Misbehavior of clipping done for ::paintEvent with hi-dpi fractional scaling

Given some fractional scaling, the clipping that is done internally for the paintEvent to the passed QRegion/QRect seems to not handle fractional scaled cases well.

For Hi-DPI and scalings like 1.5 I get rendering artifacts in e.g. Konsole because at the "borders" of the clipped regions pixels are missed to be drawn.

More details see

https://bugreports.qt.io/browse/QTBUG-66036?focusedCommentId=479439&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-479439

and

https://bugreports.qt.io/browse/QTBUG-66036?focusedCommentId=479440&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-479440

I traced that back to the internal transformation to device pixels, I think here some rounding happens into the wrong direction leading to too small clipping regions.

This is similar in the effect like https://bugreports.qt.io/browse/QTBUG-78962
but I see no workaround for this, as this is an internal behavior.