Fix bug with lite backend closing

mne/viz/_3d_overlay.py

@@ -269,9 +269,10 @@ def update(self, colors=None):
         self._apply()
 
     def _clean(self):
-        mapper = self._actor.GetMapper()
-        mapper.SetLookupTable(None)
-        self._actor.SetMapper(None)
+        if hasattr(self._actor, "GetMapper"):  # VTK; the browser backend draws dicts
+            mapper = self._actor.GetMapper()
+            mapper.SetLookupTable(None)
+            self._actor.SetMapper(None)
         self._actor = None
         self._polydata = None
         self._renderer = None

mne/viz/_brain/_brain.py

@@ -663,7 +663,7 @@ def _clean(self):
             for key in list(self.act_data_smooth.keys()):
                 self.act_data_smooth[key] = None
         # XXX this should be done in PyVista
-        for renderer in self._renderer._all_renderers:
+        for renderer in getattr(self._renderer, "_all_renderers", ()):  # VTK only
             renderer.RemoveAllLights()
         # app_window cannot be set to None because it is used in __del__
         for key in ("lighting", "interactor", "_RenderWindow"):

mne/viz/backends/_lite.py

@@ -16,6 +16,7 @@
 # License: BSD-3-Clause
 # Copyright the MNE-Python contributors.
 
+import inspect
 import weakref
 from contextlib import nullcontext
 
@@ -206,6 +207,7 @@ def __init__(
         # _PyVistaRenderer's signature, but size, shape, name and show cannot
         # be honored: the canvas is fixed and written only when show() runs
         _validate_type(fig, (None, _LiteFigure), "fig")
+        self._close_callbacks = {False: [], True: []}  # keyed by ``after``
         if fig is not None:  # plot_alignment(fig=...) composites into it
             self._figure = fig
             return
@@ -583,13 +585,31 @@ def _update(self):
         pass  # the page paints after the cell finishes
 
     def _window_close_connect(self, func, *, after=True):
-        pass  # an output cell has no close event
+        # an output cell has no close event, so close() runs these; ui_events
+        # drops its channel here, without which its subscribers pin the figure.
+        # Weak for bound methods (Brain._clean) so a figure dropped without
+        # close() still dies by refcount rather than waiting on the collector
+        if inspect.ismethod(func):
+            func = weakref.WeakMethod(func)
+        self._close_callbacks[after].append(func)
+
+    def _window_close_disconnect(self, after=True):
+        self._close_callbacks[after].clear()
+
+    def _run_close_callbacks(self, after):
+        for func in list(self._close_callbacks[after]):  # Brain._clean disconnects
+            if isinstance(func, weakref.WeakMethod):
+                func = func()
+            if func is not None:
+                func()
 
     def text3d(self, x, y, z, text, font_size, color="white", *, shadow=False):
         pass  # no camera-facing 3D text, so sensors go unlabeled
 
     def close(self):
+        self._run_close_callbacks(after=False)
         _lite_release_plotter(self.plotter)
+        self._run_close_callbacks(after=True)
 
     # -- things pyvista-js cannot do ----------------------------------------
     def contour(self, *args, **kwargs):

mne/viz/backends/tests/test_renderer.py

@@ -548,5 +548,7 @@ def test_lite_brain(renderer_lite):
         (180.0, 90.0)
     )
     brain.close()
+    assert brain._cleaned  # close() ran the close callbacks (ui_events' too)
     with pytest.raises(NotImplementedError, match="browser"):  # two columns
         mne.viz.Brain(surf="inflated", **{**kwargs, "hemi": "split"})
+    assert list(mne.viz.Brain._instances) == [brain]  # the failed one died