The rhiFlush() implementation currently assumes that
QWindow->devicePixelRatio() is the correct scale factor for
transforming device independent window geometry to source geometry.
However, this assumption does not hold if/when we add support
for drawing to a rounded-up DPR, with a downscale later in
the rhiFlush implementation.
Fix this by adding a sourceDevicePixelRatio argument to rhiFlush(),
which is set to either QWindow::devicePixelRatio() or
QWidget::devicePixelRatio(), depending on from where it is used.
Change deviceRect() and friends in qbackingstoredefualtcompositor.cpp
to be scale*() functions instead which take a scale factor instead
of a QWindow. Update call sites to use srouceDevicePixelRatio
where that makes sense.
Pick-to: 6.4
Change-Id: Idb7b1e2f36816a201e00f0defe100d2dc079cb17
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>
d38118c808