Qt OpenGL Quad not showing

[Mario1159]

What my code is missing to display a quad?
i don't get any error just the widget display the clear color, in this case black
This is my current code;

"MyOpenGLWidget.cpp"

#include "MyOpenGLWidget.h"
#include "QOpenGLWidget"
#include <QOpenGLFunctions>

MyOpenGLWidget::MyOpenGLWidget(QWidget* parent) : QOpenGLWidget(parent)
{
    qDebug("constructor");
}
void MyOpenGLWidget::initializeGL()
{
    qDebug("initialize");
    initializeOpenGLFunctions();
    glClearColor(0, 0, 0, 0);
}
void MyOpenGLWidget::paintGL()
{
    qDebug("paint");
    glClear(GL_COLOR_BUFFER_BIT);
    glLoadIdentity();
    glTranslatef(0.0, 0.0, -10.0);
    glBegin(GL_QUADS);
    glColor3f(1, 0, 0);
    glVertex2f(-0.5f, -0.5f);
    glVertex2f(0.5f, -0.5f);
    glVertex2f(-0.5f, 0.5f);
    glVertex2f(0.5f, 0.5f);
    glEnd();
    glFlush();
}
void MyOpenGLWidget::resizeGL(int width, int height)
{
    qDebug("resize");
}

"mainwindow.cpp"

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "MyOpenGLWidget.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}


MainWindow::~MainWindow()
{
    delete ui;
}

[mrjj]

Hi and welcome to the forums
My best bet is that your openGL is so new that
glBegin(GL_QUADS); is no longer supported in the core profile/openGL 3.3 ( i think)
Its part of the so called old fixed pipeline.
It might be possible to request older profile but would be better just to use
modern openGl.
https://learnopengl.com/Introduction
https://learnopengl.com/Getting-started/Hello-Triangle