Add tile queue

src/ol/tilequeue.js

@@ -0,0 +1,115 @@
+goog.provide('ol.TilePriorityFunction');
+goog.provide('ol.TileQueue');
+
+goog.require('goog.events');
+goog.require('goog.events.EventType');
+goog.require('goog.structs.PriorityQueue');
+goog.require('ol.Coordinate');
+goog.require('ol.Tile');
+goog.require('ol.TileState');
+
+
+/**
+ * @typedef {function(ol.Tile, ol.Coordinate, number): (number|undefined)}
+ */
+ol.TilePriorityFunction;
+
+
+
+/**
+ * @constructor
+ * @param {ol.TilePriorityFunction} tilePriorityFunction
+ *     Tile priority function.
+ */
+ol.TileQueue = function(tilePriorityFunction) {
+
+  /**
+   * @private
+   * @type {ol.TilePriorityFunction}
+   */
+  this.tilePriorityFunction_ = tilePriorityFunction;
+
+  /**
+   * @private
+   * @type {number}
+   */
+  this.maxTilesLoading_ = 8;
+
+  /**
+   * @private
+   * @type {number}
+   */
+  this.tilesLoading_ = 0;
+
+  /**
+   * @private
+   * @type {goog.structs.PriorityQueue}
+   */
+  this.queue_ = new goog.structs.PriorityQueue();
+
+  /**
+   * @private
+   * @type {Object.<string, boolean>}
+   */
+  this.queuedTileKeys_ = {};
+
+};
+
+
+/**
+ * @param {ol.Tile} tile Tile.
+ * @param {ol.Coordinate} tileCenter Tile center.
+ * @param {number} tileResolution Tile resolution.
+ */
+ol.TileQueue.prototype.enqueue =
+    function(tile, tileCenter, tileResolution) {
+  goog.asserts.assert(tile.getState() == ol.TileState.IDLE);
+  var tileKey = tile.getKey();
+  if (!(tileKey in this.queuedTileKeys_)) {
+    var priority = this.tilePriorityFunction_(tile, tileCenter, tileResolution);
+    if (goog.isDef(priority)) {
+      this.queue_.enqueue(priority, arguments);
+      this.queuedTileKeys_[tileKey] = true;
+    } else {
+      // FIXME fire drop event?
+    }
+  }
+};
+
+
+/**
+ * @protected
+ */
+ol.TileQueue.prototype.handleTileChange = function() {
+  --this.tilesLoading_;
+};
+
+
+/**
+ */
+ol.TileQueue.prototype.loadMoreTiles = function() {
+  var tile, tileKey;
+  while (!this.queue_.isEmpty() && this.tilesLoading_ < this.maxTilesLoading_) {
+    tile = (/** @type {Array} */ (this.queue_.remove()))[0];
+    tileKey = tile.getKey();
+    delete this.queuedTileKeys_[tileKey];
+    goog.events.listen(tile, goog.events.EventType.CHANGE,
+        this.handleTileChange, false, this);
+    tile.load();
+    ++this.tilesLoading_;
+  }
+};
+
+
+/**
+ */
+ol.TileQueue.prototype.reprioritize = function() {
+  if (!this.queue_.isEmpty()) {
+    var queue = this.queue_;
+    this.queue_ = new goog.structs.PriorityQueue();
+    this.queuedTileKeys_ = {};
+    while (!queue.isEmpty()) {
+      this.enqueue.apply(this, /** @type {Array} */ (queue.remove()));
+    }
+  }
+};