Borders and background of QWidget aren't set b

Question

I've set the stylesheet of a QWidget to change the borders and the background,

#gui {
    border: 4px inset #515c84;
    border-radius: 9px;
    background-image: url(./back.png)
}

Its name is gui but neither border nor background are shown.

Answer 1

Override paintEvent in your QWidget subclass like this:

void MyWidget::paintEvent(QPaintEvent *e)
{
    QStyleOption opt;
    opt.init(this);
    QStylePainter p(this);
    p.drawPrimitive(QStyle::PE_Widget, opt);
}

Answer 2

For the Python-QT bindings (PyQt, PySide) just setting the attribute WA_StyledBackground on the QWidget is enough to show border and background.