Added alternatvie way to initialize the map object, without passing a

div to the constructor. Original patch by tcoulter, modifications by
me and tschaub. r=tschaub (closes #1901)


git-svn-id: http://svn.openlayers.org/trunk/openlayers@9068 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Map.js

@@ -123,7 +123,18 @@ OpenLayers.Map = OpenLayers.Class({
 
     /**
      * APIProperty: div
-     * {DOMElement} The element that contains the map
+     * {DOMElement|String} The element that contains the map (or an id for
+     *     that element).  If the <OpenLayers.Map> constructor is called
+     *     with two arguments, this should be provided as the first argument.
+     *     Alternatively, the map constructor can be called with the options
+     *     object as the only argument.  In this case (one argument), a
+     *     div property may or may not be provided.  If the div property
+     *     is not provided, the map can be rendered to a container later
+     *     using the <render> method.
+     *     
+     * Note: If you calling <render> after map construction, do not use
+     *     <maxResolution>  auto.  Instead, divide your <maxExtent> by your
+     *     maximum expected dimension.
      */
     div: null,
     
@@ -382,13 +393,16 @@ OpenLayers.Map = OpenLayers.Class({
     
     /**
      * Constructor: OpenLayers.Map
-     * Constructor for a new OpenLayers.Map instance.
+     * Constructor for a new OpenLayers.Map instance.  There are two possible
+     *     ways to call the map constructor.  See the examples below.
      *
      * Parameters:
      * div - {String} Id of an element in your page that will contain the map.
+     *     May be omitted if the <div> option is provided or if you intend
+     *     to use <render> later.
      * options - {Object} Optional object with properties to tag onto the map.
      *
-     * Examples:
+     * Examples (method one):
      * (code)
      * // create a map with default options in an element with the id "map1"
      * var map = new OpenLayers.Map("map1");
@@ -402,8 +416,33 @@ OpenLayers.Map = OpenLayers.Class({
      * };
      * var map = new OpenLayers.Map("map2", options);
      * (end)
+     *
+     * Examples (method two - single argument):
+     * (code)
+     * // create a map with non-default options
+     * var map = new OpenLayers.Map({
+     *     div: "map_id",
+     *     maxExtent: new OpenLayers.Bounds(-200000, -200000, 200000, 200000),
+     *     maxResolution: 156543,
+     *     units: 'm',
+     *     projection: "EPSG:41001"
+     * });
+     *
+     * // create a map without a reference to a container - call render later
+     * var map = new OpenLayers.Map({
+     *     maxExtent: new OpenLayers.Bounds(-200000, -200000, 200000, 200000),
+     *     maxResolution: 156543,
+     *     units: 'm',
+     *     projection: "EPSG:41001"
+     * });
      */    
     initialize: function (div, options) {
+        
+        // If only one argument is provided, check if it is an object.
+        if(arguments.length === 1 && typeof div === "object") {
+            options = div;
+            div = options && options.div;
+        }
 
         // Simple-type defaults are set in class definition. 
         //  Now set complex-type defaults 
@@ -423,6 +462,12 @@ OpenLayers.Map = OpenLayers.Class({
         this.id = OpenLayers.Util.createUniqueID("OpenLayers.Map_");
 
         this.div = OpenLayers.Util.getElement(div);
+        if(!this.div) {
+            this.div = document.createElement("div");
+            this.div.style.height = "1px";
+            this.div.style.width = "1px";
+        }
+        
         OpenLayers.Element.addClass(this.div, 'olMap');
 
         // the viewPortDiv is the outermost div we modify
@@ -518,7 +563,23 @@ OpenLayers.Map = OpenLayers.Class({
 
         // always call map.destroy()
         OpenLayers.Event.observe(window, 'unload', this.unloadDestroy);
-
+    },
+    
+    /**
+     * APIMethod: render
+     * Render the map to a specified container.
+     * 
+     * Parameters:
+     * div - {String|DOMElement} The container that the map should be rendered
+     *     to. If different than the current container, the map viewport
+     *     will be moved from the current to the new container.
+     */
+    render: function(div) {
+        this.div = OpenLayers.Util.getElement(div);
+        this.events.attachToElement(this.div);
+        this.viewPortDiv.parentNode.removeChild(this.viewPortDiv);
+        this.div.appendChild(this.viewPortDiv);
+        this.updateSize();
     },
 
     /**