MNT: test coreg UI with notebook 3d backend (mne-tools#10291)

* test coreg with notebook

* fix

* again

* edit

mne/gui/_coreg.py

@@ -310,7 +310,7 @@ def _get_default(var, val):
             self._renderer.plotter.add_callback(
                 self._redraw, self._refresh_rate_ms)
         self._renderer.plotter.show_axes()
-        if block:
+        if block and self._renderer._kind != 'notebook':
             _qt_app_exec(self._renderer.figure.store["app"])
 
     def _set_subjects_dir(self, subjects_dir):

mne/gui/tests/test_coreg_gui.py

@@ -220,3 +220,17 @@ def test_coreg_gui_pyvista(tmp_path, renderer_interactive_pyvistaqt):
     coreg.close()
     # Coregistration instance should survive
     assert isinstance(coreg.coreg, Coregistration)
+
+
+@pytest.mark.slowtest
+@testing.requires_testing_data
+def test_coreg_gui_notebook(renderer_notebook, nbexec):
+    """Test the coregistration UI in a notebook."""
+    import os
+    import mne
+    from mne.datasets import testing
+    from mne.gui import coregistration
+    mne.viz.set_3d_backend('notebook')  # set the 3d backend
+    data_path = testing.data_path()
+    subjects_dir = os.path.join(data_path, 'subjects')
+    coregistration(subject='sample', subjects_dir=subjects_dir)