Qt's OpenGL vertex binding funcs problem

Bondrusiek

Hi everyone,
I have a program which use OpenGL 3.3 core. If I use Qt's function program doesn't work correctly. Now with Qt's func/properties:
glwidget.h

#include <QOpenGLWidget>
#include <QOpenGLFunctions_3_3_Core>
#include <QOpenGLBuffer>
#include <QOpenGLShaderProgram>

class MyGLWidget : public QOpenGLWidget, protected QOpenGLFunctions_3_3_Core
{
    Q_OBJECT

public:
    MyGLWidget(QWidget *parent = nullptr);
    ~MyGLWidget();

protected:
    void initializeGL() override;
    void resizeGL(int w, int h) override;
    void paintGL() override;

private:
    QOpenGLBuffer vbo;
    QOpenGLShaderProgram *shaderProgram;
};

glwidget.cpp

#include "glwidget.h"
#include <QOpenGLShader>
#include <QOpenGLVertexArrayObject>

MyGLWidget::MyGLWidget(QWidget *parent)
    : QOpenGLWidget(parent), vbo(QOpenGLBuffer::VertexBuffer)
{
}

MyGLWidget::~MyGLWidget()
{
    makeCurrent();
    vbo.destroy();
    delete shaderProgram;
    doneCurrent();
}

void MyGLWidget::initializeGL()
{
    initializeOpenGLFunctions();

    GLfloat vertices[] = {
        0.0f,  0.5f, 0.0f, // Top vertex
        -0.5f, -0.5f, 0.0f, // Bottom left vertex
        0.5f, -0.5f, 0.0f  // Bottom right vertex
    };

    vbo.create();
    vbo.bind();
    vbo.allocate(vertices, sizeof(vertices));
    shaderProgram = new QOpenGLShaderProgram();
    shaderProgram->addShaderFromSourceCode(QOpenGLShader::Vertex,
                                           "#version 330 core\n"
                                           "layout(location = 0) in vec3 position;\n"
                                           "void main()\n"
                                           "{\n"
                                           "    gl_Position = vec4(position, 1.0);\n"
                                           "}\n"
                                           );
    shaderProgram->addShaderFromSourceCode(QOpenGLShader::Fragment,
                                           "#version 330 core\n"
                                           "out vec4 fragColor;\n"
                                           "void main()\n"
                                           "{\n"
                                           "    fragColor = vec4(1.0, 0.0, 0.0, 1.0);\n"
                                           "}\n"
                                           );
    shaderProgram->link();
    shaderProgram->bind();
}

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

void MyGLWidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT);

    shaderProgram->bind();
    vbo.bind();

    int posLocation = shaderProgram->attributeLocation("position");
    shaderProgram->enableAttributeArray(posLocation);
    shaderProgram->setAttributeBuffer(posLocation, GL_FLOAT, 0, 3);

    glDrawArrays(GL_TRIANGLES, 0, 3);

    shaderProgram->disableAttributeArray(posLocation);
    vbo.release();
    shaderProgram->release();
}

main.cpp

#include "glwidget.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QSurfaceFormat fmt;
    fmt.setDepthBufferSize(24);

    // Request OpenGL 3.3 core or OpenGL ES 3.0.
    if (QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL) {
        qDebug("Requesting 3.3 core context");
        fmt.setVersion(3, 3);
        fmt.setProfile(QSurfaceFormat::CoreProfile);
    } else {
        qDebug("Requesting 3.0 context");
        fmt.setVersion(3, 0);
    }

    QSurfaceFormat::setDefaultFormat(fmt);
    MyGLWidget w;
    w.show();
    return a.exec();
}

Result:

but if I use standard OpenGL funcs everything is OK, VAO and VOB are Gluint(unsigned int).
new glwidget.cpp

...
void MyGLWidget::initializeGL()
{
    initializeOpenGLFunctions();

    GLfloat vertices[] = {
        0.0f,  0.5f, 0.0f, // Top vertex
        -0.5f, -0.5f, 0.0f, // Bottom left vertex
        0.5f, -0.5f, 0.0f  // Bottom right vertex
    };

    glGenVertexArrays(1, &VAO);
    glGenBuffers(1, &VBO);

    glBindVertexArray(VAO);

