handle changes of board size

src/sketch.js

@@ -6,6 +6,7 @@ export default class Sketch {
 
 		[
 			'getContext',
+			'getSize',
 			'onResize',
 			'render',
 		].map(method => this[method] = this[method].bind(this));
@@ -32,6 +33,13 @@ export default class Sketch {
 		return this.context;
 	}
 
+	getSize () {
+		return {
+			canvasWidth: this.container.offsetWidth,
+			canvasHeight: this.container.offsetHeight,
+		}
+	}
+
 	onResize (event) {
 		const width = this.container.offsetWidth;
 		const height = this.container.offsetHeight;