Attempt to handle IE >= 10 pointer events

Using the same technique as Leaflet, this relays MSPointer events to touch
events. Using the simulator, I can verify that even pinch-zoom works with
this change, but the visual experience is a bit jumpy. Would be great if
people could test this on physical touch devices and see how it looks/feels
there.

lib/OpenLayers/Events.js

@@ -566,6 +566,7 @@ OpenLayers.Events = OpenLayers.Class({
         this.listeners  = {};
         this.extensions = {};
         this.extensionCount = {};
+        this._msTouches = [];
         
         // if a dom element is specified, add a listeners list 
         // for browser events on the element and register them
@@ -632,11 +633,16 @@ OpenLayers.Events = OpenLayers.Class({
             );
         }
         this.element = element;
+        var msTouch = !!window.navigator.msMaxTouchPoints;
+        var type;
         for (var i = 0, len = this.BROWSER_EVENTS.length; i < len; i++) {
+            type = this.BROWSER_EVENTS[i];
             // register the event cross-browser
-            OpenLayers.Event.observe(
-                element, this.BROWSER_EVENTS[i], this.eventHandler
+            OpenLayers.Event.observe(element, type, this.eventHandler
             );
+            if (msTouch && type.indexOf('touch') === 0) {
+                this.addMsTouchListener(element, type, this.eventHandler);
+            }
         }
         // disable dragstart in IE so that mousedown/move/up works normally
         OpenLayers.Event.observe(element, "dragstart", OpenLayers.Event.stop);
@@ -1014,5 +1020,154 @@ OpenLayers.Events = OpenLayers.Class({
         ); 
     },
 
+    /**
+     * Method: addMsTouchListener
+     *
+     * Parameters:
+     * element - {DOMElement} The DOM element to register the listener on
+     * type - {String} The event type
+     * handler - {Function} the handler
+     */
+    addMsTouchListener: function (element, type, handler) {
+        var eventHandler = this.eventHandler;
+        var touches = this._msTouches;
+
+        function msHandler(evt) {
+            handler(OpenLayers.Util.applyDefaults({
+                stopPropagation: function() {
+                    for (var i=touches.length-1; i>=0; --i) {
+                        touches[i].stopPropagation();
+                    }
+                },
+                preventDefault: function() {
+                    for (var i=touches.length-1; i>=0; --i) {
+                        touches[i].preventDefault();
+                    }
+                },
+                type: type
+            }, evt));
+        }
+
+        switch (type) {
+            case 'touchstart':
+                return this.addMsTouchListenerStart(element, type, msHandler);
+            case 'touchend':
+                return this.addMsTouchListenerEnd(element, type, msHandler);
+            case 'touchmove':
+                return this.addMsTouchListenerMove(element, type, msHandler);
+            default:
+                throw 'Unknown touch event type';
+        }
+    },
+
+    /**
+     * Method: addMsTouchListenerStart
+     *
+     * Parameters:
+     * element - {DOMElement} The DOM element to register the listener on
+     * type - {String} The event type
+     * handler - {Function} the handler
+     */
+    addMsTouchListenerStart: function(element, type, handler) {
+        var touches = this._msTouches;
+
+        var cb = function(e) {
+
+            var alreadyInArray = false;
+            for (var i = 0; i < touches.length; i++) {
+                if (touches[i].pointerId == e.pointerId) {
+                    alreadyInArray = true;
+                    break;
+                }
+            }
+            if (!alreadyInArray) {
+                touches.push(e);
+            }
+
+            e.touches = touches.slice();
+            e.changedTouches = [e];
+
+            handler(e);
+        };
+
+        OpenLayers.Event.observe(element, 'MSPointerDown', cb);
+
+        // Need to also listen for end events to keep the _msTouches list
+        // accurate
+        var internalCb = function(e) {
+            for (var i = 0; i < touches.length; i++) {
+                if (touches[i].pointerId == e.pointerId) {
+                    touches.splice(i, 1);
+                    break;
+                }
+            }
+        };
+        OpenLayers.Event.observe(element, 'MSPointerUp', internalCb);
+    },
+
+    /**
+     * Method: addMsTouchListenerMove
+     *
+     * Parameters:
+     * element - {DOMElement} The DOM element to register the listener on
+     * type - {String} The event type
+     * handler - {Function} the handler
+     */
+    addMsTouchListenerMove: function (element, type, handler) {
+        var touches = this._msTouches;
+        var cb = function(e) {
+
+            //Don't fire touch moves when mouse isn't down
+            if (e.pointerType == e.MSPOINTER_TYPE_MOUSE && e.buttons == 0) {
+                return;
+            }
+
+            for (var i = 0; i < touches.length; i++) {
+                if (touches[i].pointerId == e.pointerId) {
+                    touches[i] = e;
+                    break;
+                }
+            }
+
+            e.touches = touches.slice();
+            e.changedTouches = [e];
+            e.type = type;
+
+            handler(e);
+        };
+
+        OpenLayers.Event.observe(element, 'MSPointerMove', cb);
+    },
+
+    /**
+     * Method: addMsTouchListenerEnd
+     *
+     * Parameters:
+     * element - {DOMElement} The DOM element to register the listener on
+     * type - {String} The event type
+     * handler - {Function} the handler
+     */
+    addMsTouchListenerEnd: function (element, type, handler) {
+        var touches = this._msTouches;
+
+        var cb = function(e) {
+
+            for (var i = 0; i < touches.length; i++) {
+                if (touches[i].pointerId == e.pointerId) {
+                    touches.splice(i, 1);
+                    break;
+                }
+            }
+
+            e.touches = touches.slice();
+            e.changedTouches = [e];
+            e.type = type;
+
+            handler(e);
+        };
+
+        OpenLayers.Event.observe(element, 'MSPointerUp', cb);
+    },
+
     CLASS_NAME: "OpenLayers.Events"
 });