The event fired by the mouse click on the frame

[wysota]

The heightForwidth provides useful information if you set a QLayout into the QDialog, according to the manual.

No, it doesn't say that. It says that the default implementation returns -1 or what the layout tells it. It doesn't say anything about customising it. You should reimplement the method (as you see it's virtual). Maybe it'll just work... it probably won't but you won't know until you try.