Re: Diff mode faces

[Juri Linkov <juri@jurta.org>]

>    For quite a long time (most likely from the time when color translation
>    was implemented for tty) colors of context lines in diff mode on tty
>    were yellow for light backgrounds.  There are also other faces with
>    yellow foreground for light backgrounds, like font-lock-variable-name-face.
>    Nobody complained about them so far.  So maybe yellow is the acceptable
>    color for context lines.
>
> I remember seeing people complain that they have trouble reading
> yellow on white _many_ times on this list.  I know of many people who
> have trouble reading red on black.  I have trouble with both and I
> have even more problems reading cyan on white.  I do not complain, I
> just always turn colors off on tty's.

Something has to be done about colors of diff context, because
currently it is white on black for dark backgrounds, and yellow
on white for light backgrounds.

Yellow on black would be good for dark backgrounds, but what to put as
a foreground color for light backgrounds.  Maybe green on white?
Green is a dark color, so on white it is well visible.

BTW, the formula for calculating the background mode produces different
results for different terminals:

On TTY it classifies colors as follows:

Dark:  black red green blue
Light: magenta yellow cyan white

But on xterm it is quite different:

Dark:  black red green blue magenta yellow cyan
Light: white

According to this classification, yellow is a dark color,
as it were suitable as a foreground color for light backgrounds.

OTOH, the formula I proposed in January produces the same
classification on TTY, xterm and X as:

Dark:  black red green blue magenta
Light: yellow cyan white

-- 
Juri Linkov
http://www.jurta.org/emacs/