    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
    glEnableVertexAttribArray(0);


    shaderProgram = new QOpenGLShaderProgram();
    shaderProgram->addShaderFromSourceCode(QOpenGLShader::Vertex,
                                           "#version 330 core\n"
                                           "layout(location = 0) in vec3 position;\n"
                                           "void main()\n"
                                           "{\n"
                                           "    gl_Position = vec4(position, 1.0);\n"
                                           "}\n"
                                           );
    shaderProgram->addShaderFromSourceCode(QOpenGLShader::Fragment,
                                           "#version 330 core\n"
                                           "out vec4 fragColor;\n"
                                           "void main()\n"
                                           "{\n"
                                           "    fragColor = vec4(1.0, 0.0, 0.0, 1.0);\n"
                                           "}\n"
                                           );
    shaderProgram->link();
    shaderProgram->bind();
}

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

void MyGLWidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT);

    shaderProgram->bind();
    glBindVertexArray(VAO);

    int posLocation = shaderProgram->attributeLocation("position");
    shaderProgram->enableAttributeArray(posLocation);
    shaderProgram->setAttributeBuffer(posLocation, GL_FLOAT, 0, 3);

    glDrawArrays(GL_TRIANGLES, 0, 3);

    shaderProgram->disableAttributeArray(posLocation);
    vbo.release();
    shaderProgram->release();
}

Result:

I use Qt 6.5.3 for mac.
I wanna use only Qt elements. Do you know how can I improve it ?

8Observer8

I wanted to run your first example but when I copy your code to my project I have this error: QOpenGLFunctions_3_3_Core: No such file or directory

QT += core gui openglwidgets

win32: LIBS += -lopengl32

CONFIG += c++17

SOURCES += \
    main.cpp \
    glwidget.cpp

HEADERS += \
    glwidget.h

I have tried to add QT += opengl but it did not help. I think openglwidgets includes opengl

Bondrusiek

I used this modules in CMakeLists.txt:

Core Gui OpenGL OpenGLWidgets Widgets

I also paste all CMakeLists.txt:

cmake_minimum_required(VERSION 3.5)

project(QtOpenGL3_3 VERSION 0.1 LANGUAGES CXX)

set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_AUTORCC ON)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

find_package(QT NAMES Qt6 Qt5 REQUIRED COMPONENTS Core Gui OpenGL OpenGLWidgets Widgets)
find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Core Gui OpenGL OpenGLWidgets Widgets)

set(PROJECT_SOURCES
        main.cpp
        shader.h shader.cpp
        window.h window.cpp
)

if(${QT_VERSION_MAJOR} GREATER_EQUAL 6)
    qt_add_executable(QtOpenGL3_3
        MANUAL_FINALIZATION
        ${PROJECT_SOURCES}

    )
# Define target properties for Android with Qt 6 as:
#    set_property(TARGET QtOpenGL3_3 APPEND PROPERTY QT_ANDROID_PACKAGE_SOURCE_DIR
#                 ${CMAKE_CURRENT_SOURCE_DIR}/android)
# For more information, see https://doc.qt.io/qt-6/qt-add-executable.html#target-creation
else()
    if(ANDROID)
        add_library(QtOpenGL3_3 SHARED
            ${PROJECT_SOURCES}
        )
# Define properties for Android with Qt 5 after find_package() calls as:
#    set(ANDROID_PACKAGE_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/android")
    else()
        add_executable(QtOpenGL3_3
            ${PROJECT_SOURCES}
        )
    endif()
endif()

# Resources:
set(shaders_resource_files
    "assets/shaders/fshader.glsl"
    "assets/shaders/vshader.glsl"
)

qt6_add_resources(QtOpenGL3_3 "shaders"
    PREFIX
        "/"
    FILES
        ${shaders_resource_files}
)

set(textures_resource_files
    "assets/textures/cube.png"
)

qt6_add_resources(QtOpenGL3_3 "textures"
    PREFIX
        "/"
    FILES
        ${textures_resource_files}
)

target_link_libraries(QtOpenGL3_3 PRIVATE
    Qt${QT_VERSION_MAJOR}::Core
    Qt${QT_VERSION_MAJOR}::Gui
    Qt${QT_VERSION_MAJOR}::OpenGL
    Qt${QT_VERSION_MAJOR}::OpenGLWidgets
    Qt${QT_VERSION_MAJOR}::Widgets)

