QMenuBar reserves space to right corner too when corner widget set to TopLeftCorner.

Set a corner wodget to QMenuBar with:
setCornerWidget(new QLabel("This is a corner widget: "), Qt::TopLeftCorner);
Then add several menus to QMenuBar.
--> QMenuBar will preserve the same amount of space to the right corner what is reserved to left corner widget. If corner widget is set to qt::TopRightCorner, then spacing is correct.