Expose XdgPositioner to QtBase

class QPopupPosition
{
    QPopupPosition(QWindow *transientParent, QRect parentAnchorRect);    setTransientParent(QWindow *transientParent);
    setParentAnchorRect(const QRect &parentAnchorRect);    setParentAnchor(Qt::Edge anchorEdge);
    setClientAnchor(Qt::Edge anchorEdge); // this would be the inverse of gravity to be closer to Qt API   

    setConstaintHandling(Constraint); // flip, slide, resize    // offset?    

    // used by QMenu to either follow or ignore struts, write that this may have no effect on the platform blah blah
    setUseFullscreenForPopup(bool useFullScreen);
};

// add a method in QPlatformWindow (maybe surfaced in QWindow?)

QPlatformWindow::position(const QPopupPosition &popupPosition)
{
    setTransientParent(popupPosition.transientParent());    // position window (we can copy and paste all the kwin code's here)
    QPoint pos = ...
    move(pos);
}

QWaylandWindow::position(const QPopupPosition &popupPosition)
{
    // on wayland we would cache the positioning
    m_popupPosition = position;
    // then somehow expose this to XdgShellPopup in the show method
}