How can I draw an ellipse using QPainter?

I want to draw ellipse in UI but my code doesn't work.

QWidget::paintEngine: Should no longer be calledQPainter::begin: Paint device returned engine == 0, type: 1

mainwindow.cpp:

#include "mainwindow.h"#include "ui_mainwindow.h"MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent) , ui(new Ui::MainWindow), pm(100,100){ ui->setupUi(this); //set_form_style(); draw_ellipse();}MainWindow::~MainWindow(){ delete ui;}void MainWindow::set_form_style(){ //setWindowFlags(Qt::FramelessWindowHint); //setAttribute(Qt::WA_TranslucentBackground); //ui->widget->setStyleSheet("background:transparent;"); setMouseTracking(true);}void MainWindow::draw_ellipse(){ QPainter painter(this); painter.setRenderHint(QPainter::Antialiasing); painter.setBrush(QBrush(Qt::red, Qt::SolidPattern)); painter.drawEllipse(100, 50, 150, 150);}