[webkit-dev] Accessibility Object Searching

[James Robinson]

On Wed, Jun 22, 2011 at 4:21 PM, Chris Fleizach <cfleizach at apple.com> wrote:

>
> On Jun 22, 2011, at 3:34 PM, Dominic Mazzoni wrote:
>
> > I just had another thought: how would this work in a multi-process
> browser?
> >
> > As you may know, Chrome runs an instance of webkit in a separate
> > renderer process for each tab, but the GUI and all accessibility
> > handling happens in the main browser process. Because accessibility
> > calls are synchronous, we cache accessibility information in the
> > browser process and respond to queries from that cache, rather than
> > sending an IPC to the renderer process and getting a response. I
> > realized that we wouldn't be able to use this search function very
> > easily as you've proposed it. If NSAccessibility gets such an API,
> > we'd have to write our own implementation that could run in Chrome's
> > browser process.
> >
>
> I think this is one drawback of Chrome's approach, the inability to
> retrieve dynamic information. I suspect Chrome has similar issues for the
> NSAccessibilityParameterizedAttribute attributes, and that it doesn't
> support the AXTextMarker APIs that Safari does for the same reason.
>
> To support this (along with the other things I mentioned) Chrome would need
> to synchronously called into WebCore, wait for the answer, and then return
> that information.
>

Assuming that the data is needed from the browser process (or UI process in
WebKit2 terminology) that's not acceptable from either a performance or bug
point of view.  In a multi-process browser, you can never let the browser
(or UI) process block on a synchronous message from the renderer (or web)
process.

- James



> > My understanding was that WebKit2 and Safari are moving to a
> > multi-process model as well. Is this design going to be compatible
> > with this?
> >
>
> Yes, WebKit2 works with accessibility. You'll be able to see the code to
> support that strewn throughout WebKit2. Let me know if you need more
> pointers.
>
> > - Dominic
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