OpenGL offscreen rendering in a thread

[Cruz]

show() is called by the main thread, this is true. I don't know what happens to the widget then, but I know for sure that then the run() method starts updating the widget at the rate I wanted and the rendering works fine.
In the meantime I figured out that if I set these flags in the constructor:

SimulatedCamera::SimulatedCamera(QWidget *parent) : QGLViewer(parent)
{
    setWindowFlags(Qt::CoverWindow);
    setAttribute(Qt::WA_DontShowOnScreen);
    setAutoBufferSwap(false);
}

SimulatedCamera::SimulatedCamera(QWidget *parent) : QGLViewer(parent)
{
    setWindowFlags(Qt::CoverWindow);
    setAttribute(Qt::WA_DontShowOnScreen);
    setAutoBufferSwap(false);
}

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then the widget is not shown and doesn't spam error messages related to the double buffering. I am not sure how many eyes I made roll with this approach, but it does work perfectly as expected now.