For those who weren't aware, Jack Phoenix and I have drafted a Request
for Comment and related initial patch proposing to merge the logic
from the Theme extension into MediaWiki core.
From the RfC: This will provide built-in functionality that skins can
implement in a simple and consistent manner, enabling user- or
site-selection of css variations of a given skin, such as a dark version
or a layout with more colours.
The RfC itself covers in detail the distinction between skins and themes
as well as several use cases and issues surrounding the current
situation, but the key point here is thus: with this functionality, we
will be able to not just more easily implement night, winter, and
accessibility modes in skins such as Vector and Timeless, but also
much more consistently, and in a manner that can then be developed to
better and more consistently use the variables defined by the skins even
outside of the themes themselves.
Currently, the Theme functionality is limited to the extension itself
and a few skins that replicate key parts with varying amounts of
fidelity, which not only results in a bit of a mess in terms of code
fragmentation, but also limits what we can do with the skins themselves
due to the added dependency. We would like to fix this, and thus invite
everyone interested to review our proposal and please, comment if you
have concerns or see any issues.