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

[Eli Zaretskii]

> From: Richard Copley <address@hidden>
> Date: Wed, 21 Mar 2018 09:59:37 +0000
> Cc: John Wiegley <address@hidden>, Tom Tromey <address@hidden>, 
>       Emacs Development <address@hidden>
> 
>  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.

The "unreadable" part seems to be in the eyes of the beholder.  As I
said, it's readable for me.  Color perception differs somewhat between
people, so I'm not surprised.

>  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.

That's just one example.  I'm sure there are examples with other color
pairs that point to the opposite direction.

More generally, I want to insist on making only safe changes at this
late stage in the pretest.  The current code is in Emacs for more than
a year, so suddenly discarding behavior that was tested since then and
going to a behavior that was not tested at all doesn't make sense.
Therefore, I proposed a change that will allow people who don't like
this behavior to adapt it to their color perception, without changing
the tested default.  Such a change looks safe enough to me to install
it on the release branch, even though we are long past the time for
any significant changes that don't fix grave bugs.  By contrast, your
suggestion changes user-visible behavior in incompatible ways, which
is definitely not safe at this time.