QOpenGLWidget doesn't work with QQuickWidget

Hanabear

Hello.

I am using Qt 6.5.0 under Windows 10.

I am trying to use OpenGL and QML at the same time.

So, I made a simple test project based on the Qt Quick Widget Example in Qt Creator 10.0.1.
(C:\Qt\Examples\Qt-6.5.0\quick\quickwidgets\quickwidget)

What I did is adding MyWidget class and calling addSubWindow(my_widget);

 QUrl source("qrc:quickwidget/rotatingsquare.qml");

 connect(m_quickWidget, &QQuickWidget::statusChanged,
         this, &MainWindow::quickWidgetStatusChanged);
 connect(m_quickWidget, &QQuickWidget::sceneGraphError,
         this, &MainWindow::sceneGraphError);
 m_quickWidget->resize(300,300);
 m_quickWidget->setResizeMode(QQuickWidget::SizeRootObjectToView );
 m_quickWidget->setSource(source);

 centralWidget->addSubWindow(m_quickWidget);

 MyWidget* my_widget = new MyWidget(this);
 QSurfaceFormat format_;
 format_.setDepthBufferSize(24);
 format_.setStencilBufferSize(8);
 format_.setVersion(3, 2);
 format_.setProfile(QSurfaceFormat::CoreProfile);
 my_widget->setFormat(format_);

 my_widget->setMinimumSize(300,300);
 centralWidget->addSubWindow(my_widget);

 setCentralWidget(centralWidget);

When I try to create QOpenGLWidget and QQuickWidget at the same time, I get below error message and OpenGL Window is not rendered properly.

The top-level window is not using OpenGL for composition, 'D3D11' is not compatible with QOpenGLWidget

///centralWidget->addSubWindow(m_quickWidget);

The QOpenGLWidget is correctly rendered if I comment out QQuickWidget.

Could you let me know how to use both widgets at the same time?

#include <QOpenGLWidget>
#include <QOpenGLFunctions>
#include <QtOpenGL>

class MyWidget : public QOpenGLWidget, protected QOpenGLFunctions
{
public:
    MyWidget(QWidget* parent = nullptr);

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

};

MyWidget::MyWidget(QWidget* parent)
    :QOpenGLWidget(parent)
{

}

void MyWidget::initializeGL()
{
    initializeOpenGLFunctions();
    glClearColor(1.0f, 0.1f, 1.0f, 1.0f);
}
void MyWidget::resizeGL(int w, int h)
{

}
void MyWidget::paintGL()
{

}

Ioneater

@Hanabear This might be related to this post

I had a similar situation where I wanted to use a QWebEngineView and pyqtgraph GLViewWidget in the same application.

The line suggested in the other post solved this for me.

QQuickWindow::setGraphicsApi(QSGRendererInterface::OpenGL);

or in my case (PyQt6)

from PyQt6.QtQuick import QQuickWindow, QSGRendererInterface
QQuickWindow.setGraphicsApi(QSGRendererInterface.GraphicsApi.OpenGL)

Hanabear

@Ioneater Thank you for your information.

I just created dummy QQuickWindow and called setGraphicsApi as you suggested.
By calling graphicsApi before creating the first QQuickWidget, my problem has been solved.

I also found a straightforward method not using dummy QQuickWindow by setting the QSG_RHI_BACKEND environment variable.

Have a nice day.