Start a maximum of two new tile downloads per frame

src/ol/map.js

@@ -77,6 +77,12 @@ ol.ENABLE_DOM = true;
 ol.ENABLE_WEBGL = true;
 
 
+/**
+ * @define {number} Maximum new tile loads per frame.
+ */
+ol.MAXIMUM_NEW_TILE_LOADS_PER_FRAME = 2;
+
+
 /**
  * @enum {string}
  */
@@ -556,7 +562,7 @@ ol.Map.prototype.handleMapBrowserEvent = function(mapBrowserEvent) {
  */
 ol.Map.prototype.handlePostRender = function() {
   this.tileQueue_.reprioritize(); // FIXME only call if needed
-  this.tileQueue_.loadMoreTiles();
+  this.tileQueue_.loadMoreTiles(ol.MAXIMUM_NEW_TILE_LOADS_PER_FRAME);
 
   var postRenderFunctions = this.postRenderFunctions_;
   var i;

src/ol/tilequeue.js

@@ -74,15 +74,18 @@ ol.TileQueue.prototype.handleTileChange = function() {
 
 
 /**
- *  FIXME empty description for jsdoc
+ * @param {number} limit Maximum number of new tiles to load.
  */
-ol.TileQueue.prototype.loadMoreTiles = function() {
+ol.TileQueue.prototype.loadMoreTiles = function(limit) {
   var tile;
-  while (!this.isEmpty() && this.tilesLoading_ < this.maxTilesLoading_) {
+  while (limit > 0 &&
+         !this.isEmpty() &&
+         this.tilesLoading_ < this.maxTilesLoading_) {
     tile = /** @type {ol.Tile} */ (this.dequeue()[0]);
     goog.events.listenOnce(tile, goog.events.EventType.CHANGE,
         this.handleTileChange, false, this);
     tile.load();
     ++this.tilesLoading_;
+    --limit;
   }
 };