Custom-context-QGLWidget causes problems

  • Hello!
    I have a QGLWidget with a custom QGLContext. I am trying to have regular QT Gui elements (simple QWidgets) drawn on top of it, but somehow I can't manage to do that and I think it should be possible. I tried putting the QWidgets as direct children of the QGLWidget, or to put all widget into a container-widget, but the same problem occurs every time - the normal QWidgets have black background, and their children-widgets appear different than if I'd put the QWidget as a top-level window... You would say, "then why don't you let them be separate windows floating above the QGLWidget?" - The answer is, I want to have some of the GUI to shine through (translucent).

    Here is the code of the paintEvent() function of the QGLWidget:

    The part of QGLWidget which creates the custom format in the constructor is here:

    // setFormat(fmt) is marked as deprecated so we use this other method
    QGLContext* glctx = new QGLContext(context()->format(), this);
    QGLFormat fmt = context()->format();

    // double buffer
    fmt.setDoubleBuffer( true );

    // color buffer
    fmt.setRedBufferSize( 8 );
    fmt.setGreenBufferSize( 8 );
    fmt.setBlueBufferSize( 8 );
    // setAlpha == true makes the create() function alway fail
    // even if the returned format has the requested alpha channel
    fmt.setAlphaBufferSize( 8 );
    fmt.setAlpha( true );

    fmt.setAccumBufferSize( 0);
    fmt.setAccum( false );

    // multisampling
    fmt.setSamples( 8 );
    fmt.setSampleBuffers( true );

    // depth buffer
    fmt.setDepthBufferSize( 24 );
    fmt.setDepth( true );

    // stencil buffer
    fmt.setStencilBufferSize( 8 );
    fmt.setStencil( true );

    // this function returns false when we request an alpha buffer
    // even if the created context seem to have the alpha buffer
    /*bool ok = */glctx->create(shareContext);

    //And here the paintEvent function of the QGLWidget:

    QPainter painter(this);


    //paints some native GL stuff



    //the constructor of the normal QWidget

    When the QWidget has parent=0, it appears blue as intended...

    I would appreciate any help or advice, I feel like I tried everything already...

  • So no one has an idea about where the problem is? I also tried using a QGraphicsSCene and a QGraphicsView with a viewport set to my QGLWidget, but it fails with a GLContext=null error (probably because in the QGLWidget I create a custom context...).

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