Ensure that QMenu is polished before setting the screen in popup()

Some styles alter the widget that will influence the underlying platform
window. An example is when a style would want to draw the menu with some
transparency and sets the Qt::WA_TranslucentBackground attribute. This
needs to happen before the platform window is created. However calling
QWidgetPrivate::setScreen will end up creating the window and the
surface format will be fixed at this point.

Pick-to: 5.15
Change-Id: I707cf1de5c1614382cffbea1aae8cdb01f7de44a
Reviewed-by: Nate Graham
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

src/widgets/widgets/qmenu.cpp

@@ -2373,6 +2373,8 @@ void QMenuPrivate::popup(const QPoint &p, QAction *atAction, PositionFunction po
     doChildEffects = true;
     updateLayoutDirection();
 
+    q->ensurePolished(); // Get the right font
+
     // Ensure that we get correct sizeHints by placing this window on the correct screen.
     // However if the QMenu was constructed with a Qt::Desktop widget as its parent,
     // then initialScreenIndex was set, so we should respect that for the lifetime of this menu.
@@ -2407,7 +2409,6 @@ void QMenuPrivate::popup(const QPoint &p, QAction *atAction, PositionFunction po
     q->setAttribute(Qt::WA_X11NetWmWindowTypeDropDownMenu, qobject_cast<QMenuBar *>(topCausedWidget()) != nullptr);
 #endif
 
-    q->ensurePolished(); // Get the right font
     emit q->aboutToShow();
     const bool actionListChanged = itemsDirty;