QDockWidget showMaximized()/showMinimized() not work

Question

In my project ,I create a custom TitleBar in QDockWidget containing maxButton and minButton.

But the updating QT5.15, the slot cmd "showMinimized() and showMaximized" not work. Before detaching one QDockWidget, it will add it to the windows tastbar entry, since Qt5.15 it will not.

Which should I update? Thanks..

When print isWindow(), the floating/Detaching QDockWidget is 1 ,so it is an independent window. Using

setGeometry(QGuiApplication::primaryScreen()->availableGeometry()); 

can solve max/normal error, but min can not show in taskbar entry.