Option to enable selection of overlapping features

externs/olx.js

@@ -2519,7 +2519,8 @@ olx.interaction.PointerOptions.prototype.handleUpEvent;
  *     layers: (Array.<ol.layer.Layer>|function(ol.layer.Layer): boolean|undefined),
  *     style: (ol.style.Style|Array.<ol.style.Style>|ol.style.StyleFunction|undefined),
  *     removeCondition: (ol.events.ConditionType|undefined),
- *     toggleCondition: (ol.events.ConditionType|undefined)}}
+ *     toggleCondition: (ol.events.ConditionType|undefined),
+ *     multi: (boolean|undefined)}}
  * @api
  */
 olx.interaction.SelectOptions;
@@ -2596,6 +2597,15 @@ olx.interaction.SelectOptions.prototype.removeCondition;
  */
 olx.interaction.SelectOptions.prototype.toggleCondition;
 
+/**
+ * A boolean that determines if the default behaviour should select only
+ * single features or all (overlapping) features at the clicked map
+ * position. Default is false i.e single select
+ * @type {boolean|undefined}
+ * @api
+ */
+olx.interaction.SelectOptions.prototype.multi;
+
 
 /**
  * Namespace.