04Input zoom lock — a text field that focuses without zooming the whole screen

<main class="stage">
<div class="wrap is-demo" id="wrap">
  <div class="row">
    <label class="field">
      <span class="fieldLabel">Small text</span>
      <input class="input is-small" id="inputSmall" type="text" value="query">
    </label>
    <label class="field">
      <span class="fieldLabel">Locked text</span>
      <input class="input is-lock" id="inputLock" type="text" value="query">
    </label>
  </div>
  <div class="foot">
    <span class="modeLabel" id="modeLabel">Zoom lock on</span>
    <button class="simToggle" id="simToggle" type="button" aria-pressed="false">Simulate fallback</button>
  </div>
</div>
</main>

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

// 계산 겹은 index.html 의 zoomScaleFor() 에 있다 — 실제 computed font-size 에서 배율을 구하고
// getBoundingClientRect() 중심으로 transform-origin 을 놓는다. 여기는 두 입력판의 바탕 크기와
// 전환 곡선만 맡는다.
@include stage($stage-orange);

.wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-4;
}

.row {
  display: flex;
  gap: $sp-5;
}

.field {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: $sp-2;
}

.fieldLabel {
  color: $subject-ink;
  font-size: 10px;
  font-weight: 700;
}

.input {
  width: 96px;
  padding: $sp-2 $sp-3;
  border: none;
  border-radius: $r-control;
  background: $subject-cream;
  color: $subject-ink;
  text-align: center;
  transition: transform $dur-base $ease-spring;
  transform: scale(1);

  &.is-small { font-size: 12px; }
  &.is-lock { font-size: 16px; }

  &:focus-visible {
    outline: 2px solid $subject-blue-light;
    outline-offset: 2px;
  }
}

// 시뮬레이션: 표준 잠금 기법을 강제로 무시하고 잠금판도 확대되게 한다(실제 UA 감지가 아니라
// 값을 억지로 12px 로 되돌리는 CSS 오버라이드) — 폴백 없는 환경을 그대로 보여준다
.force-fallback .input.is-lock { font-size: 12px; }

.foot {
  display: flex;
  align-items: center;
  gap: $sp-2;
}

.modeLabel {
  color: $subject-ink;
  font-size: 10px;
  font-weight: 700;
  background: rgba($stage-paper, .6);
  padding: $sp-1 $sp-2;
  border-radius: $r-xs;
}

.simToggle {
  appearance: none;
  border: none;
  border-radius: $r-pill;
  background: rgba($subject-ink, .82);
  color: $subject-cream;
  padding: $sp-1 $sp-3;
  font-size: 10px;
  font-weight: 600;
  cursor: pointer;
  transition: transform $dur-instant $ease-out;

  &:active { transform: scale(.96); }
  &[aria-pressed="true"] { background: $subject-orange-deep; }
  &:focus-visible { outline: 2px solid $subject-blue-light; outline-offset: 2px; }
}

@media (max-width: 340px) {
  .row { gap: $sp-3; }
  .input { width: 80px; }
}

@media (prefers-reduced-motion: reduce) {
  .input { transition: none; }
  .simToggle { transition: none; }
}

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);
}

.wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
}

.row {
  display: flex;
  gap: 20px;
}

.field {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
}

.fieldLabel {
  color: #17141a;
  font-size: 10px;
  font-weight: 700;
}

.input {
  width: 96px;
  padding: 8px 12px;
  border: none;
  border-radius: 12px;
  background: #fff7e6;
  color: #17141a;
  text-align: center;
  transition: transform 300ms cubic-bezier(0.2, 0.8, 0.2, 1);
  transform: scale(1);
}
.input.is-small {
  font-size: 12px;
}
.input.is-lock {
  font-size: 16px;
}
.input:focus-visible {
  outline: 2px solid #5b8cf8;
  outline-offset: 2px;
}

.force-fallback .input.is-lock {
  font-size: 12px;
}

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

.modeLabel {
  color: #17141a;
  font-size: 10px;
  font-weight: 700;
  background: rgba(255, 255, 255, 0.6);
  padding: 4px 8px;
  border-radius: 4px;
}

.simToggle {
  appearance: none;
  border: none;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.82);
  color: #fff7e6;
  padding: 4px 12px;
  font-size: 10px;
  font-weight: 600;
  cursor: pointer;
  transition: transform 140ms ease-out;
}
.simToggle:active {
  transform: scale(0.96);
}
.simToggle[aria-pressed=true] {
  background: #c93000;
}
.simToggle:focus-visible {
  outline: 2px solid #5b8cf8;
  outline-offset: 2px;
}

