Adding preserveCenter config option

examples/mobile.js

@@ -22,6 +22,9 @@ var init = function () {
         controls: [
             new OpenLayers.Control.Attribution(),
             new OpenLayers.Control.TouchNavigation({
+                pinchZoomOptions: {
+                    preserveCenter: true
+                },
                 dragPanOptions: {
                     enableKinetic: true
                 }

lib/OpenLayers/Control/PinchZoom.js

@@ -41,6 +41,12 @@ OpenLayers.Control.PinchZoom = OpenLayers.Class(OpenLayers.Control, {
      */
     autoActivate: true,
 
+    /**
+     * APIProperty: preserveCenter
+     * {Boolean} Force the map center to stay in place. Default is false.
+     */
+    preserveCenter: false,
+    
     /**
      * APIProperty: handlerOptions
      * {Object} Used to set non-default properties on the pinch handler
@@ -73,8 +79,10 @@ OpenLayers.Control.PinchZoom = OpenLayers.Class(OpenLayers.Control, {
      *     of the pinch gesture. This give us the current scale of the pinch.
      */
     pinchStart: function(evt, pinchData) {
-        this.pinchOrigin = evt.xy;
-        this.currentCenter = evt.xy;
+        var xy = (this.preserveCenter) ?
+            this.map.getPixelFromLonLat(this.map.getCenter()) : evt.xy;
+        this.pinchOrigin = xy;
+        this.currentCenter = xy;
     },
     
     /**
@@ -89,7 +97,8 @@ OpenLayers.Control.PinchZoom = OpenLayers.Class(OpenLayers.Control, {
         var scale = pinchData.scale;
         var containerOrigin = this.map.layerContainerOriginPx;
         var pinchOrigin = this.pinchOrigin;
-        var current = evt.xy;
+        var current = (this.preserveCenter) ?
+            this.map.getPixelFromLonLat(this.map.getCenter()) : evt.xy;
 
         var dx = Math.round((current.x - pinchOrigin.x) + (scale - 1) * (containerOrigin.x - pinchOrigin.x));
         var dy = Math.round((current.y - pinchOrigin.y) + (scale - 1) * (containerOrigin.y - pinchOrigin.y));