add new DistanceWithin Filter

src/ol/format/WFS.js

@@ -928,6 +928,7 @@ const GETFEATURE_SERIALIZERS = {
     'Contains': makeChildAppender(writeContainsFilter),
     'Intersects': makeChildAppender(writeIntersectsFilter),
     'Within': makeChildAppender(writeWithinFilter),
+    'DWithin': makeChildAppender(writeDWithinFilter),
     'PropertyIsEqualTo': makeChildAppender(writeComparisonFilter),
     'PropertyIsNotEqualTo': makeChildAppender(writeComparisonFilter),
     'PropertyIsLessThan': makeChildAppender(writeComparisonFilter),
@@ -949,6 +950,7 @@ const GETFEATURE_SERIALIZERS = {
     'Intersects': makeChildAppender(writeIntersectsFilter),
     'ResourceId': makeChildAppender(writeResourceIdFilter),
     'Within': makeChildAppender(writeWithinFilter),
+    'DWithin': makeChildAppender(writeDWithinFilter),
     'PropertyIsEqualTo': makeChildAppender(writeComparisonFilter),
     'PropertyIsNotEqualTo': makeChildAppender(writeComparisonFilter),
     'PropertyIsLessThan': makeChildAppender(writeComparisonFilter),
@@ -1121,6 +1123,27 @@ function writeWithinFilter(node, filter, objectStack) {
   format.prototype.writeGeometryElement(node, filter.geometry, objectStack);
 }
 
+/**
+ * @param {Node} node Node.
+ * @param {import("./filter/DWithin.js").default} filter Filter.
+ * @param {Array<*>} objectStack Node stack.
+ */
+function writeDWithinFilter(node, filter, objectStack) {
+  const parent = /** @type {Object} */ (objectStack[objectStack.length - 1]);
+  const context = parent['context'];
+  const version = context['version'];
+  context['srsName'] = filter.srsName;
+  const format = GML_FORMATS[version];
+
+  writePropertyName(version, node, filter.geometryName);
+  format.prototype.writeGeometryElement(node, filter.geometry, objectStack);
+
+  const distance = createElementNS(getFilterNS(version), 'Distance');
+  writeStringTextNode(distance, filter.distance.toString());
+  distance.setAttribute('uom', filter.unit);
+  node.appendChild(distance);
+}
+
 /**
  * @param {Node} node Node.
  * @param {import("./filter/During.js").default} filter Filter.

src/ol/format/filter.js

@@ -4,6 +4,7 @@
 import And from './filter/And.js';
 import Bbox from './filter/Bbox.js';
 import Contains from './filter/Contains.js';
+import DWithin from './filter/DWithin.js';
 import Disjoint from './filter/Disjoint.js';
 import During from './filter/During.js';
 import EqualTo from './filter/EqualTo.js';
@@ -131,6 +132,23 @@ export function within(geometryName, geometry, opt_srsName) {
   return new Within(geometryName, geometry, opt_srsName);
 }
 
+/**
+ * Create a `<DWithin>` operator to test whether a geometry-valued property
+ * is within a distance to a given geometry.
+ *
+ * @param {!string} geometryName Geometry name to use.
+ * @param {!import("../geom/Geometry.js").default} geometry Geometry.
+ * @param {!number} distance Distance.
+ * @param {!string} unit Unit.
+ * @param {string=} opt_srsName SRS name. No srsName attribute will be
+ *    set on geometries when this is not provided.
+ * @returns {!DWithin} `<DWithin>` operator.
+ * @api
+ */
+export function dwithin(geometryName, geometry, distance, unit, opt_srsName) {
+  return new DWithin(geometryName, geometry, distance, unit, opt_srsName);
+}
+
 /**
  * Creates a `<PropertyIsEqualTo>` comparison operator.
  *

src/ol/format/filter/DWithin.js

@@ -0,0 +1,38 @@
+/**
+ * @module ol/format/filter/DWithin
+ */
+import Spatial from './Spatial.js';
+
+/**
+ * @classdesc
+ * Represents a `<DWithin>` operator to test whether a geometry-valued property
+ * is within a distance to a given geometry.
+ * @api
+ */
+class DWithin extends Spatial {
+  /**
+   * @param {!string} geometryName Geometry name to use.
+   * @param {!import("../../geom/Geometry.js").default} geometry Geometry.
+   * @param {!number} distance Distance.
+   * @param {!string} unit Unit.
+   * @param {string=} opt_srsName SRS name. No srsName attribute will be
+   *    set on geometries when this is not provided.
+   */
+  constructor(geometryName, geometry, distance, unit, opt_srsName) {
+    super('DWithin', geometryName, geometry, opt_srsName);
+
+    /**
+     * @public
+     * @type {!number}
+     */
+    this.distance = distance;
+
+    /**
+     * @public
+     * @type {!string}
+     */
+    this.unit = unit;
+  }
+}
+
+export default DWithin;

test/spec/ol/format/wfs.test.js

@@ -19,6 +19,7 @@ import {
   contains as containsFilter,
   disjoint as disjointFilter,
   during as duringFilter,
+  dwithin as dwithinFilter,
   equalTo as equalToFilter,
   greaterThan as greaterThanFilter,
   greaterThanOrEqualTo as greaterThanOrEqualToFilter,
@@ -686,6 +687,48 @@ describe('ol.format.WFS', function () {
       expect(serialized.firstElementChild).to.xmleql(parse(text));
     });
 
+    it('creates a dwithin filter', function () {
+      const text =
+        '<wfs:Query xmlns:wfs="http://www.opengis.net/wfs" ' +
+        '    typeName="area" srsName="EPSG:4326" ' +
+        '    xmlns:topp="http://www.openplans.org/topp">' +
+        '  <ogc:Filter xmlns:ogc="http://www.opengis.net/ogc">' +
+        '    <ogc:DWithin>' +
+        '      <ogc:PropertyName>the_geom</ogc:PropertyName>' +
+        '      <gml:Polygon xmlns:gml="http://www.opengis.net/gml">' +
+        '        <gml:exterior>' +
+        '          <gml:LinearRing>' +
+        '            <gml:posList srsDimension="2">' +
+        '              10 20 10 25 15 25 15 20 10 20' +
+        '            </gml:posList>' +
+        '          </gml:LinearRing>' +
+        '        </gml:exterior>' +
+        '      </gml:Polygon>' +
+        '      <ogc:Distance uom="m">10</ogc:Distance>' +
+        '    </ogc:DWithin>' +
+        '  </ogc:Filter>' +
+        '</wfs:Query>';
+      const serialized = new WFS().writeGetFeature({
+        srsName: 'EPSG:4326',
+        featureTypes: ['area'],
+        filter: dwithinFilter(
+          'the_geom',
+          new Polygon([
+            [
+              [10, 20],
+              [10, 25],
+              [15, 25],
+              [15, 20],
+              [10, 20],
+            ],
+          ]),
+          10,
+          'm'
+        ),
+      });
+      expect(serialized.firstElementChild).to.xmleql(parse(text));
+    });
+
     it('creates During property filter', function () {
       const text =
         '<wfs:Query xmlns:wfs="http://www.opengis.net/wfs" ' +