05Drawing Automaton Where the Pointer Coordinate Value Toggles a Cell Directly

<main class="stage">
  <div class="rv is-demo" tabindex="0" role="button" aria-label="Seed drawing running -- draw with the pointer or press space to pause, R to reseed">
    <canvas class="rv__cv" width="480" height="300"></canvas>
    <p class="rv__hint">Draw with pointer · space to pause · R to reseed</p>
  </div>
</main>

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

@include stage($stage-ink);

.rv {
  position: relative;
  width: min(92vw, calc(160vh - 12.8vw));
  aspect-ratio: 480 / 300;
  margin: 0 auto;
  border-radius: $r-card;
  overflow: hidden;
  cursor: crosshair;
  touch-action: none;
  box-shadow: $shadow-raised;
  outline-offset: 4px;

  &:focus-visible {
    outline: 3px solid $subject-cream;
  }
}

.rv__cv {
  display: block;
  width: 100%;
  height: 100%;
}

.rv__hint {
  position: absolute;
  left: $sp-3;
  bottom: $sp-3;
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  font-size: 12px;
  line-height: 1.4;
  font-weight: 500;
  background: rgba(255, 247, 230, .85);
  color: $subject-ink;
  pointer-events: none;
}

@media (prefers-reduced-motion: reduce) {
  .rv {
    cursor: crosshair;
  }
}

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);
}

.rv {
  position: relative;
  width: min(92vw, 160vh - 12.8vw);
  aspect-ratio: 480/300;
  margin: 0 auto;
  border-radius: 16px;
  overflow: hidden;
  cursor: crosshair;
  touch-action: none;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  outline-offset: 4px;
}
.rv:focus-visible {
  outline: 3px solid #fff7e6;
}

.rv__cv {
  display: block;
  width: 100%;
  height: 100%;
}

.rv__hint {
  position: absolute;
  left: 12px;
  bottom: 12px;
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  font-size: 12px;
  line-height: 1.4;
  font-weight: 500;
  background: rgba(255, 247, 230, 0.85);
  color: #17141a;
  pointer-events: none;
}

@media (prefers-reduced-motion: reduce) {
  .rv {
    cursor: crosshair;
  }
}

(function(){
  'use strict';
  // 395-09(진행률 채움 로더)와 다른 축: 포인터 좌표 값이 칸의 생사를 직접 뒤집는 계산이 주인공.
  // 항목 05 는 click 대신 pointerdown·pointermove 로 씨앗을 그린다 — 손을 떼면 규칙표로 자동 진행.

  function makeLcg(seed){
    let s = seed >>> 0;
    return function(){
      s = (s * 1664525 + 1013904223) >>> 0;
      return s / 4294967296;
    };
  }

  const W = 480, H = 300;
  const CELL = 10, COLS = W / CELL, ROWS = H / CELL;
  const INK = '#17141a';
  const ALIVE_COLOR = '#93a4ca';
  let SEED = 50501;
  let rnd = makeLcg(SEED);

  const SURVIVE_MIN = 2, SURVIVE_MAX = 3, BIRTH_COUNT = 3;

  let grid = new Uint8Array(COLS * ROWS);
  let next = new Uint8Array(COLS * ROWS);

  function idx(x, y){ return y * COLS + x; }

  function autoSeed(){
    grid.fill(0);
    for (let y = 8; y <= 21; y++){
      for (let x = 14; x <= 33; x++){
        if (rnd() < 0.34) grid[idx(x, y)] = 1;
      }
    }
  }

  function neighborCount(x, y){
    let n = 0;
    for (let dy = -1; dy <= 1; dy++){
      for (let dx = -1; dx <= 1; dx++){
        if (dx === 0 && dy === 0) continue;
        const nx = x + dx, ny = y + dy;
        if (nx < 0 || ny < 0 || nx >= COLS || ny >= ROWS) continue;
        n += grid[idx(nx, ny)];
      }
    }
    return n;
  }

