make ol.Map inherit from goog.EventTarget, and add an ol.handler.Drag

src/ol/handler/Drag.js

@@ -0,0 +1,63 @@
+goog.provide('ol.handler.Drag');
+
+goog.require('goog.fx.Dragger');
+goog.require('goog.events');
+goog.require('goog.Disposable');
+
+/**
+ * @constructor
+ * @extends {goog.Disposable}
+ * @param {ol.Map} map The map instance.
+ * @param {Element} elt The element that will be dragged.
+ */
+ol.handler.Drag = function(map, elt) {
+
+    this.dragger_ = new goog.fx.Dragger(elt);
+    this.dragger_.defaultAction = function() {};
+
+    var prevX = 0, prevY = 0;
+
+    var handleDragStart = function(e) {
+        prevX = e.clientX;
+        prevY = e.clientY;
+        var newE = {
+            type: 'dragstart'
+        };
+        goog.events.dispatchEvent(map, newE);
+    };
+
+    var handleDrag = function(e) {
+        var newE = {
+            type: 'drag',
+            deltaX: e.clientX - prevX,
+            deltaY: e.clientY - prevY
+        };
+        prevX = e.clientX;
+        prevY = e.clientY;
+        goog.events.dispatchEvent(map, newE);
+    };
+
+    var handleDragEnd = function(e) {
+        var newE = {
+            type: 'dragend'
+        };
+        goog.events.dispatchEvent(map, newE);
+    };
+
+    goog.events.listen(this.dragger_, goog.fx.Dragger.EventType.START,
+                       handleDragStart, false, this);
+    goog.events.listen(this.dragger_, goog.fx.Dragger.EventType.DRAG,
+                       handleDrag, false, this);
+    goog.events.listen(this.dragger_, goog.fx.Dragger.EventType.END,
+                       handleDragEnd, false, this);
+};
+goog.inherits(ol.handler.Drag, goog.Disposable);
+
+/**
+ * @inheritDoc
+ */
+ol.handler.Drag.prototype.disposeInternal = function() {
+    goog.base(this, 'disposeInternal');
+    this.dragger_.dispose();
+    delete this.dragger_;
+};