From 0a131f380a4c31308d7c53ab5ae47baaa9436ee0 Mon Sep 17 00:00:00 2001
From: Pierre GIRAUD <pierre.giraud@camptocamp.com>
Date: Fri, 30 Nov 2012 13:29:12 +0100
Subject: [PATCH] Adding preserveCenter config option

---
 examples/mobile.js                  |  3 +++
 lib/OpenLayers/Control/PinchZoom.js | 15 ++++++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/examples/mobile.js b/examples/mobile.js
index 9bbcb9125a..3104cbbd63 100644
--- a/examples/mobile.js
+++ b/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
                 }
diff --git a/lib/OpenLayers/Control/PinchZoom.js b/lib/OpenLayers/Control/PinchZoom.js
index b3691d813b..e89fa287f6 100644
--- a/lib/OpenLayers/Control/PinchZoom.js
+++ b/lib/OpenLayers/Control/PinchZoom.js
@@ -40,6 +40,12 @@ OpenLayers.Control.PinchZoom = OpenLayers.Class(OpenLayers.Control, {
      *     true.
      */
     autoActivate: true,
+
+    /**
+     * APIProperty: preserveCenter
+     * {Boolean} Force the map center to stay in place. Default is false.
+     */
+    preserveCenter: false,
     
     /**
      * APIProperty: handlerOptions
@@ -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));