Fox offset calculation for prev link

test added

src/server/services/wfs3/qgswfs3handlers.cpp

@@ -1399,7 +1399,7 @@ void QgsWfs3CollectionsItemsHandler::handleRequest( const QgsServerApiContext &c
       if ( offset != 0 )
       {
         json prevLink = selfLink;
-        prevLink["href"] = QStringLiteral( "%1&offset=%2&limit=%3" ).arg( cleanedUrlAsString ).arg( std::max<long>( 0, limit - offset ) ).arg( limit ).toStdString();
+        prevLink["href"] = QStringLiteral( "%1&offset=%2&limit=%3" ).arg( cleanedUrlAsString ).arg( std::max<long>( 0, offset - limit ) ).arg( limit ).toStdString();
         prevLink["rel"] = "prev";
         prevLink["title"] = "Previous page";
         data["links"].push_back( prevLink );

tests/src/python/test_qgsserver_api.py

@@ -630,6 +630,15 @@ def test_wfs3_collection_items_limit_offset(self):
         self.assertEqual(response.body(),
                          b'[{"code":"Bad request error","description":"Argument \'limit\' is not valid. Number of features to retrieve [0-10000]"}]')  # Bad request
 
+    def test_wfs3_collection_items_limit_offset_2(self):
+        """Test WFS3 API offset 2"""
+        project = QgsProject()
+        project.read(os.path.join(self.temporary_path, 'qgis_server', 'test_project_api.qgs'))
+        request = QgsBufferServerRequest(
+            'http://server.qgis.org/wfs3/collections/testlayer%20èé/items?limit=1&offset=2')
+        self.compareApi(
+            request, project, 'test_wfs3_collections_items_testlayer_èé_limit_1_offset_2.json')
+
     def test_wfs3_collection_items_bbox(self):
         """Test WFS3 API bbox"""
         project = QgsProject()

tests/testdata/qgis_server/api/test_wfs3_collections_items_testlayer_èé_limit_1_offset_2.json

@@ -0,0 +1,46 @@
+Content-Type: application/geo+json
+
+{
+  "features": [
+    {
+      "geometry": {
+        "coordinates": [
+          8.203459,
+          44.901395
+        ],
+        "type": "Point"
+      },
+      "id": "2",
+      "properties": {
+        "id": 3,
+        "name": "three",
+        "utf8nameè": "three èé↓"
+      },
+      "type": "Feature"
+    }
+  ],
+  "links": [
+    {
+      "href": "http://server.qgis.org/wfs3/collections/testlayer%20%C3%A8%C3%A9/items.geojson?limit=1&offset=2",
+      "rel": "self",
+      "title": "Retrieve the features of the collection as GEOJSON",
+      "type": "application/geo+json"
+    },
+    {
+      "href": "http://server.qgis.org/wfs3/collections/testlayer%20%C3%A8%C3%A9/items.html?limit=1&offset=2",
+      "rel": "alternate",
+      "title": "Retrieve the features of the collection as HTML",
+      "type": "text/html"
+    },
+    {
+      "href": "http://server.qgis.org/wfs3/collections/testlayer èé/items?&offset=1&limit=1",
+      "rel": "prev",
+      "title": "Previous page",
+      "type": "application/geo+json"
+    }
+  ],
+  "numberMatched": 3,
+  "numberReturned": 1,
+  "timeStamp": "2019-07-05T12:27:07Z",
+  "type": "FeatureCollection"
+}