07Picker That Turns Its Value Into an Orbit's Arc Length

<main class="stage">
<figure class="od is-demo" id="od">
  <div class="od__zone" id="zone">
    <svg class="od__chart" id="chart" viewBox="0 0 480 300" role="img" aria-label="An orbit dial that travels around the circle; turning the handle redraws the arc from the start point to the point every instant.">
      <circle class="od__orbit" cx="240" cy="150" r="106"></circle>
      <path class="od__arc" id="arc"></path>
      <circle class="od__dot" id="dot" r="19"></circle>
    </svg>
    <button class="od__grab" id="grab" type="button" role="slider" aria-orientation="horizontal"
            aria-label="Choose orbit angle" aria-valuemin="1" aria-valuemax="99"
            aria-valuenow="35" aria-valuetext="Orbit 126 degrees">
      <svg class="od__ic" viewBox="0 0 256 256" aria-hidden="true"><g fill="currentColor"><circle cx="128" cy="128" r="96" opacity=".2"/><path d="M128 24a104 104 0 1 0 104 104A104.11 104.11 0 0 0 128 24m0 192a88 88 0 1 1 88-88 88.1 88.1 0 0 1-88 88"/></g></svg>
    </button>
    <b class="od__badge" aria-hidden="true"><span id="od-val">126</span>°</b>
  </div>

  <p class="od__hint">Drag the handle or press arrow keys — orbit arc recomputes.</p>

  <div class="sr">
    <span aria-live="polite" id="od-live"></span>
  </div>
</figure>
</main>

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

// 오빗 다이얼 피커 — 손잡이를 돌린 각도(1~99, 도 단위)를 값으로 바꾸면, 원 둘레 위
// 점의 위치를 극좌표로 다시 계산하고 시작점(위쪽)부터 그 점까지 이어진 궤도 호의
// 길이(path d 속성)를 매 프레임 다시 그린다. 값은 관성 lerp(ARC_LERP)로 목표를 뒤따른다.
// CSS @keyframes 는 0개(각도가 매 프레임 실수로 바뀌어 선언형으로 못 담는다,
// 398-01~06 과 같은 이유).
// picker-graph-orbit-dial-arc-smoothing(JS, ARC_LERP)이 변형 07 의 조정 대상.

$duration: $dur-loop;
$easing: $ease-lerp-settle;
$color: $subject-blue;

@include stage($stage-orange);

.sr {
  position: absolute; width: 1px; height: 1px; overflow: hidden;
  clip-path: inset(50%); white-space: nowrap;
}

.od {
  box-sizing: border-box;
  width: min(360px, 92vw);
  margin: 0; padding: $sp-1;
  display: flex; flex-direction: column; align-items: center; gap: $sp-1;
  border-radius: $r-card;
  background: $stage-paper;
  box-shadow: $shadow-raised;
  color: $subject-ink;
}

.od__zone {
  position: relative;
  width: min(352px, 100%);
  aspect-ratio: 480 / 300;
}

.od__chart { display: block; width: 100%; height: 100%; overflow: visible; }

.od__orbit { fill: none; stroke: rgba($subject-ink, .14); stroke-width: 2; }
.od__arc { fill: none; stroke: $subject-blue-deep; stroke-width: 40; stroke-linecap: round; }
.od__dot { fill: $subject-blue-deep; stroke: $stage-paper; stroke-width: 4; }

.od__grab {
  position: absolute; top: 0; left: 0;
  width: 30px; height: 30px;
  margin: 0; padding: 0; border: 0; border-radius: 50%;
  display: grid; place-items: center;
  background: transparent;
  color: $subject-blue-deep;
  transform: translate(-50%, -50%);
  cursor: grab;
  touch-action: none;
}
.od__grab:active { cursor: grabbing; }
.od__grab:focus-visible { outline: 2px solid $subject-blue-deep; outline-offset: 2px; border-radius: 50%; }
.od__ic { width: 15px; height: 15px; opacity: 0; }

.od__badge {
  position: absolute; top: $sp-2; right: $sp-2;
  padding: $sp-1 $sp-2;
  border-radius: $r-pill;
  background: rgba($subject-ink, .06);
  font-size: 13px; line-height: 18px; font-weight: 800;
  font-variant-numeric: tabular-nums;
  color: $subject-blue-deep;
  pointer-events: none;
}

.od__hint { margin: 0; padding: 0 $sp-2; font-size: 11px; line-height: 16px; color: rgba($subject-ink, .62); text-align: center; }

