MAINT: Refactor for mne-qt-browser

[larsoner]

Along with mne-tools/mne-qt-browser#66, before:

After:

[larsoner]

@agramfort @hoechenberger @GuillaumeFavelier feel free to have a quick look, if we merge this and mne-tools/mne-qt-browser#66 we can get qdarkstyle support for mne-qt-browser easily I think

[hoechenberger]

@larsoner Probably okay for Linux and Windows, but doesn't look "native" at all on the Mac. There, Qt has built-in dark mode support for many widgets; however, this seems to be overridden by mne-qt-browser somehow for status- and toolbar. So this is a screenshot I took with my system in Dark Mode, and without using your branch:

What I'm saying is:
Yes, the change you propose makes things slightly better, but is nothing we'd want to keep in the long term for macOS.

Similar issue with Brain.

In contrast, a positive example, except for the status bar, is CoregistrationUI:

This is how it's supposed to look. And it doesn't require qdarkstyle.

Our qdarkstyle themes look like an awful paint job in comparison 😅

But like I said, it's already making things slightly better, so why not.

[larsoner]

@larsoner Probably okay for Linux and Windows, but doesn't look "native" at all on the Mac. There, Qt has built-in dark mode support for many widgets; however, this seems to be overridden by mne-qt-browser somehow for status- and toolbar. So this is a screenshot I took with my system in Dark Mode, and without using your branch:

Are you sure you're on this branch of MNE-Python and this branch of mne-qt-browser? mne-tools/mne-qt-browser#66

To me what you have is what mine looked like without mne-tools/mne-qt-browser#66

[larsoner]

... in any case, for mne-qt-browser to look any different, this PR does nothing. It just makes mne-tools/mne-qt-browser#66 (which changes the mne-qt-browser behavior) easier/cleaner. So I'll go ahead and merge this.

BTW, this just makes mne-qt-browser behave like Brain. I think we should make mne coreg behave like Brain, as well. Then, if there are problems with that, we should address them ideally in qdarkstyle or, if not, then with some custom stylesheet here in MNE-Python.

[hoechenberger]

@larsoner Agreed! Thanks for the work!

[GuillaumeFavelier]

I think we should make mne coreg behave like Brain

I updated #8833 with:

• add support for (qdarkstyle) dark theme