bug#46396: 27.1.90; Ediff's non-focused diff section, background too light in --reverse

[Matt Armstrong]

Juri Linkov <juri@jurta.org> writes:


[...]

> After changing background colors to darker colors and adding
> :distant-foreground I tried different default foreground colors with
>
>   M-x set-foreground-color RET dark grey RET
>
> and it seems everything looks readable.
>
> Do you see more problems with the following patch?

[...]

Juri, this is a definite improvement, thank you. Committing it as it is
seems reasonable since it makes unreadable text readable again.

I applied this patch and played around with applying various light and
dark themes.

Some comments:

In the "tango-dark" theme:

 a) the non-current diff backgrounds are quite close to the theme's dark
    background color, so they are not very noticeable.
 b) the current diff (such as `ediff-current-diff-B`) is also quite close
    to the theme's background color.

In the "tango-light" theme:

 c) `ediff-current-diff-A' is quite dark (a darker blue/purple), and the
    foreground color is hard to read over it. This is a little odd,
    because `ediff-current-diff-B' is a fairly bright yellow background.

I saw similar issues in the various other standard themes (loading up
the mater branch with src/emacs -Q).

The issues I see with ediff-current-* faces are arguably a tangent to
this bug. Perhaps those faces could use :distant-foreground as well, for
similar reasons?

As for the background colors possibly being quite similar to the theme's
background, I'm not sure what to do about that.