02画面端反転 — 位置の値が画面の端に達すると開く方向の値が反対に変わる方式

<main class="stage">
<div class="cm is-demo" id="cm">
  <div class="cm__field cm__field--alt" id="cmFieldAlt">
    <span class="cm__hint">左上<br>右クリック</span>
  </div>
  <div class="cm__field" id="cmField">
    <span class="cm__hint">端で<br>右クリック</span>
  </div>
  <div class="cm__menu" id="cmMenu" role="menu">
    <button class="cm__item" type="button" role="menuitem">
      <span class="cm__ic"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256"><g fill="currentColor"><path d="M216 40v128h-48V88H88V40Z" opacity=".2"/><path d="M216 32H88a8 8 0 0 0-8 8v40H40a8 8 0 0 0-8 8v128a8 8 0 0 0 8 8h128a8 8 0 0 0 8-8v-40h40a8 8 0 0 0 8-8V40a8 8 0 0 0-8-8m-56 176H48V96h112Zm48-48h-32V88a8 8 0 0 0-8-8H96V48h112Z"/></g></svg></span>
      <span>コピー</span>
    </button>
    <button class="cm__item" type="button" role="menuitem">
      <span class="cm__ic"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256"><g fill="currentColor"><path d="M208 48v168a8 8 0 0 1-8 8H56a8 8 0 0 1-8-8V48a8 8 0 0 1 8-8h40a39.83 39.83 0 0 0-8 24v8h80v-8a39.83 39.83 0 0 0-8-24h40a8 8 0 0 1 8 8" opacity=".2"/><path d="M200 32h-36.26a47.92 47.92 0 0 0-71.48 0H56a16 16 0 0 0-16 16v168a16 16 0 0 0 16 16h144a16 16 0 0 0 16-16V48a16 16 0 0 0-16-16m-72 0a32 32 0 0 1 32 32H96a32 32 0 0 1 32-32m72 184H56V48h26.75A47.9 47.9 0 0 0 80 64v8a8 8 0 0 0 8 8h80a8 8 0 0 0 8-8v-8a47.9 47.9 0 0 0-2.75-16H200Z"/></g></svg></span>
      <span>貼り付け</span>
    </button>
    <button class="cm__item" type="button" role="menuitem">
      <span class="cm__ic"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256"><g fill="currentColor"><path d="M221.66 90.34L192 120l-56-56l29.66-29.66a8 8 0 0 1 11.31 0L221.66 79a8 8 0 0 1 0 11.34" opacity=".2"/><path d="m227.31 73.37l-44.68-44.69a16 16 0 0 0-22.63 0L36.69 152A15.86 15.86 0 0 0 32 163.31V208a16 16 0 0 0 16 16h44.69a15.86 15.86 0 0 0 11.31-4.69L227.31 96a16 16 0 0 0 0-22.63M92.69 208H48v-44.69l88-88L180.69 120ZM192 108.68L147.31 64l24-24L216 84.68Z"/></g></svg></span>
      <span>名前を変更</span>
    </button>
    <button class="cm__item cm__item--danger" type="button" role="menuitem">
      <span class="cm__ic"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256"><g fill="currentColor"><path d="M200 56v152a8 8 0 0 1-8 8H64a8 8 0 0 1-8-8V56Z" opacity=".2"/><path d="M216 48h-40v-8a24 24 0 0 0-24-24h-48a24 24 0 0 0-24 24v8H40a8 8 0 0 0 0 16h8v144a16 16 0 0 0 16 16h128a16 16 0 0 0 16-16V64h8a8 8 0 0 0 0-16M96 40a8 8 0 0 1 8-8h48a8 8 0 0 1 8 8v8H96Zm96 168H64V64h128Zm-80-104v64a8 8 0 0 1-16 0v-64a8 8 0 0 1 16 0m48 0v64a8 8 0 0 1-16 0v-64a8 8 0 0 1 16 0"/></g></svg></span>
      <span>削除</span>
    </button>
  </div>
</div>
</main>

