Round the cell width to avoid getting blurry previews.
In general it's best to use floor rather than round for this kind of thing to prevent everything from getting rounded up and potentially overflowing the bounds.
Looks like you cherry-picked the commit onto each branch, is that right? In general it's preferred to land the commit onto the oldest branch and then merge forward. See https://community.kde.org/Infrastructure/Phabricator#Landing_on_the_.22Stable_branch.22
I can help with this in the future. It can be tricky.