Bugzilla

`spoof_english` has been a bit of a pain over the years and we've found a number of places where the app language is used in web content
- forms (default labels, input formats)
- [MediaDocument.properties](https://searchfox.org/mozilla-central/source/dom/locales/en-US/chrome/layout/MediaDocument.properties)
- [validation messages](https://searchfox.org/mozilla-central/source/dom/locales/en-US/chrome/dom/dom.properties)
- [XML errors](https://searchfox.org/mozilla-central/source/dom/locales/en-US/chrome/layout/xmlparser.properties)
- other XML - e.g. Bug 1954813, 
- intl.css - Bug 1534581 (also see attachment on https://bugzilla.mozilla.org/show_bug.cgi?id=1588797#c1)
- fonts e.g. Bug 1906643
- must be some more I've missed

And spoof_english needs to set `intl.accept_languages` and the locale, which in FF may still be problematic (in Tor Browser we found languages got in a stuck state due to a years old decision upstream, which I know hasn't been addressed - hard to find the issues right now)

Also, at some point, we would like to think we can replace `spoof_english` with `spoof_language` - i.e separate app and content fully now we know all the places they leak - i.e have a german interface, but request french content

Also, live language reload misses a few things and requires a restart (which we enforce in Tor Browser)

I'm not super savvy on BiDi and why/how it is used - but emulation with `spoof_english` (which also requires RFP to be enabled) isn't going to be perfect

ni piero for any further insights, items I've missed

`spoof_english` has been a bit of a pain over the years and we've found a number of places where the app language is used in web content
- click `[example]` on https://arkenfox.github.io/TZP/tests/elementforms.html
   - forms (default labels, sizes etc), input formats
- https://arkenfox.github.io/TZP/tests/applang.html
   - [MediaDocument.properties](https://searchfox.org/mozilla-central/source/dom/locales/en-US/chrome/layout/MediaDocument.properties)
   - [validation messages](https://searchfox.org/mozilla-central/source/dom/locales/en-US/chrome/dom/dom.properties)
     - including input formats
   - [XML errors](https://searchfox.org/mozilla-central/source/dom/locales/en-US/chrome/layout/xmlparser.properties)
   - other XML - e.g. Bug 1954813 
   - intl.css - Bug 1534581 (also see attachment on https://bugzilla.mozilla.org/show_bug.cgi?id=1588797#c1)
- fonts e.g. Bug 1906643
- must be some more I've missed

And spoof_english needs to set `intl.accept_languages` and the locale, which in FF may still be problematic (in Tor Browser we found languages got in a stuck state due to a years old decision upstream, which I know hasn't been addressed - hard to find the issues right now)

Also, at some point, we would like to think we can replace `spoof_english` with `spoof_language` - i.e separate app and content fully now we know all the places they leak - i.e have a german interface, but request french content

Also, live language reload misses a few things and requires a restart (which we enforce in Tor Browser)

I'm not super savvy on BiDi and why/how it is used - but emulation with `spoof_english` (which also requires RFP to be enabled) isn't going to be perfect

ni piero for any further insights, items I've missed