This is an attempt to make the foursquare layer implementation for leafletjs

foursquare_leaflet_layer.js

/**
 * @author Jorge Avila <jorge.e.avila@gmail.com>
 * @license Mit
 * @description Adds a padding to one side of the layer, like foursquare does.
 */

//    i use the nwtjs library to get the element and height
//    you can modify it to use jquery or whatever... instead
    
updateExtended = function () {

		if (!this._map) { return; }

		var bounds = this._map.getPixelBounds(),
		    zoom = this._map.getZoom(),
		    tileSize = this.options.tileSize;

		if (zoom > this.options.maxZoom || zoom < this.options.minZoom) {
			return;
		}

    el = n.one('html');
    documentWidth = el.region().width;
    difference = Math.round (el.region().width - documentWidth);
    
		var nwTilePoint = new L.Point(
		        Math.floor((bounds.min.x - difference) / tileSize),
		        Math.floor(bounds.min.y / tileSize)),
  
		    seTilePoint = new L.Point(
		        Math.floor(bounds.max.x / tileSize),
		        Math.floor(bounds.max.y / tileSize)),

		    tileBounds = new L.Bounds(nwTilePoint, seTilePoint);

		this._addTilesFromCenterOut(tileBounds);

		if (this.options.unloadInvisibleTiles || this.options.reuseTiles) {
			this._removeOtherTiles(tileBounds);
		}
	};

L.TileLayer.APP = L.TileLayer.extend({_update:updateExt});

L.tileLayer.app = function (url, options) {
    new L.TileLayer.APP (url, options);
});