Since 5138fada0b9ce3968b23ec11df5f0d4e67544c43 HiDPI mode has rounding errors on expose events. When moving a window over a Qt applications window with HiDPI scaling, vertical and/or horizontal lines (borders from moved window) are visible (attached movies with scale 2.0 and 2.12). The bottom and/or right border of expose rectangle is not repainted due to rounding error.
Example - my idea what can be wrong:
|For Gerrit Dashboard: QTBUG-63943|
|210311,5||Fix QHighDpi::fromNativeLocalExposedRegion rounding errors||5.9||qt/qtbase||Status: MERGED||+2||0|