text: goog.provide('ol.View');
  goog.provide('ol.ViewHint');
  
  goog.require('goog.array');
  goog.require('goog.asserts');
  goog.require('ol');
  goog.require('ol.CenterConstraint');
  goog.require('ol.Constraints');
  goog.require('ol.Object');
  goog.require('ol.ResolutionConstraint');
  goog.require('ol.RotationConstraint');
  goog.require('ol.RotationConstraintType');
  goog.require('ol.Size');
  goog.require('ol.coordinate');
  goog.require('ol.extent');
  goog.require('ol.proj');
  goog.require('ol.proj.METERS_PER_UNIT');
  goog.require('ol.proj.Projection');
  goog.require('ol.proj.Units');
  
  
  /**
   * @enum {string}
   */
  ol.ViewProperty = {
    CENTER: 'center',
    RESOLUTION: 'resolution',
    ROTATION: 'rotation'
  };
  
  
  /**
   * @enum {number}
   */
  ol.ViewHint = {
    ANIMATING: 0,
    INTERACTING: 1
  };
  
  
  
  /**
   * @classdesc
   * An ol.View object represents a simple 2D view of the map.
   *
   * This is the object to act upon to change the center, resolution,
   * and rotation of the map.
   *
   * ### The view states
   *
   * An `ol.View` is determined by three states: `center`, `resolution`,
   * and `rotation`. Each state has a corresponding getter and setter, e.g.
   * `getCenter` and `setCenter` for the `center` state.
   *
   * An `ol.View` has a `projection`. The projection determines the
   * coordinate system of the center, and its units determine the units of the
   * resolution (projection units per pixel). The default projection is
   * Spherical Mercator (EPSG:3857).
   *
   * ### The constraints
   *
   * `setCenter`, `setResolution` and `setRotation` can be used to change the
   * states of the view. Any value can be passed to the setters. And the value
   * that is passed to a setter will effectively be the value set in the view,
   * and returned by the corresponding getter.
   *
   * But an `ol.View` object also has a *resolution constraint*, a
   * *rotation constraint* and a *center constraint*.
   *
   * As said above, no constraints are applied when the setters are used to set
   * new states for the view. Applying constraints is done explicitly through
   * the use of the `constrain*` functions (`constrainResolution` and
   * `constrainRotation` and `constrainCenter`).
   *
   * The main users of the constraints are the interactions and the
   * controls. For example, double-clicking on the map changes the view to
   * the "next" resolution. And releasing the fingers after pinch-zooming
   * snaps to the closest resolution (with an animation).
   *
   * The *resolution constraint* snaps to specific resolutions. It is
   * determined by the following options: `resolutions`, `maxResolution`,
   * `maxZoom`, and `zoomFactor`. If `resolutions` is set, the other three
   * options are ignored. See documentation for each option for more
   * information.
   *
   * The *rotation constraint* snaps to specific angles. It is determined
   * by the following options: `enableRotation` and `constrainRotation`.
   * By default the rotation value is snapped to zero when approaching the
   * horizontal.
   *
   * The *center constraint* is determined by the `extent` option. By
   * default the center is not constrained at all.
   *
   * @constructor
   * @extends {ol.Object}
   * @param {olx.ViewOptions=} opt_options View options.
   * @api stable
   */
  ol.View = function(opt_options) {
    goog.base(this);
    var options = goog.isDef(opt_options) ? opt_options : {};
  
    /**
     * @private
     * @type {Array.<number>}
     */
    this.hints_ = [0, 0];
  
    /**
     * @type {Object.<string, *>}
     */
    var properties = {};
    properties[ol.ViewProperty.CENTER] = goog.isDef(options.center) ?
        options.center : null;
  
    /**
     * @private
     * @type {ol.proj.Projection}
     */
    this.projection_ = ol.proj.createProjection(options.projection, 'EPSG:3857');
  
    var resolutionConstraintInfo = ol.View.createResolutionConstraint_(
        options);
  
    /**
     * @private
     * @type {number}
     */
    this.maxResolution_ = resolutionConstraintInfo.maxResolution;
  
    /**
     * @private
     * @type {number}
     */
    this.minResolution_ = resolutionConstraintInfo.minResolution;
  
