The method traversed QDockAreaLayoutInfo::item_list, to identify dock widgets tabbed with the QDockWidget argument in a tab bar It relied on bool QDockAreLayoutInfo::tabbed, which is set to true, when a QMainWindowTabBar is to be added to a QDockAreaLayoutInfo. This flag isn't cleared, when the second last dock widget is removed from the tab bar. It can't be replaced by QMainWindowLayout::isDockWidgetTabbed, because the flag also represents intermediate states, where e.g. a dock widget is hovered over, prepares to become a floating tab and then rolls back, because hovering doesn't result in a drop. In that case, tabbed must become true, which the dock widget isn't actually tabbed. Furthermore, the way to traverse item_list didn't find dock widgets in a floating tab. In that case, tabifiedDockWidgets() wrongly returned an empty list. To fix both issues, refactor QMainWindow::tabifiedDockWidgets() to read the list of dock widgets directly from the QMainWindowTabBar. Add tests in tst_QDockWidget::floatingTabs() and updateTabBarOnVisibilityChanged() Fixes: QTBUG-122001 Pick-to: 6.7 6.6 6.5 Change-Id: Ia9eb3711be642101261f34ee447521cc6accc20c Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>