Have spelling errors indicated in Braille when supported

[vincent-lg]

Summary

Spelling errors are sometimes reported by a sound when space is pressed, and by the synthesizer. It doesn't work for all applications, but it's a great feature. I would suggest to extend it so that this information would be accessible from a Braille display.

Layout

A solution could be to mark the misspelled word like a HTML tag. Obviously, this is not a great solution, first because it will take some characters away, next because it will introduce HTML landmarks in places where plain text is used.

Some systems like BRLTTY on Linux have an option to show some attributes in Braille. They do it by adding dot-7 and dot-8 beolw the word, like selection, but unlike selection, the dot-7 and dot-8 are blinking. The speed of this blinking can be configured and could be different from attributes, allowing a clear distinction. Since it's not a constant marker, it cannot be confused with selection either.

I really appreciate this solution, and would propose to have a blinking selection for spelling errors, right under the word (or groups of words) in question. This could be turned on and off, obviously.

A last thought that might not belong here: this system could be extended to show all kinds of attributes in Braille (underline/bold/italic/crossed-out content). The speed of blinking could be used to differentiate between attributes. Just a thought!

Thank you again for your very good work,

[LeonarddeR]

cc @dkager

[derekriemer]

@LeonarddeR are you guys still working on braille formatting?

[dkager]

This is a specialization of #6785.

In particular, see my thoughts in #6785 (comment).

[LeonarddeR]

Not yet, as there is still some discussion about what to do with braille formatting provided by liblouis.

[Adriani90]

The speed of blinking is a really interesting idea in my view. We could communicate a lot of information through that. cc: @michaelDCurran, @bramd