Custom screen access

Christian Comaschi

I'm asking a question that might be a little off topic because I'm not planning to develop anything for NVDA at the moment; but I'm working on an accessibility project and I'd like to know more about screen readers internals, and I think that someone here can help me find the info I need.
I'm writing custom code to improve the accessibility of an open source application (Plover), because common screen reader scripts and app modules alone don't allow me to bring it to the needed accessiblity requirements.
The problem is that at some point I need to read text from editable controls of any application in a "screen reader"-like manner, so I would like to know how screen readers can get the caret position and read the text of an editable control and the different approach of JAWS and NVDA.
I'm asking you the details of this functionality because I am trying to figure out if it could be a viable solution to read text from the screen in a "screen-reader like" manner with an approach that is valid for almost every application, or if it'stoo complex because it would require re-inventing a screen driver from scratch or re-inventing scripts for common application. In this latter case, I would consider a less stand-alone approach and make the application work in tandem with JAWS or NVDA.

After some analysis I have come to a conclusion and I would like to know if it's righgt:
- NVDA has no generic way to "read" the text given a screen position, but there are scripts for the most common applications that provide this information to the main module using the most proper technique for the single application (Win32 API, MSAA, UIA or other means);
- JAWS seems to have generic functions such as "SayLine", "SayRow" or "SaySentence" that work for most of the applications because of its video intercept driver.

As a first try, I wrote some small scripts to use just UIA to read the text and caret position inside Notepad or Winword, but it didn't work; I also tried to use the inspect tool from Microsoft, meant to analyze the windows of any application to get accessibility info, but even that tool wasn't able to get the caret position inside the edit windows.
Am I missing something or is it really that complex?
Thanks in advance

Join to automatically receive all group messages.