Add enableRotation option to ol.View2D

src/objectliterals.jsdoc

@@ -91,6 +91,8 @@
  *     The coordinate system for the center is specified with the `projection`
  *     option. Default is `undefined`, and layer sources will not be fetched if
  *     this is not set.
+ * @property {boolean|undefined} enableRotation Enable rotation. Default is
+ *     `true`.
  * @property {ol.Extent|undefined} extent The extent that constrains the center,
  *     in other words, center cannot be set outside this extent.
  *     Default is `undefined`.

src/ol/view2d.js

@@ -569,6 +569,11 @@ ol.View2D.createResolutionConstraint_ = function(options) {
  * @return {ol.RotationConstraintType} Rotation constraint.
  */
 ol.View2D.createRotationConstraint_ = function(options) {
-  // FIXME rotation constraint is not configurable at the moment
+  var enableRotation = goog.isDef(options.enableRotation) ?
+      options.enableRotation : true;
+  if (enableRotation) {
     return ol.RotationConstraint.createSnapToZero();
+  } else {
+    return ol.RotationConstraint.disable;
+  }
 };