Added documentation for the queued _this->ensureWidgetVisible(TabWidget) call

Author: githubuser0xFFFF

src/DockAreaTabBar.cpp

@@ -108,6 +108,9 @@ void DockAreaTabBarPrivate::updateTabs()
 		{
 			TabWidget->show();
 			TabWidget->setActiveTab(true);
+			// Sometimes the synchronous calculation of the rectangular area fails
+			// Therefore we use QTimer::singleShot here to execute the call
+			// within the event loop - see #520
 			QTimer::singleShot(0, [&, TabWidget]{
 			    _this->ensureWidgetVisible(TabWidget);
 			});