Make old JAWS recognise disabled buttons

[selfthinker]

What problem does the pull request solve?

JAWS 15 and below don't recognise the disabled attribute on buttons.
This adds the aria-disabled attribute to make disabled buttons compatible with older screen readers.

This does not apply to other disabled elements. I also tested the new disabled radio buttons and checkboxes, and they are fine in older JAWS versions without this change.

How has this been tested?

I tested with JAWS 14, 15 and 17.
JAWS 17 is fine without the change and reads e.g. "Save button - unavailable" but all the others read "Save button" as if it was a normal button, not making it clear that you cannot use it. Adding aria-disabled fixes that. It seems redundant but is similar to our practice to add role="main" to our <main> element to support older browsers.

I couldn't test with JAWS 16 yet. In case that also doesn't support disabled, I will update the commit message and this PR accordingly.

What type of change is it?

• Bug fix (non-breaking change which fixes an issue)

Has the documentation been updated?

I'm not sure if this needs to be documented?
I have added an item to the page.

[gemmaleigh]

Thanks @selfthinker!

For the documentation - could you please add another list item to the list of bullet points about disabled buttons:

• disabled buttons must use thearia-disabled attribute for older screen readers

[selfthinker]

I have added an item to the list. I have shortened your proposed sentence because we rarely use the word "must" (or "should" etc) within Elements and I thought it sounded a bit too formal for that bit.

[selfthinker]

Unfortunately, we can currently not test in JAWS 16. I've asked in the x-gov slack channel if anyone can test it. Otherwise, I don't think it's super important. It would just be good to know which JAWS version started to support the disabled attribute on buttons. But this could be merged without that knowledge. Let's wait until tomorrow.

[selfthinker]

@accessiblewebuk just tested and confirmed that JAWS 16 handles the buttons correctly, so it is indeed "JAWS 15 and below" as stated in the commit message and description above.

[edwardhorsford]

Would it be good to be specific about what screen readers and versions we're doing this for? I feel like this could be helpful in some years time when we can take a view if we still support those screen readers.

[selfthinker]

I was specific in the commit message ("JAWS 15 and below"), which people should always be able to find. Or did you mean making it more prominent in the guidance?

[edwardhorsford]

I mean making it explicit in the guidance - but it's only a suggestion.

[gemmaleigh]

I'm happy to merge, before I do - let me know if you would prefer to use "older screen readers" or "JAWS 15 and below".

[selfthinker]

We don’t necessarily know that it’s just older JAWS as we haven’t tested older versions of other screen readers. (Although the reason for that is that older versions of other screen readers are not used as much.)
We are also not specific in other areas either (e.g. with role="main" or many JavaScripts), so that would be inconsistent. Although, it would still be a good idea to generally do it, but it might be quite a lot of work to do it consistently.

[gemmaleigh]

Thanks @selfthinker, will merge as-is.