[D8][A11Y] Dedicated "Accessibility" section under "Configuration"

[klonos]

This is a sibling issue to #3624 (created as per @quicksketch's request during the sprint earlier today)

Ideas for what to be included in this page:

• Checkbox that enables the "show row weights" link at the top-right of all drag-enabled tables (assumes we previously have made it so that these links are not rendered by default).
• Checkbox to globally force requiring alt text for images (#3006, #1439 etc.)
• A text field to provide a default, but customizable help text for all alt fields (see #4809)
• "Dark mode" for the Seven admin theme: #3990
• ...others?

[laryn]

I like the global power switch for requiring alt text. Would that work for image fields and for WYSIWYG images? Related issue: https://github.com/backdrop/backdrop-issues/issues/3006

Other items to look at:

• https://www.drupal.org/project/a11y
• https://www.drupal.org/project/accessibility
• https://www.drupal.org/docs/7/creating-accessible-themes/contributed-modules-to-help-with-accessibility
• https://accessibility.huit.harvard.edu/developers

[klonos]

I came across https://www.drupal.org/project/drupal/issues/3067273 over in d.org:

Problem/Motivation

There have been several requests so far to provide customizable settings to adjust the admin interface to several desires/needs.

Proposed resolution

Provide a form with several settings to customize the UI. For example:

• Font Size
• Table cell padding or general spacing
• Palette
• Accent Color
• Dark mode
• Accessibility settings
  • Reduce motion
  • Highcontrast mode
  • etc.

So from this options proposed we should decide where they need to be defined and who should be able to change them:

• Settings defined accross the site (per theme / per site)
• Settings defined per user (like font size / accessibility wise)
• Settings defined per component (like decreasing table padding or thumbnail size on Media library)

Remaining tasks

Decide per setting the following:

• In which form should it live?
• Who should be able to change it (editor/content author vs site-builder)
• Which settings/values

[klonos]

...since the admin UI is basically a theme, it is hard to imagine these not being (global) theme settings. I also find it hard to imagine how a dark/high-contrast mode could be applied to all themes.

Interesting problems to figure out 🤔

[quicksketch]

it is hard to imagine these not being (global) theme settings. I also find it hard to imagine how a dark/high-contrast mode could be applied to all themes.

We could possibly have themes that support high-contrast mode put an indicator in their .info files, then this hypothetical accessibility page could show the checkbox/radios for default/high-contrast. Dark mode seems like it's a separate feature than an accessibility item, since you could easily have a low-contrast dark mode that is just as bad a low-contrast light mode.