Re: Introducing face in comments for various modes

[Christopher Dimech]

----- Christopher Dimech
Administrator General - Naiad Informatics - Gnu Project

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> Sent: Tuesday, December 13, 2022 at 3:22 AM
> From: "Yuri Khan" <yuri.v.khan@gmail.com>
> To: "Thibaut Verron" <thibaut.verron@gmail.com>
> Cc: "Heime" <heimeborgia@protonmail.com>, "Stefan Monnier" 
> <monnier@iro.umontreal.ca>, help-gnu-emacs@gnu.org
> Subject: Re: Introducing face in comments for various modes
>
> On Mon, 12 Dec 2022 at 17:53, Thibaut Verron <thibaut.verron@gmail.com> wrote:
> 
> > > If you use "modus-vivendi" for org-mode, the colours are all almost white,
> > > a big problem particularly when you fold the org headings.
> >
> > I don't like dark backgrounds, but it seems perfectly readable to me.
> 
> Heime has a point. The complaint is not about *readability* of
> modus-vivendi’s colors against the background. It is about
> *distinction* between levels of Org headings, i.e. ability to
> distinguish a level 3 heading from a level 4 just by color.
> 
> This is a nontrivial thing to solve, by the way. It’s very easy to
> fall in the trap “WCAG level AAA prescribes a contrast ratio of at
> least 7:1; I’ll make my primary foreground and all my accent
> foreground colors exactly 7:1 against the background so all will be
> readable”. Yes, but this way they are all the same luminance, and by
> that token all very similar in some sense. A color-blind person might
> even not be able to distinguish hues and rely on luminance alone to
> tell colors apart.

Correct.  WCAG Level AAA works well for a foreground upon a background colour.
Thusly it is still quite a basic scheme.  When, in addition, one considers 
colour contrast requirements upon adjacent coloured letters, the WCAG Levels
are not enough to do this.  One has to optimise colour contrast on both 
foreground
with background, as well as contrast upon adjacent colours.  

Some work on this showed that you would not be able to completely satisfy WCAG 
Levels,
if you want to optimise colour contrast between adjacent letters too. 

Still, one can use a metric.  The whole point to understand is that the colours
are not set up at the discretion of the programmer.  You are limited only to 
certain
colour tones only.  Doing anything else would always result in a sub-optimal 
result.

The original modes-themes, even though they were a huge improvements compared 
to other
themes, were found to be sub-optimal.
 
> As far as I can tell, WCAG does not give any guidance as to
> distinction between foreground colors, except for “thou shalt not make
> the user rely solely on color”.
> 
>