    /**
     * @private
     * @type {number}
     */
    this.minZoom_ = resolutionConstraintInfo.minZoom;
  
    var centerConstraint = ol.View.createCenterConstraint_(options);
    var resolutionConstraint = resolutionConstraintInfo.constraint;
    var rotationConstraint = ol.View.createRotationConstraint_(options);
  
    /**
     * @private
     * @type {ol.Constraints}
     */
    this.constraints_ = new ol.Constraints(
        centerConstraint, resolutionConstraint, rotationConstraint);
  
    if (goog.isDef(options.resolution)) {
      properties[ol.ViewProperty.RESOLUTION] = options.resolution;
    } else if (goog.isDef(options.zoom)) {
      properties[ol.ViewProperty.RESOLUTION] = this.constrainResolution(
          this.maxResolution_, options.zoom - this.minZoom_);
    }
    properties[ol.ViewProperty.ROTATION] =
        goog.isDef(options.rotation) ? options.rotation : 0;
    this.setProperties(properties);
  };
  goog.inherits(ol.View, ol.Object);
  
  
  /**
   * @param {number} rotation Target rotation.
   * @param {ol.Coordinate} anchor Rotation anchor.
   * @return {ol.Coordinate|undefined} Center for rotation and anchor.
   */
  ol.View.prototype.calculateCenterRotate = function(rotation, anchor) {
    var center;
    var currentCenter = this.getCenter();
    if (goog.isDef(currentCenter)) {
      center = [currentCenter[0] - anchor[0], currentCenter[1] - anchor[1]];
      ol.coordinate.rotate(center, rotation - this.getRotation());
      ol.coordinate.add(center, anchor);
    }
    return center;
  };
  
  
  /**
   * @param {number} resolution Target resolution.
   * @param {ol.Coordinate} anchor Zoom anchor.
   * @return {ol.Coordinate|undefined} Center for resolution and anchor.
   */
  ol.View.prototype.calculateCenterZoom = function(resolution, anchor) {
    var center;
    var currentCenter = this.getCenter();
    var currentResolution = this.getResolution();
    if (goog.isDef(currentCenter) && goog.isDef(currentResolution)) {
      var x = anchor[0] -
          resolution * (anchor[0] - currentCenter[0]) / currentResolution;
      var y = anchor[1] -
          resolution * (anchor[1] - currentCenter[1]) / currentResolution;
      center = [x, y];
    }
    return center;
  };
  
  
  /**
   * Get the constrained center of this view.
   * @param {ol.Coordinate|undefined} center Center.
   * @return {ol.Coordinate|undefined} Constrained center.
   * @api
   */
  ol.View.prototype.constrainCenter = function(center) {
    return this.constraints_.center(center);
  };
  
  
  /**
   * Get the constrained resolution of this view.
   * @param {number|undefined} resolution Resolution.
   * @param {number=} opt_delta Delta. Default is `0`.
   * @param {number=} opt_direction Direction. Default is `0`.
   * @return {number|undefined} Constrained resolution.
   * @api
   */
  ol.View.prototype.constrainResolution = function(
      resolution, opt_delta, opt_direction) {
    var delta = opt_delta || 0;
    var direction = opt_direction || 0;
    return this.constraints_.resolution(resolution, delta, direction);
  };
  
  
  /**
   * Get the constrained rotation of this view.
   * @param {number|undefined} rotation Rotation.
   * @param {number=} opt_delta Delta. Default is `0`.
   * @return {number|undefined} Constrained rotation.
   * @api
   */
  ol.View.prototype.constrainRotation = function(rotation, opt_delta) {
    var delta = opt_delta || 0;
    return this.constraints_.rotation(rotation, delta);
  };
  
  
  /**
   * @return {ol.Coordinate|undefined} The center of the view.
   * @observable
   * @api stable
   */
  ol.View.prototype.getCenter = function() {
    return /** @type {ol.Coordinate|undefined} */ (
        this.get(ol.ViewProperty.CENTER));
  };
  goog.exportProperty(
      ol.View.prototype,
      'getCenter',
      ol.View.prototype.getCenter);
  
  
  /**
   * @return {Array.<number>} Hint.
   */
  ol.View.prototype.getHints = function() {
    return goog.array.clone(this.hints_);
  };
  
