[nvda] Re: A few questions

  • From: James Teh <jamie@xxxxxxxxxxx>
  • To: nvda@xxxxxxxxxxxxx
  • Date: Fri, 20 Feb 2009 20:45:07 +1000

On 18/02/2009 11:05 AM, kendell clark wrote:
NVDA freezes and stops
performing completely when CPU usage is particularly heavy.
Remember that NVDA is an application process just like any other on the system. If something is chewing a lot of CPU cycles, NVDA's response will become extremely sluggish. Having said that...
when processing audio files in audacity I have to kill the NVDA
process and then restart it, and even then it takes about half an hour
before NVDA will start performing again.
Generally, high CPU usage will just cause NVDA to run very slowly indeed. This is true for any screen reader. However, in certain cases, NVDA seems to be completely unresponsive, acting more like it is frozen than just slow. I suspect this relates to it getting stuck on queries it is making to the offending process (Audacity in this case) which, because it is busy, are not answered until far later than they should be. I'm not sure if we can do much to work around this, but I do notice that some cases are different across screen readers, so perhaps there are ways to work around it. In some cases, it could be due to the way NVDA is designed, which is quite different to most commercial screen readers. (In technical terms, we work out of process.) However, I don't really see why this should be the case in Audacity. To be honest, I don't really know what causes this freeze like behaviour.

sometimes when starting NVDA, or when switching from
applications NVDA seemingly randomly reports, "remote key wnd pane, lost
I think this relates to the fact that when starting an application with a shortcut key, Windows sometimes fires focus to some very strange places. Is this a hgue problem for you or just a curiosity?

I've noticed that when
opening new applications, NVDA takes a few seconds to respond after the
new application window opens, and sometimes it does not respond at all.
Do you mean it freezes? I haven't experienced this.
I would assume this is because jaws has video intercept and can
detect when a window opens
No. The video intercept only helps to read text and graphics which are not otherwise accessible, but it does not allow for the detection of focus, etc.

I used to use jaws so when an
application opened it would say, For example, "AVG antivirus window:
Real-time protection is enabled... ect."
The video intercept allows JAWS to read some text that we cannot, but NVDA should at least say "pane" or similar. In other words, we detect the focus change, but might not be able to read the text.

in order for NVDA to read this, I have to use object navigation to read
this, and most of the time I cannot find it, even using previous, next
and current flow.
This is probably because it is not accessible using APIs like MSAA< so display information would be needed.

Where object navigation can find text, it is possible to have it read, but the tricky part is determining what should be read automatically. For example, in dialogs, we have some code which tries to intelligently figure out what text it should read from the dialog. It's a fine balance between reading too much information and not reading enough. Perhaps provide some specific examples of what information you think should be read automatically in what applications and why, and we might be able to see what we can do.

James Teh
Email/MSN Messenger/Jabber: jamie@xxxxxxxxxxx
Web site: http://www.jantrid.net/
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