Adding fractionalZoom property to the map. This allows zooming to an arbitrary level, making it possible to have non-discrete resolutions for layers that support it. This property should not be set to true for layers with fixed zoom levels (commercial layers or others with cached tiles). r=elemoine,crschmidt,ahocevar (closes #1243)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@5982 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Map.js

@@ -66,6 +66,14 @@ OpenLayers.Map = OpenLayers.Class({
      */
     id: null,
     
+    /**
+     * Property: fractionalZoom
+     * {Boolean} For a base layer that supports it, allow the map resolution
+     *     to be set to a value between one of the values in the resolutions
+     *     array.  Default is false.
+     */
+    fractionalZoom: false,
+    
     /**
      * APIProperty: events
      * {<OpenLayers.Events>} An events object that handles all 
@@ -1266,10 +1274,7 @@ OpenLayers.Map = OpenLayers.Class({
             if(zoom == null) { 
                 zoom = this.getZoom(); 
             }
-            var resolution = null;
-            if(this.baseLayer != null) {
-                resolution = this.baseLayer.resolutions[zoom];
-            }
+            var resolution = this.getResolutionForZoom(zoom);
             var extent = this.calculateBounds(lonlat, resolution); 
             if(!this.restrictedExtent.containsBounds(extent)) {
                 var maxCenter = this.restrictedExtent.getCenterLonLat(); 
@@ -1326,7 +1331,7 @@ OpenLayers.Map = OpenLayers.Class({
 
             if (zoomChanged) {
                 this.zoom = zoom;
-                this.resolution = this.baseLayer.getResolution();
+                this.resolution = this.getResolutionForZoom(zoom);
                 // zoom level has changed, increment viewRequestID.
                 this.viewRequestID++;
             }    
@@ -1594,6 +1599,24 @@ OpenLayers.Map = OpenLayers.Class({
         return zoom;
     },
 
+    /**
+     * APIMethod: getResolutionForZoom
+     * 
+     * Parameter:
+     * zoom - {Float}
+     * 
+     * Returns:
+     * {Float} A suitable resolution for the specified zoom.  If no baselayer
+     *     is set, returns null.
+     */
+    getResolutionForZoom: function(zoom) {
+        var resolution = null;
+        if(this.baseLayer) {
+            resolution = this.baseLayer.getResolutionForZoom(zoom);
+        }
+        return resolution;
+    },
+
     /**
      * APIMethod: getZoomForResolution
      *