Check if geometry is multipolygon.

src/main/resources/eu/simstadt/regionchooser/website/script/simstadt_openlayers.js

@@ -294,10 +294,13 @@ const regionChooser = (function(){
 	function displayInfo() {
 		dataPanel.empty();
 		var geom = sketch.getGeometry().clone().transform(sourceProj, 'EPSG:4326');
-		var coordinates = geom.getLinearRing(0).getCoordinates();
-		var area = Math.abs(wgs84Sphere.geodesicArea(coordinates));
-		//NOTE: Could show m², ha or km² depending on magnitude
-		dataPanel.append("<h3 class='clean'>Area : " + (area / 10000).toFixed(1) + " ha\n");
+
+		if (utils.is_polygon(geom)){ // It could be a MultiPolygon, for example.
+			var coordinates = geom.getLinearRing(0).getCoordinates();
+			var area = Math.abs(wgs84Sphere.geodesicArea(coordinates));
+			//NOTE: Could show m², ha or km² depending on magnitude
+			dataPanel.append("<h3 class='clean'>Area : " + (area / 10000).toFixed(1) + " ha\n");
+		}
 		dataPanel.append('<div style="visibility:hidden" id="download_region">' +
 			'<button type="button" onclick="regionChooser.downloadFromSelectedCityGMLs()" id="download_region_button" disabled>Download Region</button><br/>\n' +
 			'<a href="#" onclick="regionChooser.selectAllOrNone(true);">(Select All)</a>\n' +
@@ -381,7 +384,7 @@ const regionChooser = (function(){
 		//TODO: Show tooltip above.
 		dataPanel.append("<form id='importWKT'>\n" +
 		"<input id='wktPolygon' type='text' placeholder='WKT Polygon' " +
-		"required pattern=' *POLYGON *\\( *\\([\\-0-9\., \)\()]+\\) *\\) *' " +
+		"required pattern=' *(MULTI)?POLYGON *\\( *\\([\\-0-9\., \)\()]+\\) *\\) *' " +
 		"title='Please input a valid WKT Polygon. Example : POLYGON((9.961675 49.807053, 9.951375 49.798521, 9.969486 49.797746, 9.961675 49.807053)) '/>\n" +
 		"<input type='submit' value='Import Polygon'/>\n" +
 		"</form>\n");
@@ -411,13 +414,18 @@ const regionChooser = (function(){
 			return false;
 		}
 
+
 		// Assuming the linear ring is closed
-		var coordinatesCount = feature.getGeometry().getLinearRing(0).getCoordinates().length - 1;
+		var geom = feature.getGeometry();
 
-		if (coordinatesCount < 2){
-			console.warn("Too few points!");
-			dataPanel.prepend("<h2 class='error'>There should be at least 2 points in WKT polygon</h2><br/>\n");
-			return false;
+		if (utils.is_polygon(geom)){
+			var coordinatesCount = geom.getLinearRing(0).getCoordinates().length - 1;
+
+			if (coordinatesCount < 2){
+				console.warn("Too few points!");
+				dataPanel.prepend("<h2 class='error'>There should be at least 2 points in WKT polygon</h2><br/>\n");
+				return false;
+			}
 		}
 
 		sketch = feature;
@@ -426,7 +434,7 @@ const regionChooser = (function(){
 		drawnLayer.getFeatures().clear();
 		intersections.clear();
 		drawnLayer.addFeature(feature);
-		map.getView().fitExtent(feature.getGeometry().getExtent(), map.getSize());
+		map.getView().fitExtent(geom.getExtent(), map.getSize());
 
 		displayInfo();
 		draw.setActive(false);
@@ -460,6 +468,10 @@ const regionChooser = (function(){
 
 	publicScope.copyCoordinatesToClipboard = function(){
 		var geom = sketch.getGeometry().clone().transform(sourceProj, 'EPSG:4326');
+		if (!utils.is_polygon(geom)){
+			console.warn("Sorry, can only export single polygons.");
+			return false;
+		}
 		var wgs84Coords = geom.getLinearRing(0).getCoordinates();
 		var wktPolygon = "POLYGON((";
 		var precision = 6; // ~ 10 cm precision

src/main/resources/eu/simstadt/regionchooser/website/script/utils.js

 var utils = {};
 
-utils.groupBy = function(xs, key) {
-	return xs.reduce(function(rv, x) {
-	(rv[x[key]] = rv[x[key]] || []).push(x);
-	return rv;
+utils.groupBy = function (xs, key) {
+	return xs.reduce(function (rv, x) {
+		(rv[x[key]] = rv[x[key]] || []).push(x);
+		return rv;
 	}, {});
 }
-	
+
 // Copies a string to the clipboard. Must be called from within an
 // event handler such as click. May return false if it failed, but
 // this is not always possible. Browser support for Chrome 43+,
@@ -15,7 +15,7 @@ utils.groupBy = function(xs, key) {
 // an administrator. By default a prompt is shown the first
 // time the clipboard is used (per session).
 // https://stackoverflow.com/a/33928558/6419007
-utils.copyToClipboard = function(text, log) {
+utils.copyToClipboard = function (text, log) {
 	if (window.clipboardData && window.clipboardData.setData) {
 		// Internet Explorer-specific code path to prevent textarea being shown while dialog is visible.
 		return window.clipboardData.setData("Text", text);
@@ -40,25 +40,29 @@ utils.copyToClipboard = function(text, log) {
 		}
 	}
 }
-	
-utils.read_kml = function(url){
+
+utils.read_kml = function (url) {
 	return new ol.source.KML({
-		projection : ol.proj.get('EPSG:3857'),
-		url : url,
-		extractAttributes : false,
-		extractStyles : false
+		projection: ol.proj.get('EPSG:3857'),
+		url: url,
+		extractAttributes: false,
+		extractStyles: false
 	});
 }
-	
-utils.polygon_style = function(color, alpha) {
+
+utils.is_polygon = function (geom) {
+	return ('getType' in geom) && (geom.getType() === 'Polygon');
+}
+
+utils.polygon_style = function (color, alpha) {
 	return new ol.style.Style({
-		fill : new ol.style.Fill({
-			color : 'rgba(255, 255, 255,' + alpha + ')'
+		fill: new ol.style.Fill({
+			color: 'rgba(255, 255, 255,' + alpha + ')'
 		}),
-		stroke : new ol.style.Stroke({
-			color : color,
-			width : 2,
-			lineDash : [ 5, 10 ]
+		stroke: new ol.style.Stroke({
+			color: color,
+			width: 2,
+			lineDash: [5, 10]
 		}),
 	});
 }