02Range Slider That Fills Only Between Its Two Handles

<main class="stage">
<div class="ds is-demo" id="ds">
  <div class="ds__track" id="track">
    <div class="ds__fill" id="fill"><div class="ds__sweep" id="sweep"></div></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="20" aria-valuetext="20" 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="78" aria-valuetext="78" tabindex="0"></button>
  </div>
  <p class="ds__readout"><span id="loOut">20</span> – <span id="hiOut">78</span></p>
  <p class="ds__caption">Fill width <span id="pxOut">0</span>px</p>
</div>
</main>

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

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

// 계산 겹: paint() 가 값 두 개를 채움 %로 바꾸고, 실측 트랙 폭(getBoundingClientRect)으로 px 도 환산한다.
// 224 의 듀얼 섬과 다른 시연 — 여긴 채움 안에 sweep 밴드가 값 비율(phase)로 다시 위치를 계산해 돈다.
@include stage($stage-yellow);

.ds { width: min(280px, 84vw); color: $subject-ink; text-align: center; }
.ds__track {
  position: relative; height: 8px; border-radius: $r-pill;
  background: rgba($subject-ink, .14); margin: $sp-10 0 $sp-4;
}
.ds__fill {
  position: absolute; top: 0; bottom: 0; left: 20%; width: 58%;
  background: $color; border-radius: $r-pill; overflow: hidden;
}
.ds__sweep {
  position: absolute; top: 0; bottom: 0; left: 40%; width: 22%;
  background: linear-gradient(100deg, rgba($subject-cream, 0) 0%, rgba($subject-cream, .85) 50%, rgba($subject-cream, 0) 100%);
  transform: translateX(-50%);
}
.ds__thumb {
  position: absolute; top: 50%; left: 20%; 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: 1;
}
.ds__thumb--hi { left: 78%; }
.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, .72); }

.ds.is-demo .ds__thumb,
.ds.is-demo .ds__fill,
.ds.is-demo .ds__sweep {
  transition: left $duration $easing, width $duration $easing;
}

@media (max-width: 340px) {
  .ds { width: min(240px, 80vw); }
  .ds__readout { font-size: 16px; }
  .ds__caption { font-size: 10px; }
}

@media (prefers-reduced-motion: reduce) {
  .ds.is-demo .ds__thumb, .ds.is-demo .ds__fill, .ds.is-demo .ds__sweep { 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(280px, 84vw);
  color: #17141a;
  text-align: center;
}

.ds__track {
  position: relative;
  height: 8px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.14);
  margin: 40px 0 16px;
}

.ds__fill {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 20%;
  width: 58%;
  background: #4cd4a6;
  border-radius: 999px;
  overflow: hidden;
}

.ds__sweep {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 40%;
  width: 22%;
  background: linear-gradient(100deg, rgba(255, 247, 230, 0) 0%, rgba(255, 247, 230, 0.85) 50%, rgba(255, 247, 230, 0) 100%);
  transform: translateX(-50%);
}

.ds__thumb {
  position: absolute;
  top: 50%;
  left: 20%;
  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: 1;
}

.ds__thumb--hi {
  left: 78%;
}

.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, 0.72);
}

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

@media (max-width: 340px) {
  .ds {
    width: min(240px, 80vw);
  }
  .ds__readout {
    font-size: 16px;
  }
  .ds__caption {
    font-size: 10px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .ds.is-demo .ds__thumb, .ds.is-demo .ds__fill, .ds.is-demo .ds__sweep {
    transition: none;
  }
}

(function () {
  var MIN = 0, MAX = 100;
  var root = document.getElementById('ds');
  var track = document.getElementById('track');
  var fill = document.getElementById('fill');
  var sweep = document.getElementById('sweep');
  var lo = document.getElementById('thumbLo');
  var hi = document.getElementById('thumbHi');
  var loOut = document.getElementById('loOut');
  var hiOut = document.getElementById('hiOut');
  var pxOut = document.getElementById('pxOut');
  var v = { lo: 20, hi: 78, phase: 0.2 };

