MozillaCompoundTextInfo fails reading text when switching text direction in FireFox and Thunderbird

[LeonarddeR]

Steps to reproduce:

1. Open Firefox
2. On the address bar, type: data:text/html, <textarea />
3. In the text area, type: The first hebrew letter is א, the second is ב.
4. Use up and down arrows to move through the text.

Actual behavior:

NVDA fails to read the hebrew characters.

Expected behavior:

NVDA reads the text as provided, including Hebrew characters.

System configuration

NVDA installed/portable/running from source:

Installed

NVDA version:

alpha-31948,fdc3e9e6

Windows version:

Windows 11 23H2

Name and version of other software in use when reproducing the issue:

Firefox 126

Other information about your system:

Note that when trying to reproduce this in Edge/Chromium, this issue does not occur. I wonder whether this is an issue in Firefox.

Other questions

Does the issue still occur after restarting your computer?

Yes

Have you tried any other versions of NVDA? If so, please report their behaviors.

No

If NVDA add-ons are disabled, is your problem still occurring?

Yes

Does the issue still occur after you run the COM Registration Fixing Tool in NVDA's tools menu?

N/a

[LeonarddeR]

@jcsteh Given this issue seems to be Firefox specific, do you think this might be a Firefox issue? You know the CompoundTextInfo stuff much better than I do.
If it is FF related, happy to file an issue there.
Note that I'll try to dig on and give some more technical background later today.

[LeonarddeR]

AH, this is definitely an issue in Firefox/Gecko. The IAccessibleText object treats the RTL parts as single lines in the text.

[LeonarddeR]

Filed https://bugzilla.mozilla.org/show_bug.cgi?id=1897597

[LeonarddeR]

Thanks to @jcsteh picking this up so quickly, this is now fixed starting from FF128.