Hi anda,

I made the simplest project possible, so you can copy all of it and paste it in QtCreator to see the results.

You say that the blue widget should not show at all, does that mean that a QWidget should always call QWidget::show on himself after he is added to a QLayout ?

For the code being in the constructor, I only did it that way to have the simplest code possible to show my issue. I understand and agree with your point.

With all that said, you made me realize a very important discovery: 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.