fix(gui): app-level event filters tolerate PySide's stray QWidgetItem

CI (3.12, PR 232) failed test_font_zoom_keeps_frozen_column_aligned_and_reautosizes
with a pytest-qt CALL ERROR: PySide 6.9 handed both app-level filters a
QWidgetItem instead of a QEvent during layout teardown, and event.type()
raised. The wheel guard now keys on isinstance(event, QWheelEvent) and
returns False itself instead of super().eventFilter() (which type-checks
its arguments and would raise the same way); the cursor filter ignores
anything that is not a QEvent. Regression test for each.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/aare/gui/main_window.py

@@ -150,6 +150,10 @@ class ClickableCursorFilter(QObject):
     forbidden cursor) still win: they set it later."""
 
     def eventFilter(self, obj, event):
+        # Same PySide 6.9 quirk as WheelValueGuard: an app-level filter can be
+        # handed a QWidgetItem instead of a QEvent during layout teardown.
+        if not isinstance(event, QEvent):
+            return False
         if event.type() == QEvent.Type.Polish and isinstance(
             obj, (QAbstractButton, QComboBox, QSlider)
         ):

src/aare/gui/widgets/wheel_value_guard.py

@@ -1,4 +1,4 @@
-from PySide6.QtCore import QEvent, QObject, Qt
+from PySide6.QtCore import QObject, Qt
 from PySide6.QtGui import QWheelEvent
 from PySide6.QtWidgets import (
     QAbstractScrollArea,
@@ -26,7 +26,10 @@ class WheelValueGuard(QObject):
     GUARDED = (QAbstractSpinBox, QSlider, QDial, QComboBox, QTabBar)
 
     def eventFilter(self, obj, event):
-        if event.type() == QEvent.Type.Wheel and isinstance(obj, self.GUARDED):
+        # isinstance, not event.type(): PySide 6.9 sometimes hands an app-level
+        # filter a QWidgetItem instead of a QEvent while layouts are torn down,
+        # and .type() then raises (pytest-qt CALL ERROR on a random test).
+        if isinstance(event, QWheelEvent) and isinstance(obj, self.GUARDED):
             if event.buttons() & Qt.MouseButton.RightButton:
                 return False  # right button held: deliberate value adjustment
             area = obj.parentWidget()
@@ -45,7 +48,9 @@ class WheelValueGuard(QObject):
                 )
                 QApplication.sendEvent(area.viewport(), relayed)
             return True
-        return super().eventFilter(obj, event)
+        # Not super().eventFilter(): QObject's does nothing but type-checks its
+        # arguments, so the stray QWidgetItem would raise there instead.
+        return False
 
 
 if __name__ == "__main__":

tests/unit/gui/test_main_window.py

@@ -3,10 +3,10 @@ from unittest.mock import MagicMock, patch
 
 import pytest
 from PySide6.QtCore import QSettings, Qt
-from PySide6.QtWidgets import QApplication, QDockWidget
+from PySide6.QtWidgets import QApplication, QDockWidget, QWidget, QWidgetItem
 
 from aare.gui import styles
-from aare.gui.main_window import MainWindow
+from aare.gui.main_window import ClickableCursorFilter, MainWindow
 from aare.gui.styles import THEME_BLUEBIRD, THEME_SUNRISE, THEME_SUNSET
 
 
@@ -683,3 +683,10 @@ def test_sample_camera_frame_paints_visible_views_and_acks(qtbot, mock_ui_state,
     # No subscriber (GUI started without a sample feed): the slot must not blow up.
     win.prediction_thread = None
     win._on_sample_camera_frame(QImage(4, 6, QImage.Format.Format_RGB888))
+
+
+def test_cursor_filter_ignores_a_non_event_argument(qapp):
+    # PySide 6.9 can hand an app-level filter a QWidgetItem instead of a
+    # QEvent during layout teardown; raising there fails a random test.
+    widget = QWidget()
+    assert ClickableCursorFilter().eventFilter(widget, QWidgetItem(widget)) is False

tests/unit/gui/test_wheel_value_guard.py

@@ -5,7 +5,15 @@ deliberate right-button + wheel gesture."""
 import pytest
 from PySide6.QtCore import QPoint, QPointF, Qt
 from PySide6.QtGui import QWheelEvent
-from PySide6.QtWidgets import QApplication, QScrollArea, QSlider, QSpinBox, QVBoxLayout, QWidget
+from PySide6.QtWidgets import (
+    QApplication,
+    QScrollArea,
+    QSlider,
+    QSpinBox,
+    QVBoxLayout,
+    QWidget,
+    QWidgetItem,
+)
 
 from aare.gui.widgets.wheel_value_guard import WheelValueGuard
 
@@ -72,3 +80,11 @@ def test_bare_wheel_scrolls_the_enclosing_area(guard, qtbot):
     QApplication.sendEvent(spin, _wheel(Qt.MouseButton.NoButton))
     assert spin.value() == 50
     assert bar.value() != before
+
+
+def test_a_non_event_argument_is_ignored(guard, qtbot):
+    # PySide 6.9 can hand an app-level filter a QWidgetItem instead of a
+    # QEvent during layout teardown; raising there fails a random test.
+    widget = QWidget()
+    qtbot.addWidget(widget)
+    assert guard.eventFilter(widget, QWidgetItem(widget)) is False