BUG: Fix bug with single channel annot ypos

mne_qt_browser/_pg_figure.py

@@ -2588,19 +2588,28 @@ def __init__(self, mne, weakmain, annot, ch_name):
         self.annot = annot
         self.ch_name = ch_name
 
-        ypos = np.where(self.mne.ch_names[self.mne.ch_order] == self.ch_name)[0] + 1
-        self.ypos = ypos + np.array([-0.5, 0.5])
+        # We have a choice here: some channel-specific annotations will have
+        # channels that are not plotted (e.g., with raw.plot(..., order=[0, 1])).
+        # Here we choose to add them as invisible plot items so that if you for example
+        # remove all *visible* channels from the annot it won't suddenly become an
+        # all-channel annotation. It will instead disappear from the plot, but still
+        # live in raw.annotations. We could emit a warning, but it would probably
+        # become annoying. At some point we could add a warning
+        # *when you delete the last visible channel* to let people know that the
+        # annot still exists but can no longer be modified, or something similar.
+        # It would be good to have this be driven by an actual use case / experience.
+        idx = np.where(self.mne.ch_names[self.mne.ch_order] == self.ch_name)[0]
+        if len(idx) == 1:  # should be 1 or 0 (if channel not plotted at all)
+            self.ypos = idx + np.array([0.5, 1.5])
+        else:
+            self.ypos = np.full(2, np.nan)
 
-        # self.lower = PlotCurveItem()
-        # self.upper = PlotCurveItem()
         self.upper = PlotDataItem()
         self.lower = PlotDataItem()
 
         # init
         super().__init__(self.lower, self.upper)
 
-        # self.setCurves(self.lower, self.upper)
-
         self.update_plot_curves()
 
         color_string = self.mne.annotation_segment_colors[self.annot.description]

mne_qt_browser/tests/test_pg_specific.py

@@ -220,21 +220,23 @@ def test_ch_specific_annot(raw_orig, pg_backend):
     annots = Annotations([annot_onset], [annot_dur], "some_chs", ch_names=[ch_names])
     raw_orig.set_annotations(annots)
 
-    fig = raw_orig.plot()
+    ch_names.pop(-1)  # don't plot the last one!
+    fig = raw_orig.plot(picks=ch_names)  # omit the first one
     fig_ch_names = list(fig.mne.ch_names[fig.mne.ch_order])
     fig.test_mode = True
     annot_dock = fig.mne.fig_annotation
 
     # one FillBetweenItem for each channel in a channel specific annot
     annot = fig.mne.regions[0]
     assert (
-        len(annot.single_channel_annots) == 4
+        len(annot.single_channel_annots) == 4  # we still make them even for invisible
     )  # 4 channels in annots[0].single_channel_annots
 
     # check that a channel specific annot is plotted at the correct ypos
-    single_channel_annot = annot.single_channel_annots["MEG 0423"]
+    which_name = raw_orig.annotations.ch_names[0][-2]
+    single_channel_annot = annot.single_channel_annots[which_name]
     # the +1 is needed because ypos indexing of the traces starts at 1, not 0
-    want_index = fig_ch_names.index(raw_orig.annotations.ch_names[0][-1]) + 1
+    want_index = fig_ch_names.index(which_name) + 1
     got_index = np.mean(single_channel_annot.ypos).astype(int)
     assert got_index == want_index  # should be 28