Is it possible to add GUI for QOpenGLWindow? The button should be in the center of the OpenGL canvas.

JoeCFD

    m_pStartGameButton = new QPushButton(QString("Start Game"), this);
    m_pStartGameButton->move(0, 0);
    m_pStartGameButton->setWindowFlags(m_pStartGameButton->windowFlags() | Qt::WindowStaysOnTopHint);

8Observer8

@JoeCFD unfortunately it doesn't work:

        QVBoxLayout *rootLayout = new QVBoxLayout();
        setLayout(rootLayout);

        m_pOpenGLWindow = new OpenGLWindow();
        QWidget *container = QWidget::createWindowContainer(m_pOpenGLWindow);
        rootLayout->addWidget(container);

        m_pStartGameButton = new QPushButton(QString("Start Game"), this);
        // m_pStartGameButton->raise();
        m_pStartGameButton->move(0, 0);
        m_pStartGameButton->setWindowFlags(m_pStartGameButton->windowFlags() | Qt::WindowStaysOnTopHint);

JoeCFD

@8Observer8
Sorry. I will make a test case later.

8Observer8

@JoeCFD this is my current project: start-button-qopenglwindow-opengl21-qt6-cpp.zip

main.cpp

/*
.pro file:
QT += core gui opengl widgets
win32: LIBS += -lopengl32
HEADERS += main_window.h opengl_window.h
SOURCES += main.cpp
TARGET = app
-------------------------------
Build and run commands for CMD:
> qmake -makefile
> mingw32-make
> "release/app"
*/

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

#include <QtWidgets/QApplication>
#include <iostream>
#include "main_window.h"

int main(int argc, char *argv[])
{
#ifdef _WIN32
    if (AttachConsole(ATTACH_PARENT_PROCESS))
    {
        freopen("CONOUT$", "w", stdout);
        freopen("CONOUT$", "w", stderr);
    }
#endif
    std::cout << std::endl;

    QApplication app(argc, argv);
    MainWindow w;
    w.show();
    return app.exec();
}

main_window.h

#ifndef MAIN_WINDOW_H
#define MAIN_WINDOW_H

#include <QtCore/QSize>
#include <QtCore/QString>
#include <QtWidgets/QHBoxLayout>
#include <QtWidgets/QVBoxLayout>
#include <QtWidgets/QPushButton>
#include <QtWidgets/QWidget>

#include "opengl_window.h"

class MainWindow : public QWidget
{
public:
    explicit MainWindow(QWidget *parent=nullptr) : QWidget(parent)
    {
        setFixedSize(QSize(300, 300));
        setWindowTitle("OpenGL 2.1, Qt6, C++");

        // m_pStartGameButton->move(center);
        // QHBoxLayout *startButtonLayout = new QHBoxLayout();
        // startButtonLayout->setAlignment(Qt::AlignmentFlag::AlignHCenter);
        // startButtonLayout->addWidget(m_pStartGameButton);
        // container->setLayout(startButtonLayout);

        QVBoxLayout *rootLayout = new QVBoxLayout();
        setLayout(rootLayout);

        m_pOpenGLWindow = new OpenGLWindow();
        QWidget *container = QWidget::createWindowContainer(m_pOpenGLWindow, this);
        rootLayout->addWidget(container);

        m_pStartGameButton = new QPushButton(QString("Start Game"), this);
        // m_pStartGameButton->raise();
        m_pStartGameButton->move(0, 0);
        m_pStartGameButton->setWindowFlags(m_pStartGameButton->windowFlags() | Qt::WindowStaysOnTopHint);
    }

    ~MainWindow()
    {
        delete m_pOpenGLWindow;
    }

private:
    OpenGLWindow *m_pOpenGLWindow {};
    QPushButton *m_pStartGameButton {};
};

#endif // MAIN_WINDOW_H

opengl_window.h

#ifndef OPENGL_WINDOW_H
#define OPENGL_WINDOW_H

#include <QtCore/QSize>
#include <QtGui/QOpenGLFunctions>
#include <QtGui/QSurfaceFormat>
#include <QtOpenGL/QOpenGLWindow>

