Hello friendly accessibility technology vendors and developers.
As of the Firefox 4 beta 5, the child windows associated with browser tabs have been removed thereby breaking the expectations of most windows screen readers. Regretfully, the timing of this change and the substantial impact it has on AT caught the Mozilla accessibility team by surprise. Unfortunately this change is a critical step in our browser's technical roadmap. The good news is that this issue was quickly discovered during our a recent beta cycle and now we can work together on a fix!
Let's fix this the right way. We probably shouldn't have AT relying on window classes to indicate where browser tabs are, however convenient it might have been years ago. I think, depending on how this per browser tab separation has been used in your code, we can provide an even better solution perhaps even allowing some hack removal on your side. We've very recently been in contact with most of the main AT vendors, and some have what sounds like a fix already in hand. We want to make sure we protect all our users from potential bustage, so we want to hear from all accessibility technology developers that use Windows accessibility API and have been relying on per browser tab window classes.
Something to look for... anywhere you have code checking for a specific window class "MozillaContentWindowClass" your code will almost certainly now be broken for FF4 beta5+. Note this class used to correspond to the HWND of the child content window that received focus whenever the top level window gained focus. To see how things look now I recommend Microsoft's UISpy tool. Be sure to run this against the most recent FF 4 beta or nightly.
We have time but must move swiftly. Please contact us directly or on our accessibility community mailing list.
Thanks for reading.