FIX: Lock axes bounds in plot_joint to prevent shrinking on cursor motion (closes #14317)

doc/changes/dev/14319.bugfix.rst

@@ -0,0 +1 @@
+Fix :meth:`mne.Evoked.plot_joint` interactive plots, where the axes shrank to zero when moving the cursor over the figure (the connection lines between the time series and topomaps were inflating the constrained layout, shrinking the axes on every redraw), by `Akhil Gopu`_.

doc/changes/names.inc

@@ -5,6 +5,7 @@
 .. _Adeline Fecker: https://github.com/adelinefecker
 .. _Adina Wagner: https://github.com/adswa
 .. _Adonay Nunes: https://github.com/AdoNunes
+.. _Akhil Gopu: https://github.com/AkhilG-exe
 .. _Akhilesh S. Yadav: https://github.com/YadavAkhileshh
 .. _Akshay: https://github.com/Akshay0724
 .. _Alan Leggitt: https://github.com/leggitta

mne/viz/evoked.py

@@ -2372,6 +2372,10 @@ def plot_evoked_joint(
             zorder=1,
             clip_on=False,
         )
+        # The lines intentionally poke outside of `ts_ax`, so keep them out of the
+        # layout bbox reckoning; otherwise constrained layout grows the margin on
+        # every redraw, shrinking the axes to nothing (see #14317).
+        con.set_in_layout(False)
         ts_ax.add_artist(con)
 
     # mark times in time series plot

mne/viz/tests/test_topo.py

@@ -79,7 +79,15 @@ def _get_epochs_delayed_ssp():
 def test_plot_joint():
     """Test joint plot."""
     evoked = _get_epochs().average()
-    evoked.plot_joint(ts_args=dict(time_unit="s"), topomap_args=dict(time_unit="s"))
+    fig = evoked.plot_joint(
+        picks="grad", ts_args=dict(time_unit="s"), topomap_args=dict(time_unit="s")
+    )
+    ax = max(fig.axes, key=lambda a: a.get_position().height)
+    fig.canvas.draw()
+    pos = ax.get_position().bounds
+    for _ in range(5):
+        fig.canvas.draw()
+    assert np.allclose(pos, ax.get_position().bounds)
 
     def return_inds(d):  # to test function kwarg to zorder arg of evoked.plot
         return list(range(d.shape[0]))