Match plugin text/axis/icon colours to the napari theme.

[samcunliffe]

Change the text, axes, and icon colour to contrast with the background. I hear white text on an off-white background is not ideal.

Solves

• Hard-coded icons and axes looks bad with non-default napari themes #86

Testing:

• The theme changing via the viewer.events.theme callback is currently only tested manually. It works better than the current main but is still not perfect. (I'm going to try and make a gif to show what I mean.)
• The icon path stuff is unit tested ✅

Note for reviewer(s):

• This somewhat supersedes my plan (and what I wrote in the PR title) for Generalise stylesheet parsing to extract colours for light/dark theme callback. #105 but doesn't actually supersede the code changes.
  • ...so I'm going to keep that open for a bit longer (sorry for polluting the PR list). Will close when I decide what to do with it.
• Are you OK with two face colours? I use both theme.text and theme.foreground.
• The icons are black and not the subtle brownish grey used by napari's light theme.
• The napari.Viewer gets moved up the family tree and becomes a member of the BaseNapariMPLWidget.

[samcunliffe]

Not sure if this is the correct line, but I still don't quite have a perfect UX when switching the theme whilst the widgets are open...

Screen.Recording.2023-05-31.at.16.51.00.mov

Re-opening or doing something to the plot seems to fix.

[dstansby]

A bit of a dive into the napari source, and you might want to use something like this line to trigger something when the theme is changed?

https://github.com/napari/napari/blob/46dcc9c0976c35ec9dc64be60235f4addcadaa5c/napari/_qt/qt_main_window.py#L578

[samcunliffe]

😞

napari.settings.get_settings().appearance.events.theme.connect(
    self._on_theme_change
)

gives the same behaviour. I wonder if it might be a different way to do the same thing as

self.viewer.events.theme.connect(self._on_theme_change)

The theme-change event is undocumented* (scroll a bit from the start of § Viewer events) so I'd be up for asking and/or fixing the docs for napari.

---

*) It's also duplicated: that page is made via a script in napari/docs.

[ruaridhg]

LGTM. Could switching the theme whilst widgets are open be something to do with the napari bug I raised

[samcunliffe]

Could switching the theme whilst widgets are open be something to do with the napari bug I napari/napari#5847

I think not. Although something missing in the callbacks for a widget being loaded .... maybe.

[samcunliffe]

Also needs a note in the changelog.

• @samcunliffe : add a note in the changelog.

[samcunliffe]

Err if this is ok to merge, I think it needs a reapproval.

I pushed a release note and updated the pytest-mpl plots. Sorry for the noise.

[dstansby]

Happy to merge this (once I've checked the code), but things that need issues opening to be fixed after this:

• If I switch to the light theme, the plot looks fine but the whole widget still has a dark background.
  
• We couldn't get the theme changing event to work. Probably upstream issue, but also we should open an issue here so we don't forget.

[dstansby]

Some minor comments, but overall looking 👍

[samcunliffe]

but things that need issues opening to be fixed after this

Yeah. There are a few minor peripheral things that I noticed too...

• Axis titles are always black.
• Icons are black (and should properly be greyish brown to match the theme).

Are you ok with 3 individual minor issues?

[dstansby]

Yep, three issues sounds good