QShortcuts not beeing activated inside QMdiArea when subwindows are focused

A QShortcut parented to a QMdiArea with Qt::WidgetWithChildrenShortcut context will not get triggered when a subwindow is focused.

Attached a small code that simulates the problem.

Definition from docs on Qt::WidgetWithChildrenShortcut:
"The shortcut is active when its parent widget, or any of its children has focus. Children which are top-level widgets, except pop-ups, are not affected by this shortcut context."

As subwindows are not top-level widgets, the shortcuts should be activated.