  
  /**
   * Calculate the extent for the current view state and the passed `size`.
   * `size` is the size in pixels of the box into which the calculated extent
   * should fit. In most cases you want to get the extent of the entire map,
   * that is `map.getSize()`.
   * @param {ol.Size} size Box pixel size.
   * @return {ol.Extent} Extent.
   * @api
   */
  ol.View.prototype.calculateExtent = function(size) {
    goog.asserts.assert(this.isDef());
    var center = this.getCenter();
    var resolution = this.getResolution();
    var minX = center[0] - resolution * size[0] / 2;
    var maxX = center[0] + resolution * size[0] / 2;
    var minY = center[1] - resolution * size[1] / 2;
    var maxY = center[1] + resolution * size[1] / 2;
    return [minX, minY, maxX, maxY];
  };
  
  
  /**
   * @return {ol.proj.Projection} The projection of the view.
   * @api stable
   */
  ol.View.prototype.getProjection = function() {
    return this.projection_;
  };
  
  
  /**
   * @return {number|undefined} The resolution of the view.
   * @observable
   * @api stable
   */
  ol.View.prototype.getResolution = function() {
    return /** @type {number|undefined} */ (
        this.get(ol.ViewProperty.RESOLUTION));
  };
  goog.exportProperty(
      ol.View.prototype,
      'getResolution',
      ol.View.prototype.getResolution);
  
  
  /**
   * Get the resolution for a provided extent (in map units) and size (in pixels).
   * @param {ol.Extent} extent Extent.
   * @param {ol.Size} size Box pixel size.
   * @return {number} The resolution at which the provided extent will render at
   *     the given size.
   * @api
   */
  ol.View.prototype.getResolutionForExtent = function(extent, size) {
    var xResolution = ol.extent.getWidth(extent) / size[0];
    var yResolution = ol.extent.getHeight(extent) / size[1];
    return Math.max(xResolution, yResolution);
  };
  
  
  /**
   * Return a function that returns a value between 0 and 1 for a
   * resolution. Exponential scaling is assumed.
   * @param {number=} opt_power Power.
   * @return {function(number): number} Resolution for value function.
   */
  ol.View.prototype.getResolutionForValueFunction = function(opt_power) {
    var power = opt_power || 2;
    var maxResolution = this.maxResolution_;
    var minResolution = this.minResolution_;
    var max = Math.log(maxResolution / minResolution) / Math.log(power);
    return (
        /**
         * @param {number} value Value.
         * @return {number} Resolution.
         */
        function(value) {
          var resolution = maxResolution / Math.pow(power, value * max);
          goog.asserts.assert(resolution >= minResolution &&
              resolution <= maxResolution);
          return resolution;
        });
  };
  
  
  /**
   * @return {number|undefined} The rotation of the view.
   * @observable
   * @api stable
   */
  ol.View.prototype.getRotation = function() {
    return /** @type {number|undefined} */ (this.get(ol.ViewProperty.ROTATION));
  };
  goog.exportProperty(
      ol.View.prototype,
      'getRotation',
      ol.View.prototype.getRotation);
  
  
  /**
   * Return a function that returns a resolution for a value between
   * 0 and 1. Exponential scaling is assumed.
   * @param {number=} opt_power Power.
   * @return {function(number): number} Value for resolution function.
   */
  ol.View.prototype.getValueForResolutionFunction = function(opt_power) {
    var power = opt_power || 2;
    var maxResolution = this.maxResolution_;
    var minResolution = this.minResolution_;
    var max = Math.log(maxResolution / minResolution) / Math.log(power);
    return (
        /**
         * @param {number} resolution Resolution.
         * @return {number} Value.
         */
        function(resolution) {
          var value =
              (Math.log(maxResolution / resolution) / Math.log(power)) / max;
          goog.asserts.assert(value >= 0 && value <= 1);
          return value;
        });
  };
  
  
  /**
   * @return {olx.ViewState} View state.
   */
  ol.View.prototype.getState = function() {
    goog.asserts.assert(this.isDef());
    var center = /** @type {ol.Coordinate} */ (this.getCenter());
    var projection = this.getProjection();
    var resolution = /** @type {number} */ (this.getResolution());
    var rotation = this.getRotation();
    return /** @type {olx.ViewState} */ ({
      center: center.slice(),
      projection: goog.isDef(projection) ? projection : null,
      resolution: resolution,
      rotation: goog.isDef(rotation) ? rotation : 0
    });
  };
  
