Merge pull request #3810 from ahocevar/tilegrid-example-docs

Improve TileGrid documentation and examples

examples/xyz-esri-4326-512.js

@@ -25,7 +25,7 @@ var map = new ol.Map({
         attributions: [attribution],
         maxZoom: 16,
         projection: projection,
-        tileSize: 512,
+        tileSize: tileSize,
         tileUrlFunction: function(tileCoord) {
           return urlTemplate.replace('{z}', (tileCoord[0] - 1).toString())
                             .replace('{x}', tileCoord[1].toString())

externs/olx.js

@@ -6148,7 +6148,9 @@ olx.tilegrid.TileGridOptions.prototype.minZoom;
 
 
 /**
- * Origin, i.e. the bottom-left corner of the grid. Default is null.
+ * The tile grid origin, i.e. where the `x` and `y` axes meet (`[z, 0, 0]`).
+ * Tile coordinates increase from left to right and from bottom to top. If not
+ * specified, `extent` or `origins` must be provided.
  * @type {ol.Coordinate|undefined}
  * @api stable
  */
@@ -6156,9 +6158,11 @@ olx.tilegrid.TileGridOptions.prototype.origin;
 
 
 /**
- * Origins, i.e. the bottom-left corners of the grid for each zoom level. If
+ * Tile grid origins, i.e. where the `x` and `y` axes meet (`[z, 0, 0]`), for
- * given, the array length should match the length of the `resolutions` array,
+ * each zoom level. If given, the array length should match the length of the
- * i.e. each resolution can have a different origin.
+ * `resolutions` array, i.e. each resolution can have a different origin. Tile
+ * coordinates increase from left to right and from bottom to top. If not
+ * specified, `extent` or `origin` must be provided.
  * @type {Array.<ol.Coordinate>|undefined}
  * @api stable
  */