Accessible progressive disclosure

Jeremy Keith
Mar 11, 2016 · 3 min read

Over on The Session I have a few instances of a progressive disclosure pattern. It’s just your basic show/hide toggle: click on a button; see some more content. For example, there’s a “download” button for every tune that displays options to download the tune in different formats (ABC and midi).

To begin with, I was using the :checked pseudo-class pattern that Charlotte has documented so well. I really like that pattern. It feels nice and straightforward. But then I got some feedback from someone using the site:

the link for midi files is no longer coming up on the tune pages. I am blind so I rely on the midi’s when finding tunes for my students.

I wrote back saying the link to download midi files was revealed by the “download” option. The response:

Excellent. I have it now, I was just looking for the midi button which wasn’t there. the actual download button doesn’t read as a button under each version of the tune but now I know it’s there I know what I am doing. I am using the JAWS screen reader.

This was just one person …one person who took the time to write to me. What about other screen reader users?

I dabbled around with adding role=”button” to the checkbox or the label, but that felt really icky (contradicting the inherent role of those elements) and it didn’t seem to make much difference anyway.

I decided to refactor the progressive disclosure to use JavaScript instead just CSS. I wanted to make sure that accessibility was built into the functionality, rather than just bolted on. That’s why code I’ve written doesn’t rely on the buttons having a particular class value; instead the buttons must have an aria-controls attribute that associates the button with the element it toggles (in much the same way that a for attribute associates a label with a form field).

Here’s the logic:

  1. Find any elements that have an aria-controls attribute (these should be buttons).
  2. Grab the value of that aria-controls attribute (an ID).
  3. Hide the element with that ID by applying aria-hidden=”true” and make that element focusable by adding tabindex=”-1".
  4. Set aria-expanded=”false” on the associated button (this attribute can be a bit confusing — it doesn’t mean that this element is not expanded; it means the element it controls is not expanded).
  5. Listen for click events on those buttons.
  6. Toggle the aria-hidden and aria-expanded when there’s a click event.
  7. When aria-hidden is set to false on an element (thereby revealing it), focus that element.

You can see it action on CodePen.

I’m still playing around with this. I think the :focus styles are probably far too subtle right now — see this excellent presentation from Laura Palmaro for more on that. I’m also not sure if the revealed content should automatically take focus. I’ll see if I can get some feedback from people on The Session using screen readers — there’s quite a few of them.

Feel free to use my code but you might want to check out Jason’s code to do the same thing — his is bound to be nicer to work with.

This was originally posted on my own site.

Jeremy Keith

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A web developer and author living and working in Brighton, England.