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

[Richard Copley <rcopley@gmail.com>]

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On 21 March 2018 at 09:59, Richard Copley <rcopley@gmail.com> wrote:

> On 21 March 2018 at 07:38, Eli Zaretskii <eliz@gnu.org> wrote:
>
>> > From: Richard Copley <rcopley@gmail.com>
>> > Date: Tue, 20 Mar 2018 19:56:12 +0000
>> > Cc: John Wiegley <johnw@gnu.org>, Tom Tromey <tom@tromey.com>,
>> >       Emacs Development <emacs-devel@gnu.org>
>> >
>> > Patch 1 is a small fix for the current formula using color-distance.
>> > Patch 2 uses luminance as in Tom's original patch.
>> > I think patch 2 gives better contrast.
>>
>> Thanks, but I think this is a step backward, as it more or less goes
>> back to the code before the discussion of bug#25525.
>>
>
> Patch 2 does, yes. It's good to step backwards, because (the effect of)
> the original code was OK, whereas the current code leads to unreadable text.
>
> How about making the threshold a customizable value instead, with the
>> current hard-coded value the default?  That'd be compatible, and
>> should allow you to get the contrast of your liking.
>>
>
> It sounds like you want to insist that white-on-pale-green is somehow
> better than black-on-pale-green, or that there's some other consideration
> that's more important.
> I don't understand.
>

To put it another way:
Your argument seemed to be that Tom's original criterion (use white text on
backgrounds with luminance <50%) was invented by Tom.
Is the current criterion (use white text on backgrounds inside a sphere of
a given radius centred on black, in the color-distance metric space) a
standard way of doing things?

I'm not saying that the luminance-less-than-50% calculation is a standard,
either, but I've seen it used before, which is more than I can say for the
color-inside-a-sphere calculation.
I'm also not saying that color-distance is any more or less "invented" than
luminance.

I do believe that color-distance is less relevant here than luminance is.
I also believe that black text is more readable than white text, on a pale
green background.

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