[nvda] Re: Audacity problem

Gene wrote:
> While I knew in the past that lack of video hooks imposes
limitations in what screen-readers can do, I didn't know much about what these are. My question is, why can a screen-reader without video hooks see text in programs like Notepad, Wordpad, etc. and yet not see text as displayed by Audacity as we have been discussing.
There is no standard way to track the cursor in edit fields using MSAA and thus edit fields are not really accessible using MSAA. If NVDA was using only MSAA, Notepad and Wordpad would therefore be quite inaccessible. Fortunately, there are other APIs we can use to access the information in edit fields. Windows includes standard COM APIs and window messages for most native controls which allows both Windows itself and other software to access this information. They are not designed specifically for accessibility like MSAA or IAccessible 2, but it is quite rich and works very nicely. There are similar methods for gathering information from most controls, but some non-standard controls do not honour those APIs. We only use MSAA for radio buttons and check boxes, so it's difficult to say whether these APIs might be useable there. Note that Peter has committed some code in the latest svn revision which might help reading some of those controls in Audacity.
Another question is whether it makes sense for me to report the kind of problem I found with Audacity if I find something similar elsewhere. Is this just unnecessary information since the lack of video hooks is, evidently likely, the explanation for such problems or is it better to report further cases so they can be definitely determined to be video hook limitations or something else.
When it is related to not being able to read information in a control which looks like it could be standard (e.g. a radio button, a button, a check box, etc.), it is possible that there is a solution. The control may allow us to access the information using some standard API. However, if it is a pretty non-standard control, chances are that the developers have not bothered to expose the information using any API we can use. It is difficult to give an answer to this question; I think you will find you start to get an idea of which situation you are facing as you find more of these issues and see the responses. For now, I would post them, but be prepared to be disappointed. :) 

Jamie
Hope this all helps.


--
James Teh
Email: jamie@xxxxxxxxxxx
WWW: http://www.jantrid.net/
MSN Messenger: jamie@xxxxxxxxxxx
Jabber: jteh@xxxxxxxxxx
Yahoo: jcs_teh
To post messages to the list send email to
nvda@xxxxxxxxxxxxx
To modify your NVDA Email settings go to:
http://www.freelists.org/list/nvda
Thank you for your continued support of Nonvisual Desktop Access, an open 
source free screen reader for Microsoft Windows:
http://www.nvda-project.org/
To get the latest NVDA snapshot:
http://www.nvda-project.org/snapshots/
Report bugs or make feature requests at:
http://trac.nvda-project.org/
Message Archive:
http://www.freelists.org/archives/nvda

Other related posts: