QMessageBox: don't use a native dialog if a style sheet is active

With 6.5 we try to use the native message dialog if we can, but we
didn't account for the style sheet. This restores pre-6.5 behavior for
QMessageBox.

Other dialogs will continue to be native, even if a style sheet is in
use. While this is inconsistent, the other dialogs are substantially
more functional, so switching to the Qt version because of a style sheet
being active would be a significant change of behavior.

Fixes: QTBUG-120054
Change-Id: I07eae609bc360140e096c5eb7ad004ffa4422123
Reviewed-by: Oliver Eftevaag <[email protected]>
Reviewed-by: Tor Arne Vestbø <[email protected]>
(cherry picked from commit 1b71e2d894c2be7052518cdcb96020c9950e2dc7)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>
(cherry picked from commit 3158aa546d3a8e0430f079e0d8b2da0f330628d1)
(cherry picked from commit 04dda6cae05109ad5a3a681587ec9cd2cc49028a)
Reviewed-by: Volker Hilsheimer <[email protected]>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/widgets/dialogs/qmessagebox.cpp b/src/widgets/dialogs/qmessagebox.cpp
index 9f1a92145c3..46a6e871b14 100644
--- a/src/widgets/dialogs/qmessagebox.cpp
+++ b/src/widgets/dialogs/qmessagebox.cpp
@@ -2720,7 +2720,8 @@ bool QMessageBoxPrivate::canBeNativeDialog() const
     if (nativeDialogInUse)
         return true;
     if (QCoreApplication::testAttribute(Qt::AA_DontUseNativeDialogs)
-        || q->testAttribute(Qt::WA_DontShowOnScreen)) {
+        || q->testAttribute(Qt::WA_DontShowOnScreen)
+        || q->testAttribute(Qt::WA_StyleSheet)) {
         return false;
     }