patch for #831 - simplify the notion of untiled (now an option on grid layers called 'singleTile') and implementing loading events for gridded/untiled layers. thanks tim and chris for reviewing this beast.

git-svn-id: http://svn.openlayers.org/trunk/openlayers@3725 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Tile/Image.js

@@ -96,6 +96,15 @@ OpenLayers.Tile.Image.prototype =
         if (!OpenLayers.Tile.prototype.draw.apply(this, arguments)) {
             return false;    
         }
+        
+        if (this.isLoading) {
+            //if we're already loading, send 'reload' instead of 'loadstart'.
+            this.events.triggerEvent("reload"); 
+        } else {
+            this.isLoading = true;
+            this.events.triggerEvent("loadstart");
+        }
+        
         if (this.imgDiv == null) {
             this.initImgDiv();
         }
@@ -202,6 +211,23 @@ OpenLayers.Tile.Image.prototype =
         // we need this reference to check back the viewRequestID
         this.imgDiv.map = this.layer.map;
 
+        //bind a listener to the onload of the image div so that we 
+        // can register when a tile has finished loading.
+        var onload = function() {
+            
+            //normally isLoading should always be true here but there are some 
+            // right funky conditions where loading and then reloading a tile
+            // with the same url *really*fast*. this check prevents sending 
+            // a 'loadend' if the msg has already been sent
+            //
+            if (this.isLoading) { 
+                this.isLoading = false; 
+                this.events.triggerEvent("loadend"); 
+            }
+        }
+        OpenLayers.Event.observe(this.imgDiv, 'load',
+                                 onload.bindAsEventListener(this));
+
     },
 
     /**