Very Simple Triangle using OpenGL2, Qt6, and C++

main.cpp

// To run on laptops:
#ifdef _WIN32
#include <windows.h>
extern "C" __declspec(dllexport) DWORD NvOptimusEnablement = 0x00000001;
extern "C" __declspec(dllexport) DWORD AmdPowerXpressRequestHighPerformance = 0x00000001;
#endif

#include <QtGui/QOpenGLFunctions>
#include <QtGui/QSurfaceFormat>
#include <QtOpenGL/QOpenGLBuffer>
#include <QtOpenGL/QOpenGLShaderProgram>
#include <QtOpenGLWidgets/QOpenGLWidget>
#include <QtWidgets/QApplication>

class Widget : public QOpenGLWidget, QOpenGLFunctions
{
public:
    Widget()
    {
        setFixedSize(QSize(270, 270));
        setWindowTitle("OpenGL2 Qt6 C++");
    }

private:
    QOpenGLShaderProgram m_program;
    QOpenGLBuffer m_vertexPositionBuffer;
    int m_aPositionLocation;

private:
    void initializeGL() override
    {
        initializeOpenGLFunctions();
        glClearColor(0.2f, 0.2f, 0.2f, 1.f);

        const char *vertexShaderSource =
            "attribute vec3 aPosition;\n"
            "void main()\n"
            "{\n"
            "    gl_Position = vec4(aPosition, 1.0);"
            "}\n";

        const char *fragmentShaderSource =
            "void main()\n"
            "{\n"
            "    gl_FragColor = vec4(1.0, 0.0, 0.0, 1.0);"
            "}\n";

        m_program.create();
        m_program.addShaderFromSourceCode(QOpenGLShader::Vertex, vertexShaderSource);
        m_program.addShaderFromSourceCode(QOpenGLShader::Fragment, fragmentShaderSource);

        m_program.bind();
        m_aPositionLocation = m_program.attributeLocation("aPosition");

        float vertexPositions[] = {
            -0.5f, -0.5f, 0.f,
            0.5f, -0.5f, 0.f,
            0.f, 0.5f, 0.f
        };

        m_vertexPositionBuffer.create();
        m_vertexPositionBuffer.bind();
        m_vertexPositionBuffer.allocate(vertexPositions, sizeof(vertexPositions));
        m_program.setAttributeBuffer(m_aPositionLocation, GL_FLOAT, 0, 3);
        m_program.enableAttributeArray(m_aPositionLocation);
    }

    void resizeGL(int w, int h) override
    {
        glViewport(0, 0, w, h);
    }

    void paintGL()
    {
        glClear(GL_COLOR_BUFFER_BIT);
        glDrawArrays(GL_TRIANGLES, 0, 3);
    }
};

int main(int argc, char *argv[])
{
// To run from CMD to print messages:
#ifdef _WIN32
    if (AttachConsole(ATTACH_PARENT_PROCESS))
    {
        freopen("CONOUT$", "w", stdout);
        freopen("CONOUT$", "w", stderr);
    }
#endif

    QApplication app(argc, argv);
    Widget w;
    QSurfaceFormat format;
    format.setSamples(8);
    w.setFormat(format);
    w.show();
    return app.exec();
}

makefile

# Build commands for CMD:
# qmake -makefile
# mingw32-make
# "./release/app"

QT += core gui openglwidgets

win32: LIBS += -lopengl32

CONFIG += c++11

SOURCES += \
    main.cpp

TARGET = app

Screenshot: