05下書きとインクの2レイヤー

<main class="stage">
<div class="li is-demo" id="li">
  <div class="li__card">
    <div class="li__layers">
      <div class="li__row">
        <button type="button" class="li__layer" id="sketchBtn" aria-pressed="false"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256" fill="currentColor" class="li__ico" aria-hidden="true"><path d="M224,128a96,96,0,1,1-96-96A96,96,0,0,1,224,128Z" opacity="0.2"/><path d="M96.26,37A8,8,0,0,1,102,27.29a104.11,104.11,0,0,1,52,0,8,8,0,0,1-2,15.75,8.15,8.15,0,0,1-2-.26,88.09,88.09,0,0,0-44,0A8,8,0,0,1,96.26,37ZM53.79,55.14a104,104,0,0,0-26,45,8,8,0,1,0,15.42,4.26,87.91,87.91,0,0,1,22-38.08A8,8,0,0,0,53.79,55.14ZM43.21,151.55a8,8,0,1,0-15.42,4.28,104,104,0,0,0,26,45,8,8,0,1,0,11.41-11.21A88.14,88.14,0,0,1,43.21,151.55ZM150,213.22a88,88,0,0,1-44,0,8,8,0,1,0-4,15.49,104.11,104.11,0,0,0,52,0,8,8,0,0,0-4-15.49ZM222.65,146a8,8,0,0,0-9.85,5.57,87.88,87.88,0,0,1-22,38.09,8,8,0,1,0,11.42,11.21,104.05,104.05,0,0,0,26-45A8,8,0,0,0,222.65,146Zm-9.86-41.54a8,8,0,0,0,15.42-4.28,104,104,0,0,0-26-45,8,8,0,1,0-11.41,11.21A88.14,88.14,0,0,1,212.79,104.45Z"/></svg><span>下書き</span></button>
        <span class="li__slot">
          <input class="li__range" id="fade" type="range" min="0" max="100" value="34" aria-label="下書きの不透明度">
          <span class="li__fake" aria-hidden="true"><span class="li__fakeFill"></span><span class="li__fakeKnob"></span></span>
        </span>
      </div>
      <div class="li__row">
        <button type="button" class="li__layer" id="inkBtn" aria-pressed="true"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256" fill="currentColor" class="li__ico" aria-hidden="true"><path d="M221.66,90.34,192,120,136,64l29.66-29.66a8,8,0,0,1,11.31,0L221.66,79A8,8,0,0,1,221.66,90.34Z" opacity="0.2"/><path d="M227.32,73.37,182.63,28.69a16,16,0,0,0-22.63,0L36.69,152A15.86,15.86,0,0,0,32,163.31V208a16,16,0,0,0,16,16H92.69A15.86,15.86,0,0,0,104,219.31l83.67-83.66,3.48,13.9-36.8,36.79a8,8,0,0,0,11.31,11.32l40-40a8,8,0,0,0,2.11-7.6l-6.9-27.61L227.32,96A16,16,0,0,0,227.32,73.37ZM48,208V179.31L76.69,208Zm48-3.31L51.31,160,136,75.31,180.69,120Zm96-96L147.32,64l24-24L216,84.69Z"/></svg><span>インク</span></button>
        <button type="button" class="li__merge" id="mergeBtn"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256" fill="currentColor" class="li__ico" aria-hidden="true"><path d="M224,80l-96,56L32,80l96-56Z" opacity="0.2"/><path d="M230.91,172A8,8,0,0,1,228,182.91l-96,56a8,8,0,0,1-8.06,0l-96-56A8,8,0,0,1,36,169.09l92,53.65,92-53.65A8,8,0,0,1,230.91,172ZM220,121.09l-92,53.65L36,121.09A8,8,0,0,0,28,134.91l96,56a8,8,0,0,0,8.06,0l96-56A8,8,0,1,0,220,121.09ZM24,80a8,8,0,0,1,4-6.91l96-56a8,8,0,0,1,8.06,0l96,56a8,8,0,0,1,0,13.82l-96,56a8,8,0,0,1-8.06,0l-96-56A8,8,0,0,1,24,80Zm23.88,0L128,126.74,208.12,80,128,33.26Z"/></svg><span>2枚を重ねる</span></button>
      </div>
    </div>
    <div class="li__board" id="board">
      <canvas class="li__sketch" id="sketch" role="img" aria-label="下書きレイヤー"></canvas>
      <canvas class="li__ink" id="ink" role="img" aria-label="インクレイヤー"></canvas>
      <svg class="li__ghost" viewBox="0 0 300 88" preserveAspectRatio="none" aria-hidden="true">
        <g class="li__guide">
          <path class="li__guideCurve" d="M40,70 C60,18 110,14 130,46 C150,78 190,80 210,54 C226,33 250,26 268,36"/>
          <circle class="li__guideRing" cx="130" cy="46" r="26"/>
          <line class="li__guideBase" x1="36" y1="78" x2="264" y2="78"/>
        </g>
        <path class="li__trace" pathLength="100" d="M40,70 C60,18 110,14 130,46 C150,78 190,80 210,54 C226,33 250,26 268,36"/>
        <line class="li__finish" pathLength="100" x1="36" y1="78" x2="264" y2="78"/>
      </svg>
    </div>
  </div>
</div>
</main>

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

// 밑그림·잉크 2레이어 — 실제 동작은 canvas 두 장이다. 밑그림 판은 globalAlpha 를 낮춘 안내선을 미리 깔고,
// 슬라이더는 그 판의 CSS opacity 만 바꾸며, 「두 장 합치기」는 drawImage 로 밑그림을 잉크 판에 눌러 담는다.
// 격자 미리보기(.is-demo)는 두 판을 감추고 같은 그림을 SVG 두 겹(연한 안내선 · 잉크 획)으로 재현한다 —
// demo.py 는 CSS 애니메이션 시계로 프레임을 뽑으므로 canvas 로 그린 그림은 24장이 전부 같다.

$duration: $dur-loop;
$easing: $ease-out;
$color: $subject-ink;

@include stage($stage-ink);

.li { display: flex; justify-content: center; width: 100%; }
.li__card {
  width: min(100%, 340px); background: $stage-paper; border-radius: $r-card;
  box-shadow: $shadow-raised; overflow: hidden;
}
.li__layers {
  display: flex; flex-direction: column; gap: $sp-1;
  background: $subject-ink; padding: $sp-2 $sp-3;
}
.li__row { display: flex; align-items: center; gap: $sp-2; }
.li__layer, .li__merge {
  display: flex; align-items: center; gap: $sp-1; cursor: pointer; flex: 0 0 auto;
  border: 1px solid rgba(255, 255, 255, .34); background: transparent; color: $stage-paper;
  border-radius: $r-pill; font-family: inherit; font-weight: 700;
  font-size: clamp(9px, 2.4vw, 10px); padding: $sp-1 $sp-2; line-height: 1.3;
}
.li__layer[aria-pressed="true"] { background: $subject-blue; border-color: $subject-blue; }
.li__layer:focus-visible, .li__merge:focus-visible { outline: 3px solid $subject-blue; outline-offset: 2px; }
.li__ico { width: 14px; height: 14px; flex: 0 0 auto; }

.li__slot { position: relative; display: flex; align-items: center; flex: 1 1 auto; min-width: 0; }
.li__range { width: 100%; height: 12px; margin: 0; cursor: pointer; accent-color: $subject-blue; }
.li__range:focus-visible { outline: 3px solid $subject-blue; outline-offset: 2px; }
// 미리보기용 가짜 슬라이더 — 진짜 range 는 JS 없이 못 움직이므로 .is-demo 동안만 자리를 바꿔 보여 준다
.li__fake {
  display: none; position: absolute; left: 0; right: 0; top: 50%; height: 4px;
  transform: translateY(-50%); border-radius: $r-pill; background: rgba(255, 255, 255, .28);
}
.li__fakeFill {
  position: absolute; inset: 0; border-radius: $r-pill; background: $subject-blue;
  // 채움 막대는 시작 변에서 자란다 — 규칙 8 이 허용하는 비중심 origin
  transform-origin: left center; transform: scaleX(.34);
}
.li__fakeKnob {
  position: absolute; top: 0; bottom: 0; left: 0; width: 100%;
  // translateX 의 %는 자기 폭 기준이라, 손잡이를 트랙 폭의 %로 옮기려면 감싼 요소가 트랙과 같은 폭이어야 한다
  transform: translateX(34%);
}
.li__fakeKnob::after {
  content: ""; position: absolute; left: -4px; top: -2px; width: 8px; height: 8px;
  border-radius: 50%; background: $stage-paper;
}

.li__board { position: relative; background: $subject-cream; aspect-ratio: 300 / 88; touch-action: none; }
.li__sketch, .li__ink, .li__ghost { position: absolute; inset: 0; width: 100%; height: 100%; }
.li__sketch { opacity: .34; }        // 슬라이더가 바꾸는 값 — 밑그림 판만 옅어진다
.li__ghost { display: none; fill: none; }
.li__guide { opacity: .34; }         // 미리보기의 밑그림 겹 — 진짜 판의 opacity 와 같은 값에서 시작한다
.li__guideCurve { stroke: rgba(23, 20, 26, .55); stroke-width: 5; stroke-linecap: round; }
.li__guideRing { stroke: rgba(23, 20, 26, .55); stroke-width: 3; stroke-dasharray: 6 5; }
.li__guideBase { stroke: rgba(23, 20, 26, .55); stroke-width: 3; stroke-dasharray: 6 5; }
.li__trace {
  stroke: $color; stroke-width: 3.5; stroke-linecap: round; stroke-linejoin: round;
  stroke-dasharray: 100; stroke-dashoffset: 100.5;   // 100 이면 round 뚜껑이 길이 0에서도 점으로 찍힌다 — 반 밖으로 밀어 둔다
}
.li__finish {
  stroke: $color; stroke-width: 9; stroke-linecap: round;
  stroke-dasharray: 100; stroke-dashoffset: 100.5;
}

