How to intercept mouse events in a scene

[markmuetz]

I've subclassed the QGraphicsScene class into my own class, and tried to re-implement the method

QGraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent *event)

QGraphicsScene::mousePressEvent(QGraphicsSceneMouseEvent *event)

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so as I can do something interesting when the use clicks on the view (namely cause a QGraphicsItem object to appear). On running the code and clicking in the view though, this method is not called.

Here are the relevant parts of code (as I see them), can anybody tell me what I'm missing?

DiagramScene *scene = new DiagramScene();
    graphicsView = new QGraphicsView(scene);

DiagramScene *scene = new DiagramScene();
    graphicsView = new QGraphicsView(scene);

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class DiagramScene : public QGraphicsScene
{
    Q_OBJECT
 
public:
    DiagramScene(QObject *parent = 0);
 
protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent);
    void mouseDoubleClickEvent(QGraphicsSceneMouseEvent *mouseEvent);
};

class DiagramScene : public QGraphicsScene
{
    Q_OBJECT

public:
    DiagramScene(QObject *parent = 0);

protected:
    void mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent);
    void mouseDoubleClickEvent(QGraphicsSceneMouseEvent *mouseEvent);
};

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DiagramScene::DiagramScene(QObject *parent)
    : QGraphicsScene(parent)
{
}
 
void DiagramScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
  if (mouseEvent->button() != Qt::LeftButton)
    return;
  //do something here...
}

DiagramScene::DiagramScene(QObject *parent)
    : QGraphicsScene(parent)
{
}

void DiagramScene::mousePressEvent(QGraphicsSceneMouseEvent *mouseEvent)
{
  if (mouseEvent->button() != Qt::LeftButton)
    return;
  //do something here...
}

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[wysota]

Use a qDebug() statement to see if your event handler gets called - it should. It might not behave as you expect it, but it should at least be called.

[markmuetz]

The problem was that I was re-setting the scene in a different place, so as a new standard QGraphicsScene was being used. qDebug() statements are useful (easier to use than gdb , thanks.