FIX: correct sensor name ordering in plot_topomap when using Info object

doc/changes/dev/13686.bugfix.rst

@@ -0,0 +1 @@
+Fix sensor name ordering in :func:`~mne.viz.plot_topomap` when passing an :class:`~mne.Info` object as ``pos`` with ``names`` argument, by :newcontrib:`Famous Raj Bhat`.

mne/viz/tests/test_topomap.py

@@ -987,3 +987,21 @@ def test_plot_ch_adjacency():
     msg = "Editing a 3d adjacency plot is not supported."
     with pytest.raises(ValueError, match=msg):
         plot_ch_adjacency(info, adj, ch_names, kind="3d", edit=True)
+
+
+def test_plot_topomap_info_names_ordering():
+    """Regression test for GH-12700.
+
+    plot_topomap() must preserve correct sensor name ordering when
+    passing an Info object as pos with a names argument.
+    """
+    info = create_info(ch_names=["Fp1", "Fp2", "Fz"], sfreq=1000.0, ch_types="eeg")
+    montage = make_standard_montage("standard_1020")
+    info.set_montage(montage)
+    data = np.array([1.0, 2.0, 3.0])
+    names = ["Fp1", "Fp2", "Fz"]
+    im, _ = plot_topomap(data, info, names=names, show=False)
+    assert im is not None
+    displayed_names = [t.get_text() for t in im.axes.texts]
+    for name in names:
+        assert name in displayed_names, f"{name!r} not found in {displayed_names}"

mne/viz/topomap.py

@@ -1292,9 +1292,13 @@ def _plot_topomap(
             pos = _find_topomap_coords(pos, picks=picks[::2], sphere=sphere)
             data, _ = _merge_ch_data(data[picks], ch_type, [])
             data = data.reshape(-1)
+            if names is not None:
+                names = [names[p] for p in picks[::2]]
         else:
             picks = list(range(data.shape[0]))
             pos = _find_topomap_coords(pos, picks=picks, sphere=sphere)
+            if names is not None:
+                names = [names[p] for p in picks]
 
     extrapolate = _check_extrapolate(extrapolate, ch_type)
     if data.ndim > 1: