graphicsview receives mouse event before the item

Question

I have implemented the panning view on the QGraphicsView, using the mouse move event using

void View::mouseMoveEvent(QMouseEvent* event) {
pan();
QGraphicsView::mouseMoveEvent(event);
}

and in the scene of this view I have added few items where some of the items are resizable, so I implemented

void Item::mouseMoveEvent(QGraphicsSceneMouseEvent *event)
{
 if(m_resizeMode)
    {
      resize();
      e->accept();
    }
}

I tried to filter the mouse move not to propagate to any further using e->accept() but my View mouseMove event has been called first , so when ever I tried to resize the item, the view started to pan all the way.

How can I avoid this event propagation from view to scene.

Answer 1

You can call the base class implementation of the QGraphicsView and check if the event is accepted. However I would do this in the mousePressEvent instead of the mouseMoveEvent. After all this is where you determine if you should resize an item or do some panning. This is how I do something similar in my project:

void View::mousePressEvent(QMouseEvent *event)
{
    ...
    QGraphicsView::mousePressEvent(event);
    if(event->isAccepted())
        move = false;
    else
        move = true;
}

void View::mouseMoveEvent(QMouseEvent *event)
{
    if(!move)
    {
        QGraphicsView::mouseMoveEvent(event);
        return;
    }
    ... // you would do the panning here

    QGraphicsView::mouseMoveEvent(event);
}

void View::mouseReleaseEvent(QMouseEvent *event)
{
    if(!move)
    {
        QGraphicsView::mouseReleaseEvent(event);
        return;
    }
    else
    {
        ...
        move = false;
    }
    QGraphicsView::mouseReleaseEvent(event);
}