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

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

[Christopher Dimech]

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 .

Cannot see any consideration of accessibility in its design, as
it looks that the plan had been to make the indicator faint and
almost imperceptible.  This strategy is the worst possible thing
one can do for the cohort of visually challenged people (remember
that perceptibility changes with age, meaning that developers
could be too young and inexperienced to understand
perceptibility considerations).

Protesilaos described how the default style of
display-fill-column-indicator-mode gets a dashed vertical line.
These dashes appear further apart and feel broken if the user (i)
has a font with a tall line height, (ii) increases the value of
line-spacing, (iii) has an increased height for constructs like
headings in Org.

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.

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

[Protesilaos Stavrou]

> 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.

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.

> [... 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

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

[Christopher Dimech]

> 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
>

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

[Lars Ingebrigtsen]

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Christopher Dimech <dimech@gmx.com> writes:

> Protesilaos described how the default style of
> display-fill-column-indicator-mode gets a dashed vertical line.


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With "emacs -Q" on the current Ubuntu, the line isn't dashed.

And it looks very perceptible to me.  On which systems is it faint and
dashed?

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

[Lars Ingebrigtsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> With "emacs -Q" on the current Ubuntu, the line isn't dashed.

Oh, never mind -- I see the dashes now.  (On this HiDPI screen, the gaps
weren't visible to me before enlargening.)

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

[Christopher Dimech]

> Sent: Friday, August 26, 2022 at 10:55 PM
> From: "Lars Ingebrigtsen" <larsi@gnus.org>
> To: "Christopher Dimech" <dimech@gmx.com>
> Cc: 57424@debbugs.gnu.org
> Subject: Re: bug#57424: Perceptibility of display-fill-column-indicator-mode
>
> Lars Ingebrigtsen <larsi@gnus.org> writes:
>
> > With "emacs -Q" on the current Ubuntu, the line isn't dashed.
>
> Oh, never mind -- I see the dashes now.  (On this HiDPI screen, the gaps
> weren't visible to me before enlargening.)

Hard to see with Trisquel 9.0 when one uses Emacs with modus-vivendi
(a dark theme provided by modus-themes, specially designed for accessibility).

Could users have an accessibility flag they can turn on and off, where the line
is thick and solid (rather than dashed and thin). And be able to change colour
of background.  Can one change the foreground colour of the line?  Not too sure
if foreground line colouring is possible.