This is to support new features in Emacs where themes can specify
the set they belong to, as well as whether they are light or dark.
The built-in command is 'theme-choose-variant'.
This is in response to Emacs bug#65468:
<https://debbugs.gnu.org/cgi/bugreport.cgi?bug=65468>. Thanks to
Mauro Aranda for bringing this matter to my attention.
These are used by ansi-term, vterm, and the like. The idea is to
empower users to differentiate background and foreground values. By
convention, terminal emulators use the same value for both background
and foreground, although this is not optimal with high contrast themes
because what works as a foreground does not necessarily look nice as a
background.
The default values of the new mappings retain the prior state, just to
not break existing configurations.
Thanks to Tony Zorman for reporting the bug that provided the impetus
for this change:
<https://lists.sr.ht/~protesilaos/modus-themes/%3C87fs4wforf.fsf%40hyperspace%3E>.
After extensive testing and side-by-side comparisons, I have concluded
that the marginal increase in brightness improves the affected
interfaces.
The 'bg-dim' background is used, among others, in the header-line, the
company/corfu popup, and the Org source blocks (when the user option
'modus-themes-org-blocks' is configured appropriately).
Thanks to Olaf Meeuwissen for bringing this package to my attention
and showing me how traditional Japanese calendars style Saturdays.
This was done in issue 311 on the GitLab mirror:
<https://gitlab.com/protesilaos/modus-themes/-/issues/311>.
