add a mouse wheel handler

src/ol.js

@@ -8,6 +8,7 @@ goog.require('ol.control.Zoom');
 goog.require('ol.event.Events');
 goog.require('ol.event.Scroll');
 goog.require('ol.handler.Drag');
+goog.require('ol.handler.MouseWheel');
 goog.require("ol.map");
 goog.require("ol.loc");
 goog.require("ol.feature");

src/ol/handler/MouseWheel.js

@@ -0,0 +1,37 @@
+/**
+ * @fileoverview Map Mouse Wheel Handler.
+ *
+ * Provides a class for listening to mousewheel events on a DOM element
+ * and re-dispatching to a map instance.
+ */
+
+goog.provide('ol.handler.MouseWheel');
+
+goog.require('goog.Disposable');
+goog.require('goog.events.MouseWheelHandler');
+
+
+/**
+ * @constructor
+ * @extends {goog.Disposable}
+ * @param {ol.Map} map The map instance.
+ * @param {Element} elt The element we listen to mousewheel on.
+ */
+ol.handler.MouseWheel = function(map, elt) {
+    goog.base(this);
+
+    var handler = new goog.events.MouseWheelHandler(elt);
+    this.registerDisposable(handler);
+
+    var handleMouseWheel = function(e) {
+        e.position = goog.style.getRelativePosition(e, elt);
+        e.type = 'mousewheel';
+        goog.events.dispatchEvent(map, e);
+    };
+
+    goog.events.listen(handler,
+                       goog.events.MouseWheelHandler.EventType.MOUSEWHEEL,
+                       handleMouseWheel);
+
+};
+goog.inherits(ol.handler.MouseWheel, goog.Disposable);