02Focal Zoom That Calculates Its Center From the Pointer's Coordinates

<main class="stage">
<div class="pvz is-demo" id="pvzRoot" tabindex="0">
  <div class="pvz__view" id="pvzView">
    <div class="pvz__page" id="pvzPage"></div>
    <div class="pvz__dot" id="pvzDot"></div>
  </div>
  <p class="pvz__label" id="pvzLabel">100%</p>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;
@include stage($stage-yellow);

.pvz {
  position: relative;
  width: min(92vw, calc(160vh - 12.8vw));
  aspect-ratio: 480 / 300;
  margin: 0 auto;
  border-radius: $r-card;
  overflow: hidden;
  box-shadow: $shadow-raised;
  background: $subject-ink;
  outline: none;
}

.pvz__view {
  position: absolute;
  inset: 0;
  overflow: hidden;
}

.pvz__page {
  position: absolute;
  left: 12%;
  top: 10%;
  width: 76%;
  height: 80%;
  background: $subject-cream;
  border-radius: $r-sm;
  padding: $sp-4;
  box-sizing: border-box;
  will-change: transform;
}

.pvz__title { height: 10px; border-radius: $r-xs; background: rgba(23, 20, 26, .4); margin-bottom: $sp-2; }
.pvz__line { height: 5px; border-radius: $r-xs; background: rgba(23, 20, 26, .18); margin-top: $sp-1; }
.pvz__fig { height: 22%; margin-top: $sp-2; border-radius: $r-sm; background: rgba(47, 109, 246, .22); }

.pvz__dot {
  position: absolute;
  width: 14px;
  height: 14px;
  margin-left: -7px;
  margin-top: -7px;
  border-radius: 50%;
  background: rgba(255, 77, 31, .85);
  box-shadow: 0 0 0 4px rgba(255, 77, 31, .25);
  pointer-events: none;
  will-change: transform;
}

.pvz__label {
  position: absolute;
  left: $sp-2;
  bottom: $sp-2;
  margin: 0;
  padding: $sp-1 $sp-2;
  border-radius: $r-pill;
  background: rgba(23, 20, 26, .78);
  color: #fff;
  font-size: 11px;
  font-weight: 700;
  pointer-events: none;
}

@media (max-width: 340px) {
  .pvz__label { font-size: 9px; }
}

@media (prefers-reduced-motion: reduce) {
  .pvz__page, .pvz__dot { 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);
}

.pvz {
  position: relative;
  width: min(92vw, 160vh - 12.8vw);
  aspect-ratio: 480/300;
  margin: 0 auto;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  background: #17141a;
  outline: none;
}

.pvz__view {
  position: absolute;
  inset: 0;
  overflow: hidden;
}

.pvz__page {
  position: absolute;
  left: 12%;
  top: 10%;
  width: 76%;
  height: 80%;
  background: #fff7e6;
  border-radius: 8px;
  padding: 16px;
  box-sizing: border-box;
  will-change: transform;
}

.pvz__title {
  height: 10px;
  border-radius: 4px;
  background: rgba(23, 20, 26, 0.4);
  margin-bottom: 8px;
}

.pvz__line {
  height: 5px;
  border-radius: 4px;
  background: rgba(23, 20, 26, 0.18);
  margin-top: 4px;
}

.pvz__fig {
  height: 22%;
  margin-top: 8px;
  border-radius: 8px;
  background: rgba(47, 109, 246, 0.22);
}

.pvz__dot {
  position: absolute;
  width: 14px;
  height: 14px;
  margin-left: -7px;
  margin-top: -7px;
  border-radius: 50%;
  background: rgba(255, 77, 31, 0.85);
  box-shadow: 0 0 0 4px rgba(255, 77, 31, 0.25);
  pointer-events: none;
  will-change: transform;
}

.pvz__label {
  position: absolute;
  left: 8px;
  bottom: 8px;
  margin: 0;
  padding: 4px 8px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.78);
  color: #fff;
  font-size: 11px;
  font-weight: 700;
  pointer-events: none;
}

@media (max-width: 340px) {
  .pvz__label {
    font-size: 9px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .pvz__page, .pvz__dot {
    transition: none;
  }
}

(function () {
  // 변형 02: ZOOM_FOCAL_STEP_RATIO 1.2 → 2.4 (전값이 소스 초기값)
  // 기법: 휠(또는 시연 스케줄)이 일어난 지점의 좌표를 Page 폭·높이 기준 비율(0~1)로 바꿔
  // transform-origin 으로 쓴다. 확대율은 그 비율의 거듭제곱(ZOOM_FOCAL_STEP_RATIO^n)으로
  // 계산해, 값이 클수록 같은 조작에도 훨씬 크게 뛴다. 초점 표식(dot)의 반경은 1/scale 로
  // 역보정해 확대돼도 항상 같은 크기로 보인다(계산 전파).
  var root = document.getElementById('pvzRoot');
  var view = document.getElementById('pvzView');
  var page = document.getElementById('pvzPage');
  var dot = document.getElementById('pvzDot');
  var label = document.getElementById('pvzLabel');

