02A Popover That Springs Open from the Anchor Point

<main class="stage">
<div class="pm is-demo" id="pm" data-demo="1">
  <p class="pm__live" data-r="live" aria-live="off" aria-atomic="true"></p>
  <button class="pm__move" data-r="move" type="button">Move anchor</button>
  <i class="pm__origin" data-r="origin"></i>
  <button class="pm__anchor" data-r="anchor" type="button" aria-expanded="false" aria-controls="pm-panel" aria-label="Open quick settings"></button>
  <div class="pm__pop" id="pm-panel" data-r="pop"><b class="pm__ttl">Quick settings</b><span class="pm__row"><i class="pm__sw"></i>Alerts</span><span class="pm__row"><i class="pm__sw pm__sw--on"></i>Sound</span><span class="pm__row"><i class="pm__sw"></i>Vibrate</span></div>
</div>
</main>

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

// 핵심: transform-origin 을 앵커 중심 좌표로 계산하고, scale 만 스프링으로 풀어 앵커에서 자라난 듯 열린다.

@include stage($stage-yellow);

.pm {
  position: relative;
  box-sizing: border-box;
  overflow: hidden;
  width: min(100%, 440px);
  height: min(252px, calc(100vh - 2 * clamp(8px, 4vw, 24px)));
  border-radius: $r-card;
  background: rgba($subject-ink, .07);
  color: $subject-ink;
  font-size: 12px;
  line-height: 16px;
  font-weight: 600;
  user-select: none;
}
.pm b { font-weight: 800; font-variant-numeric: tabular-nums; }
.pm__live {
  position: absolute;
  left: $sp-3;
  top: $sp-2;
  margin: 0;
  z-index: 9;
  color: rgba($subject-ink, .72);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
  pointer-events: none;
}
.pm button { font-family: inherit; }
.pm button:focus-visible { outline: 3px solid $subject-ink; outline-offset: 2px; }


.pm__move {
  position: absolute;
  right: $sp-3;
  top: $sp-2;
  z-index: 8;
  height: 24px;
  padding: 0 $sp-3;
  border: 0;
  border-radius: $r-pill;
  background: rgba($subject-ink, .12);
  color: $subject-ink;
  font-size: 12px;
  line-height: 16px;
  font-weight: 700;
  cursor: pointer;
}
.pm__origin {
  position: absolute;
  left: 0;
  top: 0;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: $subject-ink;
  z-index: 6;
  pointer-events: none;
}
.pm__anchor {
  position: absolute;
  left: 0;
  top: 0;
  box-sizing: border-box;
  width: 28px;
  height: 28px;
  padding: 0;
  border: 0;
  border-radius: 50%;
  background: $subject-lilac;
  box-shadow: 0 0 0 4px rgba($subject-lilac, .4), $shadow-press;
  cursor: pointer;
  z-index: 5;
}
.pm__pop {
  position: absolute;
  left: 0;
  top: 0;
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  gap: $sp-1;
  width: 156px;
  height: 92px;
  padding: $sp-3;
  border-radius: $r-card;
  background: $subject-cream;
  color: $subject-ink;
  box-shadow: $shadow-raised;
  visibility: hidden;
  z-index: 4;
  will-change: transform;
}
.pm__ttl { display: block; font-size: 13px; line-height: 20px; }
.pm__row { display: flex; align-items: center; gap: $sp-2; }
.pm__sw {
  position: relative;
  width: 24px;
  height: 12px;
  border-radius: $r-pill;
  background: rgba($subject-ink, .22);
}
.pm__sw::after {
  content: "";
  position: absolute;
  left: 2px;
  top: 2px;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: $subject-cream;
}
.pm__sw--on { background: $subject-mint; }
.pm__sw--on::after { left: 14px; }
@media (prefers-reduced-motion: reduce) {
  .pm__pop { will-change: auto; }
}

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);
}

.pm {
  position: relative;
  box-sizing: border-box;
  overflow: hidden;
  width: min(100%, 440px);
  height: min(252px, 100vh - 2 * clamp(8px, 4vw, 24px));
  border-radius: 16px;
  background: rgba(23, 20, 26, 0.07);
  color: #17141a;
  font-size: 12px;
  line-height: 16px;
  font-weight: 600;
  user-select: none;
}

.pm b {
  font-weight: 800;
  font-variant-numeric: tabular-nums;
}

.pm__live {
  position: absolute;
  left: 12px;
  top: 8px;
  margin: 0;
  z-index: 9;
  color: rgba(23, 20, 26, 0.72);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
  pointer-events: none;
}

.pm button {
  font-family: inherit;
}

.pm button:focus-visible {
  outline: 3px solid #17141a;
  outline-offset: 2px;
}

.pm__move {
  position: absolute;
  right: 12px;
  top: 8px;
  z-index: 8;
  height: 24px;
  padding: 0 12px;
  border: 0;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.12);
  color: #17141a;
  font-size: 12px;
  line-height: 16px;
  font-weight: 700;
  cursor: pointer;
}

.pm__origin {
  position: absolute;
  left: 0;
  top: 0;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: #17141a;
  z-index: 6;
  pointer-events: none;
}

.pm__anchor {
  position: absolute;
  left: 0;
  top: 0;
  box-sizing: border-box;
  width: 28px;
  height: 28px;
  padding: 0;
  border: 0;
  border-radius: 50%;
  background: #b9a0ff;
  box-shadow: 0 0 0 4px rgba(185, 160, 255, 0.4), 0 6px 12px rgba(23, 20, 26, 0.32);
  cursor: pointer;
  z-index: 5;
}

.pm__pop {
  position: absolute;
  left: 0;
  top: 0;
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  gap: 4px;
  width: 156px;
  height: 92px;
  padding: 12px;
  border-radius: 16px;
  background: #fff7e6;
  color: #17141a;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  visibility: hidden;
  z-index: 4;
  will-change: transform;
}

.pm__ttl {
  display: block;
  font-size: 13px;
  line-height: 20px;
}

.pm__row {
  display: flex;
  align-items: center;
  gap: 8px;
}

.pm__sw {
  position: relative;
  width: 24px;
  height: 12px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.22);
}

.pm__sw::after {
  content: "";
  position: absolute;
  left: 2px;
  top: 2px;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #fff7e6;
}

.pm__sw--on {
  background: #4cd4a6;
}

.pm__sw--on::after {
  left: 14px;
}

@media (prefers-reduced-motion: reduce) {
  .pm__pop {
    will-change: auto;
  }
}

