add comments for spiralTileLoad() function

git-svn-id: http://svn.openlayers.org/branches/openlayers/2.0@1285 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/Grid.js

@@ -247,7 +247,15 @@ OpenLayers.Layer.Grid.prototype =
     },
     
     /** 
+     * @private 
      * 
+     *   Starts at the top right corner of the grid and proceeds in a spiral 
+     *    towards the center, adding tiles one at a time to the beginning of a 
+     *    queue. 
+     * 
+     *   Once all the grid's tiles have been added to the queue, we go back 
+     *    and iterate through the queue (thus reversing the spiral order from 
+     *    outside-in to inside-out), calling draw() on each tile. 
      */
     spiralTileLoad: function() {
         var tileQueue = new Array();
@@ -279,6 +287,8 @@ OpenLayers.Layer.Grid.prototype =
                     break;
             } 
     
+            // if the test grid coordinates are within the bounds of the 
+            //  grid, get a reference to the tile.
             var tile = null;
             if ((testRow < this.grid.length) && 
                 (testCell < this.grid[0].length)) {
@@ -286,12 +296,16 @@ OpenLayers.Layer.Grid.prototype =
             }
             
             if ((tile != null) && (!tile.queued)) {
+                //add tile to beginning of queue, mark it as queued.
                 tileQueue.unshift(tile);
                 tile.queued = true;
+                
+                //restart the directions counter and take on the new coords
                 directionsTried = 0;
                 iRow = testRow;
                 iCell = testCell;
             } else {
+                //need to try to load a tile in a different direction
                 direction = (direction + 1) % 4;
                 directionsTried++;
             }
@@ -301,6 +315,7 @@ OpenLayers.Layer.Grid.prototype =
         for(var i=0; i < tileQueue.length; i++) {
             var tile = tileQueue[i]
             tile.draw();
+            //mark tile as unqueued for the next time (since tiles are reused)
             tile.queued = false;       
         }
     },