Widget with WA_PaintOnScreen set on never got paintEvent called.

VideoWidget::VideoWidget(QWidget *parent)
    : QWidget(parent)
    , surface(0)
{
    setAutoFillBackground(false);
    setAttribute(Qt::WA_NoSystemBackground, true);
    setAttribute(Qt::WA_PaintOnScreen, true);

    QPalette palette = this->palette();
    palette.setColor(QPalette::Background, Qt::black);
    setPalette(palette);

    setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::MinimumExpanding);

    surface = new VideoWidgetSurface(this);
}
void VideoWidget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);

    ...
}