[orca-list] Lightdm GTK greeter accessibility revisited

[Peter Vágner <pvdeejay gmail com>]

Hello,

This is turning in to a little story, so please apologize for posting a 
lot of background details.
I am currently trying to run lightdm with lightdm GTK greeter working on 
my system. I would like to use it to either login into mate, or login 
into xfce4 or login directly into kodi.
Lightdm appears to be only one accessible enough from the minimalist 
desktop managers I know of.
Lightdm greeter started implementing accessibility support in a way so 
it has preferences to launch on screen keyboard, screen reader from its 
menu. The problem with this initial goal was the issue where upon 
dismissing the greeter session there was at-spi2 core bus still present 
and it was not easy to get accessibility support working inside the 
resulting user session after logging in. Here is the corresponding bug 
report https://bugs.launchpad.net/lightdm-gtk-greeter/+bug/1366534. 
While in this state I was able to hack around the fact there are lightdm 
greeter processes open after the greeter is dismissed by using 
session-setup-script and session-cleanup-script to kill these. While not 
particularly nice solution this worked pretty well.
There were issues with other stale processes so lightdm GTK greeter now 
implements a way to run some helper apps such as at-spi2-core or applet 
indicators specific processes remembers their pid's and gracefully kills 
these when exiting. While implementing this a feature that causes more 
problem than it solves crept in unfortunately. Current versions of 
lightdm GTK greeter now set NO_AT_BRIDGE environment variable. The 
original reasoning behind this is that when lightdm greeter launches 
at-spi2 it should force ATK not to launch it again by setting 
("NO_AT_BRIDGE", to true. The result of this is that orca is started, 
at-spi2 is started but these can't communicate to each other I guess. By 
experimenting I have found out that orca and ATK won't start another 
copy of at-spi2 core if one is already launched by lightdm so I think 
this can be removed without risking other possible issues. The 
corresponding bug report is at 
https://bugs.launchpad.net/lightdm-gtk-greeter/+bug/1483864 .
So given this I hoped we might see awesome accessibility related greeter 
experience very soon but unfortunately I've found another issue and this 
time I am afraid it might have something to do with orca.
When lightdm GTK greeter is configured with reader in its accessibility 
states it includes Screen reader menu item which allows starting orca. A 
keyboard equivalent of enabling that menu item is an F4 keyboard 
shortcut which is working as a toggle i.e. it switches screen reader to 
on or off. Under the hood lightdm GTK greeter launches orca or to be 
precise the command configured in its config file, remembers its pid and 
then kills that pid when the feature is toggled to off.
What I have just noticed when orca receives sigterm it appears to freeze 
here. I am however only able to reproduce this when running inside a 
lightdm greeter session and when logged into xfce for example I can kill 
orca without issues. This is with orca 3.18.2 and with orca master. 
Unfortunately I can find nothing useful in the debug*.out file orca 
generates. How would I go about trying to better troubleshoot this?

I do have some other possibly related questions:
- Orca launches other helper apps such as speech-dispatcher which in 
turn may optionally also launch pulseaudio. Should these also be tracked 
in lightdm GTK greeter the same way at-spi is?
- When lightdm is running as a systemd service and I call systemctl stop 
lightdm the greeter process is terminated however at-spi and I suspect 
the other tracked processes are still running. Is this a bug?

Greetings

Peter