final fix for #410

git-svn-id: http://svn.openlayers.org/trunk/openlayers@2852 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/HTTPRequest.js

@@ -12,10 +12,21 @@ OpenLayers.Layer.HTTPRequest = OpenLayers.Class.create();
 OpenLayers.Layer.HTTPRequest.prototype = 
   OpenLayers.Class.inherit( OpenLayers.Layer, {
 
-    /** @type String */
+    /** Used to hash URL param strings for multi-WMS server selection.
+     * Set to the Golden Ratio per Knuth's recommendation.
+     *
+     * @type Numeric
+     * @private
+     */
+    URL_HASH_FACTOR: (Math.sqrt(5) - 1) / 2,
+
+    /** This is either an array of url strings or a single url string. 
+     * 
+     * @type Array(String) or String */
     url: null,
 
     /** Hashtable of key/value parameters
+     * 
      * @type Object */
     params: null,
     
@@ -32,7 +43,7 @@ OpenLayers.Layer.HTTPRequest.prototype =
      * @constructor
      * 
      * @param {String} name
-     * @param {String} url
+     * @param {Array(String) or String} url
      * @param {Object} params
      * @param {Object} options Hashtable of extra options to tag onto the layer
      */
@@ -91,13 +102,24 @@ OpenLayers.Layer.HTTPRequest.prototype =
     },
     
     /**
+     * selectUrl() implements the standard floating-point multiplicative
+     * hash function described by Knuth, and hashes the contents of the 
+     * given param string into a float between 0 and 1. This float is then
+     * scaled to the size of the provided urls array, and used to select
+     * a URL.
+     *
      * @param {String} paramString
      * @param {Array(String)} urls
+     * 
+     * @returns An entry from the urls array, deterministically selected based
+     *           on the paramString.
+     * @type String
+     * 
      */
     selectUrl: function(paramString, urls) {
         var product = 1;
         for (var i = 0; i < paramString.length; i++) { 
-            product *= paramString.charCodeAt(i) * (Math.sqrt(5) - 1) / Math.sqrt(3);
+            product *= paramString.charCodeAt(i) * this.URL_HASH_FACTOR; 
             product -= Math.floor(product); 
         }
         return urls[Math.floor(product * urls.length)];
@@ -111,20 +133,33 @@ OpenLayers.Layer.HTTPRequest.prototype =
      *    return in formatted string like this:
      *        "server?key1=value1&key2=value2&key3=value3"
      * 
+     * WARNING: The altUrl parameter is deprecated and will be removed in 3.0.
+     *
      * @param {Object} newParams
      * @param {String} altUrl Use this as the url instead of the layer's url
+     *   
      * 
      * @type String
      */
     getFullRequestString:function(newParams, altUrl) {
-        
+
-        // use layer's url unless altUrl passed in
+        // if not altUrl passed in, use layer's url
-        var url = (altUrl == null) ? this.url : altUrl;
+        var url = altUrl || this.url;
         
         // create a new params hashtable with all the layer params and the 
         // new params together. then convert to string
         var allParams = OpenLayers.Util.extend(new Object(), this.params);
         allParams = OpenLayers.Util.extend(allParams, newParams);
+        var paramsString = OpenLayers.Util.getParameterString(allParams);
+        
+        // if url is not a string, it should be an array of strings, 
+        // in which case we will deterministically select one of them in 
+        // order to evenly distribute requests to different urls.
+        //
+        if (url instanceof Array) {
+            url = this.selectUrl(paramsString, url);
+        }   
+ 
         // ignore parameters that are already in the url search string
         var urlParams = 
             OpenLayers.Util.upperCaseObject(OpenLayers.Util.getArgs(url));
@@ -133,14 +168,7 @@ OpenLayers.Layer.HTTPRequest.prototype =
                 delete allParams[key];
             }
         }
-        var paramsString = OpenLayers.Util.getParameterString(allParams);
+        paramsString = OpenLayers.Util.getParameterString(allParams);
-        
-        // if url is not a string, it should be an array of strings, 
-        // in which case we will deterministically select one of them in 
-        // order to evenly distribute requests to different urls.
-        if (url instanceof Array) {
-            url = this.selectUrl(paramsString, url);
-        }   
         
         // requestString always starts with url
         var requestString = url;        

tests/Layer/test_HTTPRequest.html

@@ -158,9 +158,9 @@
         tUrl = ["http://octo.metacarta.com/cgi-bin/mapserv","http://labs.metacarta.com/cgi-bin/mapserv"];
         layer = new OpenLayers.Layer.HTTPRequest(name, tUrl, tParams, null);
         str = layer.getFullRequestString();
-        t.eq(str, tUrl[0] + '?' + OpenLayers.Util.getParameterString(tParams), "getFullRequestString() works for list of two urls");
+        t.eq(str, tUrl[1] + '?' + OpenLayers.Util.getParameterString(tParams), "getFullRequestString() works for list of two urls");
-        str = layer.getFullRequestString({'a':'f'});
+        str = layer.getFullRequestString({'a':'b'});
-        t.eq(str, tUrl[1] + '?' + OpenLayers.Util.getParameterString(OpenLayers.Util.extend(tParams,{'a':'f'})), "getFullRequestString() works for list of two urls and is deterministic");
+        t.eq(str, tUrl[0] + '?' + OpenLayers.Util.getParameterString(OpenLayers.Util.extend(tParams,{'a':'b'})), "getFullRequestString() works for list of two urls and is deterministic");
 
     }
 
@@ -170,10 +170,10 @@
         layer = new OpenLayers.Layer.HTTPRequest(name, url, params, options); 
 
         urls = ["wms1", "wms2", "wms3", "wms4"]; 
-        t.eq( layer.selectUrl("bbox=-180,0,0,90",  urls), "wms4", "selectUrl(-90,-180) returns 4" ); 
+        t.eq( layer.selectUrl("bbox=-180,0,0,90",  urls), "wms3", "selectUrl(-90,-180) returns 4" ); 
-        t.eq( layer.selectUrl("bbox=-180,-90,0,0", urls), "wms3", "selectUrl(90,-180) returns 3" ); 
+        t.eq( layer.selectUrl("bbox=-180,-90,0,0", urls), "wms1", "selectUrl(90,-180) returns 3" ); 
         t.eq( layer.selectUrl("bbox=0,90,180,0",   urls), "wms1", "selectUrl(-90,180) returns 1" ); 
-        t.eq( layer.selectUrl("bbox=0,0,180,90",   urls), "wms2", "selectUrl(90,180) returns 2" ); 
+        t.eq( layer.selectUrl("bbox=0,0,180,90",   urls), "wms4", "selectUrl(90,180) returns 2" ); 
     }
 
     function test_99_Layer_HTTPRequest_destroy (t) {

tests/Layer/test_WMS.html

@@ -213,7 +213,8 @@
         wmslayer.isBaseLayer=false;
         map.addLayer(wmslayer);
         map.setCenter(new OpenLayers.LonLat(0,0), 5);
-        var tile = layer.grid[0][0];
+        
+        var tile = wmslayer.grid[0][0];
         t.eq( tile.bounds.left, -22.5, "left side matches" ); 
         t.eq( tile.bounds.right, -11.25, "top side matches" ); 
         t.eq( tile.bounds.bottom.toFixed(6), '11.178402', "bottom side matches" );