[orca-list] Caret position loss in Firefox

[Nolan Darilek <nolan thewordnerd info>]

Frustrated at the lack of a decent accessible ebook reader under Linux 
(or at least, not knowing of a convenient one) I started writing 
something. I thought the best and most accessible choice would be 
browser-based, especially since it'd then work on all devices and platforms.

I have a proof of concept working, but under Linux the caret position is 
almost always lost. I'm wondering if anyone else can replicate? To do 
so, go here:

https://oasis.sandstorm.io/shared/yq8FdB-uE3iu53NmjkejPtZzJC2SdygtExM1ZMjlv6F

Don't worry about signing in, though you can if you like (Sandstorm is 
an incredible platform.) Click the "Clockwork Rocket" link. After a bit, 
you'll see a single-button toolbar followed by the book's HTML in an 
iframe. With Firefox caret mode enabled, scroll through the book, find a 
position and remember it.

If I alt-tab away from the window and return, I'm usually still at the 
position. If I switch to a different tab in Firefox, or a different 
Firefox window, my position in the book is almost always lost if I arrow 
around in the new tab. I can't pin down exactly what behaviors lose the 
position, but it always seems to pop back to the toolbar. I'm wondering 
if it has something to do with my use of an iframe? Similarly, if I use 
ctrl-f to find a phrase I remembered reading, the caret position doesn't 
seem to move to the text (or, at least, not accessibly.)

I spun up my Windows VM. In contrast, NVDA has yet to lose my position 
despite lots of reading and scrolling, switching away to other windows, 
etc. Find also works. So I suppose this could either be a Gecko issue 
with the Linux port, or something to do with Orca. Not sure which so I 
thought I'd post the question here first. I'm definitely not moving the 
caret in my app.

In any case, I'd love to get this working under Linux so I don't have to 
run ebook-convert and read all my books in Gedit. :) Similarly annoyed 
with using Windows/QRead just to read effectively.

A note about the Remove button: please don't be a troll and click it. 
Sandstorm secures unshared apps by default, and I hadn't expected to hit 
such a fundamental issue that'd require me to share this the day after I 
started using it. This is an app instance I deployed for testing, so all 
removing the book will do is make fixing this issue harder since I'll 
need to create a new one. Anyhow, just wanted to tack that on should 
anyone want to avail themselves of the "obvious" security issue. :)

Thanks for any help.