Refactor and fix QMainWindow::tabifiedDockWidgets()

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>

1 files changed, 2 insertions, 15 deletions

diff --git a/src/widgets/widgets/qmainwindow.cpp b/src/widgets/widgets/qmainwindow.cpp
index a91128ba09..30176edd49 100644
--- a/src/widgets/widgets/qmainwindow.cpp
+++ b/src/widgets/widgets/qmainwindow.cpp
@@ -1123,21 +1123,8 @@ void QMainWindow::tabifyDockWidget(QDockWidget *first, QDockWidget *second)
 
 QList<QDockWidget*> QMainWindow::tabifiedDockWidgets(QDockWidget *dockwidget) const
 {
-    QList<QDockWidget*> ret;
-    const QDockAreaLayoutInfo *info = d_func()->layout->layoutState.dockAreaLayout.info(dockwidget);
-    if (info && info->tabbed && info->tabBar) {
-        for(int i = 0; i < info->item_list.size(); ++i) {
-            const QDockAreaLayoutItem &item = info->item_list.at(i);
-            if (item.widgetItem) {
-                if (QDockWidget *dock = qobject_cast<QDockWidget*>(item.widgetItem->widget())) {
-                    if (dock != dockwidget) {
-                        ret += dock;
-                    }
-                }
-            }
-        }
-    }
-    return ret;
+    Q_D(const QMainWindow);
+    return d->layout ? d->layout->tabifiedDockWidgets(dockwidget) : QList<QDockWidget *>();
 }
 #endif // QT_CONFIG(tabbar)