// ── 미리보기 루프 (2s)
//    0~8% 밑그림이 연하게 깔려 있고 · 8~44% 잉크가 그 위를 따라 그어진다
//    46~50% 마지막 굵은 마무리 획을 빠르게 그어 poster 가 이 장이 되게 한다
//    54~68% 밑그림 겹의 opacity 가 여러 프레임에 걸쳐 0.34 → 0 으로 내려가고 슬라이더 손잡이도 왼쪽으로 간다
//    66~88% 마무리 획 → 잉크 획 순으로 되감기고 밑그림이 돌아와 0% 와 같은 상태가 된다
.li.is-demo .li__sketch, .li.is-demo .li__ink { visibility: hidden; }
.li.is-demo .li__ghost { display: block; }
.li.is-demo .li__range { visibility: hidden; }   // display:none 은 자리까지 없앤다 — 칸은 그대로 두고 감춘다
.li.is-demo .li__fake { display: block; }

.li.is-demo .li__trace {
  animation-name: liTrace;
  animation-duration: $duration;
  animation-timing-function: linear;   // 펜이 일정한 속도로 밑그림을 따라간다
  animation-iteration-count: infinite;
}
@keyframes liTrace {
  0%, 8% { stroke-dashoffset: 100.5; }
  44%, 72% { stroke-dashoffset: 0; }
  88%, 100% { stroke-dashoffset: 100.5; }
}
.li.is-demo .li__finish {
  animation-name: liFinish;
  animation-duration: $duration;
  animation-timing-function: linear;
  animation-iteration-count: infinite;
}
@keyframes liFinish {
  0%, 46% { stroke-dashoffset: 100.5; }
  50%, 66% { stroke-dashoffset: 0; }
  80%, 100% { stroke-dashoffset: 100.5; }
}

// 밑그림 겹은 여러 프레임에 걸쳐 옅어진다 — 한 프레임에 사라지면 그 장이 poster 로 뽑힌다
.li.is-demo .li__guide {
  animation-name: liFade;
  animation-duration: $duration;
  animation-timing-function: $easing;
  animation-iteration-count: infinite;
}
@keyframes liFade {
  0%, 54% { opacity: .34; }
  68%, 74% { opacity: 0; }
  88%, 100% { opacity: .34; }
}
.li.is-demo .li__fakeKnob {
  animation-name: liKnob;
  animation-duration: $duration;
  animation-timing-function: $easing;
  animation-iteration-count: infinite;
}
@keyframes liKnob {
  0%, 54% { transform: translateX(34%); }
  68%, 74% { transform: translateX(0); }
  88%, 100% { transform: translateX(34%); }
}
.li.is-demo .li__fakeFill {
  animation-name: liFill;
  animation-duration: $duration;
  animation-timing-function: $easing;
  animation-iteration-count: infinite;
}
@keyframes liFill {
  0%, 54% { transform: scaleX(.34); }
  68%, 74% { transform: scaleX(0); }
  88%, 100% { transform: scaleX(.34); }
}

@media (max-width: 340px) {
  .li__layers { padding: $sp-1 $sp-2; }
  .li__row { gap: $sp-1; }
}

@media (prefers-reduced-motion: reduce) {
  .li.is-demo .li__trace,
  .li.is-demo .li__finish,
  .li.is-demo .li__guide,
  .li.is-demo .li__fakeKnob,
  .li.is-demo .li__fakeFill { animation: none !important; }
  // 움직임 없이 잉크만 남은 최종 상태로 세운다
  .li.is-demo .li__trace,
  .li.is-demo .li__finish { stroke-dashoffset: 0 !important; }
  .li.is-demo .li__guide { opacity: 0 !important; }
  .li.is-demo .li__fakeKnob { transform: translateX(0) !important; }
  .li.is-demo .li__fakeFill { transform: scaleX(0) !important; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.li {
  display: flex;
  justify-content: center;
  width: 100%;
}

.li__card {
  width: min(100%, 340px);
  background: #ffffff;
  border-radius: 16px;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  overflow: hidden;
}

