TL;DR: We believe this ticket isn't about a single issue but an unfortunate mixture of a (new?) browser bug, a skin that didn't exist when RevisionSlider was created, and several fragile pieces of code in RevisionSlider that respond poorly to said browser bug and some of the new features the skin introduced. You can find many more details in the linked Gerrit patches.
Steps to reproduce:
Early tests made it look like this is related to the pinned tools menu on the left. Just collapsing all menus made RevisionSlider work again.
At least on hewiki the TOC in the sidebar seems to be expanded by default, which means the issue is potentially visible to all anonymous users on hewiki.
Later tests showed that parts of the issue can only be reproduced when the browser zoom is >100%. But not all zoom factors are affected (see https://gerrit.wikimedia.org/r/1007329 for details). The issue is known but appears to have a very low chance of ever being fixed, see https://issues.chromium.org/issues/41417874 and the underlying issue https://issues.chromium.org/issues/40384509 .
Screen width seems to play a role as well. A page with only a few revisions doesn't have problems. No problem on very large screens. When you zoom in or make the browser window more narrow the issue is much easier to reproduce.
Reported here: https://www.mediawiki.org/wiki/Topic:Xuaj7i4ajtzj3pem
Change 978498 had a related patch set uploaded (by Thiemo Kreuz (WMDE); author: Thiemo Kreuz (WMDE)):
[mediawiki/extensions/RevisionSlider@master] Add fail-safe to SliderView.revisionsClickHandler
https://gerrit.wikimedia.org/r/978498
Change 978498 merged by jenkins-bot:
Change 993217 had a related patch set uploaded (by Thiemo Kreuz (WMDE); author: Thiemo Kreuz (WMDE)):
[mediawiki/extensions/RevisionSlider@master] Merge large chunk of code duplication in SliderArrowView
https://gerrit.wikimedia.org/r/993217
Change 994186 had a related patch set uploaded (by Thiemo Kreuz (WMDE); author: Thiemo Kreuz (WMDE)):
[mediawiki/extensions/RevisionSlider@master] Merge a small piece of code duplication in SliderView
https://gerrit.wikimedia.org/r/994186
Change 994186 merged by jenkins-bot:
Change 993217 merged by jenkins-bot:
Change 998468 had a related patch set uploaded (by Thiemo Kreuz (WMDE); author: Thiemo Kreuz (WMDE)):
[mediawiki/extensions/RevisionSlider@master] Drop obsolete special case for Google Chrome before version 60
https://gerrit.wikimedia.org/r/998468
Change 998468 merged by jenkins-bot:
Change 999620 had a related patch set uploaded (by Thiemo Kreuz (WMDE); author: Thiemo Kreuz (WMDE)):
[mediawiki/extensions/RevisionSlider@master] Fix rounding error in revisionsPerWindow calculation
https://gerrit.wikimedia.org/r/999620
Change 999620 merged by jenkins-bot:
Change 999772 had a related patch set uploaded (by Thiemo Kreuz (WMDE); author: Thiemo Kreuz (WMDE)):
[mediawiki/extensions/RevisionSlider@master] Use existing data-pos attribute instead of pixel calculations
https://gerrit.wikimedia.org/r/999772
Change 999772 merged by jenkins-bot:
Change 1005773 had a related patch set uploaded (by WMDE-Fisch; author: WMDE-Fisch):
[mediawiki/extensions/RevisionSlider@master] Pass through pointer events from pointer-containers
https://gerrit.wikimedia.org/r/1005773
Change 1005773 merged by jenkins-bot:
Change 1007329 had a related patch set uploaded (by Thiemo Kreuz (WMDE); author: Thiemo Kreuz (WMDE)):
[mediawiki/extensions/RevisionSlider@master] Work around rounding errors in RTL scroll type detection
https://gerrit.wikimedia.org/r/1007329
Change 1007329 merged by jenkins-bot:
Change 1010589 had a related patch set uploaded (by Thiemo Kreuz (WMDE); author: Thiemo Kreuz (WMDE)):
[mediawiki/extensions/RevisionSlider@master] Drop RTL scroll type detection, obsolete since 2023
https://gerrit.wikimedia.org/r/1010589
Quick proposal for the TechNews:
Is this ok, @JStrodt_WMDE ?
Change #1010589 merged by jenkins-bot: