Layout change in a QScrollArea causes a brief visual jump

Adding a Widget to the layout of a QScrollArea causes the view to flicker. It seems that the widgets are resized at the reception of the resize event from the scroll area. This problem is especially visible with smalls CPU.

The following code demonstrate the problem:

class ScrollJump : public QWidget
{
Q_OBJECT

public:
ScrollJump(QWidget *parent = 0, Qt::WFlags flags = 0):QWidget(parent, flags)

{ QVBoxLayout *verticalLayout = new QVBoxLayout(this); QPushButton *pushButton = new QPushButton("Push me a few times"); connect(pushButton, SIGNAL(clicked()), this, SLOT(on_pushButton_clicked())); verticalLayout->addWidget(pushButton); QScrollArea *scrollArea = new QScrollArea(); scrollArea->setWidgetResizable(true); QWidget *viewport = new QWidget(); m_viewportLayout = new QVBoxLayout(viewport); scrollArea->setWidget(viewport); verticalLayout->addWidget(scrollArea); m_viewportLayout->addStretch(); }

private:
QVBoxLayout* m_viewportLayout;

private slots:
void on_pushButton_clicked()

{ static int i = 1; m_viewportLayout->insertWidget(m_viewportLayout->count() - 1, new QLabel(QString::number(i++))); }

};

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
ScrollJump w;
w.show();
return a.exec();
}