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/Layer/Vector/RootContainer.js

@@ -0,0 +1,156 @@
+/* Copyright (c) 2006-2008 MetaCarta, Inc., published under the Clear BSD
+ * license.  See http://svn.openlayers.org/trunk/openlayers/license.txt for the
+ * full text of the license. */
+
+/**
+ * @requires OpenLayers/Layer/Vector.js
+ */
+
+/**
+ * Class: OpenLayers.Layer.Vector.RootContainer
+ * A special layer type to combine multiple vector layers inside a single
+ *     renderer root container. This class is not supposed to be instantiated
+ *     from user space, it is a helper class for controls that require event
+ *     processing for multiple vector layers.
+ *
+ * Inherits from:
+ *  - <OpenLayers.Layer.Vector>
+ */
+OpenLayers.Layer.Vector.RootContainer = OpenLayers.Class(OpenLayers.Layer.Vector, {
+    
+    /**
+     * Property: displayInLayerSwitcher
+     * Set to false for this layer type
+     */
+    displayInLayerSwitcher: false,
+    
+    /**
+     * APIProperty: layers
+     * Layers that are attached to this container. Required config option.
+     */
+    layers: null,
+    
+    /**
+     * Constructor: OpenLayers.Layer.Vector.RootContainer
+     * Create a new root container for multiple vector layer. This constructor
+     * is not supposed to be used from user space, it is only to be used by
+     * controls that need feature selection across multiple vector layers.
+     *
+     * Parameters:
+     * name - {String} A name for the layer
+     * options - {Object} Optional object with non-default properties to set on
+     *           the layer.
+     * 
+     * Required options properties:
+     * layers - {Array(<OpenLayers.Layer.Vector>)} The layers managed by this
+     *     container
+     *
+     * Returns:
+     * {<OpenLayers.Layer.Vector.RootContainer>} A new vector layer root
+     *     container
+     */
+    initialize: function(name, options) {
+        OpenLayers.Layer.Vector.prototype.initialize.apply(this, arguments);
+    },
+    
+    /**
+     * Method: display
+     */
+    display: function() {},
+    
+    /**
+     * Method: getFeatureFromEvent
+     * walk through the layers to find the feature returned by the event
+     * 
+     * Parameters:
+     * evt - {Object} event object with a feature property
+     * 
+     * Returns:
+     * {<OpenLayers.Feature.Vector>}
+     */
+    getFeatureFromEvent: function(evt) {
+        var layers = this.layers;
+        var feature;
+        for(var i=0; i<layers.length; i++) {
+            feature = layers[i].getFeatureFromEvent(evt);
+            if(feature) {
+                return feature;
+            }
+        }
+    },
+    
+    /**
+     * Method: setMap
+     * 
+     * Parameters:
+     * map - {<OpenLayers.Map>}
+     */
+    setMap: function(map) {
+        OpenLayers.Layer.Vector.prototype.setMap.apply(this, arguments);
+        this.collectRoots();
+        map.events.register("changelayer", this, this.handleChangeLayer);
+    },
+    
+    /**
+     * Method: removeMap
+     * 
+     * Parameters:
+     * map - {<OpenLayers.Map>}
+     */
+    removeMap: function(map) {
+        map.events.unregister("changelayer", this, this.handleChangeLayer);
+        this.resetRoots();
+        OpenLayers.Layer.Vector.prototype.removeMap.apply(this, arguments);
+    },
+    
+    /**
+     * Method: collectRoots
+     * Collects the root nodes of all layers this control is configured with
+     * and moveswien the nodes to this control's layer
+     */
+    collectRoots: function() {
+        var layer;
+        // walk through all map layers, because we want to keep the order
+        for(var i=0; i<this.map.layers.length; ++i) {
+            layer = this.map.layers[i];
+            if(OpenLayers.Util.indexOf(this.layers, layer) != -1) {
+                layer.renderer.moveRoot(this.renderer);
+            }
+        }
+    },
+    
+    /**
+     * Method: resetRoots
+     * Resets the root nodes back into the layers they belong to.
+     */
+    resetRoots: function() {
+        var layer;
+        for(var i=0; i<this.layers.length; ++i) {
+            layer = this.layers[i];
+            if(layer.renderer.getRenderLayer() == this) {
+                this.renderer.moveRoot(layer.renderer);
+            }
+        }
+    },
+    
+    /**
+     * Method: handleChangeLayer
+     * Event handler for the map's changelayer event. We need to rebuild
+     * this container's layer dom if order of one of its layers changes.
+     * This handler is added with the setMap method, and removed with the
+     * removeMap method.
+     * 
+     * Parameters:
+     * evt - {Object}
+     */
+    handleChangeLayer: function(evt) {
+        var layer = evt.layer;
+        if(evt.property == "order" &&
+                        OpenLayers.Util.indexOf(this.layers, layer) != -1) {
+            this.resetRoots();
+            this.collectRoots();
+        }
+    },
+
+    CLASS_NAME: "OpenLayers.Layer.Vector.RootContainer"
+});