Repository navigation
UIA freezes after a large number of events is received #11002
Description
Steps to reproduce:
-
Enable "use UI Automation to access the Windows Console" from advanced preferences.
-
Run
cmd. -
Start a python interpreter:
python. -
Run:
for i in range(100000):
print("test")
Actual behavior:
"test" is read for a few seconds, then all UIA applications become completely inaccessible until NVDA is restarted.
Expected behavior:
Output stops for a few seconds, then UIA recovers.
Context
I also tried disabling UIA connection recovery and event coalescing with the following in the NVDA Python console:
import UIAHandler
UIAHandler.handler.clientObject.CoalesceEvents = 0
UIAHandler.handler.clientObject.ConnectionRecoveryBehavior = 0
After UIA dies, running uiaHandler.terminate() and UIAHandler.initialize() does not restart UIA functionality. I'm not sure how to detect when UIA breaks or how to restart it once it does.
System configuration
NVDA installed/portable/running from source:
Installed and source.
NVDA version:
Latest master (b38776a).
Windows version:
Windows 10 21H1 insider.
Name and version of other software in use when reproducing the issue:
Windows Console
Other information about your system:
Other questions
Does the issue still occur after restarting your computer?
Yes.
Have you tried any other versions of NVDA? If so, please report their behaviors.
2019.2.1, 2019.3, 2020.1 (all same result).
If addons are disabled, is your problem still occuring?
Yes.
Did you try to run the COM registry fixing tool in NVDA menu / tools?
Not applicable.
Activity
codeofdusk commentedon Apr 14, 2020
Narrator seems to work as expected here, at least with my test case.
Cc @josephsl @LeonarddeR @michaelDCurran.
LeonarddeR commentedon Apr 14, 2020
Hmm, this might be related to other UIA performance issues. cc @bramd
francipvb commentedon Apr 14, 2020
LeonarddeR commentedon Apr 21, 2020
I have the strong feeling that something @jcsteh wrote in #10508 (comment) is related to this:
I would say that a solution based on option 2 would have the least chance of regressions while having positive impact on performance.
Now, I"m not sure what thread or threads handle all these events, as the log calls them dummy threads. However, if the UIA handler is processing an event and might be unable to process the next, if processing one event takes too much time without us discarding events that are out of date, things are slowing down. I think this is exactly what we're experiencing in several situations now, particularly in Visual Studio and may be in Word as well.
Cc @michaelDCurran @josephsl @bramd
beqabeqa473 commentedon Apr 21, 2020
LeonarddeR commentedon May 1, 2020
Related to #11077
codeofdusk commentedon Jan 22, 2022
At least for consoles, a lot of this appears to be a result of us registering for the
textChangeandcaretevents in particular: rejecting them inEventHandler.shouldAcceptEventdoes not stop NVDA's UIA support from hanging, but commenting out their entries inUIAHandler.UIAEventIdsToNVDAEventNamesallows consoles with lots of text not to flood the system at the cost of autoread support.Since consoles won't need these events any more once UIA notifications support is implemented for functional autoread, we should consider a way for NVDA not to register for these events from certain spammy providers, or only register for them in known-good cases. Thoughts @LeonarddeR, @michaelDCurran, @carlos-zamora?
UI Automation in Windows Console and Windows Terminal: block SV2M2 no…
seanbudd commentedon Jul 14, 2022
Potentially related to #13334
codeofdusk commentedon Jul 15, 2022
Not quite, because Notepad on Windows 10 uses MSAA, not UIA. Notepad on Windows 11 is UIA based, and if this hang can be reproduced there it is caused by this issue. Similar issues in VS, Windows Terminal, and (UIA) console are also in scope.
Selectively register for UIA events by default on SV2 (#14018)
codeofdusk commentedon Aug 17, 2022
Further investigation is required of course, but I think something along the lines of #10556 for UIA events would go a very long way here.
Disable UIA text change events outside of Word, Windows Console, and …
Adriani90 commentedon Nov 27, 2023
This has been probably fixed by #14888. Closing as fixed, but feel free to comment in case the issue still exists in the last NVDA alpha version and we can reopen.
@LeonarddeR now that #14888 is merged, is selective registering for UIA events still needed at all? You implemented that in #11214.
LeonarddeR commentedon Nov 27, 2023
Yes, I think so. It generally doesn't make sense to register to events you don't need.
LiveText: announce large bursts via a pumped generator (#20177)