  
  /**
   * Get the current zoom level. Return undefined if the current
   * resolution is undefined or not a "constrained resolution".
   * @return {number|undefined} Zoom.
   * @api stable
   */
  ol.View.prototype.getZoom = function() {
    var offset;
    var resolution = this.getResolution();
  
    if (goog.isDef(resolution)) {
      var res, z = 0;
      do {
        res = this.constrainResolution(this.maxResolution_, z);
        if (res == resolution) {
          offset = z;
          break;
        }
        ++z;
      } while (res > this.minResolution_);
    }
  
    return goog.isDef(offset) ? this.minZoom_ + offset : offset;
  };
  
  
  /**
   * Fit the map view to the passed `extent` and `size`. `size` is the size in
   * pixels of the box to fit the extent into. In most cases you will want to
   * use the map size, that is `map.getSize()`.
   * @param {ol.Extent} extent Extent.
   * @param {ol.Size} size Box pixel size.
   * @api
   */
  ol.View.prototype.fitExtent = function(extent, size) {
    if (!ol.extent.isEmpty(extent)) {
      this.setCenter(ol.extent.getCenter(extent));
      var resolution = this.getResolutionForExtent(extent, size);
      var constrainedResolution = this.constrainResolution(resolution, 0, 0);
      if (constrainedResolution < resolution) {
        constrainedResolution =
            this.constrainResolution(constrainedResolution, -1, 0);
      }
      this.setResolution(constrainedResolution);
    }
  };
  
  
  /**
   * Fit the given geometry based on the given map size and border.
   * Take care on the map angle.
   * @param {ol.geom.SimpleGeometry} geometry Geometry.
   * @param {ol.Size} size Box pixel size.
   * @param {olx.view.FitGeometryOptions=} opt_options Options.
   * @api
   */
  ol.View.prototype.fitGeometry = function(geometry, size, opt_options) {
    var options = goog.isDef(opt_options) ? opt_options : {};
  
    var padding = goog.isDef(options.padding) ? options.padding : [0, 0, 0, 0];
    var constrainResolution = goog.isDef(options.constrainResolution) ?
        options.constrainResolution : true;
    var nearest = goog.isDef(options.nearest) ? options.nearest : false;
    var minResolution;
    if (goog.isDef(options.minResolution)) {
      minResolution = options.minResolution;
    } else if (goog.isDef(options.maxZoom)) {
      minResolution = this.constrainResolution(
          this.maxResolution_, options.maxZoom - this.minZoom_, 0);
    } else {
      minResolution = 0;
    }
    var coords = geometry.getFlatCoordinates();
  
    // calculate rotated extent
    var rotation = this.getRotation();
    goog.asserts.assert(goog.isDef(rotation));
    var cosAngle = Math.cos(-rotation);
    var sinAngle = Math.sin(-rotation);
    var minRotX = +Infinity;
    var minRotY = +Infinity;
    var maxRotX = -Infinity;
    var maxRotY = -Infinity;
    var stride = geometry.getStride();
    for (var i = 0, ii = coords.length; i < ii; i += stride) {
      var rotX = coords[i] * cosAngle - coords[i + 1] * sinAngle;
      var rotY = coords[i] * sinAngle + coords[i + 1] * cosAngle;
      minRotX = Math.min(minRotX, rotX);
      minRotY = Math.min(minRotY, rotY);
      maxRotX = Math.max(maxRotX, rotX);
      maxRotY = Math.max(maxRotY, rotY);
    }
  
    // calculate resolution
    var resolution = this.getResolutionForExtent(
        [minRotX, minRotY, maxRotX, maxRotY],
        [size[0] - padding[1] - padding[3], size[1] - padding[0] - padding[2]]);
    resolution = isNaN(resolution) ? minResolution :
        Math.max(resolution, minResolution);
    if (constrainResolution) {
      var constrainedResolution = this.constrainResolution(resolution, 0, 0);
      if (!nearest && constrainedResolution < resolution) {
        constrainedResolution = this.constrainResolution(
            constrainedResolution, -1, 0);
      }
      resolution = constrainedResolution;
    }
    this.setResolution(resolution);
  
    // calculate center
    sinAngle = -sinAngle; // go back to original rotation
    var centerRotX = (minRotX + maxRotX) / 2;
    var centerRotY = (minRotY + maxRotY) / 2;
    centerRotX += (padding[1] - padding[3]) / 2 * resolution;
    centerRotY += (padding[0] - padding[2]) / 2 * resolution;
    var centerX = centerRotX * cosAngle - centerRotY * sinAngle;
    var centerY = centerRotY * cosAngle + centerRotX * sinAngle;
  
    this.setCenter([centerX, centerY]);
  };
  
