(not a question) : how to make a main window resize to its contents

I spent quite a lot of time finding an answer to this question, so I decided to share the findings.
I was struck by the blinding flash of the obvious reading this thread, but it seems Google has not deemed it as interresting as I do.
Besides, instead of providing a lenghty example, I decided to narrow it down to the two essential lines of code.
So here it goes:

Sometimes you may want your main window to resize to its current (dynamic) contents.
In my case I wanted my silly brickout game to resize according to its level layout :
Attachment 7819Attachment 7820

The trick is simply to apply a fixed-size layout to the main window.

Code:

---

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    // trick to get the main window to resize to its contents
    layout()->setSizeConstraint(QLayout::SetFixedSize);
 
   // rest of constructor code...
}

---

In this example I use a MainWindow straight from QT designer, but the same can be done with any hand-coded class.

Hope some people will find that useful...