On Wed, Dec 04, 2024 at 10:53 PM, Aaron Jensen <aaronjensen@gmail.com>
wrote:

> Furthermore, this problem only happens *once* per Emacs session. After
> that, I cannot seem to reproduce it again until I restart Emacs. All of
> this points to a bug, in my opinion unless header-line is considered
> deprecated or somehow falls into a realm of not being able to remap for
> some reason.
>

This may be obvious to you all, and me going much further probably isn't
realistic, but I am curious if there's a problem in the resolving of
inherited remapped faces while changing windows. Specifically that it
appears to use the lack of remap in the newly created window to resolve the
remap in the original window. The remapping of the active/inactive faces
happens explicitly inside display_mode_line / init_iterator with an
explicit window reference. I don't know enough to know where the inherited
faces get remapped, but if the window used to remap them is incorrect
(because it's the current window, rather than the window the mode/header
line is being drawn in), I could see there being the issue we're observing.

Not sure if that helps, but that's as far as I was able to get in my
investigation so far.

Thanks,