  
  /**
   * Center on coordinate and view position.
   * Take care on the map angle.
   * @param {ol.Coordinate} coordinate Coordinate.
   * @param {ol.Size} size Box pixel size.
   * @param {ol.Pixel} position Position on the view to center on.
   * @api
   */
  ol.View.prototype.centerOn = function(coordinate, size, position) {
    // calculate rotated position
    var rotation = this.getRotation();
    var cosAngle = Math.cos(-rotation);
    var sinAngle = Math.sin(-rotation);
    var rotX = coordinate[0] * cosAngle - coordinate[1] * sinAngle;
    var rotY = coordinate[1] * cosAngle + coordinate[0] * sinAngle;
    var resolution = this.getResolution();
    rotX += (size[0] / 2 - position[0]) * resolution;
    rotY += (position[1] - size[1] / 2) * resolution;
  
    // go back to original angle
    sinAngle = -sinAngle; // go back to original rotation
    var centerX = rotX * cosAngle - rotY * sinAngle;
    var centerY = rotY * cosAngle + rotX * sinAngle;
  
    this.setCenter([centerX, centerY]);
  };
  
  
  /**
   * @return {boolean} Is defined.
   */
  ol.View.prototype.isDef = function() {
    return goog.isDefAndNotNull(this.getCenter()) &&
        goog.isDef(this.getResolution());
  };
  
  
  /**
   * Rotate the view around a given coordinate.
   * @param {number} rotation New rotation value for the view.
   * @param {ol.Coordinate=} opt_anchor The rotation center.
   * @api stable
   */
  ol.View.prototype.rotate = function(rotation, opt_anchor) {
    if (goog.isDef(opt_anchor)) {
      var center = this.calculateCenterRotate(rotation, opt_anchor);
      this.setCenter(center);
    }
    this.setRotation(rotation);
  };
  
  
  /**
   * Set the center of the current view.
   * @param {ol.Coordinate|undefined} center The center of the view.
   * @observable
   * @api stable
   */
  ol.View.prototype.setCenter = function(center) {
    this.set(ol.ViewProperty.CENTER, center);
  };
  goog.exportProperty(
      ol.View.prototype,
      'setCenter',
      ol.View.prototype.setCenter);
  
  
  /**
   * @param {ol.ViewHint} hint Hint.
   * @param {number} delta Delta.
   * @return {number} New value.
   */
  ol.View.prototype.setHint = function(hint, delta) {
    goog.asserts.assert(0 <= hint && hint < this.hints_.length);
    this.hints_[hint] += delta;
    goog.asserts.assert(this.hints_[hint] >= 0);
    return this.hints_[hint];
  };
  
  
  /**
   * Set the resolution for this view.
   * @param {number|undefined} resolution The resolution of the view.
   * @observable
   * @api stable
   */
  ol.View.prototype.setResolution = function(resolution) {
    this.set(ol.ViewProperty.RESOLUTION, resolution);
  };
  goog.exportProperty(
      ol.View.prototype,
      'setResolution',
      ol.View.prototype.setResolution);
  
  
  /**
   * Set the rotation for this view.
   * @param {number|undefined} rotation The rotation of the view.
   * @observable
   * @api stable
   */
  ol.View.prototype.setRotation = function(rotation) {
    this.set(ol.ViewProperty.ROTATION, rotation);
  };
  goog.exportProperty(
      ol.View.prototype,
      'setRotation',
      ol.View.prototype.setRotation);
  
  
  /**
   * Zoom to a specific zoom level.
   * @param {number} zoom Zoom level.
   * @api stable
   */
  ol.View.prototype.setZoom = function(zoom) {
    var resolution = this.constrainResolution(
        this.maxResolution_, zoom - this.minZoom_, 0);
    this.setResolution(resolution);
  };
  
  
  /**
   * @param {olx.ViewOptions} options View options.
   * @private
   * @return {ol.CenterConstraintType}
   */
  ol.View.createCenterConstraint_ = function(options) {
    if (goog.isDef(options.extent)) {
      return ol.CenterConstraint.createExtent(options.extent);
    } else {
      return ol.CenterConstraint.none;
    }
  };
  