@media (max-width: 340px) {
  .od { padding: $sp-1; gap: $sp-1; }
  .od__hint { display: none; }
  .od__badge { font-size: 12px; }
  .od__zone { width: min(210px, 100%); }
}

@media (prefers-reduced-motion: reduce) {
  .od.is-still .od__arc,
  .od.is-still .od__dot { transition: none !important; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ff4d1f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.sr {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}

.od {
  box-sizing: border-box;
  width: min(360px, 92vw);
  margin: 0;
  padding: 4px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  border-radius: 16px;
  background: #ffffff;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  color: #17141a;
}

.od__zone {
  position: relative;
  width: min(352px, 100%);
  aspect-ratio: 480/300;
}

.od__chart {
  display: block;
  width: 100%;
  height: 100%;
  overflow: visible;
}

.od__orbit {
  fill: none;
  stroke: rgba(23, 20, 26, 0.14);
  stroke-width: 2;
}

.od__arc {
  fill: none;
  stroke: #0a4fe8;
  stroke-width: 40;
  stroke-linecap: round;
}

.od__dot {
  fill: #0a4fe8;
  stroke: #ffffff;
  stroke-width: 4;
}

.od__grab {
  position: absolute;
  top: 0;
  left: 0;
  width: 30px;
  height: 30px;
  margin: 0;
  padding: 0;
  border: 0;
  border-radius: 50%;
  display: grid;
  place-items: center;
  background: transparent;
  color: #0a4fe8;
  transform: translate(-50%, -50%);
  cursor: grab;
  touch-action: none;
}

.od__grab:active {
  cursor: grabbing;
}

.od__grab:focus-visible {
  outline: 2px solid #0a4fe8;
  outline-offset: 2px;
  border-radius: 50%;
}

.od__ic {
  width: 15px;
  height: 15px;
  opacity: 0;
}

.od__badge {
  position: absolute;
  top: 8px;
  right: 8px;
  padding: 4px 8px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.06);
  font-size: 13px;
  line-height: 18px;
  font-weight: 800;
  font-variant-numeric: tabular-nums;
  color: #0a4fe8;
  pointer-events: none;
}

.od__hint {
  margin: 0;
  padding: 0 8px;
  font-size: 11px;
  line-height: 16px;
  color: rgba(23, 20, 26, 0.62);
  text-align: center;
}

@media (max-width: 340px) {
  .od {
    padding: 4px;
    gap: 4px;
  }
  .od__hint {
    display: none;
  }
  .od__badge {
    font-size: 12px;
  }
  .od__zone {
    width: min(210px, 100%);
  }
}
@media (prefers-reduced-motion: reduce) {
  .od.is-still .od__arc,
  .od.is-still .od__dot {
    transition: none !important;
  }
}

// 실제 동작: pointerdown/move/up 과 keydown 이 각도값(1~99,  degrees 단위로 환산)을 바꾸면,
// 원 둘레 위 점의 위치를 극좌표로 다시 계산하고, 시작점(위쪽)부터 그 점까지 이어진
// Orbit 호의 길이(path d 속성)를 매 프레임 다시 그린다. 값은 관성 lerp(ARC_LERP)로
// 목표를 뒤따른다. CSS @keyframes 없음(각도가 매 프레임 실수로 바뀌어 선언형으로
// 못 담는다, 398-01~06 과 같은 이유).
var root = document.getElementById('od');
var zone = document.getElementById('zone');
var arcEl = document.getElementById('arc');
var dotEl = document.getElementById('dot');
var grab = document.getElementById('grab');
var valEl = document.getElementById('od-val');
var live = document.getElementById('od-live');

var CX = 240, CY = 150, R = 106;        // picker-graph-orbit-radius — Orbit 반지름
var START = -90;
var MIN_V = 1, MAX_V = 99;
var ARC_LERP = 0.18;                    // picker-graph-orbit-dial-arc-smoothing — 변형 07 의 조정 대상
var AUTO_PERIOD = 1.5;
var STEP = 5;

var value = 35;
var current = 35;
var manual = false;
var autoT = 0;
var lastTs = 0;
var zoneRect = null;
var rafId = 0;

function reduced() {
  return window.matchMedia && window.matchMedia('(prefers-reduced-motion: reduce)').matches;
}

function polar(cx, cy, r, deg) {
  var rad = deg * Math.PI / 180;
  return { x: cx + r * Math.cos(rad), y: cy + r * Math.sin(rad) };
}

