QGraphicsScene: adding QGraphicsProxyWidget moves others QGraphicsEllipseItem

[Doxy82]

Hi,

Sorry for the silly question but I'm working with QGraphicsScene and I have "weird" behaviours that I don't understand at all.

Basically I have a simple radar representation with a main "circle" and an icon which represent the North direction.

So I have somthing like this:

QGraphicsScene* l_scene = new QGraphicsScene(this);
    ui->radar_gw->setScene(l_scene);
    ui->radar_gw->setRenderHints(QPainter::Antialiasing);
 
    m_main_offset = 2;
    m_north_space_px = 12;
 
    m_radar_gui_diameter = ui->radar_gw->width()-(m_north_space_px*2)-m_main_offset;
    m_radar_gui_radius   = m_radar_gui_diameter * 0.5;
 
    //MAIN CIRCLE
    QGraphicsEllipseItem* l_radar_circle = new QGraphicsEllipseItem(0, 0, m_radar_gui_diameter, m_radar_gui_diameter);
    l_radar_circle->setPen(QPen(QColor(Qt::green), 2));
    l_scene->addItem(l_radar_circle);
 
    //NORTH
    QPixmap l_north_pix(":/background/north.png");
    QLabel* l_north_lbl = new QLabel();
    l_north_lbl->setAutoFillBackground(false);
    l_north_lbl->setPixmap(l_north_pix.scaled(m_north_space_px, m_north_space_px, Qt::IgnoreAspectRatio, Qt::SmoothTransformation));
    QGraphicsProxyWidget* l_north_widget = l_scene->addWidget(l_north_lbl);
    l_north_widget->setPos(m_radar_gui_radius - m_north_space_px*0.5, 0);

QGraphicsScene* l_scene = new QGraphicsScene(this);
    ui->radar_gw->setScene(l_scene);
    ui->radar_gw->setRenderHints(QPainter::Antialiasing);

    m_main_offset = 2;
    m_north_space_px = 12;

    m_radar_gui_diameter = ui->radar_gw->width()-(m_north_space_px*2)-m_main_offset;
    m_radar_gui_radius   = m_radar_gui_diameter * 0.5;

    //MAIN CIRCLE
    QGraphicsEllipseItem* l_radar_circle = new QGraphicsEllipseItem(0, 0, m_radar_gui_diameter, m_radar_gui_diameter);
    l_radar_circle->setPen(QPen(QColor(Qt::green), 2));
    l_scene->addItem(l_radar_circle);

    //NORTH
    QPixmap l_north_pix(":/background/north.png");
    QLabel* l_north_lbl = new QLabel();
    l_north_lbl->setAutoFillBackground(false);
    l_north_lbl->setPixmap(l_north_pix.scaled(m_north_space_px, m_north_space_px, Qt::IgnoreAspectRatio, Qt::SmoothTransformation));
    QGraphicsProxyWidget* l_north_widget = l_scene->addWidget(l_north_lbl);
    l_north_widget->setPos(m_radar_gui_radius - m_north_space_px*0.5, 0);

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Basically this code display something like this:

1.jpg

There is a first question:

l_north_widget->setPos(m_radar_gui_radius - m_north_space_px*0.5, 0);

l_north_widget->setPos(m_radar_gui_radius - m_north_space_px*0.5, 0);

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This setPos is relative to the QGraphicsEllipseItem (l_radar_circle) dimensions and NOT to the main QGraphicsView container. Why?!? l_radar_circle is added to l_scene (QGraphicsScene) not to the QGraphicsEllipseItem. Where I'm in wrong?

-----

As you can see in the previous image, I've left the space to show the North icon outside the circle (because the North icon can move around the main circle).
So, I've tried to move up the North icon like this:

l_north_widget->setPos(m_radar_gui_radius - m_north_space_px*0.5, -m_north_space_px-m_main_offset);

l_north_widget->setPos(m_radar_gui_radius - m_north_space_px*0.5, -m_north_space_px-m_main_offset);

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And this is the result:

2.jpg

The main l_radar_circle as moved down, like the l_north_widget interacts with the l_radar_circle (and then there is not enough space at the bottom of l_radar_circle). I don't want this behaviour, just as I don't want the previous case where the North widget is relative to the main circle item.

Can you address me a way to achieve a correct beahviour? Basically, I need a method to freely draw shapes and textures without "shadow" layout and "weird" reparenting. I have to go with OpenGL directly?

Many thanks, bye