OK, this theme shouldn't cause the difference in brightness, I think. I
have another guess. Does Fedora use "site-start.el"? If so, this file
is not loaded by Guix's Emacs, because it is placed somewhere in
/usr/share/... and Guix's Emacs doesn't look at this directory (also our
emacs uses its own "site-start.el" to load emacs packages installed in
"~/.guix-profile").
You can check if Fedora's Emacs uses "site-start.el" with this:
M-x find-library site-start
But actually I don't understand how the difference in brightness can
happen at all. This is a mystery for me.
> There are text properties here:
> face variable-pitch
You can move the point to 'variable-pitch' button and press RET there to
find out if it has the same customization in both cases.
> And this is the Fedora Emacs
[...]
> xft:-PfEd-DejaVu
> Sans-normal-normal-normal-*-19-*-*-*-*-0-iso10646-1 (#x56)
OK, so Fedora's Emacs has a bigger font (19 against 13).
You can use something like this to set the font and its size:
(set-frame-font "DejaVu Sans Mono-15" nil t)
> But anyway, I made a little screenshot with Shutter just to make the
> difference between the minibuffers more evident
This should be fixed if you change the font size.
Another thing: I noticed that Guix's Emacs doesn't display some buttons
on the tool bar. This should probably (I'm not sure) be fixed by
installing some icon theme in your profile, for example
'adwaita-icon-theme'.