Pass TRANSIENT_INACTIVE flag for windows with WA_ShowWithoutActivating

When setting a transient window also evaluate the state of the window
attribute WA_ShowWithoutActivating. If that flag is set the transient
should get the inactive flag as well.

Task-number: QTBUG-55403
Change-Id: I757e5527e78f730a440e26abb52e84c9b2bb2f3a
Reviewed-by: Johan Helsing <johan.helsing@qt.io>
Reviewed-by: Giulio Camuffo <giulio.camuffo@kdab.com>

src/client/qwaylandwlshellsurface.cpp

@@ -151,6 +151,13 @@ void QWaylandWlShellSurface::setTopLevel()
     set_toplevel();
 }
 
+static inline bool testShowWithoutActivating(const QWindow *window)
+{
+    // QWidget-attribute Qt::WA_ShowWithoutActivating.
+    const QVariant showWithoutActivating = window->property("_q_showWithoutActivating");
+    return showWithoutActivating.isValid() && showWithoutActivating.toBool();
+}
+
 void QWaylandWlShellSurface::updateTransientParent(QWindow *parent)
 {
     QWaylandWindow *parent_wayland_window = static_cast<QWaylandWindow *>(parent->handle());
@@ -168,7 +175,8 @@ void QWaylandWlShellSurface::updateTransientParent(QWindow *parent)
     uint32_t flags = 0;
     Qt::WindowFlags wf = m_window->window()->flags();
     if (wf.testFlag(Qt::ToolTip)
-            || wf.testFlag(Qt::WindowTransparentForInput))
+            || wf.testFlag(Qt::WindowTransparentForInput)
+            || testShowWithoutActivating(m_window->window()))
         flags |= WL_SHELL_SURFACE_TRANSIENT_INACTIVE;
 
     set_transient(parent_wayland_window->object(),