# Qt for iOS sets MACOSX_BUNDLE_GUI_IDENTIFIER automatically since Qt 6.1.
# If you are developing for iOS or macOS you should consider setting an
# explicit, fixed bundle identifier manually though.
if(${QT_VERSION} VERSION_LESS 6.1.0)
  set(BUNDLE_ID_OPTION MACOSX_BUNDLE_GUI_IDENTIFIER com.example.QtOpenGL3_3)
endif()
set_target_properties(QtOpenGL3_3 PROPERTIES
    ${BUNDLE_ID_OPTION}
    MACOSX_BUNDLE_BUNDLE_VERSION ${PROJECT_VERSION}
    MACOSX_BUNDLE_SHORT_VERSION_STRING ${PROJECT_VERSION_MAJOR}.${PROJECT_VERSION_MINOR}
    MACOSX_BUNDLE TRUE
    WIN32_EXECUTABLE TRUE
)

include(GNUInstallDirs)
install(TARGETS QtOpenGL3_3
    BUNDLE DESTINATION .
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
)

if(QT_VERSION_MAJOR EQUAL 6)
    qt_finalize_executable(QtOpenGL3_3)
endif()

8Observer8

Could you try to run the first example using qmake? Why QOpenGLFunctions_3_3_Core could not be found in my case?

Bondrusiek

I have tried use qmake and it works.
My qmake file:

greaterThan(QT_MAJOR_VERSION, 4): QT += core gui opengl openglwidgets widgets

HEADERS += \
    glwidget.h

SOURCES += \
    glwidget.cpp \
    main.cpp

BTW. I paste also first part of QOpenGLFunctions_3_3_Core

...
#ifndef QOPENGLVERSIONFUNCTIONS_3_3_CORE_H
#define QOPENGLVERSIONFUNCTIONS_3_3_CORE_H

#include <QtOpenGL/qtopenglglobal.h>

#if !defined(QT_NO_OPENGL) && !QT_CONFIG(opengles2)

#include <QtOpenGL/QOpenGLVersionProfile>
#include <QtOpenGL/QOpenGLVersionFunctions>
#include <QtGui/qopenglcontext.h>

QT_BEGIN_NAMESPACE

class Q_OPENGL_EXPORT QOpenGLFunctions_3_3_Core : public QAbstractOpenGLFunctions
{
public:
    QOpenGLFunctions_3_3_Core();
...

@8Observer8 What OS do you have ? Windows 10 (if yes I'll also later check it on this OS and try run it).

8Observer8

@Bondrusiek said in Qt's OpenGL vertex binding funcs problem:

What OS do you have ? Windows 10

Yes. It is why I write win32: LIBS += -lopengl32 inside of the pro file. Some programs will not be compiled without this line on Windows. win32: means that this line is for Windows only and the LIBS += -lopengl32 command will be ignored on Linux, macOS, Android, and WebAssembly. It is very interesting why there is no QOpenGLFunctions_3_3_Core inside of this list:

Bondrusiek

@8Observer8 Hi!
I've checked this project on my Windows 10 and it works. I used Desktop Qt6.7 MinGW 64bit compilator.

This is a qmake file:

QT       += core gui openglwidgets opengl

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++17

SOURCES += \
    main.cpp \
    widget.cpp

HEADERS += \
    widget.h

This is interesting that you have a problem with OpenGL 3.3 on Win 10 OS. I am not an OpenGL expert but I found good program which scans GPU and you can see OpenGL status(probably it is possible to found other the solution). This is OpenGL Extensions Viewer and my result from Windows 10:

8Observer8

My laptop has two video cards: integrated on CPU and discrete GeForce. Qt uses the first one by default:

qDebug() << "OpenGL version:" << (const char*) glGetString(GL_VERSION);
qDebug() << "GLSL version: " << (const char*) glGetString(GL_SHADING_LANGUAGE_VERSION);
qDebug() << "Vendor: " << (const char*) glGetString(GL_VENDOR);

Output:

OpenGL version: 3.1.0 - Build 9.17.10.4459
GLSL version:  1.40 - Intel Build 9.17.10.4459
Vendor:  Intel

I am not expert in Qt but it is very interesting that the QOpenGLFunctions_3_3_Core.h header file is not available for me. I see it here:

But I don't see it here:

Even QOpenGLFunctions_3_1.h is not in the list.

