Merge pull request #10678 from mike-000/patch-7

Add maxResolution option to ol/tilegrid.createXYZ() and ol/source/XYZ

src/ol/source/VectorTile.js

@@ -30,9 +30,10 @@ import TileCache from '../TileCache.js';
  * @property {import("./State.js").default} [state] Source state.
  * @property {typeof import("../VectorTile.js").default} [tileClass] Class used to instantiate image tiles.
  * Default is {@link module:ol/VectorTile}.
- * @property {number} [maxZoom=22] Optional max zoom level.
- * @property {number} [minZoom] Optional min zoom level.
- * @property {number|import("../size.js").Size} [tileSize=512] Optional tile size.
+ * @property {number} [maxZoom=22] Optional max zoom level. Not used if `tileGrid` is provided.
+ * @property {number} [minZoom] Optional min zoom level. Not used if `tileGrid` is provided.
+ * @property {number|import("../size.js").Size} [tileSize=512] Optional tile size. Not used if `tileGrid` is provided.
+ * @property {number} [maxResolution] Optional tile grid resolution at level zero. Not used if `tileGrid` is provided.
  * @property {import("../tilegrid/TileGrid.js").default} [tileGrid] Tile grid.
  * @property {import("../Tile.js").LoadFunction} [tileLoadFunction]
  * Optional function to load a tile given a URL. Could look like this for pbf tiles:
@@ -105,6 +106,7 @@ class VectorTile extends UrlTile {
 
     const tileGrid = options.tileGrid || createXYZ({
       extent: extent,
+      maxResolution: options.maxResolution,
       maxZoom: options.maxZoom !== undefined ? options.maxZoom : 22,
       minZoom: options.minZoom,
       tileSize: options.tileSize || 512

src/ol/source/XYZ.js

@@ -17,8 +17,9 @@ import {createXYZ, extentFromProjection} from '../tilegrid.js';
  * @property {import("../proj.js").ProjectionLike} [projection='EPSG:3857'] Projection.
  * @property {number} [reprojectionErrorThreshold=0.5] Maximum allowed reprojection error (in pixels).
  * Higher values can increase reprojection performance, but decrease precision.
- * @property {number} [maxZoom=18] Optional max zoom level.
- * @property {number} [minZoom=0] Optional min zoom level.
+ * @property {number} [maxZoom=42] Optional max zoom level. Not used if `tileGrid` is provided.
+ * @property {number} [minZoom=0] Optional min zoom level. Not used if `tileGrid` is provided.
+ * @property {number} [maxResolution] Optional tile grid resolution at level zero. Not used if `tileGrid` is provided.
  * @property {import("../tilegrid/TileGrid.js").default} [tileGrid] Tile grid.
  * @property {import("../Tile.js").LoadFunction} [tileLoadFunction] Optional function to load a tile given a URL. The default is
  * ```js
@@ -31,9 +32,10 @@ import {createXYZ, extentFromProjection} from '../tilegrid.js';
  * by 512px images (for retina/hidpi devices) then `tilePixelRatio`
  * should be set to `2`.
  * @property {number|import("../size.js").Size} [tileSize=[256, 256]] The tile size used by the tile service.
+ * Not used if `tileGrid` is provided.
  * @property {import("../Tile.js").UrlFunction} [tileUrlFunction] Optional function to get
  * tile URL given a tile coordinate and the projection.
- * Required if url or urls are not provided.
+ * Required if `url` or `urls` are not provided.
  * @property {string} [url] URL template. Must include `{x}`, `{y}` or `{-y}`,
  * and `{z}` placeholders. A `{?-?}` template pattern, for example `subdomain{a-f}.domain.com`,
  * may be used instead of defining each one separately in the `urls` option.
@@ -78,6 +80,7 @@ class XYZ extends TileImage {
     const tileGrid = options.tileGrid !== undefined ? options.tileGrid :
       createXYZ({
         extent: extentFromProjection(projection),
+        maxResolution: options.maxResolution,
         maxZoom: options.maxZoom,
         minZoom: options.minZoom,
         tileSize: options.tileSize

src/ol/tilegrid.js

@@ -72,8 +72,9 @@ export function createForExtent(extent, opt_maxZoom, opt_tileSize, opt_corner) {
 /**
  * @typedef {Object} XYZOptions
  * @property {import("./extent.js").Extent} [extent] Extent for the tile grid. The origin for an XYZ tile grid is the
- * top-left corner of the extent. The zero level of the grid is defined by the resolution at which one tile fits in the
- * provided extent. If not provided, the extent of the EPSG:3857 projection is used.
+ * top-left corner of the extent. If `maxResolution` is not provided the zero level of the grid is defined by the resolution
+ * at which one tile fits in the provided extent. If not provided, the extent of the EPSG:3857 projection is used.
+ * @property {number} [maxResolution] Resolution at level zero.
  * @property {number} [maxZoom] Maximum zoom. The default is `42`. This determines the number of levels
  * in the grid set. For example, a `maxZoom` of 21 means there are 22 levels in the grid set.
  * @property {number} [minZoom=0] Minimum zoom.
@@ -99,7 +100,8 @@ export function createXYZ(opt_options) {
     resolutions: resolutionsFromExtent(
       extent,
       xyzOptions.maxZoom,
-      xyzOptions.tileSize
+      xyzOptions.tileSize,
+      xyzOptions.maxResolution
     )
   };
   return new TileGrid(gridOptions);
@@ -113,9 +115,10 @@ export function createXYZ(opt_options) {
  *     DEFAULT_MAX_ZOOM).
  * @param {number|import("./size.js").Size=} opt_tileSize Tile size (default uses
  *     DEFAULT_TILE_SIZE).
+ * @param {number=} opt_maxResolution Resolution at level zero.
  * @return {!Array<number>} Resolutions array.
  */
-function resolutionsFromExtent(extent, opt_maxZoom, opt_tileSize) {
+function resolutionsFromExtent(extent, opt_maxZoom, opt_tileSize, opt_maxResolution) {
   const maxZoom = opt_maxZoom !== undefined ?
     opt_maxZoom : DEFAULT_MAX_ZOOM;
 
@@ -124,8 +127,8 @@ function resolutionsFromExtent(extent, opt_maxZoom, opt_tileSize) {
 
   const tileSize = toSize(opt_tileSize !== undefined ?
     opt_tileSize : DEFAULT_TILE_SIZE);
-  const maxResolution = Math.max(
-    width / tileSize[0], height / tileSize[1]);
+  const maxResolution = opt_maxResolution > 0 ? opt_maxResolution :
+    Math.max(width / tileSize[0], height / tileSize[1]);
 
   const length = maxZoom + 1;
   const resolutions = new Array(length);