#include <iostream>

class OpenGLWindow : public QOpenGLWindow, private QOpenGLFunctions
{
public:
    OpenGLWindow()
    {
        resize(QSize(300, 300));
        setTitle("OpenGL 2.1, Qt6, C++");

        // Set format
        QSurfaceFormat format;
        format.setSamples(4);
        format.setSwapInterval(1);
        setFormat(format);
        connect(this, SIGNAL(frameSwapped()), this, SLOT(update()));
    }

private:
    void initializeGL() override
    {
        initializeOpenGLFunctions();
        glClearColor(0.2, 0.5, 0.2, 1);
    }

    void paintGL() override
    {
        glClear(GL_COLOR_BUFFER_BIT);
        // std::cout << "paintGL" << std::endl;
    }
};

#endif // OPENGL_WINDOW_H

start-button-qopenglwindow-opengl21-qt6-cpp.pro

QT += core gui opengl widgets
win32: LIBS += -lopengl32
HEADERS += main_window.h opengl_window.h
SOURCES += main.cpp
TARGET = app

SimonSchroeder

I distinctly remember that Qt at one point announced support for QWidgets within OpenGL. However, I am not quite able to find that announcement again. Maybe support has been discontinued with Qt 6.

What I have found so far is this: https://docs.huihoo.com/qt/5.x/qtwidgets-graphicsview-boxes-example.html
I haven't read through the entire code to make sure that the widgets are drawn on some OpenGL canvas. Having a quick look at QGraphicsProxyWidget suggests that it might help with what you are trying to achieve. It still seems to exist in Qt 6.

JoeCFD

@8Observer8 Sorry I could not make it with QOpenGLWindow. I use QOpenGLWidget which is ok.

You also need to add a parent to the container in order to avoid leak.
QWidget *container = QWidget::createWindowContainer(m_pOpenGLWindow, this );

8Observer8

If QOpenGLWindow is inherited from QWindow, does that mean I can use the QML GUI in QOpenGLWindow?

@JoeCFD said in Is it possible to add GUI for QOpenGLWindow? The button should be in the center of the OpenGL canvas.:

You also need to add a parent to the container in order to avoid leak.
QWidget *container = QWidget::createWindowContainer(m_pOpenGLWindow, this );

Fixed in the message above and in the archive.

8Observer8

I created a bug report:

Failed to place widget over widget container containing QOpenGLWindow
https://bugreports.qt.io/browse/QTBUG-113117

8Observer8

My steps of creation a button on QOpenGLWindow:

Collection of free GUI assets: https://itch.io/game-assets/tag-gui
This asset pack https://wenrexa.itch.io/holoui contains two textures for button: normal and active. I added a text in GIMP. The textures was packed with Free Texture Packer (.png + .json):
I wrote a shader to get a button with glReadPixels by color ID

Source code in PySide6 and OpenGL 2.1
Source code in PyQt6 and OpenGL 2.1
Demo in JavaScript and WebGL 1.0
EXE in Qt C++ for Window 10 64-bit (7.48 MB)

8Observer8

@8Observer8 said in Is it possible to add GUI for QOpenGLWindow? The button should be in the center of the OpenGL canvas.:

I created a bug report:
Failed to place widget over widget container containing QOpenGLWindow
https://bugreports.qt.io/browse/QTBUG-113117

Laszlo Agocs added a comment with the following solution to the problem:

m_pStartGameButton = new QPushButton(QString("Start Game"), this);
m_pStartGameButton->winId(); // add this
m_pStartGameButton->move(0, 0);

It works:

I added this code to center the button:

        float buttonHalfWidth = m_pStartGameButton->width() / 2.f;
        float buttonHalfHeight = m_pStartGameButton->height() / 2.f;
        m_pStartGameButton->move(width() / 2.f - buttonHalfWidth,
            height() / 2.f - buttonHalfHeight);

JoeCFD

@8Observer8 Good to know. Thanks. Actually, I wanted to ask you if you tried it.
m_pStartGameButton->winId(); // add this <<=========this is the tricky part.