add a transientParent property

if this contextmenu is done from a Dialog, add this as transientParent

src/declarativeimports/plasmacomponents/qmenu.cpp

@@ -91,6 +91,21 @@ void QMenuProxy::setVisualParent(QObject *parent)
     emit visualParentChanged();
 }
 
+QWindow *QMenuProxy::transientParent()
+{
+    return m_menu->windowHandle()->transientParent();
+}
+
+void QMenuProxy::setTransientParent(QWindow *parent)
+{
+    if (parent == m_menu->windowHandle()->transientParent()) {
+        return;
+    }
+
+    m_menu->windowHandle()->setTransientParent(parent);
+    emit transientParentChanged();
+}
+
 bool QMenuProxy::event(QEvent *event)
 {
     switch (event->type()) {

src/declarativeimports/plasmacomponents/qmenu.h

@@ -35,6 +35,11 @@ class QMenuProxy : public QObject
     Q_PROPERTY(QQmlListProperty<QMenuItem> content READ content CONSTANT)
     Q_CLASSINFO("DefaultProperty", "content")
 
+    /**
+     * This is a hint to the window manager that this window is a dialog or pop-up on behalf of the given window.
+     */
+    Q_PROPERTY(QWindow *transientParent READ transientParent WRITE setTransientParent NOTIFY transientParentChanged)
+
     /**
      * the visualParent is used to position the menu. it can be an item on the scene, like a button (that will open the menu on clicked) or another menuitem (in this case this will be a submenu)
      */
@@ -53,6 +58,9 @@ public:
     QObject *visualParent() const;
     void setVisualParent(QObject *parent);
 
+    QWindow *transientParent();
+    void setTransientParent(QWindow *parent);
+
     Q_INVOKABLE void open(int x = 0, int y = 0);
     //Q_INVOKABLE void open();
     Q_INVOKABLE void close();
@@ -66,6 +74,7 @@ protected:
 Q_SIGNALS:
     void statusChanged();
     void visualParentChanged();
+    void transientParentChanged();
     void triggered(QMenuItem *item);
     void triggeredIndex(int index);