Hi SGaist and thank for the help. For the code being in the constructor when it should not be, I only did it that way to have the simplest code possible to show my issue. I understand and agree with your point. I am working on an already existing application, I created this QtCreator project to isolate and replicate the issue. I do not call QWidget::show() in the constructor of my application. I have made an important discovery while working on this issue: calling blue_widget->show() at the end of my code in my QtCreator project does fixe the problem, but doing the same in my application does not fix the issue. This is the 1st time I see a different behavior, I thought I had manage to have the same 1:1 behavior between the QtCreator project and my application. Thanks for the help, I will keep looking.

I had some similar problem. My QMenu wasn't adjusting to a dynamically changed size of QWidgetAction. I have found this thread http://www.qtcentre.org/threads/26291-QWidgetAction-resize-in-QMenu and suggested workaround worked for me. Qt 5.9.5. QResizeEvent re (QSize(1, 1), size()); qApp->sendEvent(this, &re); adjustSize(); Where this is a pointer to QMenu object. Fake resize event forces all menu items size recalculating and adjustSize() recalculates it. I hope it will help to anyone else.

Ok, thanks.

Probably because on OS X the default menu bar is provided by the OS. See QMenuBar's documentation for more details. However I don't know if it's an OS X specific behavior of Qt Creator.

@pmendl No problem. Do bear in mind that if you decide to send the event with QApplication::sendEvent, you are responsible for the event object's deletion, so it's a good idea to create it on the stack in that case. Good luck! Kind regards.

If you mean that you want to follow the guidelines then you have nothing special to do, just use menuBar() and you're good to go.

@Streakflash Yeah I agree. But a lot of stuff is not really possible from Designer. Sadly.

@ronaroja Check out the Menus example. This creates a QWidget that is used as the application central widget. Widget are added to the QVBoxLayout of this central widget. You will have to modify this example slightly; don't use the setMenuBar() and create a QMenuBar widget that you can add to the QVBoxLayout (doesn't have to be at the top).