make a destroy method and a clear grid. preventing circular refrences and memory leaks

git-svn-id: http://svn.openlayers.org/trunk/openlayers@184 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/Grid.js

@@ -73,6 +73,10 @@ OpenLayers.Layer.Grid.prototype = Object.extend( new OpenLayers.Layer(), {
         //first of all, clear out the main div
         this.div.innerHTML = "";
 
+        //now clear out the old grid and start a new one
+        this.clearGrid();
+        this.grid = new Array();
+
         var viewSize = this.map.getSize();
         var bounds = this.map.getExtent();
         var extent = this.map.getFullExtent();
@@ -96,7 +100,6 @@ OpenLayers.Layer.Grid.prototype = Object.extend( new OpenLayers.Layer(), {
         tileoffsety = Math.round(tileoffsety);
 
         this.origin = new OpenLayers.Pixel(tileoffsetx,tileoffsety);
-        this.grid = new Array();
 
         var startX = tileoffsetx; 
         var startLon = tileoffsetlon;
@@ -223,5 +226,23 @@ OpenLayers.Layer.Grid.prototype = Object.extend( new OpenLayers.Layer(), {
             }
         }
         return requestString;
+    },
+    
+    /** go through and remove all tiles from the grid, calling
+    *    destroy() on each of them to kill circular references
+    * 
+    * @private
+    */
+    clearGrid:function() {
+        while(grid.length > 0) {
+            var row = grid[0];
+            while(row.length > 0) {
+                var tile = row[0];
+                tile.destroy();
+                row.remove(tile);
+            }
+            grid.remove(row);                   
+        }
     }
+    
 });

lib/OpenLayers/Tile.js

@@ -42,6 +42,14 @@ OpenLayers.Tile.prototype = {
             this.size = size;
         }
     },
+    
+    /** nullify references to prevent circular references and memory leaks
+    */
+    destroy:function() {
+        this.grid = null;
+        this.bounds = null;
+        this.size = null;
+    },
 
     /**
     */