Fix menu size in multiscreen setups

During QMenuPrivate::popup() and QMenuBarPrivate::popupAction(),
QMenuPrivate::popupGeometry() is called from updateActionRects() with
screen = 0 several times (from sizeHint() and various event handlers
triggered), which causes it to return the primary screen geometry
always.

To fix this for the non-QGraphicsView case, use the screen of
the menu when it is visible or the screen stored in a newly introduced
popupScreen member variable, which is set from a few places
in QMenuPrivate::popup().

Fixes: QTBUG-118434
Pick-to: 6.7 6.6 6.5
Change-Id: I6b18593d313719d628b0856004197ac59f46c270
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/widgets/widgets/qmenu.cpp

@@ -292,6 +292,13 @@ inline bool QMenuPrivate::useFullScreenForPopup() const
 QRect QMenuPrivate::popupGeometry(QScreen *screen) const
 {
     Q_Q(const QMenu);
+    if (screen == nullptr
+#if QT_CONFIG(graphicsview)
+        && q->graphicsProxyWidget() == nullptr
+#endif
+        ) {
+        screen = q->isVisible() ? q->screen() : popupScreen.data();
+    }
     if (useFullScreenForPopup())
         return screen ? screen->geometry()
                       : QWidgetPrivate::screenGeometry(q);
@@ -2309,6 +2316,9 @@ void QMenu::popup(const QPoint &p, QAction *atAction)
 void QMenuPrivate::popup(const QPoint &p, QAction *atAction, PositionFunction positionFunction)
 {
     Q_Q(QMenu);
+    popupScreen = QGuiApplication::screenAt(p);
+    QScopeGuard popupScreenGuard([this](){ popupScreen.clear(); });
+
     if (scroll) { // reset scroll state from last popup
         if (scroll->scrollOffset)
             itemsDirty = 1; // sizeHint will be incorrect if there is previous scroll
@@ -2384,6 +2394,7 @@ void QMenuPrivate::popup(const QPoint &p, QAction *atAction, PositionFunction po
         pos = QPushButtonPrivate::get(causedButton)->adjustedMenuPosition();
     else
         pos = p;
+    popupScreen = QGuiApplication::screenAt(pos);
 
     const QSize menuSizeHint(q->sizeHint());
     QSize size = menuSizeHint;
@@ -2522,6 +2533,7 @@ void QMenuPrivate::popup(const QPoint &p, QAction *atAction, PositionFunction po
             }
         }
     }
+    popupScreen = QGuiApplication::screenAt(pos);
     q->setGeometry(QRect(pos, size));
 #if QT_CONFIG(effects)
     int hGuess = q->isRightToLeft() ? QEffects::LeftScroll : QEffects::RightScroll;

src/widgets/widgets/qmenu_p.h

@@ -473,6 +473,11 @@ public:
 
     mutable quint8 ncols = 0; // "255cols ought to be enough for anybody."
 
+    // Contains the screen of the popup point during popup(QPoint).
+    // This is to make sure the screen is remembered,
+    // when the menu contains many items on multiple screens
+    QPointer<QScreen> popupScreen;
+
     mutable bool itemsDirty : 1;
     mutable bool hasCheckableItems : 1;
     bool lastContextMenu : 1;

src/widgets/widgets/qmenubar.cpp

@@ -281,17 +281,21 @@ void QMenuBarPrivate::popupAction(QAction *action, bool activateFirst)
     if (action->isEnabled() && action->menu()->isEnabled()) {
         closePopupMode = 0;
         activeMenu = action->menu();
-        activeMenu->d_func()->causedPopup.widget = q;
+        auto *activeMenuPriv = activeMenu->d_func();
-        activeMenu->d_func()->causedPopup.action = action;
+        activeMenuPriv->causedPopup.widget = q;
+        activeMenuPriv->causedPopup.action = action;
 
         QRect adjustedActionRect = actionRect(action);
         QPoint pos(q->mapToGlobal(QPoint(adjustedActionRect.left(), adjustedActionRect.bottom() + 1)));
-        QSize popup_size = activeMenu->sizeHint();
         //we put the popup menu on the screen containing the bottom-center of the action rect
         QScreen *menubarScreen = q->window()->windowHandle()->screen();
-        QScreen *popupScreen = menubarScreen->virtualSiblingAt(pos + QPoint(adjustedActionRect.width() / 2, 0));
+        QPointer<QScreen> popupScreen = menubarScreen->virtualSiblingAt(pos + QPoint(adjustedActionRect.width() / 2, 0));
         if (!popupScreen)
             popupScreen = menubarScreen;
+        std::swap(popupScreen, activeMenuPriv->popupScreen);
+        const QSize popup_size = activeMenu->sizeHint();
+        std::swap(popupScreen, activeMenuPriv->popupScreen);
+
         QRect screenRect = popupScreen->geometry();
         pos = QPoint(qMax(pos.x(), screenRect.x()), qMax(pos.y(), screenRect.y()));
         const bool fitUp = (pos.y() - popup_size.height() >= screenRect.top());