While working on the RevisionSlider and improving the mobile device support there [1][2], I stumbled over an issue with jQuery giving a wrong offsets when used with Chrome and scaled viewport. [3] This leads to misplaced tooltips since they rely on the offset() values.

Steps to reproduce:

• open some page with the RevisionSlider in Chrome on a touch device ( e.g. https://www.mediawiki.org/w/index.php?diff=2301969&oldid=2285787&title=MediaWiki&action=historysubmit&type=revision )
• click on a revision bar
• the tooltip should show below the bar pointing at it
• zoom in and click again on a bar
• you will see the tooltip somewhere or not at all and definitely not pointing at the bar :-)

Of cause this might affect also other things where $().offset() is used.

In my patch I fixed offset calculation at some other part where I needed it with the help of the workaround you find in the GitHub issue. [3]

[1] https://phabricator.wikimedia.org/T164249
[2] https://gerrit.wikimedia.org/r/#/c/351642/
[3] https://github.com/jquery/jquery/issues/3187