Bondrusiek

Hmm, you can try run it and see result. Maybe compilation sees a OpenGL version and blocks some header files:

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QSurfaceFormat fmt;
    fmt.setDepthBufferSize(24);

    // Request OpenGL 3.3 core or OpenGL ES 3.0.
    if (QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL) {
        qDebug("Requesting 3.3 core context");
        fmt.setVersion(3, 3);
        fmt.setProfile(QSurfaceFormat::CoreProfile);
    } else {
        qDebug("Requesting 3.0 context");
        fmt.setVersion(3, 0);
    }

    QSurfaceFormat::setDefaultFormat(fmt);

    return a.exec();
}

8Observer8

Output:

Requesting 3.3 core context
OpenGL version: 3.1.0 - Build 9.17.10.4459
GLSL version:  1.40 - Intel Build 9.17.10.4459
Vendor:  Intel

main.cpp

#include <QtGui/QOpenGLContext>
#include <QtGui/QOpenGLFunctions>
#include <QtGui/QSurfaceFormat>
#include <QtWidgets/QApplication>
#include <QtOpenGL/QOpenGLWindow>

class OpenGLWindow : public QOpenGLWindow, private QOpenGLFunctions
{
    void initializeGL() override
    {
        initializeOpenGLFunctions();

        qDebug() << "OpenGL version:" << (const char*) glGetString(GL_VERSION);
        qDebug() << "GLSL version: " << (const char*) glGetString(GL_SHADING_LANGUAGE_VERSION);
        qDebug() << "Vendor: " << (const char*) glGetString(GL_VENDOR);
    }
};

int main(int argc, char *argv[])
{
    QApplication::setAttribute(Qt::ApplicationAttribute::AA_UseDesktopOpenGL);
    QApplication app(argc, argv);
    QSurfaceFormat fmt;
    fmt.setDepthBufferSize(24);

    // Request OpenGL 3.3 core or OpenGL ES 3.0.
    if (QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL)
    {
        qDebug("Requesting 3.3 core context");
        fmt.setVersion(3, 3);
        fmt.setProfile(QSurfaceFormat::CoreProfile);
    }
    else
    {
        qDebug("Requesting 3.0 context");
        fmt.setVersion(3, 0);
    }

    OpenGLWindow w;
    w.setFormat(fmt);
    w.show();
    return app.exec();
}

8Observer8

I can activate the discrete GeForce (or Radeon) card by adding this code:

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

Output:

Requesting 3.3 core context
OpenGL version: 3.3.0 NVIDIA 391.35
GLSL version:  3.30 NVIDIA via Cg compiler
Vendor:  NVIDIA Corporation

main.cpp

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

#include <QtGui/QOpenGLContext>
#include <QtGui/QOpenGLFunctions>
#include <QtGui/QSurfaceFormat>
#include <QtWidgets/QApplication>
#include <QtOpenGL/QOpenGLWindow>

class OpenGLWindow : public QOpenGLWindow, private QOpenGLFunctions
{
    void initializeGL() override
    {
        initializeOpenGLFunctions();

        qDebug() << "OpenGL version:" << (const char*) glGetString(GL_VERSION);
        qDebug() << "GLSL version: " << (const char*) glGetString(GL_SHADING_LANGUAGE_VERSION);
        qDebug() << "Vendor: " << (const char*) glGetString(GL_VENDOR);
    }
};

int main(int argc, char *argv[])
{
    QApplication::setAttribute(Qt::ApplicationAttribute::AA_UseDesktopOpenGL);
    QApplication app(argc, argv);
    QSurfaceFormat fmt;
    fmt.setDepthBufferSize(24);

    // Request OpenGL 3.3 core or OpenGL ES 3.0.
    if (QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL)
    {
        qDebug("Requesting 3.3 core context");
        fmt.setVersion(3, 3);
        fmt.setProfile(QSurfaceFormat::CoreProfile);
    }
    else
    {
        qDebug("Requesting 3.0 context");
        fmt.setVersion(3, 0);
    }

    OpenGLWindow w;
    w.setFormat(fmt);
    w.show();
    return app.exec();
}

Bondrusiek

So you have a card that supports OpenGL 3.3. It's strange that Qt doesn't see this header files. If I had anything to suggest, you can update Qt via MaintenanceTool and update the graphics card drivers.

8Observer8

@Bondrusiek said in Qt's OpenGL vertex binding funcs problem:

update the graphics card drivers

I have the latest: OpenGL 4.6 for GeForce and OpenGL 3.1.0 for Intel. I cannot update OpenGL for Intel because 3.1 is maximum for my CPU.

@Bondrusiek said in Qt's OpenGL vertex binding funcs problem:

It's strange that Qt doesn't see this header files.

I see them now:

8Observer8

I don't understand why but there is no the QOpenGLFunctions_3_3_Core: No such file or directory error in your first example. It crashed: debug\opengl33-test.exe crashed. But it is crashed because I have a laptop and Qt runs with the integrated video card with OpenGL 3.1. I have added these lines to the main.cpp:

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

and your first example works now. I the the red triangle. But it prints the maximum version of OpenGL 4.6 on the discrete video card because setVersion(3 , 3) was not called:

OpenGL version: 4.6.0 NVIDIA 391.35
GLSL version:  4.60 NVIDIA
Vendor:  NVIDIA Corporation

8Observer8

Sorry. I have forgot to add setVersion(3, 3) to the main.cpp file. Now your first example prints correct version of OpenGL:

Requesting 3.3 core context
OpenGL version: 3.3.0 NVIDIA 391.35
GLSL version:  3.30 NVIDIA via Cg compiler
Vendor:  NVIDIA Corporation

But I don't see a red triangle. I can fix it only by comment the QSurfaceFormat code with setting setVersion and setProfile but it uses OpenGL 4.6 now:

main.cpp

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

#include "glwidget.h"

#include <QtGui/QSurfaceFormat>
#include <QtWidgets/QApplication>

int main(int argc, char *argv[])
{
    QApplication::setAttribute(Qt::ApplicationAttribute::AA_UseDesktopOpenGL);
    QApplication a(argc, argv);

    QSurfaceFormat fmt;
    fmt.setDepthBufferSize(24);

    // // Request OpenGL 3.3 core or OpenGL ES 3.0.
    // if (QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL) {
    //     qDebug("Requesting 3.3 core context");
    //     fmt.setVersion(3, 3);
    //     fmt.setProfile(QSurfaceFormat::CoreProfile);
    // } else {
    //     qDebug("Requesting 3.0 context");
    //     fmt.setVersion(3, 0);
    // }

    QSurfaceFormat::setDefaultFormat(fmt);

    MyGLWidget w;
    w.show();
    return a.exec();
}

Bondrusiek

Thanks for checking. As far as I know, in the case of shaders, you can also indicate what version of OpenGL you want to use.
#version 330 core
This means that you want to use 3.3 version of OpenGL. #version 460 core means set OpenGL to 4.6.

Perhaps the most important thing is that the second example does not render the triangle correctly for you either. Just like in my case, so I guess we can talk about a bug here.

8Observer8

I believe there is no need to spend time on OpenGL 3.3 Core, especially if you have just started learning the basics of OpenGL. You can defer learning OpenGL 3.3 Core until the next iteration. Take OpenGL ES 2.0. It's much smaller. It has all the basic things you need now. It works on iOS, Android and web browser. In the near future, focus on OpenGL ES 2.0 and make demos and small games on it. It will serve you for several years, and maybe a lifetime.

My simple triangle example is written using OpenGL ES 2.0. It is compiled to Desktop, Mobile, and Web from one code base.

