# Source: src/ol/interaction/keyboardzoominteraction.js

    // FIXME works for View2D only

    goog.provide('ol.interaction.KeyboardZoom');

    goog.require('goog.asserts');
    goog.require('goog.events.KeyHandler.EventType');
    goog.require('ol.events.ConditionType');
    goog.require('ol.events.condition');
    goog.require('ol.interaction.Interaction');

    /**
     * @classdesc
     * Allows the user to zoom the map using keyboard + and -.
     * Note that, although this interaction is by default included in maps,
     * the keys can only be used when browser focus is on the element to which
     * the keyboard events are attached. By default, this is the map div,
     * though you can change this with the `keyboardEventTarget` in
     * {@link ol.Map}. `document` never loses focus but, for any other element,
     * focus will have to be on, and returned to, this element if the keys are to
     * function.
     * See also {@link ol.interaction.KeyboardPan}.
     *
     * @constructor
     * @param {olx.interaction.KeyboardZoomOptions=} opt_options Options.
     * @extends {ol.interaction.Interaction}
     * @todo api
     */
    ol.interaction.KeyboardZoom = function(opt_options) {

      goog.base(this);

      var options = goog.isDef(opt_options) ? opt_options : {};

      /**
       * @private
       * @type {ol.events.ConditionType}
       */
      this.condition_ = goog.isDef(options.condition) ? options.condition :
              ol.events.condition.targetNotEditable;

      /**
       * @private
       * @type {number}
       */
      this.delta_ = goog.isDef(options.delta) ? options.delta : 1;

      /**
       * @private
       * @type {number}
       */
      this.duration_ = goog.isDef(options.duration) ? options.duration : 100;

    };
    goog.inherits(ol.interaction.KeyboardZoom, ol.interaction.Interaction);

    /**
     * @inheritDoc
     */
    ol.interaction.KeyboardZoom.prototype.handleMapBrowserEvent =
        function(mapBrowserEvent) {
      var stopEvent = false;
      if (mapBrowserEvent.type == goog.events.KeyHandler.EventType.KEY) {
        var keyEvent = /** @type {goog.events.KeyEvent} */
            (mapBrowserEvent.browserEvent);
        var charCode = keyEvent.charCode;
        if (this.condition_(mapBrowserEvent) &&
            (charCode == '+'.charCodeAt(0) || charCode == '-'.charCodeAt(0))) {
          var map = mapBrowserEvent.map;
          var delta = (charCode == '+'.charCodeAt(0)) ? this.delta_ : -this.delta_;
          map.render();
          // FIXME works for View2D only
          var view = map.getView().getView2D();
          ol.interaction.Interaction.zoomByDelta(
              map, view, delta, undefined, this.duration_);
          mapBrowserEvent.preventDefault();
          stopEvent = true;
        }
      }
      return !stopEvent;
    };