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

// 계산 겹: 메뉴 상자의 오른쪽·아래쪽 끝 좌표 값이 화면 폭·높이 값을 넘어서는지 먼저 계산하고,
// 넘어서면 펼치는 방향(transform-origin)과 앵커 좌표를 반대로 뒤집는다 (flipFor()).
@include stage($stage-yellow);

.cm {
  position: relative;
  width: 100%;
  height: 100%;
}

.cm__field {
  position: absolute;
  right: $sp-6;
  bottom: $sp-6;
  width: 168px;
  height: 108px;
  border-radius: $r-card;
  background: $subject-ink;
  color: $subject-cream;
  display: grid;
  place-items: center;
  text-align: center;
  padding: $sp-3;
  box-sizing: border-box;
  font: 600 13px/1.3 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  user-select: none;
}

.cm__field--alt {
  right: auto;
  left: $sp-4;
  top: $sp-4;
  bottom: auto;
  width: 120px;
  height: 84px;
}

.cm__hint { opacity: .75; font-weight: 500; font-size: 11px; }

.cm__menu {
  position: fixed;
  top: 0;
  left: 0;
  min-width: 172px;
  background: $stage-paper;
  border-radius: $r-sm;
  box-shadow: $shadow-raised;
  padding: $sp-1;
  display: grid;
  gap: $sp-1;
  opacity: 0;
  transform: scale(.94);
  transform-origin: top left;
  pointer-events: none;
  transition: opacity $dur-quick $ease-out, transform $dur-quick $ease-out;
  z-index: 5;

  &.is-open { opacity: 1; transform: scale(1); pointer-events: auto; }
  &.flip-x { transform-origin: top right; }
  &.flip-y { transform-origin: bottom left; }
  &.flip-x.flip-y { transform-origin: bottom right; }
}

.cm__item {
  display: flex;
  align-items: center;
  gap: $sp-2;
  padding: $sp-2 $sp-3;
  border: 0;
  background: none;
  border-radius: $r-xs;
  font: 500 13px/1.2 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: $subject-ink;
  cursor: pointer;
  text-align: left;

  &:hover, &:focus-visible { background: rgba($subject-ink, .08); }
  &--danger { color: $error; }
}

.cm__ic {
  width: 16px;
  height: 16px;
  flex: none;
  color: $subject-blue;

  svg { display: block; width: 100%; height: 100%; }
}
.cm__item--danger .cm__ic { color: $error; }

@media (max-width: 340px) {
  .cm__field { width: 140px; height: 96px; right: $sp-3; bottom: $sp-3; font-size: 11px; }
  .cm__field--alt { width: 104px; height: 76px; left: $sp-2; top: $sp-2; }
  .cm__menu { min-width: 144px; }
  .cm__item { padding: $sp-1 $sp-2; font-size: 12px; }
}

@media (prefers-reduced-motion: reduce) {
  .cm__menu { 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);
}

.cm {
  position: relative;
  width: 100%;
  height: 100%;
}

.cm__field {
  position: absolute;
  right: 24px;
  bottom: 24px;
  width: 168px;
  height: 108px;
  border-radius: 16px;
  background: #17141a;
  color: #fff7e6;
  display: grid;
  place-items: center;
  text-align: center;
  padding: 12px;
  box-sizing: border-box;
  font: 600 13px/1.3 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  user-select: none;
}

.cm__field--alt {
  right: auto;
  left: 16px;
  top: 16px;
  bottom: auto;
  width: 120px;
  height: 84px;
}

.cm__hint {
  opacity: 0.75;
  font-weight: 500;
  font-size: 11px;
}

.cm__menu {
  position: fixed;
  top: 0;
  left: 0;
  min-width: 172px;
  background: #ffffff;
  border-radius: 8px;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  padding: 4px;
  display: grid;
  gap: 4px;
  opacity: 0;
  transform: scale(0.94);
  transform-origin: top left;
  pointer-events: none;
  transition: opacity 220ms ease-out, transform 220ms ease-out;
  z-index: 5;
}
.cm__menu.is-open {
  opacity: 1;
  transform: scale(1);
  pointer-events: auto;
}
.cm__menu.flip-x {
  transform-origin: top right;
}
.cm__menu.flip-y {
  transform-origin: bottom left;
}
.cm__menu.flip-x.flip-y {
  transform-origin: bottom right;
}