function arcPath(cx, cy, r, a0, a1) {
  if (a1 - a0 < 0.6) return '';
  var s = polar(cx, cy, r, a0), e = polar(cx, cy, r, a1);
  var large = (a1 - a0) > 180 ? 1 : 0;
  return 'M ' + s.x + ' ' + s.y + ' A ' + r + ' ' + r + ' 0 ' + large + ' 1 ' + e.x + ' ' + e.y;
}

function angleOf(v) { return START + (v / 100) * 360; }

function paint() {
  var deg = angleOf(current);
  arcEl.setAttribute('d', arcPath(CX, CY, R, START, deg));
  var p = polar(CX, CY, R, deg);
  dotEl.setAttribute('cx', String(p.x));
  dotEl.setAttribute('cy', String(p.y));
  grab.style.left = (p.x / 480 * 100) + '%';
  grab.style.top = (p.y / 300 * 100) + '%';
  var rd = Math.round(deg - START);
  valEl.textContent = String(rd);
  grab.setAttribute('aria-valuenow', String(Math.round(current)));
  grab.setAttribute('aria-valuetext', 'Orbit ' + rd + ' degrees');
}

function announce() {
  live.textContent = 'Orbit ' + Math.round(angleOf(current) - START) + ' degrees recomputed';
}

function setValue(v, isManual) {
  value = Math.max(MIN_V, Math.min(MAX_V, v));
  if (isManual) { manual = true; root.classList.remove('is-demo'); }
}

function angleFromPointer(clientX, clientY) {
  if (!zoneRect) zoneRect = zone.getBoundingClientRect();
  var cx = zoneRect.left + zoneRect.width * (CX / 480);
  var cy = zoneRect.top + zoneRect.height * (CY / 300);
  var deg = Math.atan2(clientY - cy, clientX - cx) * 180 / Math.PI;
  while (deg < START) deg += 360;
  while (deg >= START + 360) deg -= 360;
  return deg;
}

function fromPointer(clientX, clientY) {
  var deg = angleFromPointer(clientX, clientY);
  var v = (deg - START) / 360 * 100;
  setValue(v, true);
}

function onDown(e) {
  zoneRect = zone.getBoundingClientRect();
  if (grab.setPointerCapture) { try { grab.setPointerCapture(e.pointerId); } catch (err) {} }
  fromPointer(e.clientX, e.clientY);
  if (reduced()) { current = value; paint(); announce(); }
}
function onMove(e) { fromPointer(e.clientX, e.clientY); if (reduced()) { current = value; paint(); announce(); } }
function onUp() { announce(); }
function onZoneDown(e) {
  zoneRect = zone.getBoundingClientRect();
  fromPointer(e.clientX, e.clientY);
  if (reduced()) { current = value; paint(); announce(); }
}

function onKey(e) {
  var map = { ArrowLeft: -STEP, ArrowDown: -STEP, ArrowRight: STEP, ArrowUp: STEP };
  if (e.key === 'Home') { setValue(MIN_V, true); e.preventDefault(); }
  else if (e.key === 'End') { setValue(MAX_V, true); e.preventDefault(); }
  else if (map[e.key] !== undefined) { setValue(value + map[e.key], true); e.preventDefault(); }
  else { return; }
  if (reduced()) { current = value; paint(); announce(); }
}

function onResize() { zoneRect = zone.getBoundingClientRect(); if (reduced()) paint(); }

function autoStep(dt) {
  autoT += dt;
  var omega = 2 * Math.PI / AUTO_PERIOD;
  value = 50 + 46 * Math.sin(autoT * omega);
}

function frame(ts) {
  if (!lastTs) lastTs = ts;
  var dt = Math.min(0.05, (ts - lastTs) / 1000);
  lastTs = ts;
  if (!manual) autoStep(dt);
  current += (value - current) * ARC_LERP;
  paint();
  rafId = requestAnimationFrame(frame);
}

grab.addEventListener('pointerdown', onDown);
grab.addEventListener('pointermove', onMove);
grab.addEventListener('pointerup', onUp);
grab.addEventListener('keydown', onKey);
zone.addEventListener('pointerdown', onZoneDown);
window.addEventListener('resize', onResize);

if (reduced()) {
  root.classList.add('is-still');
  current = value;
  paint();
} else {
  paint();
  rafId = requestAnimationFrame(frame);
}

