Re: CSS contrast (#30295) (was Re: Heads-up: Emacs 26.1 RC1)

[Eli Zaretskii]

> From: Richard Copley <address@hidden>
> Date: Wed, 21 Mar 2018 13:22:37 +0000
> Cc: John Wiegley <address@hidden>, Tom Tromey <address@hidden>, 
>       Emacs Development <address@hidden>
> 
>  We do something very similar in frame-set-background-mode and in
>  tty-color-approximate.
> 
> I don't see it. You're talking about this?
> 
>           ((>= (apply '+ (color-values bg-color frame))
>                ;; Just looking at the screen, colors whose
>                ;; values add up to .6 of the white total
>                ;; still look dark to me.
>                (* (apply '+ (color-values "white" frame)) .6))

That's the first example, yes.

> It's this particular way of using color-distance that we appear to
> have invented.

Not according to the article from which the implementation of
color-distance was taken.

> If we didn't then we took it from
> somewhere else, and someone (Tom?) should know where.

The comments in the sources of color-distance tell where we took it
from.

> I don't believe the concept of a sphere centred on black is a useful one in 
> this context, or that allowing the
> user to vary its radius makes it any better.

I suggest to read the original article mentioned above.