Accessibility issues in revisions screen

[joedolson]

In the course of assessing a functional problem with wp_text_diff, a number of accessibility concerns were unearthed regarding the revisions screen.

Once the output of wp_text_diff is settled, the other concerns noted in #25473 should be addressed here.

[sarahricker]

Hey @joedolson Would you be able to list and summarize the final a11y to-do's from #25473 in the description? Thanks!

[joedolson]

Issues that still need to be resolved in the Revisions screen:

1) Can this be reduced to a single table, so that a single set of headers ('Removed' and 'Added') can be displayed for all content, rather than having different sets for each type of data.

2) Add aria-labelledby and aria-describedby attributes to the view slider to improve the accessibility of navigating revisions.

3) Fix headings hierarchy (current H3 headings should be H2)

[rishishah]

Here is the patch for "Fix headings hierarchy (current H3 headings should be H2)"

[joedolson]

After discussion in the accessibility bug scrub, we think that making the changes I suggested for headings hierarchy and the slider labeling are still worth doing and practical, but the larger change to collapse into a single table would not be a productive use of time.

Moving the aria label related code changes from https://core.trac.wordpress.org/attachment/ticket/25473/25473.diff to this PR.

Trac ticket: https://core.trac.wordpress.org/ticket/52303

Hi, @wmalexander! Thanks for this! I added some additional things that were missing, and made a few changes to how things were implemented.

If you can give this some further testing, it would be great! One thing that didn't work in my testing was the focus styles; but I think that's just because the cache wouldn't refresh when I rebuilt, for some reason.

[joedolson]

Tested further, and confirmed that the labelling and headings changes work as expected. Modified slightly to omit Restore this revision from the aria-labelledby value, to avoid giving the impression that the slider handle also allows you to restore a revision.

No visual changes other than supporting a :focus state on the slider which was previously missing.

Marking for commit.

[joedolson]

In 59225:

Revisions: Improve accessibility of revisions selection.

Add aria-labelledby and aria-describedby attributes to revision slider selection handle. Add keyboard :focus state to revision slider handle. Move 'multiple revision' checkbox before the buttons panel, matching its visual order. Change diff Title and Content headings from h3 to h2 to correct headings hierarchy.

Props joedolson, rishishah, sarahricker, williamalexander, afercia.
Fixes #52303.

This was closed in https://core.trac.wordpress.org/changeset/59225