Please provide screenshots, steps to reproduce, etc. This will help others understand this issue better.

1. Install MediaWiki
2. Install ULS
3. Install TwnMainPage
4. Set $wgULSPosition='interlanguage'
5. Go to the main page
6. Click language selector at top right (in ltr)

Observed: language selector is partially out of the screen.

Created attachment 12284
Before click

Attached:

Created attachment 12285
After click (in English!)

Attached:

Thanks. Tipsy also behaves a bit weird in attachment 12284, top right. Maybe report that separately.

This is actually a ULS positioning issue, so component should probably be changed to ULS, as this cannot be resolved in extension TwnMainPage.

Yes I originally filed against ULS, as it is a regression with the new position parameter.

The problem is that the trigger we have on the main page acts as the main trigger - its behavior is governed by the position configuration.

It is not yet clear to me which extension we need to change, or even both.

Added a hacky fix in https://gerrit.wikimedia.org/r/#/c/65967/