Make rhiFlush() support custom source DPR

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>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/gui/painting/qrhibackingstore.cpp b/src/gui/painting/qrhibackingstore.cpp
index 71b5ccf6cf..fd7045e3f6 100644
--- a/src/gui/painting/qrhibackingstore.cpp
+++ b/src/gui/painting/qrhibackingstore.cpp
@@ -40,7 +40,7 @@ void QRhiBackingStore::flush(QWindow *window, const QRegion &region, const QPoin
 
     static QPlatformTextureList emptyTextureList;
     bool translucentBackground = m_image.hasAlphaChannel();
-    rhiFlush(window, region, offset, &emptyTextureList, translucentBackground);
+    rhiFlush(window, window->devicePixelRatio(), region, offset, &emptyTextureList, translucentBackground);
 }
 
 QT_END_NAMESPACE