Added src url parameter and a triangular lattice demo

2025-07-21 18:35:11 +02:00
parent 87a092632d
commit 1950943e55
3 changed files with 91 additions and 3 deletions
--- a/canvas/test1.html
+++ b/canvas/test1.html
@@ -10,7 +10,10 @@

 		document.addEventListener('DOMContentLoaded', async () => {

-			const initial_code = await (await fetch('initial.js')).text();
+			const params = new URLSearchParams(location.search);
+			const source_doc = params.get('src') || 'initial.js';
+			const initial_code = await (await fetch(source_doc)).text();
+
 			const initialState = cm6.createEditorState(initial_code);
 			const editor = document.getElementById("editor");
 			const view = cm6.createEditorView(initialState, editor);
--- a/canvas/triangular-lattice.js
+++ b/canvas/triangular-lattice.js
@@ -0,0 +1,81 @@
+//Create useful variables
+const aspect = W / H;
+const scale = aspect >= 1 ? H / 2 : W / 2;
+
+function setup() {
+	// Reset transform
+	C.setTransform(1, 0, 0, 1, 0, 0);
+
+	// Clear canvas
+	C.clearRect(0, 0, W, H);
+
+	// Reset common properties
+	C.globalCompositeOperation = 'source-over';
+	C.fillStyle = 'rgba(255,200,100,1)';
+	C.strokeStyle = 'rgba(0,0,0,1)';
+
+
+	// Set up transform to map -1,-1..1,1 to canvas with aspect fit
+	const offsetX = W / 2;
+	const offsetY = H / 2;
+
+	//Apply transform
+	C.translate(offsetX, offsetY);
+	C.scale(scale, -scale);
+
+	// Set 1 pixel wide lines
+	C.lineWidth = 1 / scale;
+}
+
+
+setup();
+
+function hash(x, y, low, high) {
+	const seed = x * 374761393 ^ y * 668265263; // Large primes
+	let h = seed ^ (seed >> 3) ^ (seed >> 13) ^ (seed << 2);
+	h = (h * 1274126177) & 0xffffffff;
+	return (h >>> 0) % (high - low) + low;
+}
+
+
+const s = 0.2;
+for (let y = -3; y < 3; y++) {
+	for (let x = -3; x < 3; x++) {
+		const p0 = [(x + .5) * s, y * s];
+		const p1 = [(x + 1.5) * s, y * s];
+		const p2 = [(x + 1) * s, (y + 1) * s];
+		const p3 = [(x + 0) * s, (y + 1) * s];
+
+		// Filled parallelogram
+		C.beginPath();
+		C.moveTo(...p0);
+		C.lineTo(...p1);
+		C.lineTo(...p2);
+		C.lineTo(...p3);
+		C.closePath();
+        const hue = hash(x, y, 0, 360);
+        const sat = hash(x, y, 20, 80);
+        const light = hash(x, y, 60, 90);
+		C.fillStyle = `hsl(${hue}, ${sat}%, ${light}%)`;
+		C.fill();
+
+		// Triangle lines
+		C.strokeStyle = 'black';
+		C.lineWidth = 1 / scale;
+
+		// Outline parallelogram
+		C.beginPath();
+		C.moveTo(...p0);
+		C.lineTo(...p1);
+		C.lineTo(...p2);
+		C.lineTo(...p3);
+		C.closePath();
+		C.stroke();
+
+		// Diagonal from p0 to p2
+		C.beginPath();
+		C.moveTo(...p0);
+		C.lineTo(...p2);
+		C.stroke();
+	}
+}
--- a/index.html
+++ b/index.html
@@ -6,7 +6,11 @@
 <body>
 	<ul>
 		<li>
-			<a href="canvas/test1.html">Simple canvas playground</a>
+			<h2>Simple canvas playground</h2>
+			<ul>
+				<li><a href="canvas/test1.html">Default configuration</a></li>
+				<li><a href="canvas/test1.html?src=triangular-lattice.js">Triangular lattice</a></li>
+			</ul>
 		</li>
 	</ul>