Layer.TileCache, Layer.TMS: support a subset of server resolutions. r=tschaub (closes #1944)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@8932 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/TMS.js

@@ -34,6 +34,13 @@ OpenLayers.Layer.TMS = OpenLayers.Class(OpenLayers.Layer.Grid, {
      */
     tileOrigin: null,
 
+    /**
+     * APIProperty: serverResolutions
+     * {Array} A list of all resolutions available on the server.  Only set this 
+     *     property if the map resolutions differs from the server.
+     */
+    serverResolutions: null,
+
     /**
      * Constructor: OpenLayers.Layer.TMS
      * 
@@ -98,7 +105,7 @@ OpenLayers.Layer.TMS = OpenLayers.Class(OpenLayers.Layer.Grid, {
         var res = this.map.getResolution();
         var x = Math.round((bounds.left - this.tileOrigin.lon) / (res * this.tileSize.w));
         var y = Math.round((bounds.bottom - this.tileOrigin.lat) / (res * this.tileSize.h));
-        var z = this.map.getZoom();
+        var z = this.serverResolutions != null ? this.serverResolutions.indexOf(res) : this.map.getZoom();
         var path = this.serviceVersion + "/" + this.layername + "/" + z + "/" + x + "/" + y + "." + this.type; 
         var url = this.url;
         if (url instanceof Array) {