Fix TypeError in SubjectRegistration.approxHeadCenter

NaviNIBS/Navigator/GUI/ViewPanels/SubjectRegistrationPanel.py

@@ -759,8 +759,10 @@ def _onFidTblCurrentCellChanged(self, currentRow: int, currentCol: int, previous
             lookAt = None
         if lookAt is not None:
             self._plotter.camera.focal_point = lookAt
-            vec = lookAt - subReg.approxHeadCenter
-            self._plotter.camera.position = lookAt + vec*10
+            headCenter = subReg.approxHeadCenter
+            if headCenter is not None:
+                vec = lookAt - headCenter
+                self._plotter.camera.position = lookAt + vec*10
             self._plotter.reset_camera()
 
     def _getSelectedFiducialKeys(self):

NaviNIBS/Navigator/Model/SubjectRegistration.py

@@ -509,7 +509,7 @@ def approxHeadCenter(self) -> tp.Optional[np.ndarray]:
         lpa = self.fiducials.get('LPA', None)
         rpa = self.fiducials.get('RPA', None)
         if lpa is not None and rpa is not None and lpa.plannedCoord is not None and rpa.plannedCoord is not None:
-            center = (lpa + rpa) / 2
+            center = (lpa.plannedCoord + rpa.plannedCoord) / 2
         else:
             logger.warning('Insufficient information for determining approximate header center')
             # TODO: implement more general method of estimating center, e.g. more variety of LPA/RPA naming, name-agnostic averaging, etc.

tests/test_Model/test_subjectRegistrationCalcs.py

@@ -0,0 +1,29 @@
+"""
+Regression tests for SubjectRegistration derived values.
+"""
+
+import numpy as np
+
+from NaviNIBS.Navigator.Model.SubjectRegistration import SubjectRegistration, Fiducial
+
+
+def test_approxHeadCenterAveragesPlannedCoords():
+    """
+    Previously averaged the Fiducial objects themselves instead of their
+    planned coordinates, raising TypeError whenever LPA and RPA were planned.
+    """
+    sr = SubjectRegistration()
+    sr.fiducials.addItem(Fiducial(key='LPA', plannedCoord=np.array([-80., 0., -40.])))
+    sr.fiducials.addItem(Fiducial(key='RPA', plannedCoord=np.array([80., 0., -40.])))
+
+    center = sr.approxHeadCenter
+    assert center is not None
+    np.testing.assert_allclose(center, np.array([0., 0., -40.]))
+
+
+def test_approxHeadCenterMissingFiducials():
+    sr = SubjectRegistration()
+    assert sr.approxHeadCenter is None
+
+    sr.fiducials.addItem(Fiducial(key='LPA', plannedCoord=np.array([-80., 0., -40.])))
+    assert sr.approxHeadCenter is None