  function step(){
    for (let y = 0; y < ROWS; y++){
      for (let x = 0; x < COLS; x++){
        const alive = grid[idx(x, y)] === 1;
        const n = neighborCount(x, y);
        let willLive = 0;
        if (alive){
          willLive = (n >= SURVIVE_MIN && n <= SURVIVE_MAX) ? 1 : 0;
        } else {
          willLive = (n === BIRTH_COUNT) ? 1 : 0;
        }
        next[idx(x, y)] = willLive;
      }
    }
    const tmp = grid; grid = next; next = tmp;
  }

  const cvEl = document.querySelector('.rv__cv');
  const ctx = cvEl.getContext('2d');
  const rootEl = document.querySelector('.rv');

  function render(){
    ctx.fillStyle = INK;
    ctx.fillRect(0, 0, W, H);
    ctx.fillStyle = ALIVE_COLOR;
    for (let y = 0; y < ROWS; y++){
      for (let x = 0; x < COLS; x++){
        if (grid[idx(x, y)] === 1){
          ctx.fillRect(x * CELL + 1, y * CELL + 1, CELL - 1, CELL - 1);
        }
      }
    }
  }

  const ARIA_PLAY = 'Seed drawing running -- draw with the pointer or press space to pause, R to reseed';
  const ARIA_DRAW = 'Drawing seed -- release to let the rule table take over';
  const ARIA_PAUSE = 'Seed drawing paused -- draw with the pointer or press space to resume, R to reseed';

  function updateAria(){
    rootEl.setAttribute('aria-label', isDrawing ? ARIA_DRAW : (paused ? ARIA_PAUSE : ARIA_PLAY));
  }

  let paused = false;
  let isDrawing = false;
  const reduceMQ = window.matchMedia('(prefers-reduced-motion: reduce)');

  function human(){
    if (rootEl.classList.contains('is-demo')){
      rootEl.classList.remove('is-demo');
      grid.fill(0);
    }
  }

  function reseed(){
    SEED = (SEED * 1103515245 + 12345) >>> 0;
    rnd = makeLcg(SEED || 1);
    autoSeed();
    paused = false;
  }

  function cellFromEvent(e){
    const rect = cvEl.getBoundingClientRect();
    const px = (e.clientX - rect.left) * (W / rect.width);
    const py = (e.clientY - rect.top) * (H / rect.height);
    const cx = Math.max(0, Math.min(COLS - 1, Math.floor(px / CELL)));
    const cy = Math.max(0, Math.min(ROWS - 1, Math.floor(py / CELL)));
    return [cx, cy];
  }

  function paintAt(e){
    const c = cellFromEvent(e);
    grid[idx(c[0], c[1])] = 1;
    render();
  }

  function onPointerDown(e){
    human();
    isDrawing = true;
    paused = true;
    updateAria();
    paintAt(e);
  }

  function onPointerMove(e){
    if (!isDrawing) return;
    paintAt(e);
  }

  function onPointerUp(){
    if (!isDrawing) return;
    isDrawing = false;
    paused = false;
    updateAria();
    render();
  }

  function onKey(e){
    if (e.key === 'r' || e.key === 'R'){
      human();
      reseed();
      render();
      updateAria();
      return;
    }
    if (e.key !== 'Enter' && e.key !== ' ') return;
    e.preventDefault();
    human();
    if (reduceMQ.matches){
      step();
      render();
    } else {
      paused = !paused;
      updateAria();
    }
  }

  const GEN_INTERVAL_MS = 85;
  let acc = 0, last = 0;

  function frame(now){
    if (!reduceMQ.matches){
      if (!last) last = now;
      const dt = now - last;
      last = now;
      if (!paused && !isDrawing){
        acc += dt;
        while (acc >= GEN_INTERVAL_MS){
          step();
          acc -= GEN_INTERVAL_MS;
        }
        render();
      }
      requestAnimationFrame(frame);
    }
  }

  function onResize(){ render(); }

  rootEl.addEventListener('pointerdown', onPointerDown);
  rootEl.addEventListener('pointermove', onPointerMove);
  window.addEventListener('pointerup', onPointerUp);
  rootEl.addEventListener('keydown', onKey);
  window.addEventListener('resize', onResize);

  autoSeed();
  updateAria();
  render();
  if (!reduceMQ.matches){
    requestAnimationFrame(frame);
  }

