[BRLTTY] BRLTTY as an independent terminal?

[Dave Mielke]

[quoted lines by Tomas Valusek on 2008/08/23 at 22:18 +0200]

>Unix was born in age of mainframes, where users logged in through 
>terminals. 

Yes and no. It all depends on what is meant by "terminal". I'm sure you'll 
agree, for example, that there's a huge difference between a dumb ASCII 
terminal connected through one of those old serial controllers and a 3270-type 
display station. I'm sure you'll also agree that most mainframe users very much 
preferred the "then rather intelligent" 3270 display stations over dumb ASCIi 
terminals. Those display stations, just like today's monitors (which today's 
users also very much prefer over dumb ASCII terminals), rely rather heavily on 
well-designed video subsystems within operating system kernels.

>Linux supports this philosophy and provides several virtual terminals on 
>single console.

Sure, but even each of those virtual consoles isn't simply emulating a dumb 
ASCII terminal. It, for example, is also associated with a frame buffer, has 
video memory, can do complex graphics, etc.

>When I first heard of BRLTTY, I thought it was such a terminal emulator, 
>relying on system tools in regards of coupling itself to another terminal, and 
>if a braille display was not capable of inputting characters or other input 
>related actions, BRLTTY just "borrows" console keyboard for doing this. 

But braille displays aren't simple devices. Each model has its own rich set of 
controls and capabilities.

>And if the system runs X, a screenreader just detects presence of BRLTTY and 
>interacts with it as with a text console, not worrying about terminal 
>capabilities.

Yes, that's essentially how X screen readers, e.g. Orca, work.

>But BRLTTY reminds me more of braille drivers present in MS-DOS, tightly 
>coupled with single screen and being stronlgy dependent on it.

No, that's not quite true. In Linux, for example, BRLTTY (somewhat 
simplistically) looks at video memory. It's only limited insofar as Linux 
itself exports access to that video memory. BRLTTY can actually work in a 
completely separate virtual console than is currently being used by the 
system's monitor, keyboard, and mouse. It's just that that need hasn't been in 
demand so that functionality hasn't been made all that visible (yet). One could 
also argue that it'd introduce a security hole as such operation would bypass a 
locked screen.

Of course BRLTTY needs drivers since, for example, each model of braille 
display has its own communication protocols. That's really no different from a 
server like X which has a central core of useful common functions plus 
individual drivers so that those functions can be properly implemented on the 
various types of physical devices.

>UNIX (and Linux) was about single-purpose tools, so BRLTTY should just 
>present itself as TTY for underlying OS and depend on other system tools 
>for other tasks not directly related to Braille device.

What tasks do you feel BRLTTY itself performs that should be done by some other 
application(s)?

Now please allow me to present to you another perspective. We want each and 
every blind computer user to be able to use Linux (and other Unix-based 
systems). The average such person isn't a technical expert ... not even close. 
He also, by the very fact of his blindness, has no access to his system at all 
until his braille display can be made operational on that system (I'm excluding 
speech here, of course). Getting braille to work on his system, therefore, must 
necessarily be as easy as possible for him. Asking him to install some 
innumerable number of separate applications, and then to configure each of them 
so that they all work properly together, first is an unrealistic demand. BRLTTY 
offers him a single package which, in user space, becomes the equivalent to the 
video subsystem within the kernel with his braille display being his monitor. 
What improvements would you like to suggest to this model?

-- 
Dave Mielke           | 2213 Fox Crescent | I believe that the Bible is the
Phone: 1-613-726-0014 | Ottawa, Ontario   | Word of God. Please contact me
EMail: dave at mielke.cc | Canada  K2A 1H7   | if you're concerned about Hell.
http://FamilyRadio.com/                   | http://Mielke.cc/bible/