Qt 4.5 bugs in graphics view framework?

[Cruz]

Hello,

I upgraded from Qt 4.8 to 5.4 and I noticed odd behaviors of my gui application. I'm using the graphics view framework and my setup is the standard items in a scene in a graphics view layout. The first thing I noticed is that my QGraphicsRectItems are now suddenly huge compared to before. I use the setRect() method in the constructor to define the size like so:

Foot::Foot(QGraphicsItem *parent)
    : QGraphicsRectItem(parent)
{
    setRect(-0.05, -0.035, 0.1, 0.07);
}

Foot::Foot(QGraphicsItem *parent)
    : QGraphicsRectItem(parent)
{
    setRect(-0.05, -0.035, 0.1, 0.07);
}

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It seems that now the setRect() methods add to the default size rather than replacing it, such that I have to subtract a unit rectangle to get the same size I intended before like so:

Foot::Foot(QGraphicsItem *parent)
    : QGraphicsRectItem(parent)
{
    setRect(-0.05 +0.5, -0.035 +0.5, 0.1 -1, 0.07 -1);
}

Foot::Foot(QGraphicsItem *parent)
    : QGraphicsRectItem(parent)
{
    setRect(-0.05 +0.5, -0.035 +0.5, 0.1 -1, 0.07 -1);
}

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Is this intended behavior or a bug?


The second thing I noticed is that the item discovery seems to be broken. The attached screenshot Screenshot from 2015-04-22 14:58:11.jpg was produced by the following code in my graphics view:

class GraphicsViewWidget : public QGraphicsView {...}
 
void GraphicsViewWidget::drawForeground(QPainter* painter, const QRectF& rect)
{
    painter->resetTransform(); // The painter draws in scene coordinates by default. We want draw in view coordinates.
 
    // Item detector.
    QGraphicsScene* sc = scene();
    for (int i = 0; i < width(); i+=5)
    {
        for (int j = 0; j < width(); j+=5)
        {
            int itemCount = sc->items(mapToScene(i,j)).size();
            if (itemCount > 0)
                painter->drawEllipse(i, j, itemCount, itemCount);
        }
    }
}

class GraphicsViewWidget : public QGraphicsView {...}

void GraphicsViewWidget::drawForeground(QPainter* painter, const QRectF& rect)
{
    painter->resetTransform(); // The painter draws in scene coordinates by default. We want draw in view coordinates.

    // Item detector.
    QGraphicsScene* sc = scene();
    for (int i = 0; i < width(); i+=5)
    {
        for (int j = 0; j < width(); j+=5)
        {
            int itemCount = sc->items(mapToScene(i,j)).size();
            if (itemCount > 0)
                painter->drawEllipse(i, j, itemCount, itemCount);
        }
    }
}

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The above code draws a dot at the view coordinates where at least one item was found in the scene. All items in the scene are covered by dots, but also a lot of places where there are no items. When I use the QGraphicsView::items() method, the item discovery works perfectly. QGraphicsScene::items() seems to be broken, however, and it has implications to the UI. The dotted areas respond to the mouse and the scene / the items believe that the mouse is on the item, which is not true. To me this clearly looks like a bug, but in any case, what can I do to fix this?

Cheers,
Cruz