From 3336bcbbe9243abeeb430084b704c51d56542939 Mon Sep 17 00:00:00 2001
From: Yohan Boniface <yb@enix.org>
Date: Sun, 12 Apr 2015 18:33:56 +0200
Subject: [PATCH] Fix Polygon.getCenter returning invalid LatLng when all
 points in same pixel

---
 spec/suites/layer/vector/PolygonSpec.js | 22 ++++++++++++++++++++++
 src/layer/vector/Polygon.js             | 17 +++++++++++++----
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/spec/suites/layer/vector/PolygonSpec.js b/spec/suites/layer/vector/PolygonSpec.js
index 07c0170f..40f69e33 100644
--- a/spec/suites/layer/vector/PolygonSpec.js
+++ b/spec/suites/layer/vector/PolygonSpec.js
@@ -93,4 +93,26 @@ describe('Polygon', function () {
 			expect(polygon._latlngs).to.eql([L.latLng([1, 2]), L.latLng([7, 8]), L.latLng([5, 6])]);
 		});
 	});
+
+	describe('#getCenter', function () {
+
+		it('should compute center of a big simple polygon around equator', function () {
+			var latlngs = [
+				[[0, 0], [10, 0], [10, 10], [0, 10]]
+			];
+			var layer = new L.Polygon(latlngs).addTo(map);
+			expect(layer.getCenter()).to.be.nearLatLng(L.latLng([5, 5]), 1e-1);
+		});
+
+		it('should compute center of a small simple polygon', function () {
+			var latlngs = [
+				[[0, 0], [0.010, 0], [0.010, 0.010], [0, 0.010]]
+			];
+			var layer = new L.Polygon(latlngs).addTo(map);
+			map.setZoom(0);  // Make the polygon disappear in screen.
+			expect(layer.getCenter()).to.be.nearLatLng(L.latLng([0, 0]));
+		});
+
+	});
+
 });
diff --git a/src/layer/vector/Polygon.js b/src/layer/vector/Polygon.js
index f35bc6df..dacf1633 100644
--- a/src/layer/vector/Polygon.js
+++ b/src/layer/vector/Polygon.js
@@ -9,14 +9,17 @@ L.Polygon = L.Polyline.extend({
 	},
 
 	getCenter: function () {
-		var i, j, len, p1, p2, f, area, x, y,
-		    points = this._rings[0];
+		var i, j, p1, p2, f, area, x, y, center,
+		    points = this._rings[0],
+		    len = points.length;
+
+		if (!len) { return null; }
 
 		// polygon centroid algorithm; only uses the first ring if there are multiple
 
 		area = x = y = 0;
 
-		for (i = 0, len = points.length, j = len - 1; i < len; j = i++) {
+		for (i = 0, j = len - 1; i < len; j = i++) {
 			p1 = points[i];
 			p2 = points[j];
 
@@ -26,7 +29,13 @@ L.Polygon = L.Polyline.extend({
 			area += f * 3;
 		}
 
-		return this._map.layerPointToLatLng([x / area, y / area]);
+		if (area === 0) {
+			// Polygon is so small that all points are on same pixel.
+			center = points[0];
+		} else {
+			center = [x / area, y / area];
+		}
+		return this._map.layerPointToLatLng(center);
 	},
 
 	_convertLatLngs: function (latlngs) {