Creating a Dialog in a Slot of QMainWindow

[tilm]

Thanks jpn, this was the problem. I always thought that

qmake -project

was sufficient to create a complete .pro file (I'm sure that I ran it before qmake and make). For me this was the first time that something in a .pro file created with qmake was missing. Do you know the reason for this?

[tilm]

I think I found the answer on my own: 'qmake -project' only includes dialog.cpp into the .pro file when dialog.h is included in MainWindow.h . But I first included the Dialog header file in MainWindow.cpp. That was the reason.