})();

import { useEffect, useRef } from 'react';
import styles from './PointerSeedDraw.module.scss';

function ctx2d(cv: HTMLCanvasElement): CanvasRenderingContext2D {
  const c = cv.getContext('2d');
  if (!c) throw new Error('no 2d context');
  return c;
}

function makeLcg(seed: number): () => number {
  let s = seed >>> 0;
  return function(){
    s = (s * 1664525 + 1013904223) >>> 0;
    return s / 4294967296;
  };
}

const W = 480, H = 300;
const CELL = 10, COLS = W / CELL, ROWS = H / CELL;
const INK = '#17141a';
const ALIVE_COLOR = '#93a4ca';
let SEED = 50501;
let rnd = makeLcg(SEED);

const SURVIVE_MIN = 2, SURVIVE_MAX = 3, BIRTH_COUNT = 3;

let grid = new Uint8Array(COLS * ROWS);
let next = new Uint8Array(COLS * ROWS);

function idx(x: number, y: number): number { return y * COLS + x; }

function autoSeed(): void {
  grid.fill(0);
  for (let y = 8; y <= 21; y++){
    for (let x = 14; x <= 33; x++){
      if (rnd() < 0.34) grid[idx(x, y)] = 1;
    }
  }
}

function neighborCount(x: number, y: number): number {
  let n = 0;
  for (let dy = -1; dy <= 1; dy++){
    for (let dx = -1; dx <= 1; dx++){
      if (dx === 0 && dy === 0) continue;
      const nx = x + dx, ny = y + dy;
      if (nx < 0 || ny < 0 || nx >= COLS || ny >= ROWS) continue;
      n += grid[idx(nx, ny)];
    }
  }
  return n;
}

function step(): void {
  for (let y = 0; y < ROWS; y++){
    for (let x = 0; x < COLS; x++){
      const alive = grid[idx(x, y)] === 1;
      const n = neighborCount(x, y);
      let willLive = 0;
      if (alive){
        willLive = (n >= SURVIVE_MIN && n <= SURVIVE_MAX) ? 1 : 0;
      } else {
        willLive = (n === BIRTH_COUNT) ? 1 : 0;
      }
      next[idx(x, y)] = willLive;
    }
  }
  const tmp = grid; grid = next; next = tmp;
}

function render(ctx: CanvasRenderingContext2D): void {
  ctx.fillStyle = INK;
  ctx.fillRect(0, 0, W, H);
  ctx.fillStyle = ALIVE_COLOR;
  for (let y = 0; y < ROWS; y++){
    for (let x = 0; x < COLS; x++){
      if (grid[idx(x, y)] === 1){
        ctx.fillRect(x * CELL + 1, y * CELL + 1, CELL - 1, CELL - 1);
      }
    }
  }
}

const ARIA_PLAY = '씨앗 그리기 진행 중 — 포인터로 칸을 그리거나 스페이스바로 정지, R 로 재시드';
const ARIA_DRAW = '씨앗 그리는 중 — 손을 떼면 규칙표로 자동 진행';
const ARIA_PAUSE = '씨앗 그리기 정지됨 — 포인터로 칸을 그리거나 스페이스바로 재생, R 로 재시드';

export default function PointerSeedDraw(){

  const rootRef = useRef<HTMLDivElement | null>(null);
  const cvRef = useRef<HTMLCanvasElement | null>(null);

  useEffect(() => {
    const root = rootRef.current;
    const cv = cvRef.current;
    if (!root || !cv) return;
    const rootEl: HTMLDivElement = root;
    const cvEl: HTMLCanvasElement = cv;
    const ctx = ctx2d(cvEl);

