Add angle and destinationOnSegment

spec/index.html

@@ -66,6 +66,7 @@
   <script src="test.reverse.js"></script>
   <script src="test.rotatePoint.js"></script>
   <script src="test.startsAtExtremity.js"></script>
+  <script src="test.angle.js"></script>
   <script>
     (window.mochaPhantomJS || window.mocha).run();
   </script>

spec/test.angle.js

@@ -0,0 +1,26 @@
+describe('Angle', function() {
+
+  it('It should be 45 degrees', function(done) {
+    var latlng1 = L.latLng([0.0, 0.0]),
+        latlng2 = L.latLng([1.0, 1.0]),
+        result = 45.0;
+    assert.equal(result, L.GeometryUtil.angle(map, latlng1, latlng2));
+    done();
+  });
+
+  it('It should be degrees clockwise from east, 0 degrees', function(done) {
+    var latlng1 = L.latLng([0.0, 0.0]),
+        latlng2 = L.latLng([1.0, 0.0]),
+        result = 0.0;
+    assert.equal(result, L.GeometryUtil.angle(map, latlng1, latlng2));
+    done();
+  });
+
+  it('It should not be a negative value when the angle is greater than 180', function(done) {
+    var latlng1 = L.latLng([0.0, 0.0]),
+        latlng2 = L.latLng([-1.0, 1.0]),
+        result = -135.0;
+    assert.notEqual(result, L.GeometryUtil.angle(map, latlng1, latlng2));
+    done();
+  });
+});

spec/test.destination.js

@@ -26,4 +26,4 @@ describe('Destination', function() {
     assert.latLngEqual(result, L.GeometryUtil.destination(latlng1, heading, dist));
     done();
   });
-});
+});

src/leaflet.geometryutil.js

@@ -703,8 +703,8 @@ L.GeometryUtil = L.extend(L.GeometryUtil || {}, {
        Returns the point that is a distance and heading away from
        the given origin point.
        @param {L.LatLng} latlng: origin point
-       @param {float}: heading in degrees, clockwise from 0 degrees north.
-       @param {float}: distance in meters
+       @param {float} heading: heading in degrees, clockwise from 0 degrees north.
+       @param {float} distance: distance in meters
        @returns {L.latLng} the destination point.
        Many thanks to Chris Veness at http://www.movable-type.co.uk/scripts/latlong.html
        for a great reference and examples.
@@ -728,7 +728,37 @@ L.GeometryUtil = L.extend(L.GeometryUtil || {}, {
         lon2 = lon2 * radInv;
         lon2 = lon2 > 180 ? lon2 - 360 : lon2 < -180 ? lon2 + 360 : lon2;
         return L.latLng([lat2 * radInv, lon2]);
-    }
+    },
+
+    /**
+       Returns the the angle of the given segment and the Equator in degrees,
+       clockwise from 0 degrees north.
+       @param {L.Map} map: Leaflet map to be used for this method
+       @param {L.LatLng} latlngA: geographical point A of the segment
+       @param {L.LatLng} latlngB: geographical point B of the segment
+       @returns {Float} the angle in degrees.
+    */
+    angle: function(map, latlngA, latlngB) {
+      var pointA = map.latLngToContainerPoint(latlngA),
+          pointB = map.latLngToContainerPoint(latlngB),
+          angleDeg = Math.atan2(pointB.y - pointA.y, pointB.x - pointA.x) * 180 / Math.PI + 90;
+      angleDeg += angleDeg < 0 ? 360 : 0;
+      return angleDeg;
+    },
+
+    /**
+       Returns a point snaps on the segment and heading away from the given origin point a distance.
+       @param {L.Map} map: Leaflet map to be used for this method
+       @param {L.LatLng} latlngA: geographical point A of the segment
+       @param {L.LatLng} latlngB: geographical point B of the segment
+       @param {float} distance: distance in meters
+       @returns {L.latLng} the destination point.
+    */
+    destinationOnSegment: function(map, latlngA, latlngB, distance) {
+      var angleDeg = L.GeometryUtil.angle(map, latlngA, latlngB),
+          latlng = L.GeometryUtil.destination(latlngA, angleDeg, distance);
+      return L.GeometryUtil.closestOnSegment(map, latlng, latlngA, latlngB);
+    },
 });
 
 return L.GeometryUtil;