TileQueue.js

L.TileQueue = function(callback) {
    this.callback = callback;
};

L.TileQueue.prototype = {

    _queue: [],
    _queueTimeout: null,
    
    add: function(aTile) {
        this._queue.push(aTile);
        if (!this._queueTimeout) {
            this._queueTimeout = setTimeout(L.bind(function(){
                var time, timeout, start = +new Date, tile;

                // handle empty elements, see remove
                do { 
                    tile = this._queue.shift();
                }
                while (!tile && this._queue.length > 0);

                if (tile) {
                    //console.log('adding ' + tile.key + ' ...');

                    this.callback(tile);

                    // pause a percentage of adding time to keep UI responsive
                    time = +new Date - start;
                    timeout = Math.floor(time * 0.3);
                    //console.log('added  ' + tile.key + ' (' + time + 'ms > ' + timeout + 'ms)');
                    this._queueTimeout = setTimeout(L.bind(arguments.callee, this), timeout);
                } else {
                    this._queueTimeout = null;
                }
            }, this), 0);
        }
    },

    remove: function(tile) {
        var key = tile.key, 
            val;
        for (var i = 0, len = this._queue.length; i < len; i++) {
            val = this._queue[i];
            if (val && val.key === key) {
                //console.log('##### delete ' + key);
                // set entry to undefined only for better performance (?) - 
                // queue consumer needs to handle empty entries!
                delete this._queue[i];
            }
        }
    },

    clear: function() {
        if (this._queueTimeout) {
            clearTimeout(this._queueTimeout);
            this._queueTimeout = null;
        }
        this._queue = [];
    }
};