Care with transform

Since the transform method takes an arbitrary transform function, new coordinates may not be ordered in the same way as the originals.

src/ol/extent.js

@@ -94,7 +94,8 @@ ol.Extent.prototype.getTopRight = function() {
  * @return {ol.Extent} Extent.
  */
 ol.Extent.prototype.transform = function(transformFn) {
-  var min = transformFn(new ol.Coordinate(this.minX, this.minY));
-  var max = transformFn(new ol.Coordinate(this.maxX, this.maxY));
-  return new ol.Extent(min.x, min.y, max.x, max.y);
+  var a = transformFn(new ol.Coordinate(this.minX, this.minY));
+  var b = transformFn(new ol.Coordinate(this.maxX, this.maxY));
+  return new ol.Extent(Math.min(a.x, b.x), Math.min(a.y, b.y),
+      Math.max(a.x, b.x), Math.max(a.y, b.y));
 };

test/spec/ol/extent.test.js

@@ -55,6 +55,23 @@ describe('ol.Extent', function() {
       expect(destinationExtent.maxX).toRoughlyEqual(5009377.085697311, 1e-9);
       expect(destinationExtent.maxY).toRoughlyEqual(8399737.889818361, 1e-9);
     });
+
+    it('takes arbitrary function', function() {
+      var transformFn = function(coordinate) {
+        return new ol.Coordinate(-coordinate.x, -coordinate.y);
+      }
+      var sourceExtent = new ol.Extent(-15, -30, 45, 60);
+      var destinationExtent = sourceExtent.transform(transformFn);
+      expect(destinationExtent).not.toBeUndefined();
+      expect(destinationExtent).not.toBeNull();
+      // FIXME check values with third-party tool
+      expect(destinationExtent.minX).toBe(-45);
+      expect(destinationExtent.minY).toBe(-60);
+      expect(destinationExtent.maxX).toBe(15);
+      expect(destinationExtent.maxY).toBe(30);
+    });
+
+
   });
 });