Merge pull request #322 from ahocevar/loadend

WMS loadend event does not always fire. r=@elemoine

lib/OpenLayers/Layer/Grid.js

@@ -138,6 +138,12 @@ OpenLayers.Layer.Grid = OpenLayers.Class(OpenLayers.Layer.HTTPRequest, {
      */
     tileQueue: null,
     
+    /**
+     * Property: loading
+     * {Boolean} Indicates if tiles are being loaded.
+     */
+    loading: false,
+    
     /**
      * Property: backBuffer
      * {DOMElement} The back buffer.
@@ -1050,7 +1056,8 @@ OpenLayers.Layer.Grid = OpenLayers.Class(OpenLayers.Layer.HTTPRequest, {
         
         tile.onLoadStart = function() {
             //if that was first tile then trigger a 'loadstart' on the layer
-            if (this.numLoadingTiles == 0) {
+            if (this.loading === false) {
+                this.loading = true;
                 this.events.triggerEvent("loadstart");
             }
             this.events.triggerEvent("tileloadstart", {tile: tile});
@@ -1061,7 +1068,8 @@ OpenLayers.Layer.Grid = OpenLayers.Class(OpenLayers.Layer.HTTPRequest, {
             this.numLoadingTiles--;
             this.events.triggerEvent("tileloaded", {tile: tile});
             //if that was the last tile, then trigger a 'loadend' on the layer
-            if (this.numLoadingTiles === 0) {
+            if (this.tileQueue.length === 0 && this.numLoadingTiles === 0) {
+                this.loading = false;
                 this.events.triggerEvent("loadend");
                 if(this.backBuffer) {
                     // the removal of the back buffer is delayed to prevent flash