Allow orienting with the right-hand rule

src/ol/geom/flat/orientflatgeom.js

@@ -29,22 +29,34 @@ ol.geom.flat.orient.linearRingIsClockwise =
 
 
 /**
+ * Determines if linear rings are oriented.  By default, left-hand orientation
+ * is tested (first ring must be clockwise, remaining rings counter-clockwise).
+ * To test for right-hand orientation, use the `opt_right` argument.
+ *
  * @param {Array.<number>} flatCoordinates Flat coordinates.
  * @param {number} offset Offset.
- * @param {Array.<number>} ends Ends.
+ * @param {Array.<number>} ends Array of end indexes.
  * @param {number} stride Stride.
- * @return {boolean} `true` if all rings are correctly oriented, `false`
- *     otherwise.
+ * @param {boolean=} opt_right Test for right-hand orientation
+ *     (counter-clockwise exterior ring and clockwise interior rings).
+ * @return {boolean} Rings are correctly oriented.
  */
 ol.geom.flat.orient.linearRingsAreOriented =
-    function(flatCoordinates, offset, ends, stride) {
+    function(flatCoordinates, offset, ends, stride, opt_right) {
+  var right = goog.isDef(opt_right) ? opt_right : false;
   var i, ii;
   for (i = 0, ii = ends.length; i < ii; ++i) {
     var end = ends[i];
     var isClockwise = ol.geom.flat.orient.linearRingIsClockwise(
         flatCoordinates, offset, end, stride);
-    if (i === 0 ? !isClockwise : isClockwise) {
-      return false;
+    if (i === 0) {
+      if ((right && isClockwise) || (!right && !isClockwise)) {
+        return false;
+      }
+    } else {
+      if ((right && !isClockwise) || (!right && isClockwise)) {
+        return false;
+      }
     }
     offset = end;
   }
@@ -53,19 +65,24 @@ ol.geom.flat.orient.linearRingsAreOriented =
 
 
 /**
+ * Determines if linear rings are oriented.  By default, left-hand orientation
+ * is tested (first ring must be clockwise, remaining rings counter-clockwise).
+ * To test for right-hand orientation, use the `opt_right` argument.
+ *
  * @param {Array.<number>} flatCoordinates Flat coordinates.
  * @param {number} offset Offset.
- * @param {Array.<Array.<number>>} endss Endss.
+ * @param {Array.<Array.<number>>} endss Array of array of end indexes.
  * @param {number} stride Stride.
- * @return {boolean} `true` if all rings are correctly oriented, `false`
- *     otherwise.
+ * @param {boolean=} opt_right Test for right-hand orientation
+ *     (counter-clockwise exterior ring and clockwise interior rings).
+ * @return {boolean} Rings are correctly oriented.
  */
 ol.geom.flat.orient.linearRingssAreOriented =
-    function(flatCoordinates, offset, endss, stride) {
+    function(flatCoordinates, offset, endss, stride, opt_right) {
   var i, ii;
   for (i = 0, ii = endss.length; i < ii; ++i) {
     if (!ol.geom.flat.orient.linearRingsAreOriented(
-        flatCoordinates, offset, endss[i], stride)) {
+        flatCoordinates, offset, endss[i], stride, opt_right)) {
       return false;
     }
   }
@@ -74,20 +91,29 @@ ol.geom.flat.orient.linearRingssAreOriented =
 
 
 /**
+ * Orient coordinates in a flat array of linear rings.  By default, rings
+ * are oriented following the left-hand rule (clockwise for exterior and
+ * counter-clockwise for interior rings).  To orient according to the
+ * right-hand rule, use the `opt_right` argument.
+ *
  * @param {Array.<number>} flatCoordinates Flat coordinates.
  * @param {number} offset Offset.
  * @param {Array.<number>} ends Ends.
  * @param {number} stride Stride.
+ * @param {boolean=} opt_right Follow the right-hand rule for orientation.
  * @return {number} End.
  */
 ol.geom.flat.orient.orientLinearRings =
-    function(flatCoordinates, offset, ends, stride) {
+    function(flatCoordinates, offset, ends, stride, opt_right) {
+  var right = goog.isDef(opt_right) ? opt_right : false;
   var i, ii;
   for (i = 0, ii = ends.length; i < ii; ++i) {
     var end = ends[i];
     var isClockwise = ol.geom.flat.orient.linearRingIsClockwise(
         flatCoordinates, offset, end, stride);
-    var reverse = i === 0 ? !isClockwise : isClockwise;
+    var reverse = i === 0 ?
+        (right && isClockwise) || (!right && !isClockwise) :
+        (right && !isClockwise) || (!right && isClockwise);
     if (reverse) {
       ol.geom.flat.reverse.coordinates(flatCoordinates, offset, end, stride);
     }
@@ -98,18 +124,24 @@ ol.geom.flat.orient.orientLinearRings =
 
 
 /**
+ * Orient coordinates in a flat array of linear rings.  By default, rings
+ * are oriented following the left-hand rule (clockwise for exterior and
+ * counter-clockwise for interior rings).  To orient according to the
+ * right-hand rule, use the `opt_right` argument.
+ *
  * @param {Array.<number>} flatCoordinates Flat coordinates.
  * @param {number} offset Offset.
- * @param {Array.<Array.<number>>} endss Endss.
+ * @param {Array.<Array.<number>>} endss Array of array of end indexes.
  * @param {number} stride Stride.
+ * @param {boolean=} opt_right Follow the right-hand rule for orientation.
  * @return {number} End.
  */
 ol.geom.flat.orient.orientLinearRingss =
-    function(flatCoordinates, offset, endss, stride) {
+    function(flatCoordinates, offset, endss, stride, opt_right) {
   var i, ii;
   for (i = 0, ii = endss.length; i < ii; ++i) {
     offset = ol.geom.flat.orient.orientLinearRings(
-        flatCoordinates, offset, endss[i], stride);
+        flatCoordinates, offset, endss[i], stride, opt_right);
   }
   return offset;
 };