Catch errors in Javaccript-Voronoi

mibpov.js

@@ -614,9 +614,14 @@ function getVoronoiDiagram(points, recalculate) {
 			// This should improve performance
 			voronoi.recycle(diagram);
 		}
-		diagram = voronoi.compute(sites, vbbox);
-		cachedVoronoiDiagram = diagram;
-		return diagram;
+		try {
+			diagram = voronoi.compute(sites, vbbox);
+			cachedVoronoiDiagram = diagram;
+			return diagram;
+		} catch {
+			cachedVoronoiDiagram = null;
+			return null;
+		}
 	} else {
 		return cachedVoronoiDiagram;
 	}
@@ -743,11 +748,29 @@ function draw(recalculate) {
 		updateAltitudeText();
 		return true;
 	}
-	drawError = false;
+
 	updateAltitudeText();
 
+	let voronoiError = function() {
+		context.textAlign = "center";
+		context.fillStyle = "black";
+		context.textBaseline = "middle";
+		context.font = "200% sans-serif";
+		let msg = "Error in Javascript-Voronoi!";
+		context.fillText(msg, w/2, h/2);
+		drawError = true;
+		updateAltitudeText();
+	}
+
 	let diagram = getVoronoiDiagram(points, recalculate);
 
+	if (!diagram) {
+		voronoiError();
+		drawError = true;
+		return true;
+	}
+	drawError = false;
+
 	let createHalfedgesPath = function(context, cell) {
 		context.beginPath();
 		for (let h=0; h<cell.halfedges.length; h++) {
@@ -1242,7 +1265,7 @@ voronoiCanvas.onmousedown = function(event) {
 	// select point by clicking.
 	// initiate drag-n-drop if already selected.
 	mouseIsDown = true;
-	if (!showPoints) {
+	if (drawError || !showPoints) {
 		// Points need to be shown for drag-n-drop to work
 		return;
 	}