Re: [orca-list] No braille output during flat review in Terminal applications

[Sébastien Hinderer <Sebastien Hinderer ens-lyon org>]

Илья Пащук via orca-list (2022/01/08 16:15 +0300):
> hello
>
>
> Aleksandr, please explain why brltty starts in X session at all,

Because it can read some terminal wigets like mate-terminal ones.

> what it can read by itself in the Xorg session,

Brltty has an AtSpi screen device that can follow some widgets. This
scree driver is loaded with the "-x a2" command-line options. If you do
for instance

ps aux | grep brltty | grep -v grep

on a system where X is running and where things are properly configured,
you should see two instances of brltty. One is used with the Linux
screen driver and with a real braille driver, the one of the connected
braille display. That's the so-called root instance of brltty, because
that's the one that handles the actual display for that braille device.

Then there is a second instance of brltty, the one called with the "-x
a2" options. As mentionned above it uses the a2 (AtSPI) screen driver
and uses the BrlAPI brialle driver. Thanks to this driver, this second
instance of brltty connects to the root one and sends it what needs to
be displayed in braille.



> and why Orca works when it is disabled
> and do not works when it is enabled?

The component used to let applications like Orca access the braille
display is called BrlAPI. This components includes a priority mechanism
that lets applications express how well they support some widgets. There
is an agreement on the priorities between BRLTTY and Orca so that, if
brltty is not there, then the terminals will be followed by orca but, if
brltty si there, then Orca will not follow those widgets so that they
can be rendered by brltty.

hth,

Sébastien.