Update the cached DPR on QWindow update request

Follow-up from commit 299dfe which added a similar update
for expose events. This fixes missing DPR updates for
exposed windows.

Pick-to: 6.6
Change-Id: Ic1a9a41bd979270b97303abb71f1230bff001d19
Reviewed-by: Lorn Potter <lorn.potter@gmail.com>
(cherry picked from commit 041ca2a3a818955ebcbbc0acd164138ffd561a6c)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/src/gui/kernel/qplatformwindow.cpp b/src/gui/kernel/qplatformwindow.cpp
index 3baa48247b..5c0ae2ee2a 100644
--- a/src/gui/kernel/qplatformwindow.cpp
+++ b/src/gui/kernel/qplatformwindow.cpp
@@ -778,6 +778,15 @@ void QPlatformWindow::deliverUpdateRequest()
 
     QWindow *w = window();
     QWindowPrivate *wp = qt_window_private(w);
+
+    // We expect that the platform plugins send DevicePixelRatioChange events.
+    // As a fail-safe make a final check here to make sure the cached DPR value is
+    // always up to date before delivering the update request.
+    if (wp->updateDevicePixelRatio()) {
+        qWarning() << "The cached device pixel ratio value was stale on window update. "
+                   << "Please file a QTBUG which explains how to reproduce.";
+    }
+
     wp->updateRequestPending = false;
     QEvent request(QEvent::UpdateRequest);
     QCoreApplication::sendEvent(w, &request);