give Style a unique id and a clone method. r=elemoine (closes #2605)

git-svn-id: http://svn.openlayers.org/trunk/openlayers@10315 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Style.js

@@ -15,6 +15,12 @@
  */
 OpenLayers.Style = OpenLayers.Class({
 
+    /**
+     * Property: id
+     * {String} A unique id for this session.
+     */
+    id: null,
+    
     /**
      * APIProperty: name
      * {String}
@@ -119,6 +125,7 @@ OpenLayers.Style = OpenLayers.Class({
         this.setDefaultStyle(style ||
                              OpenLayers.Feature.Vector.style["default"]);
 
+        this.id = OpenLayers.Util.createUniqueID(this.CLASS_NAME + "_");
     },
 
     /** 
@@ -369,6 +376,29 @@ OpenLayers.Style = OpenLayers.Class({
         }
     },
     
+    /**
+     * APIMethod: clone
+     * Clones this style.
+     * 
+     * Returns:
+     * {<OpenLayers.Style>} Clone of this style.
+     */
+    clone: function() {
+        var options = OpenLayers.Util.extend({}, this);
+        // clone rules
+        if(this.rules) {
+            options.rules = [];
+            for(var i=0, len=this.rules.length; i<len; ++i) {
+                options.rules.push(this.rules[i].clone());
+            }
+        }
+        // clone context
+        options.context = this.context && OpenLayers.Util.extend({}, this.context);
+        //clone default style
+        var defaultStyle = OpenLayers.Util.extend({}, this.defaultStyle);
+        return new OpenLayers.Style(defaultStyle, options);
+    },
+    
     CLASS_NAME: "OpenLayers.Style"
 });