Fix positioning of dynamically populated QToolButton::MenuButtonPopup's in screen corners

The existing code positioning the menu in
QToolButtonPrivate::popupTimerDone() had a clause checking
whether any receivers were connnected to QMenu::aboutToShow()
causing the sizeHint to be -1,-1 in that case (apparently
trying to accommodate menus populated in slots). In that
case, the checking for screen borders would not work, causing
the similar checks in QMenu::popup() to trigger, potentially
positioning the menu over the mouse.

To solve this dilemma, add a parameter taking a std::function
calulating the position of the menu from the sizeHint to
QMenuPrivate::exec()/popup() and invoke that in QMenuPrivate::popup()
after emitting QMenu::aboutToShow() when the sizeHint is known.

Fixes: QTBUG-78966
Change-Id: I180bd2dc7eadcaca6cadca13745ed4a2dd89e412
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

1 files changed, 6 insertions, 2 deletions

diff --git a/src/widgets/widgets/qmenu_p.h b/src/widgets/widgets/qmenu_p.h
index 7d2d0ab487..02fe9f31a1 100644
--- a/src/widgets/widgets/qmenu_p.h
+++ b/src/widgets/widgets/qmenu_p.h
@@ -64,6 +64,8 @@
 
 #include <qpa/qplatformmenu.h>
 
+#include <functional>
+
 QT_REQUIRE_CONFIG(menu);
 
 QT_BEGIN_NAMESPACE
@@ -302,6 +304,8 @@ class QMenuPrivate : public QWidgetPrivate
 {
     Q_DECLARE_PUBLIC(QMenu)
 public:
+    using PositionFunction = std::function<QPoint(const QSize &)>;
+
     QMenuPrivate() :
         itemsDirty(false),
         hasCheckableItems(false),
@@ -351,8 +355,8 @@ public:
     QRect popupGeometry(int screen) const;
     bool useFullScreenForPopup() const;
     int getLastVisibleAction() const;
-    void popup(const QPoint &p, QAction *atAction);
-    QAction *exec(const QPoint &p, QAction *action);
+    void popup(const QPoint &p, QAction *atAction, PositionFunction positionFunction = {});
+    QAction *exec(const QPoint &p, QAction *action, PositionFunction positionFunction = {});
 
     //selection
     static QMenu *mouseDown;