widget with Qt::WA_NoSystemBackground attribute make text coincides with previous text

[hello qter]

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QWidget widget;
    widget.setAttribute(Qt::WA_NoSystemBackground);
    widget.resize(100,100);
    QLabel* lable = new QLabel(&widget);
    lable->setStyleSheet("color:blue");
    lable->setText("1111111");
    QPushButton button("button",&widget);
    QVBoxLayout v;
    v.addWidget(lable);
    v.addWidget(&button);
    widget.setLayout(&v);
    QObject::connect(&button,&QPushButton::clicked,[=]()
    {
        lable->setText("222222222");
    });
    widget.show();
    return a.exec();
}

[Added code tags ~kshegunov]

[SGaist]

Hi,

What is your question ?

[hello qter]

@SGaist

in this programm,when i change the label's text,the previous text does't disappear,old and new text show together
and i must have the code(widget.setAttribute(Qt::WA_NoSystemBackground);) to solve some issue

[SGaist]

What issues do you have that requires that attribute set ?

[hello qter]

@SGaist sorry for reply later and my unskilled english
Because flicker appears When i run my application in embedeed system,then i found that set that attribute will solve the issue,But another issue comes,as you see in that picture,the previouse text and the new text show together.Yestoday i found that setAttribute(Qt::WA_TranslucentBackground) worked,But it makes the widget's background transparent

[SGaist]

Did you try to track the reason of the flickering ?

What else are you doing that could trigger that ?

[hello qter]

@SGaist The reason of the flickering i have asked in another topic,the main code bring the issue is
QGraphicsView view;
view.setViewport(new QGLWidget)
i don't know how it happen

thank you very much

[SGaist]

Ok, then can you explain exactly what is the original problem you have since everything seems related to that flickering issue ? Are you trying to put a label over a QGraphicsScene ? Are you trying to have text on that scene ?

[hello qter]

@SGaist neither,the original problem is my application flicker in embedded system, i tracked that
QGraphicsView view;
view.setViewport(new QGLWidget)
this code case the problem,But i have no any idea why,I have tryed to track the Qt open-source but failed,then i found that
this->setAttribute(Qt::WA_NoSystemBackground)
this code is effective,But it bring a new problem that the text overlapping,Then i found that set the transparent attribute will solve the overlapping problem,
so this problem seems has solved

[SGaist]

Did you check that your embedded system has proper OpenGL support ?

[hello qter]

@SGaist Yes,it support OpenGL