Set FRAME-BACKGROUND-MODE on theme change

[tokenrove]

A bunch of things decide colors based on this value, and this seems to help a lot, particularly for org agendas. I guess that some themes do set FRAME-BACKGROUND-MODE, but many don't. In any case, we know which mode we want, at a given time of day.

(I've had effectively this change in my own private fork for years now, because I didn't notice this was still maintained. Glad to see it is!)

[swflint]

I see what you're saying, at the same time, because we have theme-changer-post-change-hook, I'm not sure that this is the way to do it (because some themes do set it themselves).

[tokenrove]

Oh yeah, I didn't even see that this hook had been added after I forked. One problem with the hook is it doesn't communicate whether the change was from day to night, so to do this you'd have to check which list the theme came from or otherwise store that information. Anyway, I suppose the best thing is really to fix themes that don't do this, but for me this fixed the behavior of a substantial number of themes.

I'm happy to close this (and continue using my fork) or perhaps rework the hook to pass a day/night symbol, as you see fit.

[swflint]

It does communicate which theme was changed to. That being said, I'd rather rework the hook, and make it a bit more flexible. Perhaps make it so that an alist is passed containing relevant information? Something like ((:theme . new-theme) (:state . :night) (:next-change . time))?