bug#57424: Perceptibility of display-fill-column-indicator-mode

[Christopher Dimech <dimech@gmx.com>]

> Sent: Friday, August 26, 2022 at 6:27 PM
> From: "Protesilaos Stavrou" <info@protesilaos.com>
> To: "Christopher Dimech" <dimech@gmx.com>, 57424@debbugs.gnu.org
> Subject: Re: bug#57424: Perceptibility of display-fill-column-indicator-mode
>
> > From: Christopher Dimech <dimech@gmx.com>
> > Date: Fri, 26 Aug 2022 07:44:23 +0200
> >
> > Have followed the customisation discussion about
> > display-fill-column-indicator-mode
> >
> > Have consulted with Protesilaos Stavrou, author of
> > modus-themes.  I agree that the default indicator character is
> > too thin.  Changing the character to something wider does not
> > change things much.  A solution that works is that of setting a
> > background colour, rather than changing the foreground colour .
>
> Christopher, please don't take words out of context.  State what you
> think the bug is without involving me or other people.

Was not meant to involve you.  But mentioned changes you suggested as
context of what one can try and see how things look like.

> My involvement in this only concerns the modus-themes.  I explained via
> a private channel why the modus-themes style the fill-column-indicator
> like this:
>
>     ;; Not actual code, but true to form:
>     (set-face-attribute 'fill-column-indicator nil :height 1 :background "gray50" :foreground "gray50")
>
> The default face of fill-column-indicator creates a dashed line when (i)
> the user applies a default font with a tall line height, (ii) increases
> the value of 'line-spacing', (iii) applies an increased height to
> certain elements, such as scaling the faces of Org headings.
>
> Because of these common scenaria, users would tell me that the visuals
> looked broken.  Changing the face, as shown above, produces a contiguous
> line.  This is a compromise, so that I stop getting the same issue over
> and over that the themes are broken.

The report is not about modus-themes, so you can do the compromise for
the themes, and I can change that should I want, following your comments.

> > [... 15 lines elided]
>
> > The only way to ensure a contiguous vertical line is to
> > explicitly set the :height of the face to a small value.  This
> > brings out the perceptibility problem.
> >
> > Studying carefully WCAG 2.1, Section 1.4.3 Contrast (Minimum),
> > the contrast ratio is also subject to change according to the
> > thinness of the characters.  For instance, With larger thicker
> > text, the contrast ratio of at least 4.5:1 can be modified to to
> > at least 3:1.
> >
> > I see the requirement of a contiguous indicator line is mainly about
> > aesthetics.  But practical usability should be of higher concern.
>
> I shared code with you on how to change the face to the effect that it
> widens the width of the line.  Please use it.  I also stated in clear
> terms why this decision was made.  You insist on dismissing it as
> "aesthetics".  There is nothing more I can do about it.
>
> --
> Protesilaos Stavrou
> https://protesilaos.com
>