lab 4

lectures/04/game_of_life/index.js

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+import init, { Cell, Universe } from "./pkg/game_of_life.js";
+
+const CELL_SIZE = 10; // px
+const GRID_COLOR = "#CCCCCC";
+const DEAD_COLOR = "#FFFFFF";
+const ALIVE_COLOR = "#000000";
+
+const { memory } = await init();
+
+const universe = Universe.new();
+const width = universe.width();
+const height = universe.height();
+
+const canvas = document.getElementById("game-of-life-canvas");
+canvas.height = (CELL_SIZE + 1) * height + 1;
+canvas.width = (CELL_SIZE + 1) * width + 1;
+
+const ctx = canvas.getContext("2d");
+
+const getIndex = (row, column) => row * width + column;
+
+const drawGrid = () => {
+	ctx.beginPath();
+	ctx.strokeStyle = GRID_COLOR;
+
+	for (let i = 0; i <= width; i++) {
+		ctx.moveTo(i * (CELL_SIZE + 1) + 1, 0);
+		ctx.lineTo(i * (CELL_SIZE + 1) + 1, (CELL_SIZE + 1) * height + 1);
+	}
+
+	for (let j = 0; j <= height; j++) {
+		ctx.moveTo(0, j * (CELL_SIZE + 1) + 1);
+		ctx.lineTo((CELL_SIZE + 1) * width + 1, j * (CELL_SIZE + 1) + 1);
+	}
+
+	ctx.stroke();
+};
+
+const drawCells = () => {
+	const cellsPtr = universe.cells();
+	const cells = new Uint8Array(memory.buffer, cellsPtr, width * height);
+
+	ctx.beginPath();
+
+	for (let row = 0; row < height; row++) {
+		for (let col = 0; col < width; col++) {
+			const idx = getIndex(row, col);
+
+			ctx.fillStyle = cells[idx] === Cell.Dead ? DEAD_COLOR : ALIVE_COLOR;
+
+			ctx.fillRect(
+				col * (CELL_SIZE + 1) + 1,
+				row * (CELL_SIZE + 1) + 1,
+				CELL_SIZE,
+				CELL_SIZE,
+			);
+		}
+	}
+
+	ctx.stroke();
+};
+
+let animationId = null;
+
+const isPaused = () => animationId === null;
+
+const renderLoop = () => {
+	universe.tick();
+
+	drawGrid();
+	drawCells();
+
+	animationId = requestAnimationFrame(renderLoop);
+};
+
+const playPauseButton = document.getElementById("play-pause");
+
+const play = () => {
+	playPauseButton.textContent = "⏸";
+	renderLoop();
+};
+
+const pause = () => {
+	playPauseButton.textContent = "▶";
+	cancelAnimationFrame(animationId);
+	animationId = null;
+};
+
+playPauseButton.addEventListener("click", () => {
+	if (isPaused()) {
+		play();
+	} else {
+		pause();
+	}
+});
+
+const clearButton = document.getElementById("clear");
+
+clearButton.addEventListener("click", () => {
+	universe.clear();
+
+	drawGrid();
+	drawCells();
+});
+
+const cellAtEvent = (event) => {
+	const boundingRect = canvas.getBoundingClientRect();
+
+	const scaleX = canvas.width / boundingRect.width;
+	const scaleY = canvas.height / boundingRect.height;
+
+	const canvasLeft = (event.clientX - boundingRect.left) * scaleX;
+	const canvasTop = (event.clientY - boundingRect.top) * scaleY;
+
+	const row = Math.min(Math.floor(canvasTop / (CELL_SIZE + 1)), height - 1);
+	const col = Math.min(Math.floor(canvasLeft / (CELL_SIZE + 1)), width - 1);
+
+	return [row, col];
+};
+
+// Bresenham's line algorithm, so fast drags don't leave gaps between cells.
+const forEachCellOnLine = (row0, col0, row1, col1, callback) => {
+	let row = row0;
+	let col = col0;
+
+	const dRow = Math.abs(row1 - row0);
+	const dCol = Math.abs(col1 - col0);
+	const stepRow = row1 > row0 ? 1 : -1;
+	const stepCol = col1 > col0 ? 1 : -1;
+
+	let err = dRow - dCol;
+
+	while (true) {
+		callback(row, col);
+
+		if (row === row1 && col === col1) {
+			break;
+		}
+
+		const err2 = err * 2;
+
+		if (err2 > -dCol) {
+			err -= dCol;
+			row += stepRow;
+		}
+
+		if (err2 < dRow) {
+			err += dRow;
+			col += stepCol;
+		}
+	}
+};
+
+let isDrawing = false;
+let lastCell = null;
+
+canvas.addEventListener("mousedown", (event) => {
+	const [row, col] = cellAtEvent(event);
+
+	isDrawing = true;
+	lastCell = [row, col];
+
+	universe.toggle_cell(row, col);
+
+	drawGrid();
+	drawCells();
+});
+
+canvas.addEventListener("mousemove", (event) => {
+	if (!isDrawing) {
+		return;
+	}
+
+	const [row, col] = cellAtEvent(event);
+
+	if (row === lastCell[0] && col === lastCell[1]) {
+		return;
+	}
+
+	forEachCellOnLine(lastCell[0], lastCell[1], row, col, (r, c) => {
+		universe.set_alive(r, c);
+	});
+
+	lastCell = [row, col];
+
+	drawGrid();
+	drawCells();
+});
+
+const stopDrawing = () => {
+	isDrawing = false;
+	lastCell = null;
+};
+
+window.addEventListener("mouseup", stopDrawing);
+canvas.addEventListener("mouseleave", stopDrawing);
+
+drawGrid();
+drawCells();
+play();