[BRLTTY] Linux console hacking (was: Re: Footsteps towards better accessibility in Linux)

[Nicolas Pitre]

On Sun, 29 Mar 2026, Sébastien Hinderer wrote:

> Nicolas Pitre (2026/03/28 20:41 -0400):
> > The alternate screen is not cleared "at program exit". It doesn't know
> > if a program exited or not.
> >
> > What happens here is:
> >
> > - When the sequence "\e[?1049h" is sent to the terminal, the alternate
> >   screen is activated. It is always blank upon activation.
> >
> > - When "\e[?1049l" is sent to the terminal, the normal screen is
> >   restored i.e. you'll end up with the same screen content that existed
> >   at the moment "\e[?1049h" was sent and the alternate screen with its
> >   content is discarded.
> >
> > You can even play with this using echo -e at the shell prompt.
> > Really there isn't more to it than that.
> 
> Okay thanks for having explained the mechanism. However I continue to
> observe that when an application knows how to use the alternative
> screen, then right after the switch to the alternatvie screen BRLTTY
> pornounces unrelated content, as if there were some leftover of a
> previous session under the alternative screeen.

Does the braille display contain unrelated content too, even if only for 
a fraction of a second?

Without a good way to reproduce, it is hard to debug.


Nicolas