Qt Designer can't promote QMainWindow

Question

There is something I do not understand about Qt Designer. I have been working with it for a while now, and still I always end up editing the .ui files manually.

As it can be seen in every single tutorial on Qt, one of the very first thing you do when you create a GUI is to subclass QMainWindow - in order to catch and redefine the closeEvent() function, for example.

However, it is not possible to subclass ("promote") QMainWindow in Qt Designer - you can do it with many other class, but not this one.

What I usually do is edit the .ui file and change:

<class>MainWindow</class>
  <widget class="QMainWindow" name="MainWindow">

by:

< widget class="MyMainWindow" name="MainWindow">

So that my code can subclass QMainWindow properly in my code:

class MyMainWindow(QMainWindow, object):
    ''' I can redefine closeEvent here! '''

Obviously, this is weird - and I probably miss something about the right way to do it with Designer. But I cannot find any explanation.

Why is it not possible to subclass QMainWindow in Designer, or how to structure my application differently to avoid the need for it?

Thanks

Answer 1

You generally don't need to promote the root element of UI tree. If you properly initialize your class using UI file, you can redefine closeEvent without it. This answer shows how to do it properly.

Answer 2

I know this is old. I somehow ran into the same problem. I want to use docking features in a sub window. When I tried to promote the QMinWindow, I don't see it in the list. Then I tried using QWidget in the drop down list, it magically went through.

Just my experience.