[PyQt] MdiSubWindows: what causes inactive (or hidden) subwindows?

[Anonymous]

Let's say i have an MdiArea whose ViewMode is set as TabbedView. It seems when i call a function that adds a new subwindow, the window doesn't show and i can't close the subwindow by right-clicking on the tab and close. Ironically, when i call the function before the main window appears, the subwindows aren't inactive (or hidden). I've attempted to add the subwindow to the MdiArea two that doesn't solve my problem: first way was through QMdiSubWindow.addSubWindow(), second way was making a new instance of QMdiSubWindow with its parent being the MdiArea.

I'm not sure what i'm ignorant of or how to solve this.