Taken from https://stackoverflow.com/questions/1508939/qt-layout-on-qmainwindow as note
You don't have to create a QVBoxLayout manually. Just select your central QWidget and press a make-layout button
https://stackoverflow.com/a/1508954
Add at least one widget on your MainWindow
. Then select your window by clicking on it and click on the VerticalLayout
Button at the top of QTCreator
. You Vertical Layout is automatically added to the central widget and fills all the surface.
https://stackoverflow.com/a/1508969