.li__layers {
  display: flex;
  flex-direction: column;
  gap: 4px;
  background: #17141a;
  padding: 8px 12px;
}

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

.li__layer, .li__merge {
  display: flex;
  align-items: center;
  gap: 4px;
  cursor: pointer;
  flex: 0 0 auto;
  border: 1px solid rgba(255, 255, 255, 0.34);
  background: transparent;
  color: #ffffff;
  border-radius: 999px;
  font-family: inherit;
  font-weight: 700;
  font-size: clamp(9px, 2.4vw, 10px);
  padding: 4px 8px;
  line-height: 1.3;
}

.li__layer[aria-pressed=true] {
  background: #2f6df6;
  border-color: #2f6df6;
}

.li__layer:focus-visible, .li__merge:focus-visible {
  outline: 3px solid #2f6df6;
  outline-offset: 2px;
}

.li__ico {
  width: 14px;
  height: 14px;
  flex: 0 0 auto;
}

.li__slot {
  position: relative;
  display: flex;
  align-items: center;
  flex: 1 1 auto;
  min-width: 0;
}

.li__range {
  width: 100%;
  height: 12px;
  margin: 0;
  cursor: pointer;
  accent-color: #2f6df6;
}

.li__range:focus-visible {
  outline: 3px solid #2f6df6;
  outline-offset: 2px;
}

.li__fake {
  display: none;
  position: absolute;
  left: 0;
  right: 0;
  top: 50%;
  height: 4px;
  transform: translateY(-50%);
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.28);
}

.li__fakeFill {
  position: absolute;
  inset: 0;
  border-radius: 999px;
  background: #2f6df6;
  transform-origin: left center;
  transform: scaleX(0.34);
}

.li__fakeKnob {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  width: 100%;
  transform: translateX(34%);
}

.li__fakeKnob::after {
  content: "";
  position: absolute;
  left: -4px;
  top: -2px;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #ffffff;
}

.li__board {
  position: relative;
  background: #fff7e6;
  aspect-ratio: 300/88;
  touch-action: none;
}

.li__sketch, .li__ink, .li__ghost {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}

.li__sketch {
  opacity: 0.34;
}

.li__ghost {
  display: none;
  fill: none;
}

.li__guide {
  opacity: 0.34;
}

.li__guideCurve {
  stroke: rgba(23, 20, 26, 0.55);
  stroke-width: 5;
  stroke-linecap: round;
}

.li__guideRing {
  stroke: rgba(23, 20, 26, 0.55);
  stroke-width: 3;
  stroke-dasharray: 6 5;
}

.li__guideBase {
  stroke: rgba(23, 20, 26, 0.55);
  stroke-width: 3;
  stroke-dasharray: 6 5;
}

.li__trace {
  stroke: #17141a;
  stroke-width: 3.5;
  stroke-linecap: round;
  stroke-linejoin: round;
  stroke-dasharray: 100;
  stroke-dashoffset: 100.5;
}

.li__finish {
  stroke: #17141a;
  stroke-width: 9;
  stroke-linecap: round;
  stroke-dasharray: 100;
  stroke-dashoffset: 100.5;
}

.li.is-demo .li__sketch, .li.is-demo .li__ink {
  visibility: hidden;
}

.li.is-demo .li__ghost {
  display: block;
}

.li.is-demo .li__range {
  visibility: hidden;
}

.li.is-demo .li__fake {
  display: block;
}

.li.is-demo .li__trace {
  animation-name: liTrace;
  animation-duration: 2s;
  animation-timing-function: linear;
  animation-iteration-count: infinite;
}

@keyframes liTrace {
  0%, 8% {
    stroke-dashoffset: 100.5;
  }
  44%, 72% {
    stroke-dashoffset: 0;
  }
  88%, 100% {
    stroke-dashoffset: 100.5;
  }
}
.li.is-demo .li__finish {
  animation-name: liFinish;
  animation-duration: 2s;
  animation-timing-function: linear;
  animation-iteration-count: infinite;
}

@keyframes liFinish {
  0%, 46% {
    stroke-dashoffset: 100.5;
  }
  50%, 66% {
    stroke-dashoffset: 0;
  }
  80%, 100% {
    stroke-dashoffset: 100.5;
  }
}
.li.is-demo .li__guide {
  animation-name: liFade;
  animation-duration: 2s;
  animation-timing-function: ease-out;
  animation-iteration-count: infinite;
}

@keyframes liFade {
  0%, 54% {
    opacity: 0.34;
  }
  68%, 74% {
    opacity: 0;
  }
  88%, 100% {
    opacity: 0.34;
  }
}
.li.is-demo .li__fakeKnob {
  animation-name: liKnob;
  animation-duration: 2s;
  animation-timing-function: ease-out;
  animation-iteration-count: infinite;
}