// OrbitDialArcLength — vanilla 판(run/398/demo/07-picker-graph-orbit-dial-arc-length/index.html) 의
// React 포트. 손잡이를 돌린 각도를 값으로 바꾸면, 원 둘레 위 점의 위치를 극좌표로 다시
// 계산하고 시작점(위쪽)부터 그 점까지 이어진 궤도 호의 길이를 매 프레임 값에 맞춰 다시 그린다.
import { useEffect, useRef } from "react";
import styles from "./OrbitDialArcLength.module.scss";

type Box<T> = { current: T };
type KeyEvt = { key: string; preventDefault(): void };
type PtrEvt = { clientX: number; clientY: number; pointerId: number };

const CX = 240, CY = 150, R = 106;   // picker-graph-orbit-radius — 궤도 반지름
const START = -90;
const MIN_V = 1, MAX_V = 99;
const ARC_LERP = 0.18;               // picker-graph-orbit-dial-arc-smoothing — 변형 07 의 조정 대상
const AUTO_PERIOD = 1.5;
const STEP = 5;

function polar(cx: number, cy: number, r: number, deg: number): { x: number; y: number } {
  const rad = (deg * Math.PI) / 180;
  return { x: cx + r * Math.cos(rad), y: cy + r * Math.sin(rad) };
}

function arcPath(cx: number, cy: number, r: number, a0: number, a1: number): string {
  if (a1 - a0 < 0.6) return "";
  const s = polar(cx, cy, r, a0);
  const e = polar(cx, cy, r, a1);
  const large = a1 - a0 > 180 ? 1 : 0;
  return "M " + s.x + " " + s.y + " A " + r + " " + r + " 0 " + large + " 1 " + e.x + " " + e.y;
}

function angleOf(v: number): number {
  return START + (v / 100) * 360;
}

export default function OrbitDialArcLength() {
  const rootRef = useRef<HTMLElement | null>(null);
  const zoneRef = useRef<HTMLDivElement | null>(null);
  const arcRef = useRef<SVGPathElement | null>(null);
  const dotRef = useRef<SVGCircleElement | null>(null);
  const grabRef = useRef<HTMLButtonElement | null>(null);
  const valRef = useRef<HTMLElement | null>(null);
  const liveRef = useRef<HTMLSpanElement | null>(null);

  const value = useRef(35) as Box<number>;
  const current = useRef(35) as Box<number>;
  const manual = useRef(false) as Box<boolean>;
  const autoT = useRef(0) as Box<number>;
  const lastTs = useRef(0) as Box<number>;
  const zoneRect = useRef<DOMRect | null>(null) as Box<DOMRect | null>;
  const rafId = useRef(0) as Box<number>;

  function reduced(): boolean {
    return window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  }

  function paint(): void {
    const deg = angleOf(current.current);
    arcRef.current?.setAttribute("d", arcPath(CX, CY, R, START, deg));
    const p = polar(CX, CY, R, deg);
    dotRef.current?.setAttribute("cx", String(p.x));
    dotRef.current?.setAttribute("cy", String(p.y));
    const grab = grabRef.current;
    if (grab) {
      grab.style.left = (p.x / 480) * 100 + "%";
      grab.style.top = (p.y / 300) * 100 + "%";
      grab.setAttribute("aria-valuenow", String(Math.round(current.current)));
      grab.setAttribute("aria-valuetext", "궤도 " + Math.round(deg - START) + "도");
    }
    const rd = Math.round(deg - START);
    if (valRef.current) valRef.current.textContent = String(rd);
  }

  function announce(): void {
    if (liveRef.current) {
      liveRef.current.textContent = "궤도 " + Math.round(angleOf(current.current) - START) + "도로 다시 계산됨";
    }
  }

  function setValue(v: number, isManual: boolean): void {
    value.current = Math.max(MIN_V, Math.min(MAX_V, v));
    if (isManual) {
      manual.current = true;
      rootRef.current?.classList.remove("is-demo");
    }
  }

  function angleFromPointer(clientX: number, clientY: number): number {
    if (!zoneRect.current && zoneRef.current) zoneRect.current = zoneRef.current.getBoundingClientRect();
    const rect = zoneRect.current;
    if (!rect) return START;
    const cx = rect.left + rect.width * (CX / 480);
    const cy = rect.top + rect.height * (CY / 300);
    let deg = (Math.atan2(clientY - cy, clientX - cx) * 180) / Math.PI;
    while (deg < START) deg += 360;
    while (deg >= START + 360) deg -= 360;
    return deg;
  }

  function fromPointer(clientX: number, clientY: number): void {
    const deg = angleFromPointer(clientX, clientY);
    const v = ((deg - START) / 360) * 100;
    setValue(v, true);
  }

  function reflectNow(): void {
    current.current = value.current;
    paint();
    announce();
  }

