QMenu size fix - Mark items dirty on screen change

It seems like an optimization on the itemsDirty flag
caused a bug to be re-introduced. When a popup is shown
on a new screen, the itemsDirty must however be set to
ensure that new correct sizes are calculated.

Task-number: QTBUG-59794
Change-Id: Ifb5c233b1f9d4d38bd0cd7a9a71cc32ad3212f8c
Reviewed-by: Morten Kristensen <msk@nullpointer.dk>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>
Reviewed-by: Christian Ehrlicher <ch.ehrlicher@gmx.de>

src/widgets/kernel/qwidget.cpp

@@ -2580,14 +2580,15 @@ void QWidgetPrivate::createWinId()
 /*!
 \internal
 Ensures that the widget is set on the screen point is on. This is handy getting a correct
-size hint before a resize in e.g QMenu and QToolTip
+size hint before a resize in e.g QMenu and QToolTip.
+Returns if the screen was changed.
 */
 
-void QWidgetPrivate::setScreenForPoint(const QPoint &pos)
+bool QWidgetPrivate::setScreenForPoint(const QPoint &pos)
 {
     Q_Q(QWidget);
     if (!q->isWindow())
-        return;
+        return false;
     // Find the screen for pos and make the widget undertand it is on that screen.
     const QScreen *currentScreen = windowHandle() ? windowHandle()->screen() : nullptr;
     QScreen *actualScreen = QGuiApplication::screenAt(pos);
@@ -2596,7 +2597,9 @@ void QWidgetPrivate::setScreenForPoint(const QPoint &pos)
             createWinId();
         if (windowHandle())
             windowHandle()->setScreen(actualScreen);
+        return true;
     }
+    return false;
 }
 
 /*!

src/widgets/kernel/qwidget_p.h

@@ -355,7 +355,7 @@ public:
     void createRecursively();
     void createWinId();
 
-    void setScreenForPoint(const QPoint &pos);
+    bool setScreenForPoint(const QPoint &pos);
 
     void createTLExtra();
     void createExtra();

src/widgets/widgets/qmenu.cpp

@@ -73,6 +73,7 @@
 #endif
 #include "qpushbutton.h"
 #include "qtooltip.h"
+#include <qwindow.h>
 #include <private/qpushbutton_p.h>
 #include <private/qaction_p.h>
 #include <private/qguiapplication_p.h>
@@ -2356,8 +2357,10 @@ void QMenu::popup(const QPoint &p, QAction *atAction)
     d->motions = 0;
     d->doChildEffects = true;
     d->updateLayoutDirection();
-    // Ensure that we get correct sizeHints by placing this window on the right screen.
-    d->setScreenForPoint(p);
+
+    // Ensure that we get correct sizeHints by placing this window on the correct screen.
+    if (d->setScreenForPoint(p))
+        d->itemsDirty = true;
 
     const bool contextMenu = d->isContextMenu();
     if (d->lastContextMenu != contextMenu) {