:-moz-locale-dir(rtl) not work

Currently my extension does not include RTL localization, and I’m checking if it’s UI shows correctly in RTL environment.

I’ve installed the Hebrew language pack, changed general.useragent.locale to he, and had a restart to apply.

My extension’s dialogs show in English, with the RTL direction as expected. However, all CSS selectors that use :-moz-locale-dir(rtl) don’t work.

Is there any good practice for workaround?

Make sure that e10s is off, there are some problems with the content process and RTL.

https://bugzilla.mozilla.org/showdependencytree.cgi?id=1254277&hide_resolved=1 tracks the problems. Feel free to file more bugs if you think that your issue isn’t covered.