rewrite of Untiled.js to only create the div's once, and from then on just modify the attributes. this should be faster.

git-svn-id: http://svn.openlayers.org/trunk/openlayers@930 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/WMS/Untiled.js

@@ -89,6 +89,15 @@ OpenLayers.Layer.WMS.Untiled.prototype =
     },
     
     
+    /** Once HTTPRequest has set the map, we can load the image div
+     * 
+     * @param {OpenLayers.Map} map
+     */
+    setMap: function(map) {
+        OpenLayers.Layer.HTTPRequest.prototype.setMap.apply(this, arguments);
+        this.loadImageDiv();
+    },
+
     /** When it is not a minor move (ie when panning or when done dragging)
      *   reload and recenter the div.
      * 
@@ -98,59 +107,120 @@ OpenLayers.Layer.WMS.Untiled.prototype =
      */
     moveTo:function(bounds, zoomChanged, minor) {
 
+        
+
         if (!minor) {
         
+            if (bounds == null) {
+                bounds = this.map.getExtent();
+            }
             
             var size = this.map.getSize().copyOf();
 
-
+            // get the url
-            //get the url
             var url = this.getFullRequestString( {BBOX: bounds.toBBOX(),
                                                   WIDTH: size.w,
                                                   HEIGHT: size.h} );
         
 
-            //clear previous wms image
+            // always position at upper left corner of current viewspace
-            this.div.innerHTML = "";
-            
-            //always position at upper left corner of current viewspace
             var tl = new OpenLayers.Pixel(0,0);
             var pos = this.map.getLayerPxFromViewPortPx(tl);
 
-            //create div
+            // first hide before all modifications            
+            Element.hide(this.imgDiv);
+            
+            // update div
+            var img = this.imgDiv;
             if (this.transparent) {
-                this.imgDiv = OpenLayers.Util.createAlphaImageDiv(null,
+                OpenLayers.Util.modifyAlphaImageDiv(this.imgDiv, 
-                                                                  pos,
+                                                    null, 
-                                                                  size,
+                                                    pos, 
-                                                                  url,
+                                                    size,
-                                                                  "absolute");
+                                                    url);
+                img = this.imgDiv.childNodes[0];
             } else {
-                this.imgDiv = OpenLayers.Util.createImage(null,
+                OpenLayers.Util.modifyDOMElement(this.imgDiv, 
-                                                          pos,
+                                                 null, 
-                                                          size,
+                                                 pos, 
-                                                          url,
+                                                 size);
-                                                          "absolute");
+                this.imgDiv.src = url;
             }
     
-            this.div.appendChild(this.imgDiv);            
+            // wait until image is done loading to show again
+            Event.observe(img, 
+                          "load", 
+                          this.showDiv.bindAsEventListener(this));
         }
     },
     
-    /** 
+    /** Helper function that allows us to first hide the imgDiv, then make all 
+     *   the changes (position, size, url). Then when the url is done loading,
+     *   we call this function to show the imgDiv.
+     * 
+     * @private
+     */
+    showDiv: function() {
+        Element.show(this.imgDiv);
+    },
+    
+    /** Once HTTPRequest has updated the url, reload the image div
      * @param {String} newUrl
      */
     setUrl: function(newUrl) {
         OpenLayers.Layer.HTTPRequest.prototype.setUrl.apply(this, arguments);
-        this.moveTo(this.map.getExtent());
+        this.moveTo();
     },
 
-    /**
+    /** Once HTTPRequest has updated new params, reload the image div
      * @param {Object} newParams
      */
     mergeNewParams:function(newParams) {
         OpenLayers.Layer.HTTPRequest.prototype.mergeNewParams.apply(this, 
                                                                    arguments);
-        this.moveTo(this.map.getExtent());
+        this.moveTo();
+    },
+    
+    /** This function first removes the previous image div, then adds a new
+     *   one according to the transparency property.
+     * 
+     * @private
+     */
+    loadImageDiv: function() {
+        
+        var size = this.map.getSize().copyOf();
+        var bounds = this.map.getExtent();
+
+        var url = "";            
+        if (bounds != null) {
+            url = this.getFullRequestString( {BBOX: bounds.toBBOX(),
+                                              WIDTH: size.w,
+                                              HEIGHT: size.h} );
+        }
+        
+        //clear previous wms image (removes imgDiv)
+        this.div.innerHTML = "";
+        
+        //always position at upper left corner of current viewspace
+        var tl = new OpenLayers.Pixel(0,0);
+        var pos = this.map.getLayerPxFromViewPortPx(tl);
+        
+        //create div
+        if (this.transparent) {
+            this.imgDiv = OpenLayers.Util.createAlphaImageDiv(null,
+                                                              pos,
+                                                              size,
+                                                              url,
+                                                              "absolute");
+        } else {
+            this.imgDiv = OpenLayers.Util.createImage(null,
+                                                      pos,
+                                                      size,
+                                                      url,
+                                                      "absolute");
+        }
+        
+        this.div.appendChild(this.imgDiv);
     },
         
     /** @final @type String */