[orca-list] Getting notified on scrolling

[Cornelius MÃller <cornimueller googlemail com>]

Dear list,

I want to have a program which captures user actions and especially the
text which is currently on screen (to later use these data for user
adaptive systems).
Current approaches are something like making a video capture of the
screen and then using OCR to get the text, but this is obviously quite
slow and inaccurate.
So I thought using the AT-SPI for this task instead would be a good
idea. And that it would be even easier if I work on this by modifying
Orca as Orca already has many useful features (like keeping track of the
user actions and focus changes, or the Flat Review feature).
But after some reading into Orca and the AT-SPI I'm kind of stuck, which
leads me to the question:

Is it possible to keep track of the scrolling a user does in a scroll pane?
I tried it and none of the events (object:children-changed,
object:state-changed, ...) seems to get fired. Did I oversee the event
which is responsible for scrolling?
Or is there any other possibility to be notified when the user scrolls?

This is important as I only want to capture the text which is currently
on screen, not the other text. And as this changes, I need to be
informed of changes - constantly doing something like the Flat Review
would be to slow.

Thanks
Cornelius