@keyframes liKnob {
  0%, 54% {
    transform: translateX(34%);
  }
  68%, 74% {
    transform: translateX(0);
  }
  88%, 100% {
    transform: translateX(34%);
  }
}
.li.is-demo .li__fakeFill {
  animation-name: liFill;
  animation-duration: 2s;
  animation-timing-function: ease-out;
  animation-iteration-count: infinite;
}

@keyframes liFill {
  0%, 54% {
    transform: scaleX(0.34);
  }
  68%, 74% {
    transform: scaleX(0);
  }
  88%, 100% {
    transform: scaleX(0.34);
  }
}
@media (max-width: 340px) {
  .li__layers {
    padding: 4px 8px;
  }
  .li__row {
    gap: 4px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .li.is-demo .li__trace,
  .li.is-demo .li__finish,
  .li.is-demo .li__guide,
  .li.is-demo .li__fakeKnob,
  .li.is-demo .li__fakeFill {
    animation: none !important;
  }
  .li.is-demo .li__trace,
  .li.is-demo .li__finish {
    stroke-dashoffset: 0 !important;
  }
  .li.is-demo .li__guide {
    opacity: 0 !important;
  }
  .li.is-demo .li__fakeKnob {
    transform: translateX(0) !important;
  }
  .li.is-demo .li__fakeFill {
    transform: scaleX(0) !important;
  }
}

var li = document.getElementById('li');
var board = document.getElementById('board');
var sketch = document.getElementById('sketch');
var ink = document.getElementById('ink');
var range = document.getElementById('fade');
var sketchBtn = document.getElementById('sketchBtn');
var inkBtn = document.getElementById('inkBtn');
var sketchCtx = sketch.getContext('2d');
var inkCtx = ink.getContext('2d');
var active = 'ink';                 // 기본 활성 레이어는 インクレイヤー
var drawing = false;

// 고DPI 대응 — 두 판 다 배킹 스토어를 devicePixelRatio 배로 키우고 좌표계는 CSS 픽셀 그대로 쓴다
function resize() {
  var r = board.getBoundingClientRect(), dpr = window.devicePixelRatio || 1;
  [sketch, ink].forEach(function (c) {
    c.width = Math.round(r.width * dpr);
    c.height = Math.round(r.height * dpr);
    c.getContext('2d').setTransform(dpr, 0, 0, dpr, 0, 0);
  });
  drawGuide(r.width);
}

// 下書き 판은 마운트 때 연한 안내선을 깔아 둔다 — globalAlpha 로 낮춘 잉크라 판 자체의 opacity 와 겹쳐 작동한다
function drawGuide(width) {
  var s = width / 300;              // プレビュー SVG 와 같은 300×88 좌표계로 그린다
  sketchCtx.clearRect(0, 0, sketch.width, sketch.height);
  sketchCtx.save();
  sketchCtx.scale(s, s);
  sketchCtx.globalAlpha = 0.55;
  sketchCtx.strokeStyle = '#17141a';
  sketchCtx.lineCap = 'round';
  sketchCtx.lineWidth = 5;
  sketchCtx.beginPath();
  sketchCtx.moveTo(40, 70);
  sketchCtx.bezierCurveTo(60, 18, 110, 14, 130, 46);
  sketchCtx.bezierCurveTo(150, 78, 190, 80, 210, 54);
  sketchCtx.bezierCurveTo(226, 33, 250, 26, 268, 36);
  sketchCtx.stroke();
  sketchCtx.lineWidth = 3;
  sketchCtx.setLineDash([6, 5]);
  sketchCtx.beginPath();
  sketchCtx.arc(130, 46, 26, 0, Math.PI * 2);
  sketchCtx.stroke();
  sketchCtx.beginPath();
  sketchCtx.moveTo(36, 78);
  sketchCtx.lineTo(264, 78);
  sketchCtx.stroke();
  sketchCtx.restore();
}

function activeCtx() { return active === 'sketch' ? sketchCtx : inkCtx; }

function setActive(name) {
  active = name;
  sketchBtn.setAttribute('aria-pressed', name === 'sketch' ? 'true' : 'false');
  inkBtn.setAttribute('aria-pressed', name === 'ink' ? 'true' : 'false');
}

function toLocal(e) {
  var r = ink.getBoundingClientRect();
  return { x: e.clientX - r.left, y: e.clientY - r.top };
}

board.addEventListener('pointerdown', function (e) {
  li.classList.remove('is-demo');
  var c = activeCtx(), p = toLocal(e);
  drawing = true;
  c.lineCap = 'round';
  c.lineJoin = 'round';
  c.globalAlpha = active === 'sketch' ? 0.55 : 1;
  c.strokeStyle = '#17141a';
  c.lineWidth = active === 'sketch' ? 4 : 3;
  c.beginPath();
  c.moveTo(p.x, p.y);
  board.setPointerCapture(e.pointerId);
});
board.addEventListener('pointermove', function (e) {
  if (!drawing) { return; }
  var p = toLocal(e);
  activeCtx().lineTo(p.x, p.y);
  activeCtx().stroke();
});
window.addEventListener('pointerup', function () { drawing = false; });

// 슬라이더는 下書き 판의 CSS opacity 만 바꾼다 — 그린 것은 그대로 있고 보이기만 옅어진다
range.addEventListener('input', function () {
  li.classList.remove('is-demo');
  sketch.style.opacity = String(range.value / 100);
});
// 2枚を重ねる — 下書き 판을 지금 보이는 진하기 그대로 インク 판에 눌러 담고 下書き 판을 비운다
document.getElementById('mergeBtn').addEventListener('click', function () {
  li.classList.remove('is-demo');
  inkCtx.save();
  inkCtx.setTransform(1, 0, 0, 1, 0, 0);
  inkCtx.globalAlpha = Number(sketch.style.opacity || 0.34);
  inkCtx.drawImage(sketch, 0, 0);
  inkCtx.restore();
  sketchCtx.clearRect(0, 0, sketch.width, sketch.height);
});
sketchBtn.addEventListener('click', function () { li.classList.remove('is-demo'); setActive('sketch'); });
inkBtn.addEventListener('click', function () { li.classList.remove('is-demo'); setActive('ink'); });
window.addEventListener('resize', resize);
resize();

// SketchInkLayers — vanilla 판(run/287/demo/05-canvas-layer-ink/index.html) 의 React 포트.
// canvas 두 장을 겹친다 — 밑그림 판은 globalAlpha 를 낮춘 안내선을 미리 깔고, 활성 레이어에만 포인터 궤적을 그린다.
// 슬라이더는 밑그림 판의 CSS opacity 만 바꾸고, 「두 장 합치기」는 drawImage 로 밑그림을 잉크 판에 눌러 담는다.
import { useCallback, useEffect, useRef, useState } from "react";
import type { CSSProperties, PointerEvent as ReactPointerEvent } from "react";
import styles from "./SketchInkLayers.module.scss";

export type SketchInkLayersProps = {
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & { "--duration"?: string; "--easing"?: string; "--color"?: string };

const GUIDE_ALPHA = 0.55;   // 밑그림 잉크 자체의 진하기 — canvas 안에서 한 번, CSS opacity 로 또 한 번 겹쳐 옅어진다
const DEFAULT_OPACITY = 0.34;

function applyGuide(ctx: CanvasRenderingContext2D, width: number, height: number): void {
  // 미리보기 SVG 와 같은 300×88 좌표계로 그린다 — 판 폭이 변해도 모양 비율이 유지된다
  const s = width / 300;
  ctx.clearRect(0, 0, width, height);
  ctx.save();
  ctx.scale(s, s);
  ctx.globalAlpha = GUIDE_ALPHA;
  ctx.strokeStyle = "#17141a";
  ctx.lineCap = "round";
  ctx.lineWidth = 5;
  ctx.beginPath();
  ctx.moveTo(40, 70);
  ctx.bezierCurveTo(60, 18, 110, 14, 130, 46);
  ctx.bezierCurveTo(150, 78, 190, 80, 210, 54);
  ctx.bezierCurveTo(226, 33, 250, 26, 268, 36);
  ctx.stroke();
  ctx.lineWidth = 3;
  ctx.setLineDash([6, 5]);
  ctx.beginPath();
  ctx.arc(130, 46, 26, 0, Math.PI * 2);
  ctx.stroke();
  ctx.beginPath();
  ctx.moveTo(36, 78);
  ctx.lineTo(264, 78);
  ctx.stroke();
  ctx.restore();
}

export default function SketchInkLayers({
  duration = 2000,
  easing = "ease-out",
  color = "#17141a",
}: SketchInkLayersProps) {
  const boardRef = useRef<HTMLDivElement | null>(null);
  const sketchRef = useRef<HTMLCanvasElement | null>(null);
  const inkRef = useRef<HTMLCanvasElement | null>(null);
  const drawingRef = useRef(false);
  const [demo, setDemo] = useState(true);
  const [active, setActive] = useState("ink");
  const [fade, setFade] = useState(34);
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };

  const activeCtx = useCallback((): CanvasRenderingContext2D | null => {
    const canvas = active === "sketch" ? sketchRef.current : inkRef.current;
    if (!canvas) return null;
    return canvas.getContext("2d");
  }, [active]);