  function onDown(e: PtrEvt): void {
    if (zoneRef.current) zoneRect.current = zoneRef.current.getBoundingClientRect();
    const grab = grabRef.current;
    if (grab && typeof grab.setPointerCapture === "function") {
      try { grab.setPointerCapture(e.pointerId); } catch { /* 캡처 실패는 치명적이지 않다 */ }
    }
    fromPointer(e.clientX, e.clientY);
    if (reduced()) reflectNow();
  }
  function onMove(e: PtrEvt): void {
    fromPointer(e.clientX, e.clientY);
    if (reduced()) reflectNow();
  }
  function onUp(): void {
    announce();
  }
  function onZoneDown(e: PtrEvt): void {
    if (zoneRef.current) zoneRect.current = zoneRef.current.getBoundingClientRect();
    fromPointer(e.clientX, e.clientY);
    if (reduced()) reflectNow();
  }

  function onKey(e: KeyEvt): void {
    const map: Record<string, number> = { ArrowLeft: -STEP, ArrowDown: -STEP, ArrowRight: STEP, ArrowUp: STEP };
    if (e.key === "Home") { setValue(MIN_V, true); e.preventDefault(); }
    else if (e.key === "End") { setValue(MAX_V, true); e.preventDefault(); }
    else if (map[e.key] !== undefined) { setValue(value.current + map[e.key], true); e.preventDefault(); }
    else { return; }
    if (reduced()) reflectNow();
  }

  function onResize(): void {
    if (zoneRef.current) zoneRect.current = zoneRef.current.getBoundingClientRect();
    if (reduced()) paint();
  }

  function autoStep(dt: number): void {
    autoT.current += dt;
    const omega = (2 * Math.PI) / AUTO_PERIOD;
    value.current = 50 + 46 * Math.sin(autoT.current * omega);
  }

  function frame(ts: number): void {
    if (!lastTs.current) lastTs.current = ts;
    const dt = Math.min(0.05, (ts - lastTs.current) / 1000);
    lastTs.current = ts;
    if (!manual.current) autoStep(dt);
    current.current += (value.current - current.current) * ARC_LERP;
    paint();
    rafId.current = requestAnimationFrame(frame);
  }

  useEffect(() => {
    window.addEventListener("resize", onResize);
    if (reduced()) {
      rootRef.current?.classList.add("is-still");
      reflectNow();
    } else {
      paint();
      rafId.current = requestAnimationFrame(frame);
    }
    return () => {
      window.removeEventListener("resize", onResize);
      cancelAnimationFrame(rafId.current);
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  return (
    <main className={styles.stage}>
      <figure className={styles.od + " is-demo"} ref={rootRef}>
        <div className={styles.zone} ref={zoneRef} onPointerDown={onZoneDown}>
          <svg
            className={styles.chart}
            viewBox="0 0 480 300"
            role="img"
            aria-label="원 둘레를 도는 오빗 다이얼, 손잡이를 돌리면 시작점부터 점까지 이어진 궤도 호의 길이가 매 순간 다시 그려진다"
          >
            <circle className={styles.orbit} cx={CX} cy={CY} r={R} />
            <path className={styles.arc} ref={arcRef} />
            <circle className={styles.dot} ref={dotRef} r={19} />
          </svg>
          <button
            className={styles.grab}
            ref={grabRef}
            type="button"
            role="slider"
            aria-orientation="horizontal"
            aria-label="궤도 각도 고르기"
            aria-valuemin={MIN_V}
            aria-valuemax={MAX_V}
            aria-valuenow={35}
            aria-valuetext="궤도 126도"
            onPointerDown={onDown}
            onPointerMove={onMove}
            onPointerUp={onUp}
            onKeyDown={onKey}
          >
            <svg className={styles.ic} viewBox="0 0 256 256" aria-hidden="true">
              <g fill="currentColor">
                <circle cx={128} cy={128} r={96} opacity={0.2} />
                <path d="M128 24a104 104 0 1 0 104 104A104.11 104.11 0 0 0 128 24m0 192a88 88 0 1 1 88-88 88.1 88.1 0 0 1-88 88" />
              </g>
            </svg>
          </button>
          <b className={styles.badge} aria-hidden="true"><span ref={valRef}>126</span>°</b>
        </div>

        <p className={styles.hint}>손잡이를 끌거나 화살표키를 누르면 궤도 호의 길이가 다시 계산됩니다</p>

        <div className={styles.sr}>
          <span aria-live="polite" ref={liveRef} />
        </div>
      </figure>
    </main>
  );
}