DockFocusController: Avoid using sender() for visibilityChanged()

Use Qt::SingleShotConnection connection instead and remove
disconnect.

Change-Id: If3ec082bb2341277bfeb781b13986492a88172e6
Reviewed-by: Henning Gründl <henning.gruendl@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

src/libs/advanceddockingsystem/dockfocuscontroller.cpp

@@ -158,24 +158,14 @@ void DockFocusControllerPrivate::updateDockWidgetFocus(DockWidget *dockWidget)
         emit m_dockManager->focusedDockWidgetChanged(old, dockWidget);
     } else {
         m_oldFocusedDockWidget = old;
-        QObject::connect(dockWidget,
+        QObject::connect(dockWidget, &DockWidget::visibilityChanged, q,
-                         &DockWidget::visibilityChanged,
+                         [this, dockWidget](bool visible) {
-                         q,
+            if (visible)
-                         &DockFocusController::onDockWidgetVisibilityChanged);
+                emit m_dockManager->focusedDockWidgetChanged(m_oldFocusedDockWidget, dockWidget);
+        }, Qt::SingleShotConnection);
     }
 }
 
-void DockFocusController::onDockWidgetVisibilityChanged(bool visible)
-{
-    auto dockWidget = qobject_cast<DockWidget *>(sender());
-    QObject::disconnect(dockWidget,
-                        &DockWidget::visibilityChanged,
-                        this,
-                        &DockFocusController::onDockWidgetVisibilityChanged);
-    if (dockWidget && visible)
-        emit d->m_dockManager->focusedDockWidgetChanged(d->m_oldFocusedDockWidget, dockWidget);
-}
-
 DockFocusController::DockFocusController(DockManager *dockManager)
     : QObject(dockManager)
     , d(new DockFocusControllerPrivate(this))

src/libs/advanceddockingsystem/dockfocuscontroller.h

@@ -30,7 +30,6 @@ private:
     void onFocusWindowChanged(QWindow *focusWindow);
     void onFocusedDockAreaViewToggled(bool open);
     void onStateRestored();
-    void onDockWidgetVisibilityChanged(bool visible);
 
 public:
     /**