[tex4ht] [bug #339] remove/rewrite braille code

[Michal Hoftich]

Quoting Karl Berry (2016-11-01 18:08:22)
>     what kind of system/code/workflow Antonis refers to as
>     "Braille support in tex4ht"
> 
> Those were my words, not his.  He's referring to what tex4ht-html-speech
> outputs -- some form of XML.  His actual words are below.
> 

Ah, this is Emacsspeak format. One can get it with 

   mk4ht eslatex

It is normal HTML, but with additional textual information. It doesn't
really looks useful for braille conversion, it is geared towards screen
readers.


> I contacted then the developers of liblouis through the liblouis list
> and their answer was that first they do not care about TeX (their target
> is Office) and as to why it does not work they wrote to me that the xml
> produced by tex4ht is not what is expected by liblouis to convert
> correctly. [...]

I've tried Liblouis again, xhtml+mathml seems to produce something which
seems that it might be a good result, but only someone who can
understand American grade 2 braille can tell us whether it is really
good. 

This sample document:


    \documentclass{article}
    \usepackage{amsmath}
    \begin{document}
    
    hello world
    
    Simple: $(\overline{x+y})=\overline{x}\overline{y}$
    
    \begin{equation}
    \label{eq:hello}
    a = \sqrt{b^2 + c^2}
    \end{equation} 
    
    See equation~\ref{eq:hello}
    
    Now some multiline
    
    \begin{multline*}
      p(x) = 3x^6 + 14x^5y + 590x^4y^2 + 19x^3y^3\\ 
      - 12x^2y^4 - 12xy^5 + 2y^6 - a^3b^3
    \end{multline*}
    
    Align:
    
    \begin{align*} 
      2x - 5y &=  8 \\ 
      3x + 9y &=  -12
    \end{align*}
    
    
    Align*:
    
    \begin{align*}
      x&=y           &  w &=z              &  a&=b+c\\
      2x&=-y         &  3w&=\frac{1}{2}z   &  a&=b\\
      -4 + 5x&=2+y   &  w+2&=-1+w          &  ab&=cb
    \end{align*}
    
    \end{document}

produces the following braille code, without any configuration:


      hello _w
      ,simple3 ("x+y<}) .k "x:"y:
    
    a .k >b~2"+c~2"} 7#a7
    
      ,see equ,n #a
      ,n{ "s multil9e
    `,(p(x) .k #3x~6"+14x~5"y+590x~-
    4"y~2"+19x~3"y~3"`,)
    `,(-12x~2"y~4"-12xy~5"+2y~6"-a~-
    3"b~3"`,)
    e
      ,align3
    `,(2x-5y   .k #8      `,)
    `,(3x+9y   .k -12     `,)
    e
      ,align993
    `,(x       .k y     w     .k
    z       a    .k b+
    c               `,)
    `,(2x      .k -y    3
    w    .k ?1/2#z  a    .k
    b                 `,)
    `,(-4+5x   .k #2+y  w+
    2   .k -1+w    ab   .k c
    b                `,)


If I understand it correctly, grade 2 braille uses system of
shortenings, so world becomes _w, for example. I thought that it was
really horrible error at first :)

The question is, what is the best way to support accessibility nowadays.
Instead of approach of tex4ht-html-speech, we probably should use WAI-ARIA
attributes and HTML 5 semantic elements. So, maybe this issue should
stay open at the moment.

Best regards,
Michal