Allow changing the map extent properly when showing the map (#62)

Prevent map from panning to first layer's extent upon processing events

Author: Joonalai

CHANGELOG.md

@@ -4,11 +4,11 @@
 
 * Add `clean_qgis_layer` decorator back alongside with automatic cleaning [#45](https://github.com/GispoCoding/pytest-qgis/pull/45)
 
-
 ## Fixes
 
-* [#55](https://github.com/GispoCoding/pytest-qgis/pull/55) Allows using MagicMocks to mock layers without problems
+* [#53](https://github.com/GispoCoding/pytest-qgis/pull/53) Allow using MagicMocks to mock layers without problems
 * [#60](https://github.com/GispoCoding/pytest-qgis/pull/60) Allows using CRS properly again
+* [#62](https://github.com/GispoCoding/pytest-qgis/pull/62) Map does no longer zoom to the first added layer upon processing the events when using `qgis_show_map` marker
 
 # Version 2.0.0 (29-11-2023)
 

src/pytest_qgis/pytest_qgis.py

@@ -158,6 +158,7 @@ def qgis_app(request: "SubRequest") -> QgsApplication:
 
     if not request.config._plugin_settings.qgis_init_disabled:
         assert _APP
+        QgsProject.instance().legendLayersAdded.disconnect(_APP.processEvents)
         if not sip.isdeleted(_CANVAS) and _CANVAS is not None:
             _CANVAS.deleteLater()
         _APP.exitQgis()
@@ -303,6 +304,16 @@ def _start_and_configure_qgis_app(config: "Config") -> None:
 
         mock.patch("qgis.utils.iface", _IFACE).start()
 
+    if _APP is not None:
+        # QGIS zooms to the layer's extent if it
+        # is the first layer added to the map.
+        # If the qgis_show_map marker is used, this zooming might occur
+        # at some later time when events are processed (e.g. at qtbot.wait call)
+        # and this might change the extent unexpectedly.
+        # It is better to process events right after adding the
+        # layer to avoid these kind of problems.
+        QgsProject.instance().legendLayersAdded.connect(_APP.processEvents)
+
 
 def _initialize_processing(qgis_app: QgsApplication) -> None:
     python_plugins_path = os.path.join(qgis_app.pkgDataPath(), "python", "plugins")

tests/visual/test_show_map.py

@@ -126,3 +126,19 @@ def test_show_map_crs_change_to_4326_2(layer_polygon, layer_points, layer_polygo
     QgsProject.instance().addMapLayers(
         [layer_points, layer_polygon_3067, layer_polygon]
     )
+
+
+@pytest.mark.qgis_show_map(timeout=DEFAULT_TIMEOUT, zoom_to_common_extent=False)
+def test_map_extent_should_not_change_to_layers_extent_when_processing_events(
+    layer_polygon_3067, qgis_canvas, qgis_app
+):
+    extent_smaller_than_layer = QgsRectangle(475804, 7145949.5, 549226, 7219371.5)
+
+    QgsProject.instance().addMapLayer(layer_polygon_3067)
+    qgis_canvas.setExtent(extent_smaller_than_layer)
+
+    # This triggers the map to set the extent based on the layer
+    # if events are not processed after adding the layer
+    qgis_app.processEvents()
+
+    assert qgis_canvas.extent().height() == extent_smaller_than_layer.height()