[BRLTTY] Brltty support on OpenBSD

[Dave Mielke]

[quoted lines by Crystal Kolipe on 2023/06/25 at 13:02 -0300]

>The current release of brltty does not compile on OpenBSD due to some missing includes:

Thanks for figuring those out. I could add them, or perhaps you might crate a PRs for this and further OpenBSD work.

>With these changes, it's possible to compile brltty-6.5 on OpenBSD 7.3 using the following configure options:
>
>./configure --disable-speech-support --disable-api --without-pcm-package --disable-icu

Such things are usually handled by adding a platform-specific cfg-* script, e.g. cfg-openbsd, in the top-level directory. Again, I can do that.

>and noticed that on OpenBSD brltty has always used a patched version of screen to provide access to the display, 

We're trying to eliminate that. It's replacement is brltty's (new) Terminal Emulator screen driver. It can easily be used in conjunction with the brltty-term script. It runs a command (typcially a shell or terminal manager) via a pty, and also maintains a much better shared memory segment than the screen patch does. It also creates a message queue so that things like typing on a braille device's keyboard can be supported. The Terminal Emulator screen driver is at the other end of the message queue, and also monitors the shared segment for screen changes.

>The documentation on brltty.com 

FYI: While brltty.com still works, the correct domain name is brltty.app.

>it would probably be better to have a separate screen driver for the OpenBSD console, and in that case it wouldn't make much sense for my kernel patch to necessarily emulate the data format of the linux vcsa device at all, we might as well send the data out as the raw unicode codepoints from the wscons display buffer.  This would likely keep the code simpler, and potentially give more flexibility when handling non-ASCII characters.

Yes! Please do it that way, i.e. with a modern, OpenBSD-specific screen driver.

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