@media (max-width: 340px) {
  .row {
    gap: 12px;
  }
  .input {
    width: 80px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .input {
    transition: none;
  }
  .simToggle {
    transition: none;
  }
}

(function () {
  var LOCK_FONT_PX = 16; // 이 값 이상이면 초점 확대가 걸리지 않는다 — 잠금판의 목표 크기
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  var wrap = document.getElementById('wrap');
  var inputSmall = document.getElementById('inputSmall');
  var inputLock = document.getElementById('inputLock');
  var simToggle = document.getElementById('simToggle');
  var modeLabel = document.getElementById('modeLabel');
  var isDemo = true;

  function human() { if (isDemo) { wrap.classList.remove('is-demo'); isDemo = false; } }

  // 실제 요소 크기에서 확대 배율을 구한다 — 하드코딩 배율이 아니라 현재 폰트 크기 기준
  function zoomScaleFor(el) {
    var css = getComputedStyle(el);
    var current = parseFloat(css.fontSize) || LOCK_FONT_PX;
    return Math.max(1, LOCK_FONT_PX / current);
  }

  function applyFocusZoom(el, on) {
    if (on) {
      var rect = el.getBoundingClientRect();
      var originX = rect.width / 2;
      var originY = rect.height / 2;
      el.style.transformOrigin = originX + 'px ' + originY + 'px';
      el.style.transform = 'scale(' + zoomScaleFor(el) + ')';
    } else {
      el.style.transform = 'scale(1)';
    }
  }

  inputSmall.addEventListener('focus', function () { human(); applyFocusZoom(inputSmall, true); });
  inputSmall.addEventListener('blur', function () { applyFocusZoom(inputSmall, false); });

  // 잠금판: 실제 font-size 가 이미 LOCK_FONT_PX 이므로 zoomScaleFor 가 1을 반환 — 확대가 걸리지 않는다
  inputLock.addEventListener('focus', function () { human(); applyFocusZoom(inputLock, true); });
  inputLock.addEventListener('blur', function () { applyFocusZoom(inputLock, false); });

  var simOn = false;
  function setSim(on) {
    simOn = on;
    wrap.classList.toggle('force-fallback', on);
    simToggle.setAttribute('aria-pressed', String(on));
    modeLabel.textContent = on ? 'Zoom lock off' : 'Zoom lock on';
  }
  simToggle.addEventListener('click', function () { human(); setSim(!simOn); });

  var last = 0;
  var STEP_MS = 680;
  var phase = 0;
  function loop(ts) {
    if (!last) last = ts;
    if (isDemo && !reduce && ts - last >= STEP_MS) {
      last = ts;
      phase = (phase + 1) % 4;
      if (phase === 1) { applyFocusZoom(inputSmall, true); applyFocusZoom(inputLock, true); }
      else if (phase === 3) { applyFocusZoom(inputSmall, false); applyFocusZoom(inputLock, false); }
      else if (phase === 0) { setSim(!simOn); }
    }
    requestAnimationFrame(loop);
  }
  requestAnimationFrame(loop);
})();

// InputFocusZoomLock — vanilla 판(run/375/demo/04-compat-input-focus-zoom-lock/index.html) 의 React 포트.
// 작은 글자판은 초점을 얻으면 확대되고, 잠금 글자판은 font-size 16px 기법 때문에 배율이 1로 고정된다.
import { useEffect, useRef } from "react";
import styles from "./InputFocusZoomLock.module.scss";

type Box<T> = { current: T };

const LOCK_FONT_PX = 16; // 이 값 이상이면 초점 확대가 걸리지 않는다 — 잠금판의 목표 크기
const STEP_MS = 680;

export default function InputFocusZoomLock() {
  const rootRef = useRef(null) as unknown as Box<HTMLDivElement>;
  const inputSmallRef = useRef(null) as unknown as Box<HTMLInputElement>;
  const inputLockRef = useRef(null) as unknown as Box<HTMLInputElement>;
  const simToggleRef = useRef(null) as unknown as Box<HTMLButtonElement>;
  const modeLabelRef = useRef(null) as unknown as Box<HTMLSpanElement>;
  const rafRef = useRef(0) as unknown as Box<number>;

  useEffect(() => {
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    const wrap = rootRef.current;
    const inputSmall = inputSmallRef.current;
    const inputLock = inputLockRef.current;
    const simToggle = simToggleRef.current;
    const modeLabel = modeLabelRef.current;
    if (!wrap || !inputSmall || !inputLock || !simToggle || !modeLabel) return;

    let isDemo = true;

    function human() { if (isDemo) { wrap!.classList.remove(styles.isDemo); isDemo = false; } }

