[liblouis-liblouisxml] dotsIO weirdness, table for 8 dot computer braille
- From: James Teh <jamie@xxxxxxxxxxx>
- To: liblouis/liblouisxml mailing list <liblouis-liblouisxml@xxxxxxxxxxxxx>
- Date: Mon, 15 Sep 2008 21:17:16 +1000
Hi all,
I am one of the core developers of NVDA (http://www.nvda-project.org/)
and am currently in the process of implementing braille support for
NVDA. We're using liblouis for braille translation.
Rather than having liblouis output braille in text form, I prefer to
have the braille output in dot patterns. This eliminates the need for
the braille display driver to be aware of braille character set tables
and the like. (Even though we can use brltty, I'd rather users not have
to deal with two sets of braille table configuration.) Thus, we use
liblouis with the dotsIO mode.
One oddity I discovered with dotsIO is that it seems to produce dot
patterns with the highest order bit in the widechar set. With a 16 bit
widechar, this means that everything has a base of 0x8000. This is
easily fixed by simply ignoring the higher order byte, but it seems
strange nevertheless.
Now for the actual purpose behind this email:
Because we use dotsIO, we are using liblouis even for translation into
computer braille. However, using en-us-comp8.ctb as my translation
table, dots 7 and 8 are not ever set for capital letters and the like.
If I use the compbrlAtCursor mode and specify a cursor position, the
expanded word contains dots 7 and 8 if appropriate, but none of the
other braille does. I can specify computer_braille (8) as the typeform
for every character to manage this. However, I was hoping that the user
would just be able to set the appropriate braille table and have it use
dots 7 and 8 if appropriate.
Is there some table other than en-us-comp8.ctb that I should be using to
achieve this?
There is a mode constant named comp8Dots which I figured might achieve
this. However, this constant is never checked in the source; the mode is
unimplemented.
Is there any other way to achieve this?
If not, what is the reason for this behaviour and is there any chance of
it being changed?
Thanks!
Jamie
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James Teh
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