QWidget and background transparency

[simopi]

My constructor:

@
TestWidget::TestWidget(QWidget *parent): QWidget(parent)
{

setStyleSheet("background: transparent;");
setAttribute(Qt::WA_TranslucentBackground,true);
setWindowFlags(Qt::FramelessWindowHint);
setAutoFillBackground(false);
setAttribute(Qt::WidgetAttribute::WA_ContentsPropagated);

}
@

And nothing works. Can you help me? Thanks in advance...
[Edited: Please use code tags “@@” – p3c0]