add a destroy() function and a clone() function -- they are mostly empty but they are there for people to add on. Also added a check to make sure that a grid has been loaded before trying to re-init tiles after a mergeParams. added extensive tests.

git-svn-id: http://svn.openlayers.org/trunk/openlayers@907 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/WMS.js

@@ -43,7 +43,39 @@ OpenLayers.Layer.WMS.prototype =
         }
     },    
 
+    /**
+     * 
+     */
+    destroy: function() {
+        // for now, nothing special to do here. 
+        OpenLayers.Layer.Grid.prototype.destroy.apply(this, arguments);  
+    },
+
     
+    /**
+     * @param {Object} obj
+     * 
+     * @returns An exact clone of this OpenLayers.Layer.WMS
+     * @type OpenLayers.Layer.WMS
+     */
+    clone: function (obj) {
+        
+        if (obj == null) {
+            obj = new OpenLayers.Layer.WMS(this.name,
+                                           this.url,
+                                           this.params,
+                                           this.options);
+        }
+
+        //get all additions from superclasses
+        obj = OpenLayers.Layer.Grid.prototype.clone.apply(this, [obj]);
+
+        // copy/set any non-init, non-simple values here
+
+        return obj;
+    },    
+
+
     /** WMS layer is never a base class. 
      * @type Boolean
      */
@@ -51,25 +83,6 @@ OpenLayers.Layer.WMS.prototype =
         return (this.params.TRANSPARENT != 'true');
     },
     
-    /**
-    * @param {String} name
-    * @param {hash} params
-    *
-    * @returns A clone of this OpenLayers.Layer.WMS, with the passed-in
-    *          parameters merged in.
-    * @type OpenLayers.Layer.WMS
-    */
-    clone: function (name, params) {
-        var mergedParams = {};
-        Object.extend(mergedParams, this.params);
-        Object.extend(mergedParams, params);
-        var obj = new OpenLayers.Layer.WMS(name, this.url, mergedParams);
-        if (this.tileSize) {
-            obj.setTileSize(this.tileSize);
-        }    
-        return obj;
-    },
-
     /**
     * addTile creates a tile, initializes it, and 
     * adds it to the layer div. 
@@ -103,7 +116,9 @@ OpenLayers.Layer.WMS.prototype =
         var newArguments = [upperParams];
         OpenLayers.Layer.Grid.prototype.mergeNewParams.apply(this, newArguments);
 
-        this._initTiles();
+        if (this.grid != null) {
+            this._initTiles();
+        }
     },
 
     /** combine the layer's url with its params and these newParams.