(function () {
    const root = document.getElementById("pm");
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let demo = !reduce;
    let raf = 0;
    let t0 = -1;
    let last = -1;
    let acc = 0;
    let clock = 0;
    const offs = [];
    const live = root.querySelector("[data-r=live]");
    function q(sel) {
        return root.querySelector(sel);
    }
    function clamp(v, lo, hi) {
        return Math.max(lo, Math.min(hi, v));
    }
    function seg(t, a, b) {
        const c = clamp((t - a) / (b - a), 0, 1);
        return c * c * (3 - 2 * c);
    }
    function on(el, type, fn) {
        el.addEventListener(type, fn);
        offs.push(() => el.removeEventListener(type, fn));
    }
    function stopDemo() {
        if (!demo)
            return;
        demo = false;
        root.removeAttribute("data-demo");
        root.classList.remove("is-demo");
        live.setAttribute("aria-live", "polite");
    }
    if (reduce)
        live.setAttribute("aria-live", "polite");
    let shown = "";
    function say(s) {
        if (s === shown)
            return;
        shown = s;
        live.textContent = s;
    }
    function makeRng(seed) {
        let s = seed >>> 0;
        return () => {
            s = (Math.imul(s, 1664525) + 1013904223) >>> 0;
            return s / 4294967296;
        };
    }
    function local(e) {
        const r = root.getBoundingClientRect();
        return { x: e.clientX - r.left, y: e.clientY - r.top };
    }
    function sync() {
        if (reduce) {
            snap();
            render();
        }
    }
    // 기법: transform-origin 을 앵커 중심(ORIGIN_X, ORIGIN_Y)으로 계산해 두고, scale 을 스프링으로 풀면 목표 1 을 넘었다 돌아오며 앵커에서 자란 것처럼 보인다.
    const STIFFNESS = 0.14;
    const DAMPING = 0.66;
    const PANEL_W = 156;
    const PANEL_H = 92;
    const ANCHOR_R = 14;
    const SLOTS = [0.16, 0.5, 0.84];
    const ANCHOR_NY = 0.22;
    const PAD = 8;
    const CYCLE_MS = 2400;
    const anchor = q("[data-r=anchor]");
    const pop = q("[data-r=pop]");
    const origin = q("[data-r=origin]");
    const moveBtn = q("[data-r=move]");
    let ORIGIN_X = 0;
    let ORIGIN_Y = 0;
    let size = 0;
    let vel = 0;
    let want = reduce;
    let slot = 1;
    let nx = SLOTS[1];
    let expanded = false;
    let peak = 0;
    function place() {
        const w = root.clientWidth;
        const h = root.clientHeight;
        const ax = nx * w;
        const ay = ANCHOR_NY * h;
        const x = clamp(ax - PANEL_W / 2, PAD, w - PAD - PANEL_W);
        const y = ay + ANCHOR_R + 10;
        ORIGIN_X = ax - x;
        ORIGIN_Y = ay - y;
        return [ax, ay, x, y];
    }
    function tick(ms) {
        if (demo) {
            const cycle = Math.floor(ms / CYCLE_MS);
            const phase = ms - cycle * CYCLE_MS;
            want = phase >= 250 && phase < 1350;
            slot = (cycle + (phase >= 1900 ? 1 : 0)) % SLOTS.length;
        }
        nx += (SLOTS[slot] - nx) * 0.2;
        vel = (vel + ((want ? 1 : 0) - size) * STIFFNESS) * DAMPING;
        size += vel;
        if (size < 0) {
            size = 0;
            vel = 0;
        }
        if (want)
            peak = Math.max(peak, size);
        else if (size < 0.02)
            peak = 0;
    }
    function snap() {
        nx = SLOTS[slot];
        size = want ? 1 : 0;
        vel = 0;
        peak = size;
    }
    function render() {
        const p = place();
        anchor.style.transform = "translate3d(" + (p[0] - ANCHOR_R).toFixed(1) + "px," + (p[1] - ANCHOR_R).toFixed(1) + "px,0)";
        origin.style.transform = "translate3d(" + (p[0] - 3).toFixed(1) + "px," + (p[1] - 3).toFixed(1) + "px,0)";
        pop.style.transformOrigin = ORIGIN_X.toFixed(1) + "px " + ORIGIN_Y.toFixed(1) + "px";
        pop.style.transform = "translate3d(" + p[2].toFixed(1) + "px," + p[3].toFixed(1) + "px,0) scale(" + size.toFixed(3) + ")";
        pop.style.opacity = String(clamp(size * 1.8, 0, 1));
        pop.style.visibility = size > 0.01 ? "visible" : "hidden";
        if (want !== expanded) {
            expanded = want;
            anchor.setAttribute("aria-expanded", want ? "true" : "false");
        }
        say("scale " + size.toFixed(2) + "  peak " + peak.toFixed(2));
    }
    function toggle() {
        stopDemo();
        want = !want;
        sync();
    }
    on(anchor, "click", toggle);
    on(moveBtn, "click", () => {
        stopDemo();
        slot = (slot + 1) % SLOTS.length;
        sync();
    });
    on(root, "keydown", (e) => {
        if (e.key !== "Escape" || !want)
            return;
        e.preventDefault();
        stopDemo();
        want = false;
        anchor.focus({ preventScroll: true });
        sync();
    });
    const FRAME_MS = 1000 / 60;
    function frame(ts) {
        if (t0 < 0) {
            t0 = ts;
            last = ts;
        }
        acc += Math.min(100, ts - last);
        last = ts;
        let n = 0;
        while (acc >= FRAME_MS && n < 6) {
            clock += FRAME_MS;
            tick(clock);
            acc -= FRAME_MS;
            n += 1;
        }
        if (n === 6)
            acc = 0;
        render();
        raf = requestAnimationFrame(frame);
    }
    const ro = new ResizeObserver(() => sync());
    ro.observe(root);
    if (reduce) {
        stopDemo();
        snap();
        render();
    }
    else {
        raf = requestAnimationFrame(frame);
    }
    return () => {
        cancelAnimationFrame(raf);
        offs.forEach((f) => f());
        ro.disconnect();
    };
})();

