Merge pull request #568 from OpenGeoscience/allow-override-of-tiles-a…

…t-zoom

Allow overriding the tilesAtZoom function.

examples/tiles/main.js

@@ -1,3 +1,4 @@
+/* globals $, geo */
 // This example should be tried with different query strings.
 
 /* Many parameters can be adjusted via url query parameters:
@@ -27,8 +28,8 @@
  * maxBoundsTop: maximum bounds top value.
  * opacity: a css opacity value (typically a float from 0 to 1).
  * projection: 'parallel' or 'projection' for the camera projection.
- * renderer: 'vgl' (default), 'canvas', 'd3', 'null', or 'html'. This picks the
- * renderer for map tiles. null or html uses the html renderer.
+ * renderer: 'vgl' (default), 'canvas', 'd3', 'null', or 'html'. This picks
+ * the renderer for map tiles. null or html uses the html renderer.
  * round: 'round' (default), 'floor', 'ceil'.
  * subdomains: a comma-separated string of subdomains to use in the {s} part
  * of the url parameter. If there are no commas in the string, each letter
@@ -159,6 +160,13 @@ $(function () {
  };
  layerParams.attribution = '';
  layerParams.tileRounding = Math.ceil;
+ layerParams.tilesAtZoom = function (level) {
+ var scale = Math.pow(2, layerParams.maxLevel - level);
+ return {
+ x: Math.ceil(w / (layerParams.tileWidth || 256) / scale),
+ y: Math.ceil(h / (layerParams.tileHeight || 256) / scale)
+ };
+ };
  }
  // Parse additional query options
  if (query.x !== undefined) {

src/tileLayer.js

@@ -81,6 +81,9 @@ module.exports = (function () {
  * The tile width as displayed without overlap
  * @param {number} [options.tileHeight=256]
  * The tile height as displayed without overlap
+ * @param {function} [options.tilesAtZoom=null]
+ * A function that is given a zoom level and returns {x: (num), y: (num)}
+ * with the number of tiles at that zoom level.
  * @param {number} [options.cacheSize=400] The maximum number of tiles to
  * cache. The default is 200 if keepLower is false.
  * @param {bool} [options.keepLower=true]
@@ -230,6 +233,9 @@ module.exports = (function () {
  * @returns {{x: nx, y: ny}} The number of tiles in each axis
  */
  this.tilesAtZoom = function (level) {
+ if (this._options.tilesAtZoom) {
+ return this._options.tilesAtZoom.call(this, level);
+ }
  var s = Math.pow(2, level);
  return {x: s, y: s};
  };

tests/cases/tileLayer.js

@@ -347,7 +347,11 @@ describe('geo.tileLayer', function () {
  tileRounding: function () {},
  attribution: 'My awesome layer',
  tileOffset: function () {},
- topDown: true
+ topDown: true,
+ tilesAtZoom: function (level) {
+ var s = Math.pow(2, level);
+ return {x: s, y: Math.ceil(s * 3 / 4)};
+ }
  };
  opts.originalUrl = opts.url;
  it('Check tileLayer options', function () {
@@ -401,6 +405,15 @@ describe('geo.tileLayer', function () {
  l.subdomains(['ab', 'c']);
  expect(l.subdomains()).toEqual(['ab', 'c']);
  });
+ it('tilesAtZoom', function () {
+ var m = map(), l;
+ opts.map = m;
+ l = geo.tileLayer(opts);
+ expect(l.tilesAtZoom(0)).toEqual({x: 1, y: 1});
+ expect(l.tilesAtZoom(1)).toEqual({x: 2, y: 2});
+ expect(l.tilesAtZoom(2)).toEqual({x: 4, y: 3});
+ expect(l.tilesAtZoom(3)).toEqual({x: 8, y: 6});
+ });
  });
  describe('Public utility methods', function () {
  describe('isValid', function () {