  // 고DPI 대응 — 배킹 스토어를 devicePixelRatio 배로 키우고 좌표계는 CSS 픽셀 그대로 쓴다
  const resize = useCallback(() => {
    const board = boardRef.current;
    if (!board) return;
    const r = board.getBoundingClientRect();
    const dpr = window.devicePixelRatio || 1;
    for (const canvas of [sketchRef.current, inkRef.current]) {
      if (!canvas) continue;
      canvas.width = Math.round(r.width * dpr);
      canvas.height = Math.round(r.height * dpr);
      const ctx = canvas.getContext("2d");
      if (!ctx) continue;
      ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
    }
    const sketch = sketchRef.current;
    const sketchCtx = sketch ? sketch.getContext("2d") : null;
    if (sketchCtx) applyGuide(sketchCtx, r.width, r.height);
  }, []);

  useEffect(() => {
    resize();
    window.addEventListener("resize", resize);
    return () => window.removeEventListener("resize", resize);
  }, [resize]);

  useEffect(() => {
    function onUp(): void {
      drawingRef.current = false;
    }
    window.addEventListener("pointerup", onUp);
    return () => window.removeEventListener("pointerup", onUp);
  }, []);

  function toLocal(event: ReactPointerEvent<HTMLDivElement>): { x: number; y: number } | null {
    const canvas = inkRef.current;
    if (!canvas) return null;
    const r = canvas.getBoundingClientRect();
    return { x: event.clientX - r.left, y: event.clientY - r.top };
  }

  function onPointerDown(event: ReactPointerEvent<HTMLDivElement>): void {
    setDemo(false);
    const board = boardRef.current;
    const ctx = activeCtx();
    const p = toLocal(event);
    if (!board || !ctx || !p) return;
    drawingRef.current = true;
    ctx.lineCap = "round";
    ctx.lineJoin = "round";
    ctx.globalAlpha = active === "sketch" ? GUIDE_ALPHA : 1;
    ctx.strokeStyle = color;
    ctx.lineWidth = active === "sketch" ? 4 : 3;
    ctx.beginPath();
    ctx.moveTo(p.x, p.y);
    board.setPointerCapture(event.pointerId);
  }

  function onPointerMove(event: ReactPointerEvent<HTMLDivElement>): void {
    if (!drawingRef.current) return;
    const ctx = activeCtx();
    const p = toLocal(event);
    if (!ctx || !p) return;
    ctx.lineTo(p.x, p.y);
    ctx.stroke();
  }

  function onFade(event: { target: EventTarget | null }): void {
    setDemo(false);
    const input = event.target as HTMLInputElement | null;
    if (!input) return;
    const value = Number(input.value);
    setFade(value);
    const sketch = sketchRef.current;
    if (sketch) sketch.style.opacity = String(value / 100);
  }

  // 두 장 합치기 — 밑그림 판을 지금 보이는 진하기 그대로 잉크 판에 눌러 담고 밑그림 판을 비운다
  function onMerge(): void {
    setDemo(false);
    const sketch = sketchRef.current;
    const ink = inkRef.current;
    if (!sketch || !ink) return;
    const inkCtx = ink.getContext("2d");
    if (!inkCtx) return;
    inkCtx.save();
    inkCtx.setTransform(1, 0, 0, 1, 0, 0);
    inkCtx.globalAlpha = sketch.style.opacity ? Number(sketch.style.opacity) : DEFAULT_OPACITY;
    inkCtx.drawImage(sketch, 0, 0);
    inkCtx.restore();
    const sketchCtx = sketch.getContext("2d");
    if (sketchCtx) sketchCtx.clearRect(0, 0, sketch.width, sketch.height);
  }

  function onLayer(name: string): void {
    setDemo(false);
    setActive(name);
  }

