QPlainTextEdit::appendPlainText() lead to very high CPU consumption

#include <QApplication>
#include <QPlainTextEdit>
#include <QTimer>


static int counter = 0;

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    auto textEdit = new QPlainTextEdit;
    textEdit->setMaximumBlockCount(10);
    textEdit->show();
    auto timer = new QTimer;
    QCoreApplication::connect(timer, &QTimer::timeout, [textEdit]() {
        textEdit->appendPlainText(QString::number(++counter));
    });
    timer->start(1);
    return a.exec();
}