[Meta] Improve the accessibility of the Default Admin theme

Problem/Motivation

Meta issue for core's Default Admin theme accessibility issues in the path to stable.

Gin accessibility issues that apply to the Default Admin theme should be copied to new core issues as children of this Meta.

Steps to reproduce

Proposed resolution

Remaining tasks

Evaluate outstanding Gin accessibility issues against Default Admin and create corresponding child issues here.

For an example of an issue that was copied over, see #3583486: Adjust default_admin's top bar to the landmark used with the navigation module.

Critical Priority

Gin issues to be evaluated.

Major Priority

• #3604037: [PP-1] Indicate that grouping elements have child element errors for UX and a11y
• #3617875: Better Dark Mode Support for Disabled Elements
• #3618140: Improve the accessibility of focus outlines (color contrast, forced-colors)
• Gin issues to be evaluated.

Normal Priority

Color contrast

• #3506333: Improve the perceptibility of contextual link buttons (also forced-colors).
  Possibly eventually needs a new issue, as this one may still apply to Gin. See issue comments for details.
• #3618127: Navigation top bar action buttons in dark mode have low color contrast
• #3621109: Skip link in dark mode has low color contrast
• #3621244: Navigation mobile sidebar close button in dark mode has low color contrast
• Gin issues to be evaluated.

Forced colors

• Gin issues to be evaluated.

Other

• #3583518: Modernize table sticky header by using position: sticky
• #3583516: Breadcrumb separators are exposed to the accessibility tree
• #3583486: Adjust default_admin's top bar to the landmark used with the navigation module
• #3593539: [PP-1] Replace compact mode link with a switch to improve accessibility
• #3594809: Do not use toggle switches for checkboxes on forms that require submission
• #3595627: [PP-1] Sticky table header hides responsive tables toggle button
• #3612323: Do not use strong element for vertical tabs titles
• #3618906: [Meta] Forms sidebar accessibility issues
• #3621157: Admin theme should override top-bar.html.twig directly instead of adding an unconditional top_bar__default_admin suggestion
• Gin issues to be evaluated.

Completed

• #3587758: [PP-1] Labels for accent color choices on settings form are hidden from accessible technology
• #3587995: Default admin theme settings form color pickers missing accessible names
• #3604071: Change default to auto for light/dark mode
• #3595092: [regression] Local tasks styles on narrow viewport are wrong
• #3616351: [regression] Vertical tabs have Claro styles

None yet.

Reference

List of issues in Default Admin Theme tagged with 'Accessibility'.

List of issues in Gin Admin Theme tagged with 'Accessibility'

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet