--- a/static/tiles2.js	Mon Jul 07 21:32:38 2008 +0300
+++ b/static/tiles2.js	Mon Jul 07 22:31:07 2008 +0300
@@ -1,4 +1,4 @@
-
+// A source of tile images of a specific width/height, zoom level range, and some other attributes
 var Source = Class.create({
     initialize: function (path, tile_width, tile_height, zoom_min, zoom_max) {
         this.path = path;
@@ -10,11 +10,8 @@
         this.refresh = false;
         this.opt_key = this.opt_value = null;
     },
-
-    isValidZoomLevel: function (zoom_level) {
-        return (zoom_level >= this.zoom_min && zoom_level <= this.zoom_max);
-    },
-
+    
+    // build a URL for the given tile image
     build_url: function (col, row, zl, sw, sh) {
         // two-bit hash (0-4) based on the (col, row)
         var hash = ( (col % 2) << 1 | (row % 2) ) + 1;
@@ -23,7 +20,7 @@
         var subdomain = "";
         
         if (0)
-            subdomain = "tile" + h + ".";
+            subdomain = "tile" + hash + ".";
 
         // the (x, y) co-ordinates
         var x = col * this.tile_width;
@@ -41,6 +38,7 @@
     },
 });
 
+// a viewport that contains a substrate which contains several zoom layers which contain many tiles
 var Viewport = Class.create({
     initialize: function (source, viewport_id) {
         this.source = source;
@@ -256,7 +254,7 @@
             this.zoom_layer = this.zoom_layers[delta];
             
             // enable it
-            this.zoom_layer.enable(10);
+            this.zoom_layer.enable(11);
             
             // no need to .update_tiles or anything like that
             
@@ -274,6 +272,11 @@
                 this.zoom_timer = null;
             }
             
+            // get other zoom layers out of the way
+            this.zoom_layers.each(function (zl) {
+                zl.disable();
+            });
+            
             // update the zoom layer
             this.zoom_layer = zoom_new;
             
@@ -390,6 +393,7 @@
     this.style.display = "block";
 }
 
+// a zoom layer containing the tiles for one zoom level
 var ZoomLayer = Class.create({
     initialize: function (source, zoom_level) {
         this.source = source;
@@ -400,20 +404,25 @@
         this.tiles = [];
     },
     
+    // add a tile to this zoom layer
     add_tile: function (tile) {
         this.div.appendChild(tile);
         this.tiles.push(tile);
     },
-
+    
+    // make this zoom layer visible with the given z-index
     enable: function (z_index) {
         this.div.style.zIndex = z_index;
         this.div.show();
     },
-    
+   
+    // hide this zoom layer
     disable: function (z_index) {
         this.div.hide();
     },
     
+    // update the tiles in this zoom layer so that they are in the correct position and of the correct size when
+    // viewed with the given zoom level
     update_tiles: function (zoom_level) {
         var zd = zoom_level - this.level;
 
@@ -439,7 +448,8 @@
 
 });
 
-// scale the given co-ordinate by a zoom delta, if we zoom in (dz > 0), n will become larger, and if we zoom out (dz < 0), n will become smaller
+// scale the given co-ordinate by a zoom delta. If we zoom in (dz > 0), n will become larger, and if we zoom 
+// out (dz < 0), n will become smaller.
 function scaleByZoomDelta (n, dz) {
     if (dz > 0)
         return n << dz;