Hi,

Reported by @tspivey via Skype: UIA responds slowly when pressing Alt+Tab from WinDbg.

Steps to reproduce:

1. Install Windows SDK.
2. Open WinDbg (any version will do).
3. With WinDbg open, press Control+D to open crash dumps.
4. Press Alt+Tab.

Actual behavior:

Switching between apps is very slow.

Expected behavior:

Switching between apps is snappy.

System configuration:

NVDA Installed/portable/running from source:

Installed

NVDA version:

2018.2.1 and alpha.15634

Windows version:

Windows 10 versions 1803 and Insider Preview

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

WinDbg

Other information about your system:

@tspivey uses version 1803, while I use Insider Preview.

Other questions:

Does the issue still occur after restarting your PC?

Yes

Have you tried any other versions of NVDA?

No

Technical:

Possibly caused by WinDbg itself.

Workarounds:

For Version 1803 (build 17134), remove UIA name and value properties from properties to event ID's dictionary in UIA handler. This resolves this, although it raises the question as to which window is causing performance issues when firing name change and/or value change events.

In Insider Preview, use IUIAutomation6::CoalesceEvents (RS5, the flag must be set to 1/enabled).

Thanks.