sg: Fix dpr when grabbing a not-yet-shown QQuickWindowHEADdev

The scenegraph is not initialized when the window has not been
exposed yet, and calling QQuickWindow::grabWindow() takes a whole
different code path in this case. This was not communicating a
scale factor to the renderer at all.

Pick-to: 6.10 6.9 6.8 6.5
Fixes: QTBUG-116675
Change-Id: I73b21dfd06a04dbdc2ff3cb1a17bbe0364ca0624
Reviewed-by: Tor Arne Vestbø <[email protected]>

1 files changed, 5 insertions, 1 deletions

diff --git a/src/quick/scenegraph/qsgrhisupport.cpp b/src/quick/scenegraph/qsgrhisupport.cpp
index 6e773b4c32..fa325f8b3e 100644
--- a/src/quick/scenegraph/qsgrhisupport.cpp
+++ b/src/quick/scenegraph/qsgrhisupport.cpp
@@ -1393,7 +1393,11 @@ QImage QSGRhiSupport::grabOffscreen(QQuickWindow *window)
 
     // There was no rendercontrol which means a custom render target
     // should not be set either. Set our own, temporarily.
-    window->setRenderTarget(QQuickRenderTarget::fromRhiRenderTarget(rt.data()));
+    auto renderTarget = QQuickRenderTarget::fromRhiRenderTarget(rt.data());
+    // Pass on the scale factor. No need to use effectiveDevicePixelRatio(),
+    // because there is no rendercontrol anyway.
+    renderTarget.setDevicePixelRatio(window->devicePixelRatio());
+    window->setRenderTarget(renderTarget);
 
     QRhiCommandBuffer *cb = nullptr;
     if (rhi->beginOffscreenFrame(&cb) != QRhi::FrameOpSuccess) {