Layer.XYZ: support a subset of server resolutions, p=bbinet, r=me (closes #2909)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@10903 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/XYZ.js

@@ -40,10 +40,19 @@ OpenLayers.Layer.XYZ = OpenLayers.Class(OpenLayers.Layer.Grid, {
      *     for a requested tile.  For example, if you supply a zoomOffset
      *     of 3, when the map is at the zoom 0, tiles will be requested from
      *     level 3 of your cache.  Default is 0 (assumes cache level and map
-     *     zoom are equivalent).
+     *     zoom are equivalent).  Using <zoomOffset> is an alternative to
+     *     setting <serverResolutions> if you only want to expose a subset
+     *     of the server resolutions.
      */
     zoomOffset: 0,
     
+    /**
+     * 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.XYZ
      *
@@ -114,7 +123,9 @@ OpenLayers.Layer.XYZ = OpenLayers.Class(OpenLayers.Layer.Grid, {
             / (res * this.tileSize.w));
         var y = Math.round((this.maxExtent.top - bounds.top) 
             / (res * this.tileSize.h));
-        var z = this.map.getZoom() + this.zoomOffset;
+        var z = this.serverResolutions != null ?
+            OpenLayers.Util.indexOf(this.serverResolutions, res) :
+            this.map.getZoom() + this.zoomOffset;
 
         var url = this.url;
         var s = '' + x + y + z;

tests/Layer/XYZ.html

@@ -148,6 +148,31 @@
         map.destroy();
     }
 
+    function test_Layer_XYZ_serverResolutions(t) {
+        t.plan(2);
+
+        var map = new OpenLayers.Map('map', {
+            resolutions: [13,11]
+        });
+
+        var layer = new OpenLayers.Layer.XYZ(name, url, options);
+        map.addLayer(layer);
+        map.setCenter(new OpenLayers.LonLat(0,0), 1);
+
+        var tileurl = layer.getURL(new OpenLayers.Bounds(0,0,0,0));
+        var level = parseInt(tileurl.split('/')[7]);
+        t.eq(map.getZoom(), level, "Tile zoom level is correct without serverResolutions");
+
+        layer.serverResolutions = [14,13,12,11,10];
+        tileurl = layer.getURL(new OpenLayers.Bounds(0,0,0,0));
+        level = parseInt(tileurl.split('/')[7]);
+        var res = map.getResolution();
+        var gotLevel = OpenLayers.Util.indexOf(layer.serverResolutions, res);
+        t.eq(gotLevel, level, "Tile zoom level is correct with serverResolutions");
+
+        map.destroy();
+    }
+
     function test_zoomOffset(t) {
 
         t.plan(2);