Carousel: Improve keyboard and screen reader accessibility

[ryelle]

Fixes #39926, though it seemed to be opposite when I tested (clicking gave the carousel, while keyboard took me to the attachment page). Throughout the images and galleries, the behavior between mouse and keyboard are now the same. This also improves the carousel keyboard behavior by creating a focus trap so that keyboard users can effectively navigate (and close) the carousel.

Proposed changes:

• Removes the tabindex and aria label from images, this created an extra tab stop and prevented the images' alt text from being read
• Ensure all images with carousels are wrapped in links† so that they are focusable and interactive, without creating additional tab stops.
• Insert a .screen-reader-text span into the link, which will indicate the button's action without overwriting the alt text on the image
• Moves focus onto the overlay container when the carousel is open, so that the next interactive element is the close button
• Moves the button up in the carousel source order so that it's first in tab order (before the slide arrows)
• Sets up a focus trap so that tabbing while the carousel is open cycles through the elements on screen, nothing behind the carousel
• Moves focus back to the opening image when the carousel closes‡
• Adds any alt text to the slide image for screen readers

† These are already in links, generally, so for compatibility I stayed with links, with role=button to indicate correct keyboard interactions.

‡ This works great in "normal" cases where someone opens and closes an image, but there's an edge case if the page reloads with carousel open. If a page has the same image multiple times and is reloaded, on close it will focus back to the first instance of the photo. In general I think the focus improvement is worth this, but I'm open to feedback.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Does this pull request change what data or activity we track or use?

No

Testing instructions:

1. Check that Carousel is enabled in Jetpack > Settings > Writing tab > Media section
2. Find or create posts with images, a gallery, a tiled gallery block, and/or gallery shortcode (this works, but it's not pretty 😆)
3. For image blocks, make sure the Link is set to "Attachment page"; gallery blocks use carousel regardless of selection (including none, see Images in Gallery Blocks remain clickable when settings set to "Link to None" #28030)
4. View the post on the frontend
5. Click your images, you should see the carousel
6. Tab through the page
7. Each image should be only one tab stop (the link wrapper)
8. Hit space or enter, the carousel should open
9. Hit tab once, it should focus the close button
10. Tab a few times, it should cycle through the buttons on screen (you should be able to visually follow the focus with the outline)
11. Hit enter or space on the close button, it should close the carousel
12. Focus is back on the image you started on, so you can continue tabbing through the page

Try running through the same steps with a screen reader, though it's a little janky, it is a better experience. The image alt text is actually read aloud now, and is included on the large image too.

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack), and enable the update/carousel-accessibility branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack update/carousel-accessibility

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

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  • Scheduled release: March 4, 2025
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[jp-launch-control]

Code Coverage Summary

Coverage changed in 2 files.

File	Coverage	Δ%	Δ Uncovered
projects/plugins/jetpack/modules/carousel/jetpack-carousel.js	0/829 (0.00%)	0.00%	37 💔
projects/plugins/jetpack/modules/carousel/jetpack-carousel.php	54/616 (8.77%)	-0.01%	1 ❤️‍🩹

Full summary · PHP report · JS report

_{If appropriate, add one of these labels to override the failing coverage check: Covered by non-unit tests Use to ignore the Code coverage requirement check when E2Es or other non-unit tests cover the code Coverage tests to be added later Use to ignore the Code coverage requirement check when tests will be added in a follow-up PR I don't care about code coverage for this PR Use this label to ignore the check for insufficient code coveage.}