SelectFeature control can now select across multiple vector

layers when passed an array of layers instead of a single layer with 
the constructor. This changeset also introduces a new layer type, 
Layer.Vector.RootContainer, which will be set as the topmost layer by 
the SelectFeature control and collect the svg/vml/canvas roots of 
multiple vector layers. r=crschmidt (closes #1666)


git-svn-id: http://svn.openlayers.org/trunk/openlayers@9116 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Renderer/Elements.js

@@ -331,12 +331,6 @@ OpenLayers.Renderer.Elements = OpenLayers.Class(OpenLayers.Renderer, {
      */
     rendererRoot: null,
     
-    /**
-     * Property: root
-     * {DOMElement}
-     */
-    root: null,
-
     /**
      * Property: xmlns
      * {String}
@@ -887,6 +881,36 @@ OpenLayers.Renderer.Elements = OpenLayers.Class(OpenLayers.Renderer, {
      */
     createNode: function(type, id) {},
 
+    /**
+     * Method: moveRoot
+     * moves this renderer's root to a different renderer.
+     * 
+     * Parameters:
+     * renderer - {<OpenLayers.Renderer>} target renderer for the moved root
+     */
+    moveRoot: function(renderer) {
+        var root = this.root;
+        if(renderer.root.parentNode == this.rendererRoot) {
+            root = renderer.root;
+        }
+        root.parentNode.removeChild(root);
+        renderer.rendererRoot.appendChild(root);
+    },
+    
+    /**
+     * Method: getRenderLayer
+     * Gets the layer that this renderer's output appears on. If moveRoot was
+     * used, this will be different from the layer containing the features
+     * rendered by this renderer.
+     * 
+     * Returns:
+     * {<OpenLayers.Layer.Vector>} the output layer, if any (i.e. this method
+     * will not return a layer if it is not added to a map).
+     */
+    getRenderLayer: function() {
+        return this.map.getLayer(this.root.parentNode.parentNode.id);
+    },
+    
     /**
      * Method: isComplexSymbol
      * Determines if a symbol cannot be rendered using drawCircle