[BRLTTY] skipping broken cells

[Aura Kelloniemi]

Hello list,

Dave Mielke <Dave at mielke.cc> writes:
 > [quoted lines by Rob on 2019/05/14 at 04:41 -0500]
 > >It could be a config setting
 > >skip-cells = 01-03-12
 > >or similar.

 > What about those with more than one braille device? There'd need to be a way to
 > specify which one it applies to. Perhaps each device has a different set of
 > broken cells.

It would be quite a coincidence, if they had the same cells broken.

Also, most often the whole cell is not defunct, but some particular dots are.
BRLTTY could take this into account and still use the broken cell if the
broken dots are not needed in the braille pattern that is to be written to the
cell.

But... dots can be defunct in (at least) two ways: most often they don't rise,
but sometimes they don't go down, but instead stay completely (or halfway) up
all the time. This would increase complexity, if BRLTTY would take into
account specific dots instead of just whole cells.

And what should BRLTTY write to the cells which the user has reported as
non-working? Should they be left empty (which might lead to confusion about
whitespaces) or should all (working) dots be raised up? Maybe this would be
configurable, because marking defunct cells already requires configuration.

Suggestion: maybe add broken dots lists to configuration file items. User
could then choose from the configured lists in the preferences menu, or choose
no list (similarly to language profiles). Some devices probably allow their
serial number to be queried, which at least in theory could be used to choose
the correct list without user intervention.

Currently I'm lucky not to have a single broken dot in my display, but I have
another issue which could potentially be solved by this feature. When the
battery of my Focus Blue is low (<=10%), the firmware writes a status
indicator at the righthand side of my display. This indicator cannot be
disabled and it is shown all the time. The firmware uses dots 7 and 8 in this
indicator (which is 1-5 cells wide, depending on the battery status).
Unfortunately I use a braille table which extensively uses dots 7 and 8, so
the battery status indicator completely garbles all characters in the last
five cells. Currently I work around this issue by setting Window overlap to
the width of the status indicator whenever this problem appears. But I would
prefer to have those cells be filled with the pattern ⣿ (all dots up). This
would be much less confusing than having garbled text at the end of each
braille window. However, even though some other people with Focus displays may
suffer from this same problem, I think it is a rather specific issue and
should not guide development decisions very much.

-- 
Aura