QOpenGlWidget format resetting when calling show()

johansson_gbg

Hi !

I have noticed that pushing in QSurfaceFormat settings to my QOpenGlWidget gets resetted after i call show() on it. Is there a reason why this occurs and how do i prevent it?

    QSurfaceFormat glFormat;
    glFormat.setVersion(4, 5);
    glFormat.setProfile(QSurfaceFormat::CoreProfile);
    glFormat.setSamples(4); //anti aliasing
    QSurfaceFormat::setDefaultFormat(glFormat);

    QApplication qapp(argc, argv);

    QOpenGLWidget* openGlWidget = new QOpenGLWidget();

    openGlWidget->setFormat(glFormat);

    openGlWidget->show();

    QSurfaceFormat format1 = openGlWidget->format();

    std::cout << format1.samples() << std::endl; //samples == 0 here, not 4

    return qapp.exec();

SGaist

Hi,

Are you sure it is ?
The call to show does not in fact show anything, it schedules a show event that will be processed by the event loop. Thus, your widget will not be shown until after app.exec() started.

johansson_gbg

Hi!

I'm ofcourse not 100 % sure, i checked the source code and couldnt see that the method does apply anything on the QSurfaceFormat settings. However, i checked the value on the SurfaceFormat before and after the show() and it does indeed change at this method specifically. Any other source of reason why this is occuring? Why does the settings reset at all? How do i prevent it?

Regards Dan

SGaist

That's my point: you do it too early. Call it after the widget has actually been shown. As I wrote before, calling show just schedule the widget to appear, it does not make it appear.

maruker

Hi, I can't get anti-aliasing to work on QOpenGlWidget either and I noticed the exact same thing:
The value of samples() is correct initially but gets reset.

Since this thread also shows up on Google, I would like to ask if someone found a solution

Nominate our 2022 Qt Champions!

QOpenGlWidget format resetting when calling show()