Allow lasso selection sensors in a plot_evoked_topo

[wmvanvliet]

This adds plot_evoked_topo(select=True) which will allow you to use a lasso selection tool in the same manner as plot_sensors("select"). It currently doesn't do anything with this selection other than publishing an SelectChannels UI-Event. This is a part of the planned XFit-like GUI, but could have other uses as well. For example, we could in the future make plot_evoked_topo open up a figure with the average of the selected sensors when you select them, similar to what happens when you click on a sensor.

The main change this PR makes is to refactor mne.viz.utils.SelectFromCollection a bit to make it more general purpose. Where the names of the variables and such were first tightly coupled to raw.plot_sensors, things are now named from the perspective of a matplotlib figure with a Collection of patches. The translation from "selecting matplotlib patches" to "selecting channels" is now happening though UI-events. You can register a callback function with mne.viz.utils.SelectFromCollection for when a selection is made. Raw and Evoked use this to emit SelectChannels UI-events whenever the user uses the lasso to select channels.

The main unit test for this class has been moved from viz/tests/test_raw.py to viz/tests/test_util.py. Smaller unit tests are now in place for raw.plot_sensors and evoked.plot_topo.

In addition to using CTRL to "add to selection" you can now also use CTRL+SHIFT to "remove from selection".

At the moment, this doesn't work yet when unified=False. If there is a pressing need for it, I can add it, but perhaps this can also be left to a later PR.

[wmvanvliet]

It's been a while, but this PR is finally ready for review (and at some point, merge).

[drammock]

My only complaint is that I can't remove sensors from the selection because Alt+click+drag is an OS-level "drag this whole window around the screen" shortcut in Linux. Can we use another key?

[wmvanvliet]

Can we use another key?

I now make it that CTRL adds to the selection, as it was before, and CTRL+SHIFT removes from the selection. Does that work better on OSX?

[drammock]

failures look like they're probably related:

FAILED mne/viz/tests/test_topo.py::test_plot_topo - TypeError: hasattr expected 2 arguments, got 1
FAILED mne/viz/tests/test_topo.py::test_plot_topo_single_ch - TypeError: hasattr expected 2 arguments, got 1
FAILED mne/viz/tests/test_topo.py::test_plot_topo_image_epochs - TypeError: hasattr expected 2 arguments, got 1
FAILED mne/viz/tests/test_topo.py::test_plot_topo_select - TypeError: hasattr expected 2 arguments, got 1
FAILED mne/viz/tests/test_topo.py::test_plot_tfr_topo - Failed: DID NOT WARN. No warnings of type (<class 'RuntimeWarning'>,) were emitted.
 Emitted warnings: [].

[wmvanvliet]

done!

[drammock]

thanks @wmvanvliet awesome work

[larsoner]

@wmvanvliet this main failure looks related can you look?

https://app.circleci.com/pipelines/github/mne-tools/mne-python/26528/workflows/ba13e032-bf8a-4341-b4ee-2de33755c932/jobs/71283?invite=true#step-143-15504_86

maybe just missing an event=None default or something?

[wmvanvliet]

looks like it, lets see: #13086