diff --git a/lib/OpenLayers/Control/PanZoomBar.js b/lib/OpenLayers/Control/PanZoomBar.js
index df9f352de4..7047e0682c 100644
--- a/lib/OpenLayers/Control/PanZoomBar.js
+++ b/lib/OpenLayers/Control/PanZoomBar.js
@@ -165,7 +165,8 @@ OpenLayers.Control.PanZoomBar = OpenLayers.Class(OpenLayers.Control.PanZoom, {
                        "absolute");
         this.slider = slider;
         
-        this.sliderEvents = new OpenLayers.Events(this, slider, null, true);
+        this.sliderEvents = new OpenLayers.Events(this, slider, null, true,
+                                            {includeXY: true});
         this.sliderEvents.on({
             "mousedown": this.zoomBarDown,
             "mousemove": this.zoomBarDrag,
@@ -197,7 +198,8 @@ OpenLayers.Control.PanZoomBar = OpenLayers.Class(OpenLayers.Control.PanZoom, {
         
         this.zoombarDiv = div;
         
-        this.divEvents = new OpenLayers.Events(this, div, null, true);
+        this.divEvents = new OpenLayers.Events(this, div, null, true, 
+                                                {includeXY: true});
         this.divEvents.on({
             "mousedown": this.divClick,
             "mousemove": this.passEventToSlider,
diff --git a/lib/OpenLayers/Events.js b/lib/OpenLayers/Events.js
index 334c1f6091..a81a3dba1b 100644
--- a/lib/OpenLayers/Events.js
+++ b/lib/OpenLayers/Events.js
@@ -392,6 +392,34 @@ OpenLayers.Events = OpenLayers.Class({
      */
     fallThrough: null,
 
+    /** 
+     * APIProperty: includeXY
+     * {Boolean} Should the .xy property automatically be created for browser
+     *    mouse events? In general, this should be false. If it is true, then
+     *    mouse events will automatically generate a '.xy' property on the 
+     *    event object that is passed. (Prior to OpenLayers 2.7, this was true
+     *    by default.) Otherwise, you can call the getMousePosition on the
+     *    relevant events handler on the object available via the 'evt.object'
+     *    property of the evt object. So, for most events, you can call:
+     *    function named(evt) { 
+     *        this.xy = this.object.events.getMousePosition(evt) 
+     *    } 
+     *
+     *    This option typically defaults to false for performance reasons:
+     *    when creating an events object whose primary purpose is to manage
+     *    relatively positioned mouse events within a div, it may make
+     *    sense to set it to true.
+     *
+     *    This option is also used to control whether the events object caches
+     *    offsets. If this is false, it will not: the reason for this is that
+     *    it is only expected to be called many times if the includeXY property
+     *    is set to true. If you set this to true, you are expected to clear 
+     *    the offset cache manually (using this.clearMouseCache()) if:
+     *        the border of the element changes
+     *        the location of the element in the page changes
+    */
+    includeXY: false,      
+
     /**
      * Constructor: OpenLayers.Events
      * Construct an OpenLayers.Events object.
@@ -402,8 +430,10 @@ OpenLayers.Events = OpenLayers.Class({
      * eventTypes - {Array(String)} Array of custom application events 
      * fallThrough - {Boolean} Allow events to fall through after these have
      *                         been handled?
+     * options - {Object} Options for the events object.
      */
-    initialize: function (object, element, eventTypes, fallThrough) {
+    initialize: function (object, element, eventTypes, fallThrough, options) {
+        OpenLayers.Util.extend(this, options);
         this.object     = object;
         this.element    = element;
         this.fallThrough = fallThrough;
@@ -691,10 +721,24 @@ OpenLayers.Events = OpenLayers.Class({
      * evt - {Event} 
      */
     handleBrowserEvent: function (evt) {
-        evt.xy = this.getMousePosition(evt); 
+        if (this.includeXY) {
+            evt.xy = this.getMousePosition(evt);
+        } 
         this.triggerEvent(evt.type, evt);
     },
 
+    /**
+     * APIMethod: clearMouseCache
+     * Clear cached data about the mouse position. This should be called any 
+     *     time the element that events are registered on changes position 
+     *     within the page.
+     */
+    clearMouseCache: function() { 
+        this.element.scrolls = null;
+        this.element.lefttop = null;
+        this.element.offsets = null;
+    },      
+
     /**
      * Method: getMousePosition
      * 
@@ -706,20 +750,38 @@ OpenLayers.Events = OpenLayers.Class({
      *                      for offsets
      */
     getMousePosition: function (evt) {
-        if (!this.element.offsets) {
-            this.element.offsets = OpenLayers.Util.pagePosition(this.element);
-            this.element.offsets[0] += (document.documentElement.scrollLeft
+        if (!this.includeXY) {
+            this.clearMouseCache();
+        } else if (!this.element.hasScrollEvent) {
+            OpenLayers.Event.observe(window, 'scroll', 
+                OpenLayers.Function.bind(this.clearMouseCache, this)); 
+            this.element.hasScrollEvent = true;
+        }
+        
+        if (!this.element.scrolls) {
+            this.element.scrolls = [];
+            this.element.scrolls[0] = (document.documentElement.scrollLeft
                          || document.body.scrollLeft);
-            this.element.offsets[1] += (document.documentElement.scrollTop
+            this.element.scrolls[1] = (document.documentElement.scrollTop
                          || document.body.scrollTop);
         }
+
+        if (!this.element.lefttop) {
+            this.element.lefttop = [];
+            this.element.lefttop[0] = (document.documentElement.clientLeft || 0);
+            this.element.lefttop[1] = (document.documentElement.clientTop || 0);
+        }
+        
+        if (!this.element.offsets) {
+            this.element.offsets = OpenLayers.Util.pagePosition(this.element);
+            this.element.offsets[0] += this.element.scrolls[0];
+            this.element.offsets[1] += this.element.scrolls[1];
+        }
         return new OpenLayers.Pixel(
-            (evt.clientX + (document.documentElement.scrollLeft
-                         || document.body.scrollLeft)) - this.element.offsets[0]
-                         - (document.documentElement.clientLeft || 0), 
-            (evt.clientY + (document.documentElement.scrollTop
-                         || document.body.scrollTop)) - this.element.offsets[1]
-                         - (document.documentElement.clientTop || 0)
+            (evt.clientX + this.element.scrolls[0]) - this.element.offsets[0]
+                         - this.element.lefttop[0], 
+            (evt.clientY + this.element.scrolls[1]) - this.element.offsets[1]
+                         - this.element.lefttop[1]
         ); 
     },
 
diff --git a/lib/OpenLayers/Map.js b/lib/OpenLayers/Map.js
index fbd0bce7b7..e6339be061 100644
--- a/lib/OpenLayers/Map.js
+++ b/lib/OpenLayers/Map.js
@@ -426,7 +426,8 @@ OpenLayers.Map = OpenLayers.Class({
         this.events = new OpenLayers.Events(this, 
                                             this.div, 
                                             this.EVENT_TYPES, 
-                                            this.fallThrough);
+                                            this.fallThrough, 
+                                            {includeXY: true});
         this.updateSize();
         if(this.eventListeners instanceof Object) {
             this.events.on(this.eventListeners);
@@ -1202,7 +1203,7 @@ OpenLayers.Map = OpenLayers.Class({
      */
     updateSize: function() {
         // the div might have moved on the page, also
-        this.events.element.offsets = null;
+        this.events.clearMouseCache();
         var newSize = this.getCurrentSize();
         var oldSize = this.getSize();
         if (oldSize == null) {