fix for #60

conversions to/from lonlat/px need to take into account
the offset of the layersContainerDiv. 


I have introduced the following functions for converting
between layer and screen pixel values:

getLayerPxFromScreenPx() and getScreenPxFromLayerPx()

they are pretty self-explanitory.


I then renamed:

getPixelFromLonLat() and getLonLatFromPixel()

to:

getScreenPxFromLonLat() and getLonLatFroScreenmPx()

and added:

getLayerPxFromLonLat() and getLonLatFromLayerPx()


updates were made throughout the code, demos, and tests
so everything should still run smoothly.

-e-

git-svn-id: http://svn.openlayers.org/trunk/openlayers@329 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Control/MouseDefaults.js

@@ -19,7 +19,7 @@ OpenLayers.Control.MouseDefaults.prototype =
     * @param {Event} evt
     */
     defaultDblClick: function (evt) {
-        var newCenter = this.map.getLonLatFromPixel( evt.xy ); 
+        var newCenter = this.map.getLonLatFromScreenPx( evt.xy ); 
         this.map.setCenter(newCenter, this.map.zoom + 1);
     },
 
@@ -68,7 +68,7 @@ OpenLayers.Control.MouseDefaults.prototype =
                 var size = this.map.getSize();
                 var newXY = new OpenLayers.Pixel(size.w / 2 + deltaX,
                                                  size.h / 2 + deltaY);
-                var newCenter = this.map.getLonLatFromPixel( newXY ); 
+                var newCenter = this.map.getLonLatFromScreenPx( newXY ); 
                 this.map.setCenter(newCenter);
                 this.mouseDragStart = evt.xy.copyOf();
             }
@@ -80,8 +80,8 @@ OpenLayers.Control.MouseDefaults.prototype =
     */
     defaultMouseUp: function (evt) {
         if (this.zoomBox) {
-            var start = this.map.getLonLatFromPixel( this.mouseDragStart ); 
-            var end = this.map.getLonLatFromPixel( evt.xy );
+            var start = this.map.getLonLatFromScreenPx( this.mouseDragStart ); 
+            var end = this.map.getLonLatFromScreenPx( evt.xy );
             var top = Math.max(start.lat, end.lat);
             var bottom = Math.min(start.lat, end.lat);
             var left = Math.min(start.lon, end.lon);