Use typed syntax in calls to QMetaObject::invokeMethod

We do it wherever possible. Some places can't be fixed
since they still rely on dynamic introspection
(mainly QQuickItem cases).

Change-Id: Ia00b4a04d8b995c9a43b7bf2dbe76a60364bb8ca
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/help/helpindexfilter.cpp

@@ -180,8 +180,8 @@ QList<LocatorFilterEntry> HelpIndexFilter::matchesFor(QFutureInterface<LocatorFi
 
     if (forceUpdate) {
         QStringList indices;
-        QMetaObject::invokeMethod(this, "allIndices", Qt::BlockingQueuedConnection,
-                                  Q_RETURN_ARG(QStringList, indices));
+        QMetaObject::invokeMethod(this, [this] { return allIndices(); },
+                                  Qt::BlockingQueuedConnection, &indices);
         m_mutex.lock(); // guard m_needsUpdate
         m_needsUpdate = false;
         m_mutex.unlock();

src/plugins/help/searchwidget.cpp

@@ -155,7 +155,7 @@ void SearchWidget::showEvent(QShowEvent *event)
         connect(searchEngine, &QHelpSearchEngine::indexingFinished, this,
             &SearchWidget::indexingFinished);
 
-        QMetaObject::invokeMethod(&LocalHelpManager::helpEngine(), "setupFinished",
+        QMetaObject::invokeMethod(&LocalHelpManager::helpEngine(), &QHelpEngine::setupFinished,
             Qt::QueuedConnection);
     }
 }