Feature bipolar references

[gdolle]

• Add a button to set bipolar references
• Add a dialog to select channel by pair
• Add the feature to save/open the selected channels to create bipolar reference profile (which (seems/) does not exist yet in MNE)

[updated]

[cbrnr]

Thanks for your PR! Would you mind splitting it up so that one PR tackles exactly one issue?

Regarding the arguments, can you explain the issue with the current implementation and how your fix works?

Regarding the bipolar reference feature, currently you hard-code the derivations, but I'd prefer that the user decides which channels are anodes and which channels are cathodes. Based on this input, custom bipolar derivations could be computed.

Let me know what you think and if you need help implementing these changes!

[gdolle]

Thanks for your PR! Would you mind splitting it up so that one PR tackles exactly one issue?

Yes ok I'll split in 2 PR.

Regarding the arguments, can you explain the issue with the current implementation and how your fix works?

I will explain in the specific new PR (and add a specific issue also)

Regarding the bipolar reference feature, currently you hard-code the derivations, but I'd prefer that the user decides which channels are anodes and which channels are cathodes. Based on this input, custom bipolar derivations could be computed.

I agree with you. Also maybe add a load/save button to create bipolar reference profile (to avoid setting every time)
I'll have a look (@Qdelannoy)

Let me know what you think and if you need help implementing these changes!

[gdolle]

@cbrnr (@Qdelannoy) I updated this PR to select the channels via a dialog, you can give it a try ?