// SpringFromAnchor - vanilla 판(02-pm-spring-from-anchor) 의 React 포트. 같은 계산을 useEffect 안에서 돌린다.
import { useEffect, useRef } from "react";
import styles from "./SpringFromAnchor.module.scss";

export default function SpringFromAnchor() {
  const rootRef = useRef<HTMLDivElement | null>(null);

  useEffect(() => {
    const rootEl = rootRef.current;
    if (!rootEl) return;
    const root: HTMLElement = rootEl;
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let demo = !reduce;
    let raf = 0;
    let t0 = -1;
    let last = -1;
    let acc = 0;
    let clock = 0;
    const offs: Array<() => void> = [];
    const live = root.querySelector("[data-r=live]") as HTMLElement;

    function q<T extends Element>(sel: string): T {
      return root.querySelector(sel) as T;
    }
    function clamp(v: number, lo: number, hi: number): number {
      return Math.max(lo, Math.min(hi, v));
    }
    function seg(t: number, a: number, b: number): number {
      const c = clamp((t - a) / (b - a), 0, 1);
      return c * c * (3 - 2 * c);
    }
    function on(el: EventTarget, type: string, fn: (e: any) => void): void {
      el.addEventListener(type, fn);
      offs.push(() => el.removeEventListener(type, fn));
    }
    function stopDemo(): void {
      if (!demo) return;
      demo = false;
      root.removeAttribute("data-demo");
      root.classList.remove("is-demo");
      live.setAttribute("aria-live", "polite");
    }
    if (reduce) live.setAttribute("aria-live", "polite");
    let shown = "";
    function say(s: string): void {
      if (s === shown) return;
      shown = s;
      live.textContent = s;
    }
    function makeRng(seed: number): () => number {
      let s = seed >>> 0;
      return () => {
        s = (Math.imul(s, 1664525) + 1013904223) >>> 0;
        return s / 4294967296;
      };
    }
    function local(e: PointerEvent): { x: number; y: number } {
      const r = root.getBoundingClientRect();
      return { x: e.clientX - r.left, y: e.clientY - r.top };
    }
    function sync(): void {
      if (reduce) {
        snap();
        render();
      }
    }

    // 기법: transform-origin 을 앵커 중심(ORIGIN_X, ORIGIN_Y)으로 계산해 두고, scale 을 스프링으로 풀면 목표 1 을 넘었다 돌아오며 앵커에서 자란 것처럼 보인다.
    const STIFFNESS = 0.14;
    const DAMPING = 0.66;
    const PANEL_W = 156;
    const PANEL_H = 92;
    const ANCHOR_R = 14;
    const SLOTS = [0.16, 0.5, 0.84];
    const ANCHOR_NY = 0.22;
    const PAD = 8;
    const CYCLE_MS = 2400;
    const anchor = q<HTMLElement>("[data-r=anchor]");
    const pop = q<HTMLElement>("[data-r=pop]");
    const origin = q<HTMLElement>("[data-r=origin]");
    const moveBtn = q<HTMLElement>("[data-r=move]");
    let ORIGIN_X = 0;
    let ORIGIN_Y = 0;
    let size = 0;
    let vel = 0;
    let want = reduce;
    let slot = 1;
    let nx = SLOTS[1];
    let expanded = false;
    let peak = 0;

    function place(): number[] {
      const w = root.clientWidth;
      const h = root.clientHeight;
      const ax = nx * w;
      const ay = ANCHOR_NY * h;
      const x = clamp(ax - PANEL_W / 2, PAD, w - PAD - PANEL_W);
      const y = ay + ANCHOR_R + 10;
      ORIGIN_X = ax - x;
      ORIGIN_Y = ay - y;
      return [ax, ay, x, y];
    }
    function tick(ms: number): void {
      if (demo) {
        const cycle = Math.floor(ms / CYCLE_MS);
        const phase = ms - cycle * CYCLE_MS;
        want = phase >= 250 && phase < 1350;
        slot = (cycle + (phase >= 1900 ? 1 : 0)) % SLOTS.length;
      }
      nx += (SLOTS[slot] - nx) * 0.2;
      vel = (vel + ((want ? 1 : 0) - size) * STIFFNESS) * DAMPING;
      size += vel;
      if (size < 0) {
        size = 0;
        vel = 0;
      }
      if (want) peak = Math.max(peak, size);
      else if (size < 0.02) peak = 0;
    }
    function snap(): void {
      nx = SLOTS[slot];
      size = want ? 1 : 0;
      vel = 0;
      peak = size;
    }
    function render(): void {
      const p = place();
      anchor.style.transform = "translate3d(" + (p[0] - ANCHOR_R).toFixed(1) + "px," + (p[1] - ANCHOR_R).toFixed(1) + "px,0)";
      origin.style.transform = "translate3d(" + (p[0] - 3).toFixed(1) + "px," + (p[1] - 3).toFixed(1) + "px,0)";
      pop.style.transformOrigin = ORIGIN_X.toFixed(1) + "px " + ORIGIN_Y.toFixed(1) + "px";
      pop.style.transform = "translate3d(" + p[2].toFixed(1) + "px," + p[3].toFixed(1) + "px,0) scale(" + size.toFixed(3) + ")";
      pop.style.opacity = String(clamp(size * 1.8, 0, 1));
      pop.style.visibility = size > 0.01 ? "visible" : "hidden";
      if (want !== expanded) {
        expanded = want;
        anchor.setAttribute("aria-expanded", want ? "true" : "false");
      }
      say("scale " + size.toFixed(2) + "  peak " + peak.toFixed(2));
    }
    function toggle(): void {
      stopDemo();
      want = !want;
      sync();
    }
    on(anchor, "click", toggle);
    on(moveBtn, "click", () => {
      stopDemo();
      slot = (slot + 1) % SLOTS.length;
      sync();
    });
    on(root, "keydown", (e: KeyboardEvent) => {
      if (e.key !== "Escape" || !want) return;
      e.preventDefault();
      stopDemo();
      want = false;
      anchor.focus({ preventScroll: true });
      sync();
    });

    const FRAME_MS = 1000 / 60;
    function frame(ts: number): void {
      if (t0 < 0) {
        t0 = ts;
        last = ts;
      }
      acc += Math.min(100, ts - last);
      last = ts;
      let n = 0;
      while (acc >= FRAME_MS && n < 6) {
        clock += FRAME_MS;
        tick(clock);
        acc -= FRAME_MS;
        n += 1;
      }
      if (n === 6) acc = 0;
      render();
      raf = requestAnimationFrame(frame);
    }
    const ro = new ResizeObserver(() => sync());
    ro.observe(root);
    if (reduce) {
      stopDemo();
      snap();
      render();
    } else {
      raf = requestAnimationFrame(frame);
    }
    return () => {
      cancelAnimationFrame(raf);
      offs.forEach((f) => f());
      ro.disconnect();
    };

  }, []);

  return (
    <main className={styles["stage"]}>
      <div ref={rootRef} className={styles["pm"] + " is-demo"} data-demo="1">
        <p className={styles["pm__live"]} data-r="live" aria-live="off" aria-atomic="true"></p>
        <button className={styles["pm__move"]} data-r="move" type="button">자리 옮기기</button>
        <i className={styles["pm__origin"]} data-r="origin"></i>
        <button className={styles["pm__anchor"]} data-r="anchor" type="button" aria-expanded="false" aria-controls="pm-panel" aria-label="빠른 설정 열기"></button>
        <div className={styles["pm__pop"]} id="pm-panel" data-r="pop"><b className={styles["pm__ttl"]}>빠른 설정</b><span className={styles["pm__row"]}><i className={styles["pm__sw"]}></i>알림</span><span className={styles["pm__row"]}><i className={styles["pm__sw"] + " " + styles["pm__sw--on"]}></i>소리</span><span className={styles["pm__row"]}><i className={styles["pm__sw"]}></i>진동</span></div>
      </div>
    </main>
  );
}