    // 실제 요소 크기에서 확대 배율을 구한다 — 하드코딩 배율이 아니라 현재 폰트 크기 기준
    function zoomScaleFor(el: HTMLInputElement) {
      const css = window.getComputedStyle(el);
      const current = parseFloat(css.fontSize) || LOCK_FONT_PX;
      return Math.max(1, LOCK_FONT_PX / current);
    }

    function applyFocusZoom(el: HTMLInputElement, on: boolean) {
      if (on) {
        const rect = el.getBoundingClientRect();
        const originX = rect.width / 2;
        const originY = rect.height / 2;
        el.style.transformOrigin = originX + "px " + originY + "px";
        el.style.transform = "scale(" + zoomScaleFor(el) + ")";
      } else {
        el.style.transform = "scale(1)";
      }
    }

    function onSmallFocus() { human(); applyFocusZoom(inputSmall!, true); }
    function onSmallBlur() { applyFocusZoom(inputSmall!, false); }
    inputSmall.addEventListener("focus", onSmallFocus);
    inputSmall.addEventListener("blur", onSmallBlur);

    // 잠금판: 실제 font-size 가 이미 LOCK_FONT_PX 이므로 zoomScaleFor 가 1을 반환 — 확대가 걸리지 않는다
    function onLockFocus() { human(); applyFocusZoom(inputLock!, true); }
    function onLockBlur() { applyFocusZoom(inputLock!, false); }
    inputLock.addEventListener("focus", onLockFocus);
    inputLock.addEventListener("blur", onLockBlur);

    let simOn = false;
    function setSim(on: boolean) {
      simOn = on;
      wrap!.classList.toggle(styles.forceFallback, on);
      simToggle!.setAttribute("aria-pressed", String(on));
      modeLabel!.textContent = on ? "확대 잠금 꺼짐" : "확대 잠금 켜짐";
    }
    function onSimClick() { human(); setSim(!simOn); }
    simToggle.addEventListener("click", onSimClick);

    let last = 0;
    let phase = 0;
    function loop(ts: number) {
      if (!last) last = ts;
      if (isDemo && !reduce && ts - last >= STEP_MS) {
        last = ts;
        phase = (phase + 1) % 4;
        if (phase === 1) { applyFocusZoom(inputSmall!, true); applyFocusZoom(inputLock!, true); }
        else if (phase === 3) { applyFocusZoom(inputSmall!, false); applyFocusZoom(inputLock!, false); }
        else if (phase === 0) { setSim(!simOn); }
      }
      rafRef.current = requestAnimationFrame(loop);
    }
    rafRef.current = requestAnimationFrame(loop);

    return () => {
      inputSmall!.removeEventListener("focus", onSmallFocus);
      inputSmall!.removeEventListener("blur", onSmallBlur);
      inputLock!.removeEventListener("focus", onLockFocus);
      inputLock!.removeEventListener("blur", onLockBlur);
      simToggle!.removeEventListener("click", onSimClick);
      cancelAnimationFrame(rafRef.current);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={styles.wrap + " " + styles.isDemo} ref={rootRef}>
        <div className={styles.row}>
          <label className={styles.field}>
            <span className={styles.fieldLabel}>작은 글자판</span>
            <input className={styles.input + " " + styles.isSmall} ref={inputSmallRef} type="text" defaultValue="검색어" />
          </label>
          <label className={styles.field}>
            <span className={styles.fieldLabel}>잠금 글자판</span>
            <input className={styles.input + " " + styles.isLock} ref={inputLockRef} type="text" defaultValue="검색어" />
          </label>
        </div>
        <div className={styles.foot}>
          <span className={styles.modeLabel} ref={modeLabelRef}>확대 잠금 켜짐</span>
          <button className={styles.simToggle} ref={simToggleRef} type="button" aria-pressed="false">폴백 흉내내기</button>
        </div>
      </div>
    </main>
  );
}