Fix problems with Braille output devices

[dpvc]

This PR fixes problems identified with using a Braille output device in JAWS and NVDA on Windows. It turns out that for the aria-braillelabel to be read in JAWS, the role being application doesn't work, while role="img" does. But we need the speech element to be in an element with role="application" in order to remain in focus mode, so this PR wraps the speech node in an additional mjx-speech-container element with role="application" and makes the speech node have role="img".

Not all screen readers handle the aria-braillelabel attribute, however (e.g., NVDA), but if Braille is in the aria-label, they will pass it on to the Braille device. So we have added a menu option to include the Braille as part of the speech string. This lists the Braille first, followed by 40 blank Braille cells, followed by the speech string. The brail device should show the braille, but the speech will be off the right-hand edge and will not be displayed, but it will be spoken. In NVDA the Braille itself is not spoken (but in JAWS and some other readers it is, so this can't be the default setting).

We also add an option to replace the speech with the Braille, but that item is hidden and only kept as a backup in case it is needed.

Finally, we set the aria-braillroledescription to try to override the img role description, for those screen readers that process it.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.48%. Comparing base (a14d976) to head (6663405).
⚠️ Report is 13 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1396      +/-   ##
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- Coverage    86.49%   86.48%   -0.01%     
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  Files          340      340              
  Lines        85813    85818       +5     
  Branches      3177     4815    +1638     
===========================================
- Hits         74220    74218       -2     
+ Misses       11593    11577      -16     
- Partials         0       23      +23     

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[zorkow]

Only one comment.

I suppose we should also add a line for NVDA to the helpData in KeyExplorer.

[zorkow]

Could that be wrapped into the noRerender method?

[dpvc]

Yes it should. I think it wasn't available in the develop branch when the top-braille branch (on which this was based) was created. I'll make the change.

[dpvc]

I suppose we should also add a line for NVDA to the helpData in KeyExplorer.

I had written a paragraph about Braille output and thought it was included (one of the commits even says that). But it seems to be missing, so I must have messed up the commit and lost it. I'll write it again.

[dpvc]

I've made the changes. It looks like the hiding of the "replace speech" menu item was also lost, so I added that again, too. Not sure what I did wrong, there.

Do you want to re-review, or shall I just merge?

[zorkow]

lgtm.

[dpvc]

I've added the "b" key to toggle the Braille menus' "Combine with Speech" option from within the explorer, as requested, and updated the help dialog to include it.