Demo in the browser using QOpenGLWindow
Demo in the browser using QOpenGLWidget

main.cpp

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

class OpenGLWindow : public QOpenGLWidget, private QOpenGLFunctions
{
public:
    OpenGLWindow()
    {
        setWindowTitle("OpenGL ES 2.0, Qt6, C++");
        resize(350, 350);
    }

    void initializeGL() override
    {
        initializeOpenGLFunctions();
        glClearColor(48.f / 255.f, 56.f / 255.f, 65.f / 255.f, 1.f);

        QString vertShaderSrc =
            "attribute vec2 aPosition;\n"
            "void main()\n"
            "{\n"
            "    gl_Position = vec4(aPosition, 0.0, 1.0);\n"
            "}\n";

        QString fragShaderSrc =
            "#ifdef GL_ES\n"
            "precision mediump float;\n"
            "#endif\n"
            "void main()\n"
            "{\n"
            "    gl_FragColor = vec4(0.2, 0.7, 0.3, 1.0);\n"
            "}\n";

        m_program.create();
        m_program.addShaderFromSourceCode(QOpenGLShader::ShaderTypeBit::Vertex, vertShaderSrc);
        m_program.addShaderFromSourceCode(QOpenGLShader::ShaderTypeBit::Fragment, fragShaderSrc);
        m_program.link();
        m_program.bind();

        float vertPositions[] = {
            -0.5f, -0.5f,
            0.5f, -0.5f,
            0.f, 0.5f
        };
        m_vertPosBuffer.create();
        m_vertPosBuffer.bind();
        m_vertPosBuffer.allocate(vertPositions, sizeof(vertPositions));
    }

    void paintGL() override
    {
        glClear(GL_COLOR_BUFFER_BIT);
        m_program.bind();
        m_vertPosBuffer.bind();
        m_program.setAttributeBuffer("aPosition", GL_FLOAT, 0, 2);
        m_program.enableAttributeArray("aPosition");
        glDrawArrays(GL_TRIANGLES, 0, 3);
    }

private:
    QOpenGLShaderProgram m_program;
    QOpenGLBuffer m_vertPosBuffer;
};

int main(int argc, char *argv[])
{
    QApplication::setAttribute(Qt::ApplicationAttribute::AA_UseDesktopOpenGL);
    QApplication app(argc, argv);
    OpenGLWindow w;
    w.show();
    return app.exec();
}

QT += core gui openglwidgets

win32: LIBS += -lopengl32

CONFIG += c++17

SOURCES += \
    main.cpp

8Observer8

I have created the bug report: https://bugreports.qt.io/browse/QTBUG-126389

I have tested with QOpenGLWindow. The result is the same.

8Observer8

My bug report was closed with the comment: You need a VAO to use a Core profile.

I have added solution examples to the bug report:

Steps to solve the problem:

Add #include <QtOpenGL/QOpenGLVertexArrayObject> inside of the glwidget.h
Create the QOpenGLVertexArrayObject vao; member inside of the MyGLWidget class
Create and bind vao inside of the initializeGL method:

void MyGLWidget::initializeGL()
{
    initializeOpenGLFunctions();
    vao.create();
    vao.bind();

Delete a binding of the vbo inside of the paintGL()
Add a binding of the vao inside of the paintGL()
Move attributeLocation, enableAttributeArray and setAttributeBuffer inside of the initializeGL method:
I don't think that you should release the shader program inside of the paintGL() method
Release vao inside of the paintGL() method
I think you don't need to call disableAttributeArray inside of the paintGL() method

So, VAO allows to bind VBO and call enableAttributeArray and setAttributeBuffer only one time. You can bind VAO only inside of the paintGL() method. Now the program works:

pro

QT += core gui openglwidgets opengl

win32: LIBS += -lopengl32

CONFIG += c++17

SOURCES += \
    main.cpp \
    glwidget.cpp

HEADERS += \
    glwidget.h

glwidget.h

#ifndef GLWIDGET_H
#define GLWIDGET_H

#include <QOpenGLWidget>
#include <QOpenGLFunctions_3_3_Core>
#include <QOpenGLBuffer>
#include <QOpenGLShaderProgram>
#include <QtOpenGL/QOpenGLVertexArrayObject>

class MyGLWidget : public QOpenGLWidget, protected QOpenGLFunctions_3_3_Core
{
    Q_OBJECT

        public:
                 MyGLWidget(QWidget *parent = nullptr);
    ~MyGLWidget();

protected:
    void initializeGL() override;
    void resizeGL(int w, int h) override;
    void paintGL() override;

private:
    QOpenGLBuffer vbo;
    QOpenGLVertexArrayObject vao;
    QOpenGLShaderProgram *shaderProgram;
};

#endif // GLWIDGET_H

glwidget.cpp

#include "glwidget.h"

MyGLWidget::MyGLWidget(QWidget *parent)
    : QOpenGLWidget(parent), vbo(QOpenGLBuffer::VertexBuffer)
{
    setWindowTitle("Trianlge, OpenGL 3.3 Core");
    resize(500, 500);
}

MyGLWidget::~MyGLWidget()
{
    makeCurrent();
    vao.destroy();
    vbo.destroy();
    delete shaderProgram;
    doneCurrent();
}

void MyGLWidget::initializeGL()
{
    initializeOpenGLFunctions();

    qDebug() << "OpenGL version:" << (const char*) glGetString(GL_VERSION);
    qDebug() << "GLSL version: " << (const char*) glGetString(GL_SHADING_LANGUAGE_VERSION);
    qDebug() << "Vendor: " << (const char*) glGetString(GL_VENDOR);

    shaderProgram = new QOpenGLShaderProgram();
    shaderProgram->addShaderFromSourceCode(QOpenGLShader::Vertex,
        "#version 330 core\n"
        "layout(location = 0) in vec3 position;\n"
        "void main()\n"
        "{\n"
        "    gl_Position = vec4(position, 1.0);\n"
        "}\n"
        );
    shaderProgram->addShaderFromSourceCode(QOpenGLShader::Fragment,
        "#version 330 core\n"
        "out vec4 fragColor;\n"
        "void main()\n"
        "{\n"
        "    fragColor = vec4(1.0, 0.0, 0.0, 1.0);\n"
        "}\n"
        );
    shaderProgram->link();
    shaderProgram->bind();

    vao.create();
    vao.bind();
    vbo.create();
    vbo.bind();

    GLfloat vertices[] = {
        0.0f,  0.5f, 0.0f, // Top vertex
        -0.5f, -0.5f, 0.0f, // Bottom left vertex
        0.5f, -0.5f, 0.0f  // Bottom right vertex
    };

    vbo.allocate(vertices, sizeof(vertices));

    int posLocation = shaderProgram->attributeLocation("position");
    shaderProgram->enableAttributeArray(posLocation);
    shaderProgram->setAttributeBuffer(posLocation, GL_FLOAT, 0, 3);

    vao.release();
}

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

void MyGLWidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT);

    shaderProgram->bind();
    vao.bind();

    glDrawArrays(GL_TRIANGLES, 0, 3);

    vao.release();
}

main.cpp

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

#include "glwidget.h"

#include <QtGui/QSurfaceFormat>
#include <QtWidgets/QApplication>

int main(int argc, char *argv[])
{
    QApplication::setAttribute(Qt::ApplicationAttribute::AA_UseDesktopOpenGL);
    QApplication a(argc, argv);

    QSurfaceFormat fmt;
    fmt.setDepthBufferSize(24);

    // Request OpenGL 3.3 core or OpenGL ES 3.0.
    if (QOpenGLContext::openGLModuleType() == QOpenGLContext::LibGL) {
        qDebug("Requesting 3.3 core context");
        fmt.setVersion(3, 3);
        fmt.setProfile(QSurfaceFormat::CoreProfile);
    } else {
        qDebug("Requesting 3.0 context");
        fmt.setVersion(3, 0);
    }

    QSurfaceFormat::setDefaultFormat(fmt);

    MyGLWidget w;
    w.show();
    return a.exec();
}

8Observer8

I think it is a solution. You can mark it as a solution: