__readout"><span id="loOut">30</span> – <span id="hiOut">72</span></p>
  <p class="ds__caption">Highlights only the chosen span over the bar distribution</p>
</div>
</main>

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

// 변수 3개
$duration: $dur-loop;
$easing: $ease-out;
$color: $subject-mint;

// 계산 겹: 고정 배열 막대의 중심 좌표가 선택 구간 안인지 매 프레임 재계산해 강조를 다시 칠한다.
@include stage($stage-yellow);

.ds { width: min(300px, 86vw); color: $subject-ink; text-align: center; }
.ds__hist {
  position: relative; height: 48px; margin-bottom: $sp-2;
}
.ds__bar {
  position: absolute; bottom: 0; background: rgba($subject-ink, .18);
  border-radius: $r-xs $r-xs 0 0;
}
.ds__bar.is-in { background: $color; }
.ds__track {
  position: relative; height: 6px; border-radius: $r-pill;
  background: rgba($subject-ink, .14); margin: 0 0 $sp-4;
}
.ds__fill {
  position: absolute; top: 0; bottom: 0; left: 30%; width: 42%;
  background: $color; border-radius: $r-pill;
}
.ds__thumb {
  position: absolute; top: 50%; left: 30%; width: 18px; height: 18px;
  appearance: none; border: 0; border-radius: 50%; background: $subject-ink;
  box-shadow: $shadow-press; cursor: grab; touch-action: none; padding: 0;
  transform: translate(-50%, -50%); z-index: 2;
}
.ds__thumb--hi { left: 72%; }
.ds__thumb:focus-visible { outline: 2px solid $subject-blue-deep; outline-offset: 2px; }
.ds__thumb:active { cursor: grabbing; }
.ds__readout { margin: 0; font-weight: 700; font-size: 18px; line-height: 1.2; font-variant-numeric: tabular-nums; }
.ds__caption { margin: $sp-1 0 0; font-weight: 600; font-size: 11px; color: rgba($subject-ink, .68); }

.ds.is-demo .ds__thumb,
.ds.is-demo .ds__fill {
  transition: left $duration $easing, width $duration $easing;
}
.ds__bar { transition: background $dur-quick $ease-out; }

@media (max-width: 340px) {
  .ds { width: min(250px, 82vw); }
  .ds__hist { height: 38px; }
  .ds__readout { font-size: 16px; }
}

@media (prefers-reduced-motion: reduce) {
  .ds.is-demo .ds__thumb, .ds.is-demo .ds__fill { transition: none; }
  .ds__bar { 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);
}

.ds {
  width: min(300px, 86vw);
  color: #17141a;
  text-align: center;
}

.ds__hist {
  position: relative;
  height: 48px;
  margin-bottom: 8px;
}

.ds__bar {
  position: absolute;
  bottom: 0;
  background: rgba(23, 20, 26, 0.18);
  border-radius: 4px 4px 0 0;
}

.ds__bar.is-in {
  background: #4cd4a6;
}

.ds__track {
  position: relative;
  height: 6px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.14);
  margin: 0 0 16px;
}

.ds__fill {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 30%;
  width: 42%;
  background: #4cd4a6;
  border-radius: 999px;
}

.ds__thumb {
  position: absolute;
  top: 50%;
  left: 30%;
  width: 18px;
  height: 18px;
  appearance: none;
  border: 0;
  border-radius: 50%;
  background: #17141a;
  box-shadow: 0 6px 12px rgba(23, 20, 26, 0.32);
  cursor: grab;
  touch-action: none;
  padding: 0;
  transform: translate(-50%, -50%);
  z-index: 2;
}

.ds__thumb--hi {
  left: 72%;
}

.ds__thumb:focus-visible {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
}

.ds__thumb:active {
  cursor: grabbing;
}

.ds__readout {
  margin: 0;
  font-weight: 700;
  font-size: 18px;
  line-height: 1.2;
  font-variant-numeric: tabular-nums;
}

.ds__caption {
  margin: 4px 0 0;
  font-weight: 600;
  font-size: 11px;
  color: rgba(23, 20, 26, 0.68);
}

.ds.is-demo .ds__thumb,
.ds.is-demo .ds__fill {
  transition: left 2s ease-out, width 2s ease-out;
}

.ds__bar {
  transition: background 220ms ease-out;
}

@media (max-width: 340px) {
  .ds {
    width: min(250px, 82vw);
  }
  .ds__hist {
    height: 38px;
  }
  .ds__readout {
    font-size: 16px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .ds.is-demo .ds__thumb, .ds.is-demo .ds__fill {
    transition: none;
  }
  .ds__bar {
    transition: none;
  }
}

(function () {
  var MIN = 0, MAX = 100;
  // 결정론적 분포 — Math.random 없이 고정 배열로 막대 높이를 정한다 (%, 0~100)
  var HEIGHTS = [22, 40, 65, 38, 52, 70, 45, 60, 33, 48, 80, 55, 42, 66, 30, 58, 44, 72, 50, 36, 62, 48, 54, 40];
  var root = document.getElementById('ds');
  var hist = document.getElementById('hist');
  var track = document.getElementById('track');
  var fill = document.getElementById('fill');
  var lo = document.getElementById('thumbLo');
  var hi = document.getElementById('thumbHi');
  var loOut = document.getElementById('loOut');
  var hiOut = document.getElementById('hiOut');
  var v = { lo: 30, hi: 72 };
  var bars = [];

  HEIGHTS.forEach(function (h, i) {
    var bar = document.createElement('div');
    bar.className = 'ds__bar';
    bar.style.left = (i / HEIGHTS.length * 100) + '%';
    bar.style.width = (100 / HEIGHTS.length * 0.7) + '%';
    bar.style.height = h + '%';
    hist.appendChild(bar);
    bars.push({ el: bar, center: (i + 0.5) / HEIGHTS.length * 100 });
  });

  // 계산 겹: 막대의 실제 중심 위치(%)가 [lo, hi] 구간 안에 들어오는지로 강조 여부를 결정한다.
  function paintBars() {
    bars.forEach(function (b) {
      b.el.classList.toggle('is-in', b.center >= v.lo && b.center <= v.hi);
    });
  }
  function paint() {
    lo.style.left = v.lo + '%'; hi.style.left = v.hi + '%';
    fill.style.left = v.lo + '%'; fill.style.width = (v.hi - v.lo) + '%';
    lo.setAttribute('aria-valuenow', String(v.lo)); hi.setAttribute('aria-valuenow', String(v.hi));
    lo.setAttribute('aria-valuetext', String(v.lo)); hi.setAttribute('aria-valuetext', String(v.hi));
    loOut.textContent = String(v.lo); hiOut.textContent = String(v.hi);
    paintBars();
  }
  function setLo(n) { v.lo = Math.max(MIN, Math.min(n, v.hi)); paint(); }
  function setHi(n) { v.hi = Math.min(MAX, Math.max(n, v.lo)); paint(); }
  function pctFromX(x) {
    var r = track.getBoundingClientRect();
    return Math.round(Math.max(0, Math.min(100, ((x - r.left) / r.width) * 100)));
  }
  function human() { root.classList.remove('is-demo'); clearInterval(timer); }
  function drag(thumb, setter, isLo) {
    thumb.addEventListener('pointerdown', function (e) {
      human(); thumb.setPointerCapture(e.pointerId);
      function move(ev) { setter(pctFromX(ev.clientX)); }
      function up() { thumb.removeEventListener('pointermove', move); thumb.removeEventListener('pointerup', up); }
      thumb.addEventListener('pointermove', move); thumb.addEventListener('pointerup', up);
    });
    thumb.addEventListener('keydown', function (e) {
      var step = { ArrowRight: 1, ArrowLeft: -1, ArrowUp: 1, ArrowDown: -1 }[e.key];
      if (step !== undefined) { e.preventDefault(); human(); setter((isLo ? v.lo : v.hi) + step); }
      else if (e.key === 'Home') { e.preventDefault(); human(); setter(isLo ? MIN : v.lo); }
      else if (e.key === 'End') { e.preventDefault(); human(); setter(isLo ? v.hi : MAX); }
    });
  }
  drag(lo, setLo, true); drag(hi, setHi, false);

  var presets = [[10, 35], [55, 90], [0, 100], [42, 48], [20, 65]];
  var pi = 0;
  function tick() {
    var p = presets[pi % presets.length]; pi++;
    v.lo = p[0]; v.hi = p[1]; paint();
  }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var timer = reduce ? null : setInterval(tick, 480);
  paint();
}());

import { useEffect, useRef } from 'react';
import styles from './DualSliderHistogramTrackBg.module.scss';

const MIN = 0;
const MAX = 100;
const TICK_MS = 480;
// 결정론적 분포 — Math.random 없이 고정 배열로 막대 높이를 정한다 (%, 0~100)
const HEIGHTS = [22, 40, 65, 38, 52, 70, 45, 60, 33, 48, 80, 55, 42, 66, 30, 58, 44, 72, 50, 36, 62, 48, 54, 40];
const PRESETS: [number, number][] = [[10, 35], [55, 90], [0, 100], [42, 48], [20, 65]];

export default function DualSliderHistogramTrackBg() {
  const rootRef = useRef<HTMLDivElement>(null);
  const trackRef = useRef<HTMLDivElement>(null);
  const fillRef = useRef<HTMLDivElement>(null);
  const loRef = useRef<HTMLButtonElement>(null);
  const hiRef = useRef<HTMLButtonElement>(null);
  const loOutRef = useRef<HTMLSpanElement>(null);
  const hiOutRef = useRef<HTMLSpanElement>(null);
  const barRefs = useRef<HTMLDivElement[]>([]);

  useEffect(() => {
    const root = rootRef.current;
    const track = trackRef.current;
    const fill = fillRef.current;
    const lo = loRef.current;
    const hi = hiRef.current;
    const loOut = loOutRef.current;
    const hiOut = hiOutRef.current;
    if (!root || !track || !fill || !lo || !hi || !loOut || !hiOut || !barRefs.current) return undefined;
    const bars = barRefs.current;
    if (bars.length !== HEIGHTS.length) return undefined;

    const v = { lo: 30, hi: 72 };
    const centers = HEIGHTS.map((_, i) => (i + 0.5) / HEIGHTS.length * 100);

