Neither vertical-tabs-rtl.css from core/misc or from Seven are recognized for RTL. Vertical tabs are not a module, its 2 stylesheets and 1 js file are at the top level of core/misc. The only other stylesheets at that location are print. The 2 stylesheets are overridden in Seven.

Dev tools show no vertical-tabs-rtl.css used while displaying RTL.
Screenshot is showing color red tested in Seven's vertical-tabs.css but not showing an override of color green tested in Seven's vertical-tabs-rtl.css (in addition to not rendering any of the RTL css).

no-rtl-css-vertical-tabs.png

test-vertical-tabs.png

test-vertical-tabs-rtl.png

CommentFileSizeAuthor
#1 source-rtl.png36.15 KBechoz
test-vertical-tabs-rtl.png9.71 KBechoz
test-vertical-tabs.png9.56 KBechoz
no-rtl-css-vertical-tabs.png66.24 KBechoz
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Comments

echoz’s picture

echoz CreditAttribution: echoz commented
FileSize
source-rtl.png36.15 KB

An oddity that is perhaps a clue, seven's vertical-tabs.css is called twice in the RTL source. Not so for any other stylesheet.

source-rtl.png

echoz’s picture

echoz CreditAttribution: echoz commented
Status: Active » Fixed

Resolved with #2015789: Remove language_css_alter() (RTL stylesheets) in favor of HTML 'dir' attribute !
Marking as fixed because I'm confident 2015789 is going through :-)

Automatically closed -- issue fixed for 2 weeks with no activity.