patch for #809 - add the addEventType() function to the OpenLayers.Events objects so that subclasses can safely add new event types without modifying their parents' constant values

git-svn-id: http://svn.openlayers.org/trunk/openlayers@3622 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Events.js

@@ -410,7 +410,7 @@ OpenLayers.Events.prototype = {
         // custom application event.
         if (this.eventTypes != null) {
             for (var i = 0; i < this.eventTypes.length; i++) {
-                this.listeners[ this.eventTypes[i] ] = new Array();
+                this.addEventType(this.eventTypes[i]);
             }
         }
         
@@ -437,6 +437,20 @@ OpenLayers.Events.prototype = {
         this.eventHandler = null;
     },
 
+    /**
+     * APIMethod: addEventType
+     * Add a new event type to this events object.
+     * If the event type has already been added, do nothing.
+     * 
+     * Parameters:
+     * eventName - {String}
+     */
+    addEventType: function(eventName) {
+        if (!this.listeners[eventName]) {
+            this.listeners[eventName] = new Array();
+        }
+    },
+
     /**
      * Method: attachToElement
      *
@@ -449,9 +463,7 @@ OpenLayers.Events.prototype = {
 
             // every browser event has a corresponding application event 
             // (whether it's listened for or not).
-            if (this.listeners[eventType] == null) {
-                this.listeners[eventType] = new Array();
-            }
+            this.addEventType(eventType);
             
             // use Prototype to register the event cross-browser
             OpenLayers.Event.observe(element, eventType, this.eventHandler);