    // 계산 겹: 막대의 실제 중심 위치(%)가 [lo, hi] 구간 안에 들어오는지로 강조 여부를 결정한다.
    function paintBars() {
      bars.forEach((el, i) => {
        el.classList.toggle(styles['is-in'], centers[i] >= v.lo && centers[i] <= v.hi);
      });
    }
    function paint() {
      lo!.style.left = v.lo + '%'; hi!.style.left = v.hi + '%';
      fill!.style.left = v.lo + '%'; fill!.style.width = (v.hi - v.lo) + '%';
      lo!.setAttribute('aria-valuenow', String(v.lo)); hi!.setAttribute('aria-valuenow', String(v.hi));
      lo!.setAttribute('aria-valuetext', String(v.lo)); hi!.setAttribute('aria-valuetext', String(v.hi));
      loOut!.textContent = String(v.lo); hiOut!.textContent = String(v.hi);
      paintBars();
    }
    function setLo(n: number) { v.lo = Math.max(MIN, Math.min(n, v.hi)); paint(); }
    function setHi(n: number) { v.hi = Math.min(MAX, Math.max(n, v.lo)); paint(); }
    function pctFromX(x: number) {
      const r = track!.getBoundingClientRect();
      return Math.round(Math.max(0, Math.min(100, ((x - r.left) / r.width) * 100)));
    }
    let timer = 0;
    function human() { root!.classList.remove(styles['is-demo']); window.clearInterval(timer); }

    function bindDrag(thumb: HTMLButtonElement, setter: (n: number) => void, isLo: boolean) {
      function onDown(e: PointerEvent) {
        human(); thumb.setPointerCapture(e.pointerId);
        function move(ev: PointerEvent) { setter(pctFromX(ev.clientX)); }
        function up() { thumb.removeEventListener('pointermove', move); thumb.removeEventListener('pointerup', up); }
        thumb.addEventListener('pointermove', move); thumb.addEventListener('pointerup', up);
      }
      function onKey(e: KeyboardEvent) {
        const step = ({ ArrowRight: 1, ArrowLeft: -1, ArrowUp: 1, ArrowDown: -1 } as Record<string, number>)[e.key];
        if (step !== undefined) { e.preventDefault(); human(); setter((isLo ? v.lo : v.hi) + step); }
        else if (e.key === 'Home') { e.preventDefault(); human(); setter(isLo ? MIN : v.lo); }
        else if (e.key === 'End') { e.preventDefault(); human(); setter(isLo ? v.hi : MAX); }
      }
      thumb.addEventListener('pointerdown', onDown);
      thumb.addEventListener('keydown', onKey);
      return () => { thumb.removeEventListener('pointerdown', onDown); thumb.removeEventListener('keydown', onKey); };
    }
    const offLo = bindDrag(lo, setLo, true);
    const offHi = bindDrag(hi, setHi, false);

    let pi = 0;
    function tick() {
      const p = PRESETS[pi % PRESETS.length]; pi++;
      v.lo = p[0]; v.hi = p[1]; paint();
    }
    const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
    if (!reduce) timer = window.setInterval(tick, TICK_MS);
    paint();

    return () => { offLo(); offHi(); window.clearInterval(timer); };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.ds + ' ' + styles['is-demo']} ref={rootRef}>
        <div className={styles.dsHist} aria-hidden="true">
          {HEIGHTS.map((h, i) => (
            <div
              key={i}
              className={styles.dsBar}
              ref={(el: HTMLDivElement | null) => { if (el && barRefs.current) barRefs.current[i] = el; }}
              style={{ left: (i / HEIGHTS.length * 100) + '%', width: (100 / HEIGHTS.length * 0.7) + '%', height: h + '%' }}
            />
          ))}
        </div>
        <div className={styles.dsTrack} ref={trackRef}>
          <div className={styles.dsFill} ref={fillRef} />
          <button type="button" className={styles.dsThumb + ' ' + styles.dsThumbLo} ref={loRef} role="slider"
            aria-label="최소값" aria-valuemin={0} aria-valuemax={100} aria-valuenow={30} aria-valuetext="30" tabIndex={0} />
          <button type="button" className={styles.dsThumb + ' ' + styles.dsThumbHi} ref={hiRef} role="slider"
            aria-label="최대값" aria-valuemin={0} aria-valuemax={100} aria-valuenow={72} aria-valuetext="72" tabIndex={0} />
        </div>
        <p className={styles.dsReadout}><span ref={loOutRef}>30</span> – <span ref={hiOutRef}>72</span></p>
        <p className={styles.dsCaption}>막대 분포 위에서 구간만 밝힌다</p>
      </div>
    </main>
  );
}