On Wed, Dec 04, 2024 at 5:49 AM, Eli Zaretskii <eliz@gnu.org> wrote:

Aaron, it would have been more useful to CC Trevor, who is the author of that changeset. I've added him now.

You're right, I realized that too late. Thank you for the reminder.

I'm able to reproduce this with the mode-line as well, so it appears that there may be a bug there too in the code that was copied to implement the active/inactive faces in the header line. It's entirely possible that there's a bug in nano-modeline, but it seems suspect that code was added to consider windows and now this issue triggers when new windows are created (and possibly when selection changes, I haven't eliminated whether or not that's a factor yet).
You were able to reproduce what? I don't think you posted a recipe to reproduce the problem. Please do, if at all possible, preferably starting from "emacs -Q".

I didn't — I thought I mentioned that. I had intended to provide one as soon as I had a chance to, but it turns out that Eshel encountered the same issue and provided a recipe (thank you, Eshel). The only difference in my case is that face-remap-set-base is used, rather than face-remap-add-relative.

As far as I can tell, this same bug occurs in the mode-line as well as the header-line. I.e., there was an existing bug in the mode-line and it was replicated to the header-line after the two new faces were added.

Thanks,

Aaron