  const cls = [styles.root, demo ? styles.isDemo : ""].filter(Boolean).join(" ");
  return (
    <main className={styles.stage}>
      <div className={cls} style={vars}>
        <div className={styles.card}>
          <div className={styles.layers}>
            <div className={styles.row}>
              <button type="button" className={styles.layer} aria-pressed={active === "sketch"} onClick={() => onLayer("sketch")}>
                <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256" fill="currentColor" className={styles.ico} aria-hidden="true"><path d="M224,128a96,96,0,1,1-96-96A96,96,0,0,1,224,128Z" opacity="0.2"/><path d="M96.26,37A8,8,0,0,1,102,27.29a104.11,104.11,0,0,1,52,0,8,8,0,0,1-2,15.75,8.15,8.15,0,0,1-2-.26,88.09,88.09,0,0,0-44,0A8,8,0,0,1,96.26,37ZM53.79,55.14a104,104,0,0,0-26,45,8,8,0,1,0,15.42,4.26,87.91,87.91,0,0,1,22-38.08A8,8,0,0,0,53.79,55.14ZM43.21,151.55a8,8,0,1,0-15.42,4.28,104,104,0,0,0,26,45,8,8,0,1,0,11.41-11.21A88.14,88.14,0,0,1,43.21,151.55ZM150,213.22a88,88,0,0,1-44,0,8,8,0,1,0-4,15.49,104.11,104.11,0,0,0,52,0,8,8,0,0,0-4-15.49ZM222.65,146a8,8,0,0,0-9.85,5.57,87.88,87.88,0,0,1-22,38.09,8,8,0,1,0,11.42,11.21,104.05,104.05,0,0,0,26-45A8,8,0,0,0,222.65,146Zm-9.86-41.54a8,8,0,0,0,15.42-4.28,104,104,0,0,0-26-45,8,8,0,1,0-11.41,11.21A88.14,88.14,0,0,1,212.79,104.45Z"/></svg>
                <span>밑그림</span>
              </button>
              <span className={styles.slot}>
                <input className={styles.range} type="range" min="0" max="100" value={fade} aria-label="밑그림 불투명도" onChange={onFade}></input>
                <span className={styles.fake} aria-hidden="true"><span className={styles.fakeFill}></span><span className={styles.fakeKnob}></span></span>
              </span>
            </div>
            <div className={styles.row}>
              <button type="button" className={styles.layer} aria-pressed={active === "ink"} onClick={() => onLayer("ink")}>
                <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256" fill="currentColor" className={styles.ico} aria-hidden="true"><path d="M221.66,90.34,192,120,136,64l29.66-29.66a8,8,0,0,1,11.31,0L221.66,79A8,8,0,0,1,221.66,90.34Z" opacity="0.2"/><path d="M227.32,73.37,182.63,28.69a16,16,0,0,0-22.63,0L36.69,152A15.86,15.86,0,0,0,32,163.31V208a16,16,0,0,0,16,16H92.69A15.86,15.86,0,0,0,104,219.31l83.67-83.66,3.48,13.9-36.8,36.79a8,8,0,0,0,11.31,11.32l40-40a8,8,0,0,0,2.11-7.6l-6.9-27.61L227.32,96A16,16,0,0,0,227.32,73.37ZM48,208V179.31L76.69,208Zm48-3.31L51.31,160,136,75.31,180.69,120Zm96-96L147.32,64l24-24L216,84.69Z"/></svg>
                <span>잉크</span>
              </button>
              <button type="button" className={styles.merge} onClick={onMerge}>
                <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 256" fill="currentColor" className={styles.ico} aria-hidden="true"><path d="M224,80l-96,56L32,80l96-56Z" opacity="0.2"/><path d="M230.91,172A8,8,0,0,1,228,182.91l-96,56a8,8,0,0,1-8.06,0l-96-56A8,8,0,0,1,36,169.09l92,53.65,92-53.65A8,8,0,0,1,230.91,172ZM220,121.09l-92,53.65L36,121.09A8,8,0,0,0,28,134.91l96,56a8,8,0,0,0,8.06,0l96-56A8,8,0,1,0,220,121.09ZM24,80a8,8,0,0,1,4-6.91l96-56a8,8,0,0,1,8.06,0l96,56a8,8,0,0,1,0,13.82l-96,56a8,8,0,0,1-8.06,0l-96-56A8,8,0,0,1,24,80Zm23.88,0L128,126.74,208.12,80,128,33.26Z"/></svg>
                <span>두 장 합치기</span>
              </button>
            </div>
          </div>
          <div className={styles.board} ref={boardRef} onPointerDown={onPointerDown} onPointerMove={onPointerMove}>
            <canvas className={styles.sketch} ref={sketchRef} role="img" aria-label="밑그림 판" style={{ opacity: fade / 100 }}></canvas>
            <canvas className={styles.ink} ref={inkRef} role="img" aria-label="잉크 판"></canvas>
            <svg className={styles.ghost} viewBox="0 0 300 88" preserveAspectRatio="none" aria-hidden="true">
              <g className={styles.guide}>
                <path className={styles.guideCurve} d="M40,70 C60,18 110,14 130,46 C150,78 190,80 210,54 C226,33 250,26 268,36"/>
                <circle className={styles.guideRing} cx="130" cy="46" r="26"/>
                <line className={styles.guideBase} x1="36" y1="78" x2="264" y2="78"/>
              </g>
              <path className={styles.trace} pathLength="100" d="M40,70 C60,18 110,14 130,46 C150,78 190,80 210,54 C226,33 250,26 268,36"/>
              <line className={styles.finish} pathLength="100" x1="36" y1="78" x2="264" y2="78"/>
            </svg>
          </div>
        </div>
      </div>
    </main>
  );
}