  
  /**
   * @private
   * @param {olx.ViewOptions} options View options.
   * @return {{constraint: ol.ResolutionConstraintType, maxResolution: number,
   *     minResolution: number}}
   */
  ol.View.createResolutionConstraint_ = function(options) {
    var resolutionConstraint;
    var maxResolution;
    var minResolution;
  
    // TODO: move these to be ol constants
    // see https://github.com/openlayers/ol3/issues/2076
    var defaultMaxZoom = 28;
    var defaultZoomFactor = 2;
  
    var minZoom = goog.isDef(options.minZoom) ?
        options.minZoom : ol.DEFAULT_MIN_ZOOM;
  
    var maxZoom = goog.isDef(options.maxZoom) ?
        options.maxZoom : defaultMaxZoom;
  
    var zoomFactor = goog.isDef(options.zoomFactor) ?
        options.zoomFactor : defaultZoomFactor;
  
    if (goog.isDef(options.resolutions)) {
      var resolutions = options.resolutions;
      maxResolution = resolutions[0];
      minResolution = resolutions[resolutions.length - 1];
      resolutionConstraint = ol.ResolutionConstraint.createSnapToResolutions(
          resolutions);
    } else {
      // calculate the default min and max resolution
      var projection = ol.proj.createProjection(options.projection, 'EPSG:3857');
      var extent = projection.getExtent();
      var size = goog.isNull(extent) ?
          // use an extent that can fit the whole world if need be
          360 * ol.proj.METERS_PER_UNIT[ol.proj.Units.DEGREES] /
              ol.proj.METERS_PER_UNIT[projection.getUnits()] :
          Math.max(ol.extent.getWidth(extent), ol.extent.getHeight(extent));
  
      var defaultMaxResolution = size / ol.DEFAULT_TILE_SIZE / Math.pow(
          defaultZoomFactor, ol.DEFAULT_MIN_ZOOM);
  
      var defaultMinResolution = defaultMaxResolution / Math.pow(
          defaultZoomFactor, defaultMaxZoom - ol.DEFAULT_MIN_ZOOM);
  
      // user provided maxResolution takes precedence
      maxResolution = options.maxResolution;
      if (goog.isDef(maxResolution)) {
        minZoom = 0;
      } else {
        maxResolution = defaultMaxResolution / Math.pow(zoomFactor, minZoom);
      }
  
      // user provided minResolution takes precedence
      minResolution = options.minResolution;
      if (!goog.isDef(minResolution)) {
        if (goog.isDef(options.maxZoom)) {
          if (goog.isDef(options.maxResolution)) {
            minResolution = maxResolution / Math.pow(zoomFactor, maxZoom);
          } else {
            minResolution = defaultMaxResolution / Math.pow(zoomFactor, maxZoom);
          }
        } else {
          minResolution = defaultMinResolution;
        }
      }
  
      // given discrete zoom levels, minResolution may be different than provided
      maxZoom = minZoom + Math.floor(
          Math.log(maxResolution / minResolution) / Math.log(zoomFactor));
      minResolution = maxResolution / Math.pow(zoomFactor, maxZoom - minZoom);
  
      resolutionConstraint = ol.ResolutionConstraint.createSnapToPower(
          zoomFactor, maxResolution, maxZoom - minZoom);
    }
    return {constraint: resolutionConstraint, maxResolution: maxResolution,
      minResolution: minResolution, minZoom: minZoom};
  };
  
  
  /**
   * @private
   * @param {olx.ViewOptions} options View options.
   * @return {ol.RotationConstraintType} Rotation constraint.
   */
  ol.View.createRotationConstraint_ = function(options) {
    var enableRotation = goog.isDef(options.enableRotation) ?
        options.enableRotation : true;
    if (enableRotation) {
      var constrainRotation = options.constrainRotation;
      if (!goog.isDef(constrainRotation) || constrainRotation === true) {
        return ol.RotationConstraint.createSnapToZero();
      } else if (constrainRotation === false) {
        return ol.RotationConstraint.none;
      } else if (goog.isNumber(constrainRotation)) {
        return ol.RotationConstraint.createSnapToN(constrainRotation);
      } else {
        goog.asserts.fail();
        return ol.RotationConstraint.none;
      }
    } else {
      return ol.RotationConstraint.disable;
    }
  };
  