.cm__item {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border: 0;
  background: none;
  border-radius: 4px;
  font: 500 13px/1.2 -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  color: #17141a;
  cursor: pointer;
  text-align: left;
}
.cm__item:hover, .cm__item:focus-visible {
  background: rgba(23, 20, 26, 0.08);
}
.cm__item--danger {
  color: #c2361a;
}

.cm__ic {
  width: 16px;
  height: 16px;
  flex: none;
  color: #2f6df6;
}
.cm__ic svg {
  display: block;
  width: 100%;
  height: 100%;
}

.cm__item--danger .cm__ic {
  color: #c2361a;
}

@media (max-width: 340px) {
  .cm__field {
    width: 140px;
    height: 96px;
    right: 12px;
    bottom: 12px;
    font-size: 11px;
  }
  .cm__field--alt {
    width: 104px;
    height: 76px;
    left: 8px;
    top: 8px;
  }
  .cm__menu {
    min-width: 144px;
  }
  .cm__item {
    padding: 4px 8px;
    font-size: 12px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .cm__menu {
    transition: none;
  }
}

(function () {
  var field = document.getElementById('cmField');
  var fieldAlt = document.getElementById('cmFieldAlt');
  var menu = document.getElementById('cmMenu');
  var root = document.getElementById('cm');
  var GAP = 4;

  function flipFor(x, y) {
    var mw = menu.offsetWidth, mh = menu.offsetHeight;
    var vw = document.documentElement.clientWidth, vh = document.documentElement.clientHeight;
    // 계산 겹: 메뉴 상자의 오른쪽·아래쪽 끝(x+mw, y+mh)이 화면 폭·높이 값을 넘어서는지 먼저 재고,
    // 넘어서는 축만 앵커에서 메뉴 크기만큼 반대로 밀어 펼치는 방향을 뒤집는다.
    var flipX = (x + mw) > vw;
    var flipY = (y + mh) > vh;
    var px = flipX ? (x - mw) : x;
    var py = flipY ? (y - mh) : y;
    px = Math.max(GAP, Math.min(px, vw - mw - GAP));
    py = Math.max(GAP, Math.min(py, vh - mh - GAP));
    menu.style.left = px.toFixed(0) + 'px';
    menu.style.top = py.toFixed(0) + 'px';
    menu.classList.toggle('flip-x', flipX);
    menu.classList.toggle('flip-y', flipY);
  }

  function open(x, y) {
    flipFor(x, y);
    menu.classList.add('is-open');
  }
  function close() { menu.classList.remove('is-open'); }

  function wireField(el) {
    el.addEventListener('contextmenu', function (e) {
      e.preventDefault();
      root.classList.remove('is-demo'); stopAutoplay();
      var r = el.getBoundingClientRect();
      open(e.clientX - r.left > r.width / 2 ? r.right - 2 : r.left + 2, e.clientY);
    });
  }
  wireField(field);
  wireField(fieldAlt);
  document.addEventListener('pointerdown', function (e) {
    if (menu.classList.contains('is-open') && !menu.contains(e.target) && e.target !== field && e.target !== fieldAlt) {
      close();
    }
  });
  menu.addEventListener('click', close);

  // 자동 루프: 左上 필드(뒤집힘 없음)와 오른쪽 아래 필드(가로·세로 모두 뒤집힘)를 번갈아 열어
  // 같은 flipFor() 경로가 두 경우 모두 다른 방향으로 뒤집는 것을 보여준다.
  var seq = [
    function () { var r = fieldAlt.getBoundingClientRect(); open(r.left + 8, r.top + 8); },
    close,
    function () { var r = field.getBoundingClientRect(); open(r.right - 8, r.bottom - 8); },
    close
  ];
  var si = 0, autoTimer = null;
  function autoTick() { seq[si % seq.length](); si++; }
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  function stopAutoplay() { if (autoTimer) { clearInterval(autoTimer); autoTimer = null; } }
  if (!reduce) { autoTimer = setInterval(autoTick, 280); autoTick(); }
})();

