feat: keep action elements focusable when disabled

[TomMenga]

Notes to reviewer

I believe that not all the button-like components that previously extended the SbbDisabledTabIndexActionMixin should be part of this development.
The components that, imho, should be excluded are:

• sbb-popover-trigger
• sbb-slider

Not sure about:

• sbb-mini-button => In some cases it should be focusable (mini-button-group) and in others it should not (e.g. when it's part of a form field)
• link and button-links

TODO

• Decide what to do with arrow navigation (especially for the sbb-menu)

Preflight Checklist

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• I have searched the pull request tracker for a Pull Request (PR) that matches the one I want to submit, without success.

Issue

This PR Closes #2862

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

See Review Guidelines for more information what is checked during review process.

Changes

Changes in this pull request:

• For a11y purposes, keep button-like elements focusable when disabled

Browsers

I tested the build on the following browsers:

• Firefox Desktop
• Chrome Desktop
• Edge Desktop
• Safari Desktop
• Chrome Mobile
• Safari Mobile

Screen readers

I tested the build on the following browsers:

• JAWS Firefox Desktop
• JAWS Chrome Desktop
• NVDA Firefox Desktop
• NVDA Chrome Desktop
• VoiceOver Safari Desktop
• VoiceOver Chrome Desktop
• VoiceOver Safari Mobile
• Android Accessibility Suite Chrome Mobile

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

Does this introduce a breaking change?

• Yes
• No

Other information

[jeripeierSBB]

A topic that came to my mind was that we have several components where we implemented arrow key navigation. Normally (as I remember) we exclude the disabled ones (e.g. menu.ts line 153). Maybe this still makes sense, but it would not be the same as arriving with tab there. Especially for the menu where both navigations are possible. But there are other components I think.

[TomMenga]

A topic that came to my mind was that we have several components where we implemented arrow key navigation. Normally (as I remember) we exclude the disabled ones (e.g. menu.ts line 153). Maybe this still makes sense, but it would not be the same as arriving with tab there. Especially for the menu where both navigations are possible. But there are other components I think.

I believe the menu is the only component allowing both arrow and tab navigation. In general, if there is arrow navigation, you cannot tab between them

[jeripeierSBB]

A topic that came to my mind was that we have several components where we implemented arrow key navigation. Normally (as I remember) we exclude the disabled ones (e.g. menu.ts line 153). Maybe this still makes sense, but it would not be the same as arriving with tab there. Especially for the menu where both navigations are possible. But there are other components I think.

I believe the menu is the only component allowing both arrow and tab navigation. In general, if there is arrow navigation, you cannot tab between them

Ok, this can be. But also with only arrow-navigation components, should disabled buttons be reached now? Or don't we have any such case?

[TomMenga]

A topic that came to my mind was that we have several components where we implemented arrow key navigation. Normally (as I remember) we exclude the disabled ones (e.g. menu.ts line 153). Maybe this still makes sense, but it would not be the same as arriving with tab there. Especially for the menu where both navigations are possible. But there are other components I think.

I believe the menu is the only component allowing both arrow and tab navigation. In general, if there is arrow navigation, you cannot tab between them

Ok, this can be. But also with only arrow-navigation components, should disabled buttons be reached now? Or don't we have any such case?

I'm not sure about it. Because in lists and groups, like the stepper or tab-group, screen readers allow users to navigate between items (even when disabled). Maybe we could ask for advice from an a11y expert

[jeripeierSBB]

LGTM, thank you!

[kyubisation]

LGTM 👍
Nice work! 😃