Add aria-describedby to image gallery output

[joedolson]

With the addition of figcaption and figure support to gallery output, there's limited support for assistive technology to programmatically associate images with their descriptions. Adding aria-describedby to the output would improve cross-browser support as well as adding a programmatic relationship when figcaption/figure is not being used.

See: #26697

[joedolson]

Add aria-describedby support to gallery output

[DrewAPicture]

Seems like this would be a logical pairing with the HTML5 stuff added in #26697.

Looking at 27402.patch​, should we not also add the attribute to the $captiontag/figcaption section a few lines down?

[joedolson]

Yes; there are problems with this patch. I didn't look carefully enough at what the variables actually represented. I'll take another stab at it. Rally, the $selector-$id ID pair should be moved off $icontag and onto $captiontag.

Will upload update patch shortly.

[joedolson]

Actually, I'm going to need to pass the aria-describedby parameter into the <img> element, otherwise, this won't work properly in screen readers. Will revise and update.

[joedolson]

Sets aria-describedby directly to img

[joedolson]

Patch updated. In order to make this work, I had to be able to pass an $attr array through wp_get_attachment_link into wp_get_attachment_image. Tested and works; hopefully I updated the docs appropriately, as well.

[nacin]

I did some reading on this. I think it's a good change, but it came in a bit late for 3.9. (It also doesn't factor into the HTML5 caption stuff, as in it isn't critical to be paired with it.) Let's get this thoroughly tested and ship it in 4.0.

[DrewAPicture]

standards

[DrewAPicture]

27402.3.patch​ adds some coding standards stuff and clarifies the parameter description for $attr.

[wonderboymusic]

$image_output = wp_get_attachment_link( $id, $size, false, false, false, $attr ); .... good times.

[rianrietveld]

Refresh of 27402.4.patch

[rianrietveld]

Added a refresh of 27402.3.patch (meaning version 3.patch in stead of 4.patch as I mentioned in the description with the patch)

[bramd]

Tested with NVDA + Firefox, works fine. However, be aware most users will read the page line by line (e.g. in virtual mode) en miss the semantic relation.
We can't fix that and just have to wait until fig and figcaption improves in user agents and assistive tech.

[arush]

Expected behavior by screen reader users is that links are accessible in the tab order while captions are generally read using the arrow keys. Browsers are not passing the figcaption info correctly to the DOM yet, so this info isn't getting passed to screen readers. Nonetheless this is the correct way to use the standard and browsers/screen readers will catch up so I recommend this patch be passes.

[arush]

Tested with VoiceOver and it works.

[arush]

Tested with Jaws, see comment above concerning screen reader expected behavior

[wonderboymusic]

In 29914:

Add a 6th (!) attribute to wp_get_attachment_link() to allow aria-describedby to be added to gallery output.

Props joedolson, DrewAPicture, rianrietveld.
Fixes #27402.

[bradyvercher]

Galleries that have photos with captions and link to the media files are throwing errors. It looks like the attributes array needs to be passed to wp_get_attachment_link() as the 6th(!) parameter rather than the 5th.

[wonderboymusic]

In 30161:

In gallery_shortcode(), when the link attribute is equal to file, make sure to pass $attr as the 6th (!) argument, not 5th, to wp_get_attachment_link().

Props bradyvercher.
Fixes #27402.