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

const ICON_COPY = '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256"><g fill="currentColor"><path d="M216 40v128h-48V88H88V40Z" opacity=".2"/><path d="M216 32H88a8 8 0 0 0-8 8v40H40a8 8 0 0 0-8 8v128a8 8 0 0 0 8 8h128a8 8 0 0 0 8-8v-40h40a8 8 0 0 0 8-8V40a8 8 0 0 0-8-8m-56 176H48V96h112Zm48-48h-32V88a8 8 0 0 0-8-8H96V48h112Z"/></g></svg>';
const ICON_PASTE = '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256"><g fill="currentColor"><path d="M208 48v168a8 8 0 0 1-8 8H56a8 8 0 0 1-8-8V48a8 8 0 0 1 8-8h40a39.83 39.83 0 0 0-8 24v8h80v-8a39.83 39.83 0 0 0-8-24h40a8 8 0 0 1 8 8" opacity=".2"/><path d="M200 32h-36.26a47.92 47.92 0 0 0-71.48 0H56a16 16 0 0 0-16 16v168a16 16 0 0 0 16 16h144a16 16 0 0 0 16-16V48a16 16 0 0 0-16-16m-72 0a32 32 0 0 1 32 32H96a32 32 0 0 1 32-32m72 184H56V48h26.75A47.9 47.9 0 0 0 80 64v8a8 8 0 0 0 8 8h80a8 8 0 0 0 8-8v-8a47.9 47.9 0 0 0-2.75-16H200Z"/></g></svg>';
const ICON_RENAME = '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256"><g fill="currentColor"><path d="M221.66 90.34L192 120l-56-56l29.66-29.66a8 8 0 0 1 11.31 0L221.66 79a8 8 0 0 1 0 11.34" opacity=".2"/><path d="m227.31 73.37l-44.68-44.69a16 16 0 0 0-22.63 0L36.69 152A15.86 15.86 0 0 0 32 163.31V208a16 16 0 0 0 16 16h44.69a15.86 15.86 0 0 0 11.31-4.69L227.31 96a16 16 0 0 0 0-22.63M92.69 208H48v-44.69l88-88L180.69 120ZM192 108.68L147.31 64l24-24L216 84.68Z"/></g></svg>';
const ICON_TRASH = '<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256"><g fill="currentColor"><path d="M200 56v152a8 8 0 0 1-8 8H64a8 8 0 0 1-8-8V56Z" opacity=".2"/><path d="M216 48h-40v-8a24 24 0 0 0-24-24h-48a24 24 0 0 0-24 24v8H40a8 8 0 0 0 0 16h8v144a16 16 0 0 0 16 16h128a16 16 0 0 0 16-16V64h8a8 8 0 0 0 0-16M96 40a8 8 0 0 1 8-8h48a8 8 0 0 1 8 8v8H96Zm96 168H64V64h128Zm-80-104v64a8 8 0 0 1-16 0v-64a8 8 0 0 1 16 0m48 0v64a8 8 0 0 1-16 0v-64a8 8 0 0 1 16 0"/></g></svg>';

export type ViewportEdgeFlipProps = {
  color?: string;
};

export default function ViewportEdgeFlip({
  color = "#2f6df6",
}: ViewportEdgeFlipProps) {
  const rootRef = useRef<HTMLDivElement | null>(null);

  useEffect(() => {
    const root = rootRef.current;
    if (!root) return;
    const field = root.querySelector<HTMLDivElement>(`.${styles.field}`);
    const fieldAlt = root.querySelector<HTMLDivElement>(`.${styles.fieldAlt}`);
    const menu = root.querySelector<HTMLDivElement>(`.${styles.menu}`);
    if (!field || !fieldAlt || !menu) return;
    const GAP = 4;

    // 계산 겹: 메뉴 상자의 오른쪽·아래쪽 끝이 뷰포트를 넘는지 먼저 재고, 넘는 축만 앵커에서
    // 메뉴 크기만큼 반대로 밀어 펼치는 방향을 뒤집는다.
    function flipFor(x: number, y: number) {
      const mw = menu!.offsetWidth, mh = menu!.offsetHeight;
      const vw = document.documentElement.clientWidth, vh = document.documentElement.clientHeight;
      const flipX = (x + mw) > vw;
      const flipY = (y + mh) > vh;
      let px = flipX ? (x - mw) : x;
      let py = flipY ? (y - mh) : y;
      px = Math.max(GAP, Math.min(px, vw - mw - GAP));
      py = Math.max(GAP, Math.min(py, vh - mh - GAP));
      menu!.style.left = px.toFixed(0) + "px";
      menu!.style.top = py.toFixed(0) + "px";
      menu!.classList.toggle(styles.flipX, flipX);
      menu!.classList.toggle(styles.flipY, flipY);
    }
    function open(x: number, y: number) { flipFor(x, y); menu!.classList.add(styles.open); }
    function close() { menu!.classList.remove(styles.open); }

    function wireField(el: HTMLDivElement) {
      const handler = (e: MouseEvent) => {
        e.preventDefault();
        stopAutoplay();
        const r = el.getBoundingClientRect();
        open(e.clientX - r.left > r.width / 2 ? r.right - 2 : r.left + 2, e.clientY);
      };
      el.addEventListener("contextmenu", handler);
      return () => el.removeEventListener("contextmenu", handler);
    }
    const un1 = wireField(field);
    const un2 = wireField(fieldAlt);
    function onDocDown(e: PointerEvent) {
      if (menu!.classList.contains(styles.open) && !menu!.contains(e.target as Node) && e.target !== field && e.target !== fieldAlt) close();
    }
    document.addEventListener("pointerdown", onDocDown);
    menu.addEventListener("click", close);

    const seq = [
      () => { const r = fieldAlt.getBoundingClientRect(); open(r.left + 8, r.top + 8); },
      close,
      () => { const r = field.getBoundingClientRect(); open(r.right - 8, r.bottom - 8); },
      close,
    ];
    let si = 0;
    let autoTimer: number | null = null;
    function autoTick() { seq[si % seq.length](); si++; }
    function stopAutoplay() { if (autoTimer !== null) { window.clearInterval(autoTimer); autoTimer = null; } }
    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    if (!reduce) { autoTimer = window.setInterval(autoTick, 280); autoTick(); }

    return () => {
      stopAutoplay();
      un1(); un2();
      document.removeEventListener("pointerdown", onDocDown);
    };
  }, []);

  return (
    <div ref={rootRef} className={styles.stage}>
      <div className={styles.cm}>
        <div className={`${styles.field} ${styles.fieldAlt}`}>
          <span className={styles.hint}>왼쪽 위<br />우클릭</span>
        </div>
        <div className={styles.field}>
          <span className={styles.hint}>가장자리에서<br />우클릭</span>
        </div>
        <div className={styles.menu} role="menu">
          <button type="button" className={styles.item} role="menuitem">
            <span className={styles.ic} style={{ color }} dangerouslySetInnerHTML={{ __html: ICON_COPY }} />
            <span>복사</span>
          </button>
          <button type="button" className={styles.item} role="menuitem">
            <span className={styles.ic} style={{ color }} dangerouslySetInnerHTML={{ __html: ICON_PASTE }} />
            <span>붙여넣기</span>
          </button>
          <button type="button" className={styles.item} role="menuitem">
            <span className={styles.ic} style={{ color }} dangerouslySetInnerHTML={{ __html: ICON_RENAME }} />
            <span>이름 바꾸기</span>
          </button>
          <button type="button" className={`${styles.item} ${styles.danger}`} role="menuitem">
            <span className={styles.ic} dangerouslySetInnerHTML={{ __html: ICON_TRASH }} />
            <span>삭제</span>
          </button>
        </div>
      </div>
    </div>
  );
}