  var ZOOM_FOCAL_STEP_RATIO = 1.2;
  var LOOP_MS = 2000;

  function seedRand(seed) { var s = seed >>> 0; return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; }; }
  var rnd = seedRand(430021);
  var lineCount = 7;
  var linesHTML = '<div class="pvz__title" style="width:52%"></div>';
  for (var i = 0; i < lineCount; i += 1) linesHTML += '<div class="pvz__line" style="width:' + (40 + rnd() * 52) + '%"></div>';
  linesHTML += '<div class="pvz__fig"></div>';
  page.innerHTML = linesHTML;

  var L1 = ZOOM_FOCAL_STEP_RATIO;
  var L2 = ZOOM_FOCAL_STEP_RATIO * ZOOM_FOCAL_STEP_RATIO;
  var KF = [
    { t: 0, s: 1, x: .5, y: .5 },
    { t: 300, s: L1, x: .28, y: .38 },
    { t: 900, s: L2, x: .28, y: .38 },
    { t: 1300, s: 1, x: .28, y: .38 },
    { t: 1500, s: L1, x: .7, y: .64 },
    { t: 2000, s: 1, x: .7, y: .64 }
  ];

  function easeInOut(t) { return t * t * (3 - 2 * t); }
  function render(scale, ox, oy) {
    page.style.transformOrigin = (ox * 100) + '% ' + (oy * 100) + '%';
    page.style.transform = 'scale(' + scale.toFixed(3) + ')';
    var vr = view.getBoundingClientRect();
    dot.style.left = (ox * vr.width) + 'px';
    dot.style.top = (oy * vr.height) + 'px';
    dot.style.transform = 'translate(-50%,-50%) scale(' + (1 / scale).toFixed(3) + ')';
    label.textContent = Math.round(scale * 100) + '%';
  }

  function scheduled(elapsed) {
    var phase = elapsed % LOOP_MS;
    var i = 0;
    while (i < KF.length - 1 && phase >= KF[i + 1].t) i += 1;
    var a = KF[i], b = KF[Math.min(i + 1, KF.length - 1)];
    var span = Math.max(1, b.t - a.t);
    var t = easeInOut(Math.max(0, Math.min(1, (phase - a.t) / span)));
    var s = a.s + (b.s - a.s) * t;
    render(s, b.x, b.y);
  }

  var manual = { s: 1, x: .5, y: .5 };
  function applyWheel(dir, ox, oy) {
    manual.s = Math.max(1, Math.min(L2 * 1.4, manual.s * Math.pow(ZOOM_FOCAL_STEP_RATIO, dir * 0.6)));
    manual.x = ox; manual.y = oy;
    render(manual.s, manual.x, manual.y);
  }

  var userActive = false;
  function markActive() { if (!userActive) { userActive = true; root.classList.remove('is-demo'); manual.s = 1; render(1, .5, .5); } }

  view.addEventListener('wheel', function (e) {
    e.preventDefault();
    markActive();
    var r = view.getBoundingClientRect();
    var ox = Math.max(0, Math.min(1, (e.clientX - r.left) / r.width));
    var oy = Math.max(0, Math.min(1, (e.clientY - r.top) / r.height));
    applyWheel(e.deltaY < 0 ? 1 : -1, ox, oy);
  }, { passive: false });

  root.addEventListener('keydown', function (e) {
    if (e.key === '+' || e.key === '=' || e.key === '-' || e.key === 'ArrowUp' || e.key === 'ArrowDown') {
      e.preventDefault();
      markActive();
      var dir = (e.key === '+' || e.key === '=' || e.key === 'ArrowUp') ? 1 : -1;
      applyWheel(dir, manual.x, manual.y);
    }
  });

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (reduce) { root.classList.remove('is-demo'); userActive = true; render(1, .5, .5); }

  var lastTs = null, elapsed = 0;
  function tick(ts) {
    if (lastTs === null) lastTs = ts;
    var dt = Math.min(ts - lastTs, 48);
    lastTs = ts;
    if (!userActive) { elapsed += dt; scheduled(elapsed); }
    requestAnimationFrame(tick);
  }
  render(1, .5, .5);
  requestAnimationFrame(tick);
})();

import { useEffect, useRef } from "react";
import styles from "./PdfViewerPointerZoomFocalPoint.module.scss";

type KeyEvt = { key: string; preventDefault(): void };
type WheelEvt = { deltaY: number; clientX: number; clientY: number; preventDefault(): void };

export default function PdfViewerPointerZoomFocalPoint() {
  const rootRef = useRef<HTMLDivElement>(null);
  const viewRef = useRef<HTMLDivElement>(null);
  const pageRef = useRef<HTMLDivElement>(null);
  const dotRef = useRef<HTMLDivElement>(null);
  const labelRef = useRef<HTMLParagraphElement>(null);

  useEffect(() => {
    const root = rootRef.current, view = viewRef.current, page = pageRef.current;
    const dot = dotRef.current, label = labelRef.current;
    if (!root || !view || !page || !dot || !label) return;

    // 변형 02: ZOOM_FOCAL_STEP_RATIO 1.2 → 2.4 (전값이 소스 초기값)
    const ZOOM_FOCAL_STEP_RATIO = 1.2;
    const LOOP_MS = 2000;

    function seedRand(seed: number) {
      let s = seed >>> 0;
      return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
    }
    const rnd = seedRand(430020);
    let linesHTML = '<div class="' + styles.title + '" style="width:52%"></div>';
    for (let i = 0; i < 7; i += 1) linesHTML += '<div class="' + styles.line + '" style="width:' + (40 + rnd() * 52) + '%"></div>';
    linesHTML += '<div class="' + styles.fig + '"></div>';
    page.innerHTML = linesHTML;

    const L1 = ZOOM_FOCAL_STEP_RATIO;
    const L2 = ZOOM_FOCAL_STEP_RATIO * ZOOM_FOCAL_STEP_RATIO;
    const KF = [
      { t: 0, s: 1, x: .5, y: .5 },
      { t: 300, s: L1, x: .28, y: .38 },
      { t: 900, s: L2, x: .28, y: .38 },
      { t: 1300, s: 1, x: .28, y: .38 },
      { t: 1500, s: L1, x: .7, y: .64 },
      { t: 2000, s: 1, x: .7, y: .64 }
    ];

    function easeInOut(t: number) { return t * t * (3 - 2 * t); }
    function render(scale: number, ox: number, oy: number) {
      page!.style.transformOrigin = (ox * 100) + "% " + (oy * 100) + "%";
      page!.style.transform = "scale(" + scale.toFixed(3) + ")";
      const vr = view!.getBoundingClientRect();
      dot!.style.left = (ox * vr.width) + "px";
      dot!.style.top = (oy * vr.height) + "px";
      dot!.style.transform = "translate(-50%,-50%) scale(" + (1 / scale).toFixed(3) + ")";
      label!.textContent = Math.round(scale * 100) + "%";
    }

    function scheduled(elapsed: number) {
      const phase = elapsed % LOOP_MS;
      let i = 0;
      while (i < KF.length - 1 && phase >= KF[i + 1].t) i += 1;
      const a = KF[i], b = KF[Math.min(i + 1, KF.length - 1)];
      const span = Math.max(1, b.t - a.t);
      const t = easeInOut(Math.max(0, Math.min(1, (phase - a.t) / span)));
      const s = a.s + (b.s - a.s) * t;
      render(s, b.x, b.y);
    }

    const manual = { s: 1, x: .5, y: .5 };
    let userActive = false;
    function applyWheel(dir: number, ox: number, oy: number) {
      manual.s = Math.max(1, Math.min(L2 * 1.4, manual.s * Math.pow(ZOOM_FOCAL_STEP_RATIO, dir * 0.6)));
      manual.x = ox; manual.y = oy;
      render(manual.s, manual.x, manual.y);
    }
    function markActive() { if (!userActive) { userActive = true; root!.classList.remove("is-demo"); manual.s = 1; render(1, .5, .5); } }

    function onWheel(e: WheelEvt) {
      e.preventDefault();
      markActive();
      const r = view!.getBoundingClientRect();
      const ox = Math.max(0, Math.min(1, (e.clientX - r.left) / r.width));
      const oy = Math.max(0, Math.min(1, (e.clientY - r.top) / r.height));
      applyWheel(e.deltaY < 0 ? 1 : -1, ox, oy);
    }
    function onKeydown(e: KeyEvt) {
      if (e.key === "+" || e.key === "=" || e.key === "-" || e.key === "ArrowUp" || e.key === "ArrowDown") {
        e.preventDefault();
        markActive();
        const dir = (e.key === "+" || e.key === "=" || e.key === "ArrowUp") ? 1 : -1;
        applyWheel(dir, manual.x, manual.y);
      }
    }
    view.addEventListener("wheel", onWheel as unknown as EventListener, { passive: false });
    root.addEventListener("keydown", onKeydown as unknown as EventListener);

    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (reduce) { root.classList.remove("is-demo"); userActive = true; render(1, .5, .5); }

    let lastTs: number | null = null, elapsed = 0, raf = 0;
    function tick(ts: number) {
      if (lastTs === null) lastTs = ts;
      const dt = Math.min(ts - lastTs, 48);
      lastTs = ts;
      if (!userActive) { elapsed += dt; scheduled(elapsed); }
      raf = requestAnimationFrame(tick);
    }
    render(1, .5, .5);
    raf = requestAnimationFrame(tick);

    return () => {
      cancelAnimationFrame(raf);
      view.removeEventListener("wheel", onWheel as unknown as EventListener);
      root.removeEventListener("keydown", onKeydown as unknown as EventListener);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={`${styles.pvz} is-demo`} ref={rootRef} tabIndex={0}>
        <div className={styles.view} ref={viewRef}>
          <div className={styles.page} ref={pageRef} />
          <div className={styles.dot} ref={dotRef} />
        </div>
        <p className={styles.label} ref={labelRef}>100%</p>
      </div>
    </main>
  );
}