demm Don't. I'll rebuild all of Plasma on new Qt & rebuild frameworks. So far I tried to get away with just kwin, clearly not enough.
mendez I checked it anyway 😉 Yes, problem only with new Qt. And looks like just a problem with breeze dark, only.
demm Rebuild might not fix, already reported other places too, example https://bbs.archlinux.org/viewtopic.php?id=244988 But will do a full rebuild anyway, always better.
demm Rebuild did not fix, so I'm afraid it is an issue for breeze dark & new Qt 5.12.2, not a distro/build issue.
demm If you disable composting, issue is gone. Bug report is opened in KDE, please vote for it, so it gets the needed attention: https://bugs.kde.org/show_bug.cgi?id=405548
demm One more update, fix is in review https://phabricator.kde.org/D19821, I won't post any further here now, once the patch lands, plasma-framework will be rebuild.
bvbfan It looks correct patch, Qt's change https://code.qt.io/cgit/qt/qtsvg.git/commit/?h=5.12.2&id=dcc4e2c4d96a6ad1447b9fb679afca21bb381218
demm Patch is not correct/complete, only fixes kicker & notifications, not the tooltips, so not applying until the complete fix has landed in git.