QGraphicsView enables autoFillBackground on the viewport widget, so
the dirty area is cleared before repaint. Then QGraphicsView fills the
same area with the background color. However, under fractional DPR
scaling, the scaled version of the dirty rect may end up covering only
a fractional part of the pixels on the edges. If antialising is
enabled, such pixels will be only partially filled with the background
color, leaving the clear color partially visible as glitches. This can
be seen in the dragdroprobot example.
Fix by disabling AA during background filling, as it has no purpose
then anyway.
Task-number: QTBUG-96223
Pick-to: 6.3 6.2 5.15
Change-Id: Ica00997141701faa0cf368caced84ae50ba017d0
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
6963190581