1461237 - RPC crashes caused by UI Automation

Status: RESOLVED WORKSFORME

(Core :: Disability Access APIs, defect, P2)

Description

[James Teh [:Jamie]]

Spun off bug 1424505 comment 108, as the immediate crisis has been dealt with and that bug is becoming unwieldy.

UI Automation seems to be causing intermittent RPC crashes for certain clients on Windows 7. This was particularly nasty for Sticky Password after accFocus for remote content (bug 1421144) landed. After months of failing to make any headway in debugging this, we eventually disabled accFocus for remote content for Windows 7 altogether:
https://hg.mozilla.org/mozilla-central/rev/68bfd841265f
Even with this workaround, we still see a small number of these crashes.

I'm still not able to reproduce this. We've now established contact with Sticky Password, so I'm hoping they might be able to provide some details about their use of UI Automation that might give us some further ideas on what might have been triggering this.

Comment 1

[Trevor Skywalker]

(In reply to James Teh [:Jamie] from comment #0)
> Spun off bug 1424505 comment 108, as the immediate crisis has been dealt
> with and that bug is becoming unwieldy.
> 
> UI Automation seems to be causing intermittent RPC crashes for certain
> clients on Windows 7. This was particularly nasty for Sticky Password after
> accFocus for remote content (bug 1421144) landed. After months of failing to
> make any headway in debugging this, we eventually disabled accFocus for
> remote content for Windows 7 altogether:
> https://hg.mozilla.org/mozilla-central/rev/68bfd841265f
> Even with this workaround, we still see a small number of these crashes.
> 
> I'm still not able to reproduce this. We've now established contact with
> Sticky Password, so I'm hoping they might be able to provide some details
> about their use of UI Automation that might give us some further ideas on
> what might have been triggering this.

What are the practical implications of disabling accFocus for remote content (in layman's terms)? How would this impact the user? Would many users be affected? 

Will an explanation of this change be published in the release notes for end-users?

https://www.mozilla.org/en-US/firefox/60.0/releasenotes/

Is this "fix" (disabling a feature) expected to be a temporary workaround or a permanent "solution"? 

Thanks

Comment 2

[James Teh [:Jamie]]

(In reply to Trevor Skywalker from comment #1)
> What are the practical implications of disabling accFocus for remote content
> (in layman's terms)? How would this impact the user? Would many users be
> affected? 

This affects third party products which need to programmatically query for information about the focus on demand. It's difficult to know all practical effects this will have on users because we don't have full visibility into what third party products use this functionality and when they use it. The original reason for fixing this bug was that without the fix, the NVDA screen reader will not report focus correctly if the user opens the system menu and then dismisses it. While this is annoying, I expect users would not have cause to do this often, and when they do it, the workaround is trivial (just move focus again).

> Will an explanation of this change be published in the release notes for
> end-users?

There are no plans to document this in the release notes. I don't think this will make sense to the majority of users, and given the limited occurrences in which users will encounter this, I expect it to be mostly ignored. Also given the low number of instances, I think we can deal with any queries regarding this.

> Is this "fix" (disabling a feature) expected to be a temporary workaround or
> a permanent "solution"? 

Ideally, a temporary workaround. In practice, I think it might end up being permanent because we have no idea what's causing this and it may in fact be a bug in Windows itself. And if the latter is true,  because it's Windows 7, Microsoft aren't going to fix it.

Comment 3

[James Teh [:Jamie]]

This should be resolved by Cache the World, which is enabled by default in Firefox 113.