  // 계산 겹: 두 값을 트랙 채움 %로 바꾸고, 실측 트랙 폭(getBoundingClientRect)으로 채움을 px 로도 환산한다.
  function paint() {
    lo.style.left = v.lo + '%'; hi.style.left = v.hi + '%';
    fill.style.left = v.lo + '%'; fill.style.width = (v.hi - v.lo) + '%';
    var sweepPct = v.lo + (v.hi - v.lo) * v.phase;
    var trackPct = v.hi - v.lo === 0 ? 0 : (sweepPct - v.lo) / (v.hi - v.lo) * 100;
    sweep.style.left = trackPct + '%';
    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);
    var r = track.getBoundingClientRect();
    pxOut.textContent = String(Math.round(r.width * (v.hi - v.lo) / 100));
  }
  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);

  window.addEventListener('resize', paint);

  var presets = [[8, 92, 0.15], [30, 55, 0.9], [45, 88, 0.35], [12, 40, 0.7], [60, 96, 0.5]];
  var pi = 0;
  function tick() {
    var p = presets[pi % presets.length]; pi++;
    v.lo = p[0]; v.hi = p[1]; v.phase = p[2];
    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 './DualSliderFillRangeTrack.module.scss';

const MIN = 0;
const MAX = 100;
const TICK_MS = 480;
const PRESETS: [number, number, number][] = [[8, 92, 0.15], [30, 55, 0.9], [45, 88, 0.35], [12, 40, 0.7], [60, 96, 0.5]];

export default function DualSliderFillRangeTrack() {
  const rootRef = useRef<HTMLDivElement>(null);
  const trackRef = useRef<HTMLDivElement>(null);
  const fillRef = useRef<HTMLDivElement>(null);
  const sweepRef = useRef<HTMLDivElement>(null);
  const loRef = useRef<HTMLButtonElement>(null);
  const hiRef = useRef<HTMLButtonElement>(null);
  const loOutRef = useRef<HTMLSpanElement>(null);
  const hiOutRef = useRef<HTMLSpanElement>(null);
  const pxOutRef = useRef<HTMLSpanElement>(null);

  useEffect(() => {
    const root = rootRef.current;
    const track = trackRef.current;
    const fill = fillRef.current;
    const sweep = sweepRef.current;
    const lo = loRef.current;
    const hi = hiRef.current;
    const loOut = loOutRef.current;
    const hiOut = hiOutRef.current;
    const pxOut = pxOutRef.current;
    if (!root || !track || !fill || !sweep || !lo || !hi || !loOut || !hiOut || !pxOut) return undefined;

    const v = { lo: 20, hi: 78, phase: 0.2 };

    // 계산 겹: 두 값을 트랙 채움 %로 바꾸고, 실측 트랙 폭(getBoundingClientRect)으로 채움을 px 로도 환산한다.
    function paint() {
      lo!.style.left = v.lo + '%'; hi!.style.left = v.hi + '%';
      fill!.style.left = v.lo + '%'; fill!.style.width = (v.hi - v.lo) + '%';
      const sweepPct = v.lo + (v.hi - v.lo) * v.phase;
      const trackPct = v.hi - v.lo === 0 ? 0 : (sweepPct - v.lo) / (v.hi - v.lo) * 100;
      sweep!.style.left = trackPct + '%';
      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);
      const r = track!.getBoundingClientRect();
      pxOut!.textContent = String(Math.round(r.width * (v.hi - v.lo) / 100));
    }
    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);
    window.addEventListener('resize', paint);

    let pi = 0;
    function tick() {
      const p = PRESETS[pi % PRESETS.length]; pi++;
      v.lo = p[0]; v.hi = p[1]; v.phase = p[2];
      paint();
    }
    const reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
    if (!reduce) timer = window.setInterval(tick, TICK_MS);
    paint();

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

  return (
    <main className={styles.stage}>
      <div className={styles.ds + ' ' + styles['is-demo']} ref={rootRef}>
        <div className={styles.dsTrack} ref={trackRef}>
          <div className={styles.dsFill} ref={fillRef}>
            <div className={styles.dsSweep} ref={sweepRef} />
          </div>
          <button type="button" className={styles.dsThumb + ' ' + styles.dsThumbLo} ref={loRef} role="slider"
            aria-label="최소값" aria-valuemin={0} aria-valuemax={100} aria-valuenow={20} aria-valuetext="20" 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={78} aria-valuetext="78" tabIndex={0} />
        </div>
        <p className={styles.dsReadout}><span ref={loOutRef}>20</span> – <span ref={hiOutRef}>78</span></p>
        <p className={styles.dsCaption}>채움 폭 <span ref={pxOutRef}>0</span>px</p>
      </div>
    </main>
  );
}