I've been following this discussion, and I'll propose a little
We're discussing here about switching themes for different kind of
manipulations (dark for better colour perception, light for better on-
paper look, etc.).
I think that, as Sven pointed out (from elle's comments), that the
padding color is the most important adjustment piece, not necessarily
If your theme is neutral, middle-ish gray and you can tweak the padding
color, then you don't have to switch themes for different kind of
In that case, having a tool for fast-switching the padding color would
be, in my opinion, far more interesting and useful than a theme
I've been working with graphics programs for years, and it never
crossed my mind to switch themes "per project" and believe me, I do
know how a theme can affect your perception.
For instance, I always end up tweaking the curves of images that are
inteded for print, as the dark UI of darktable makes them look
But I wouldn't fix that by making darktable's UI lighter, as I would be
producing washed out images for other targets.
So, in my experience I found that middle gray in the padding area is a
reasonable default, while being able to choose quickly between darker
or lighter padding would be a really useful per-project setting.
Once you have the appropriate padding color the UI theme doesn't matter
much (as long as it's achromatic).
And regarding special themes for print, I think it's a flawed approach.
In a pre-press environment you tweak your screen white point to match
the white point and white level of white paper under controlled
So you can't predict if your screen white is brighter or darker than
paper white, so picking the white level for the UI elements is just
And a white UI is visually exhausting too, so it's not really a good
idea for a theme.