[BRLTTY] BRLTTY and Seika 40 display

[James Teh]

On 28/10/2008 1:37 AM, Sébastien Hinderer wrote:
> It may be wise to think about it very deeply before including braille
> drivers into nvda rather than using something like brltty.
We have given it quite a bit of thought. There are several reasons for 
writing our own drivers:
* Setting up braille using BRLTTY under Windows can be complicated at 
best for Windows users. It requires installation of both libusb-win32 
and brltty itself. These are dependencies that no other Windows screen 
reader has.
* Configuring BRLTTY is likewise alien to Windows users. This could be 
fixed by the creation of some sort of GUI configuration tool.
* Manufacturers provide their own drivers under Windows, so it makes 
sense to use them. Some of these drivers provide their own API, such as 
the Freedom Scientific and Handy Tech displays. Unfortunately, some of 
them, like the Baum drivers, simply emulate a serial port, so we would 
have to write a protocol driver. This is where nasty code duplication 
would occur.
* BRLTTY is not portable; i.e. it must be installed on the system and 
requires administrative privileges to be installed and run. This is 
because it needs to run as a Windows service (similar to a Unix daemon). 
Currently, there is only one braille display (the Alva BC640) that 
doesn't require Windows drivers to be installed, so this is less of an 
issue right now. However, with such a display, it will be possible to 
run NVDA with braille on any Windows computer without requiring 
administrative privileges.
* libusb-win32 is flakey at best under Windows. Using BRLTTY and 
libusb-win32, I can easily get my system into a state where USB will not 
work at all until I reboot; the system literally refuses to detect any 
added or removed USB devices. Unfortunately, no one seems ot be working 
on this project now and I do not even know where to begin to fix this.

> Indeed, if a braille device is supported by brltty, including a driver
> for this device in NVDA does not only duplicate code, it will also
> prevent concurrent access to the display.
This is very true. This is certainly one advantage of BRLTTY/brlapi. 
However, in order for users to take advantage of this, other screen 
readers would need to use brlapi.

Jamie

-- 
James Teh
Email/MSN Messenger/Jabber: jamie at jantrid.net
Web site: http://www.jantrid.net/