Merge pull request #60243 from elpaso/bugfix-gh59818-server-wms-gfi-tolerance

[server][wms] GFI: fix sub-pixel tolerance

src/server/services/wms/qgswmsrenderer.cpp

@@ -3153,6 +3153,9 @@ namespace QgsWms
       }
     }
 
+    // Make sure the map unit tolerance is at least 1 pixel
+    mapUnitTolerance = std::max( mapUnitTolerance, 1.0 * rct.mapToPixel().mapUnitsPerPixel() );
+
     QgsRectangle mapRectangle( infoPoint.x() - mapUnitTolerance, infoPoint.y() - mapUnitTolerance, infoPoint.x() + mapUnitTolerance, infoPoint.y() + mapUnitTolerance );
     return ( mapSettings.mapToLayerCoordinates( ml, mapRectangle ) );
   }

tests/src/python/test_qgsserver_wms_getfeatureinfo.py

@@ -37,9 +37,15 @@ from qgis.core import (
     QgsMemoryProviderUtils,
     QgsProject,
     QgsWkbTypes,
+    QgsPointXY,
+)
+from qgis.PyQt.QtCore import QVariant, QUrl
+from qgis.server import (
+    QgsBufferServerRequest,
+    QgsBufferServerResponse,
+    QgsServer,
+    QgsServerRequest,
 )
-from qgis.PyQt.QtCore import QVariant
-from qgis.server import QgsBufferServerRequest, QgsBufferServerResponse
 from qgis.testing import unittest, QgisTestCase
 from test_qgsserver_wms import TestQgsServerWMSTestBase
 
@@ -1357,6 +1363,61 @@ class TestQgsServerWMSGetFeatureInfo(TestQgsServerWMSTestBase):
             "test_project_values.qgz",
         )
 
+    def test_getfeatureinfo_sub_px_tolerance(self):
+
+        # create a memory layer with points
+        fields = QgsFields()
+        fields.append(QgsField("id", QVariant.Int))
+        fields.append(QgsField("name", QVariant.String))
+        layer = QgsMemoryProviderUtils.createMemoryLayer(
+            "points",
+            fields,
+            QgsWkbTypes.Point,
+            QgsCoordinateReferenceSystem("EPSG:4326"),
+        )
+
+        provider = layer.dataProvider()
+        self.assertTrue(layer.isValid())
+
+        # add some features
+        f = QgsFeature(fields)
+        f.setAttribute("id", 1)
+        f.setAttribute("name", "point1")
+        f.setGeometry(QgsGeometry.fromPointXY(QgsPointXY(0, 0)))
+        provider.addFeature(f)
+
+        f = QgsFeature(fields)
+        f.setAttribute("id", 2)
+        f.setAttribute("name", "point2")
+        f.setGeometry(QgsGeometry.fromPointXY(QgsPointXY(1, 1)))
+        provider.addFeature(f)
+
+        f = QgsFeature(fields)
+        f.setAttribute("id", 2)
+        f.setAttribute("name", "point2")
+        f.setGeometry(QgsGeometry.fromPointXY(QgsPointXY(-1, -1)))
+        provider.addFeature(f)
+
+        project = QgsProject()
+        project.addMapLayer(layer)
+
+        # set up the WMS server
+        server = QgsServer()
+        request = QgsServerRequest()
+        # Choose a small extent to trigger the sub-pixel tolerance adjustment
+        w = 10
+        w2 = int(w / 2)
+        request.setUrl(
+            QUrl(
+                f"?SERVICE=WMS&REQUEST=GetFeatureInfo&LAYERS=points&QUERY_LAYERS=points&INFO_FORMAT=application/json&FEATURE_COUNT=1&WIDTH={w}&HEIGHT={w}&CRS=EPSG:4326&STYLES=&BBOX=-1,-1,1,1&X={w2}&Y={w2}&VERSION=1.3.0"
+            )
+        )
+        response = QgsBufferServerResponse()
+
+        server.handleRequest(request, response, project)
+        body = response.body().data().decode("utf8").replace("\n", "")
+        self.assertEqual(len(json.loads(body)["features"]), 1)
+
 
 if __name__ == "__main__":
     unittest.main()