NVDA takes an incredibly long time to gain focus on Firefox when the system is under high load

[Neurrone]

CC @jcsteh

Steps to reproduce:

1. Perform a CPU intensive operation, in my case I was compiling a rust application
2. Switch to Firefox while the background operation is in progress, I was reading some docs while waiting for the compile to complete.

Actual behavior:

NVDA takes up to 10 seconds to gain focus, and a few instances of the following error is logged:

ERROR - api.setFocusObject (19:16:17.722) - MainThread (15268):
Error updating tree interceptor
Traceback (most recent call last):
  File "api.pyc", line 158, in setFocusObject
  File "treeInterceptorHandler.pyc", line 33, in update
  File "NVDAObjects\__init__.pyc", line 422, in _get_treeInterceptor
  File "treeInterceptorHandler.pyc", line 25, in getTreeInterceptor
  File "virtualBuffers\gecko_ia2.pyc", line 302, in __contains__
  File "comtypes\__init__.pyc", line 856, in __call__
  File "monkeyPatches\comtypesMonkeyPatches.pyc", line 39, in __call__
exceptions.CallCancelled: COM call cancelled

Expected behavior:

NVDA should not take up to 10 seconds to gain focus on Firefox. I don't see this extreme lag happening when switching focus to other applications like the desktop.

NVDA logs, crash dumps and other attachments:

System configuration

NVDA installed/portable/running from source:

Installed

NVDA version:

alpha-26524,bc1f92f9 (2022.4.0.26524)

Windows version:

10.0.19044.1889

Name and version of other software in use when reproducing the issue:

Firefox 105.0b9

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.

If NVDA add-ons are disabled, is your problem still occurring?

Does the issue still occur after you run the COM Registration Fixing Tool in NVDA's tools menu?

[jcsteh]

We're tracking this in https://bugzilla.mozilla.org/show_bug.cgi?id=1626789. It should be fixed by our current major re-architecture of the Firefox accessibility engine. If you are willing to run Nightly builds, you could give this a try to see if it fixes the problem for you. Note that it is not enabled by default yet even in Nightly. See this blog post for instructions.

[jcsteh]

Our major re-architecture of the Firefox accessibility engine fixes this. This is now enabled by default in Firefox 113 release.