    function updateAria(): void {
      rootEl.setAttribute('aria-label', isDrawing ? ARIA_DRAW : (paused ? ARIA_PAUSE : ARIA_PLAY));
    }

    let paused = false;
    let isDrawing = false;
    const reduceMQ = window.matchMedia('(prefers-reduced-motion: reduce)');

    function human(): void {
      if (rootEl.classList.contains('is-demo')){
        rootEl.classList.remove('is-demo');
        grid.fill(0);
      }
    }

    function reseed(): void {
      SEED = (SEED * 1103515245 + 12345) >>> 0;
      rnd = makeLcg(SEED || 1);
      autoSeed();
      paused = false;
    }

    function cellFromEvent(e: PointerEvent): [number, number] {
      const rect = cvEl.getBoundingClientRect();
      const px = (e.clientX - rect.left) * (W / rect.width);
      const py = (e.clientY - rect.top) * (H / rect.height);
      const cx = Math.max(0, Math.min(COLS - 1, Math.floor(px / CELL)));
      const cy = Math.max(0, Math.min(ROWS - 1, Math.floor(py / CELL)));
      return [cx, cy];
    }

    function paintAt(e: PointerEvent): void {
      const c = cellFromEvent(e);
      grid[idx(c[0], c[1])] = 1;
      render(ctx);
    }

    function onPointerDown(e: PointerEvent): void {
      human();
      isDrawing = true;
      paused = true;
      updateAria();
      paintAt(e);
    }

    function onPointerMove(e: PointerEvent): void {
      if (!isDrawing) return;
      paintAt(e);
    }

    function onPointerUp(): void {
      if (!isDrawing) return;
      isDrawing = false;
      paused = false;
      updateAria();
      render(ctx);
    }

    function onKey(e: KeyboardEvent): void {
      if (e.key === 'r' || e.key === 'R'){
        human();
        reseed();
        render(ctx);
        updateAria();
        return;
      }
      if (e.key !== 'Enter' && e.key !== ' ') return;
      e.preventDefault();
      human();
      if (reduceMQ.matches){
        step();
        render(ctx);
      } else {
        paused = !paused;
        updateAria();
      }
    }

    const GEN_INTERVAL_MS = 85;
    let acc = 0, last = 0, rafId = 0;

    function frame(now: number): void {
      if (!reduceMQ.matches){
        if (!last) last = now;
        const dt = now - last;
        last = now;
        if (!paused && !isDrawing){
          acc += dt;
          while (acc >= GEN_INTERVAL_MS){
            step();
            acc -= GEN_INTERVAL_MS;
          }
          render(ctx);
        }
        rafId = requestAnimationFrame(frame);
      }
    }

    function onResize(): void { render(ctx); }

    rootEl.addEventListener('pointerdown', onPointerDown);
    rootEl.addEventListener('pointermove', onPointerMove);
    window.addEventListener('pointerup', onPointerUp);
    rootEl.addEventListener('keydown', onKey);
    window.addEventListener('resize', onResize);

    autoSeed();
    updateAria();
    render(ctx);
    if (!reduceMQ.matches){
      rafId = requestAnimationFrame(frame);
    }

    return () => {
      rootEl.removeEventListener('pointerdown', onPointerDown);
      rootEl.removeEventListener('pointermove', onPointerMove);
      window.removeEventListener('pointerup', onPointerUp);
      rootEl.removeEventListener('keydown', onKey);
      window.removeEventListener('resize', onResize);
      if (rafId) cancelAnimationFrame(rafId);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div ref={rootRef} className={`${styles.rv} is-demo`} tabIndex={0} role="button" aria-label="씨앗 그리기 진행 중 — 포인터로 칸을 그리거나 스페이스바로 정지, R 로 재시드">
        <canvas ref={cvRef} className={styles.rv__cv} width={480} height={300} />
        <p className={styles.rv__hint}>포인터로 그리기 · 스페이스바 정지 · R 재시드</p>
      </div>
    </main>
  );
}