[BRLTTY] Jaws/BRLTTY sleep mode

[Samuel Thibault]

Hi,

I had a look at COM port sharing. The ReadFile() FILE_SHARED_READ/WRITE
flags should permit sharing, but it doesn't seem to work: the second
program always get an ERROR_ACCESS_DENIED error.

I don't know what JAWS does, but I guess that it opens the port, and
when going into sleep mode it closes the port, which then lets BRLTTY
open it. Lee, can you confirm (with CombiBraille since Alva still
doesn't seem to work) that BRLTTY only works if JAWS enters braille
sleep mode? BTW, How does it enter braille sleep mode? Is it manual or
automatic (in that case, how is it triggered?)

I think things should be able to work nicely, let's use the scenario
"explorer window" then "console window" then "explorer window" again:

- JAWS is running, and reads the explorer window.
- Focus gets on a console window. BRLTTY sees that, but fails to re-open
the braille device (error ignored).
- JAWS enters braille sleep mode, which releases the port.
- BRLTTY can re-open the braille device and read the console window.
- Focus gets on the explorer window again. JAWS can't re-open the
braille device
- BRLTTY closes the driver, hence releases the port.
- JAWS can re-open the braille device and read the explorer window.

The only problem is with the delay of switching from one to the other:
by default, BRLTTY retries to open the device every 5 seconds. Maybe
this value should be put down to a more responsive value, at least as
long as the device can't be opened because of an ERROR_ACCESS_DENIED
error.

Regards,
Samuel