Bugzilla

(In reply to James Teh [:Jamie] from comment #9)
> Technical speculation: Perhaps the UIA -> IA2 proxy makes things worse for us here?

It does appear that way. The profile shows that the proxy queries whether an element is a control element, and for some reason, that wants to get the LiveSetting property (live region). Why should whether an element is a live region impact whether it is a control element? Anyway, in IA2, that means fetching object attributes, which isn't super fast if called on every node (3 sec in the profile)... plus the way the proxy processes the attributes seems *very* slow (11 sec of the profile) involving regexp parsing and other stuff. The IA2 proxy is unlikely to get any attention from Microsoft in future, so a native UIA implementation is probably the only sustainable path forward here.

(In reply to James Teh [:Jamie] from comment #9)
> Technical speculation: Perhaps the UIA -> IA2 proxy makes things worse for us here?

It does appear that way. The profile shows that the proxy queries whether an element is a control element, and for some reason, that wants to get the LiveSetting property (live region). Why should whether an element is a live region impact whether it is a control element? Anyway, in IA2, that means fetching object attributes, which isn't super fast if called on every node (3 sec in the profile)... plus the way the proxy processes the attributes seems *very* slow (11 sec of the profile) involving regexp parsing and other stuff. The IA2 proxy is unlikely to get any attention from Microsoft in future, so a native UIA implementation is probably the only sustainable path forward here.

> We could consider blocking this tool in the short term,

Our UIA instantiator detection fails to detect this as per the support info in comment 10. Edge seems to be able to detect it, though. I reached out to Microsoft last week to ask how we can properly detect UIA clients. If that proves fruitful, blocking seems like a possible short term solution.