Qt unable to add widget dynamically in clicked slot

[Cupidvogel]

Here is my situation. I have a QFrame, inside which I have a QPushButton. When I click on the button, it invokes a slot, where I eventually find out which button was clicked, from that its parent widget (which here is the QFrame), and then add some other widget to it. This is what I have so far:

QFrame *base = new QFrame(parent);
    base->setGeometry(50,50,160,30);
    base->setStyleSheet("background: #ffffff; border-radius: 5px;");
    base->setCursor(Qt::PointingHandCursor);
 
    QPushButton *button = new QPushButton("Some text",base);
    button->setGeometry(0,0,160,30);
    button->setCheckable(false);
    button->setStyleSheet("background: transparent; border-radius: 5px; padding-left: 9px; text-align: left; ");
    connect(button,SIGNAL(clicked()),this,SLOT(myslot()));
 
void MyClass::myslot()
{
    QObject* pObject = sender();
    QPushButton *button = qobject_cast<QPushButton* >(pObject);
    QFrame *container = qobject_cast<QFrame* >(button->parentWidget());
    int x = container->rect().height();
 
    qDebug() << "Height : " << x << endl; //prints correct value
    qDebug() << "Text: " << button->text() << endl; // prints correctly as well
    button->setVisible(false); //this works
 
    QFrame *newWidget = new QFrame(container);
    newWidget->setGeometry(0,0,160,150);
    newWidget->setStyleSheet("background: #ffffff; border-radius: 5px;");
    newWidget->setCursor(Qt::PointingHandCursor); //doesn't work
    container->stackUnder(newWidget);
}

QFrame *base = new QFrame(parent);
    base->setGeometry(50,50,160,30);
    base->setStyleSheet("background: #ffffff; border-radius: 5px;");
    base->setCursor(Qt::PointingHandCursor);

    QPushButton *button = new QPushButton("Some text",base);
    button->setGeometry(0,0,160,30);
    button->setCheckable(false);
    button->setStyleSheet("background: transparent; border-radius: 5px; padding-left: 9px; text-align: left; ");
    connect(button,SIGNAL(clicked()),this,SLOT(myslot()));

void MyClass::myslot()
{
    QObject* pObject = sender();
    QPushButton *button = qobject_cast<QPushButton* >(pObject);
    QFrame *container = qobject_cast<QFrame* >(button->parentWidget());
    int x = container->rect().height();

    qDebug() << "Height : " << x << endl; //prints correct value
    qDebug() << "Text: " << button->text() << endl; // prints correctly as well
    button->setVisible(false); //this works

    QFrame *newWidget = new QFrame(container);
    newWidget->setGeometry(0,0,160,150);
    newWidget->setStyleSheet("background: #ffffff; border-radius: 5px;");
    newWidget->setCursor(Qt::PointingHandCursor); //doesn't work
    container->stackUnder(newWidget);
}

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As you see, I ma getting the parent container QFrame and the button all right, as evident from getting the correct values for them. But the child widget which I am now adding doesn't show up at all. What am I doing wrong, and how do I fix this?