keep QGraphicsItem away from other QGraphicitems

[hayzel]

I have QGraphicsScene/QGraphicsView with some QGraphicItem items of specific type. I want to drag move them on the view and also keep them away of the others (check to not collide).
In my subclass of QGraphicsItem is reimplemented itemChange to snap the newpos into my snap grid. In the same method I check if there is a collision with other items, and if so , i set the newpos to the oldpos before movement. This prevents my item to be dragged over another item, but when it collides, it remains stick with the other item, and I cannot pull it away of it.
Any ideas how to implement it ?

QVariant saItemSteelNode::itemChange(GraphicsItemChange change, const QVariant &value)
{
  double s;   
  if (change == QGraphicsItem::ItemPositionChange) {
    QPointF newPos = value.toPointF();  
    if(Settings::snapOn()==1)
    {
      s=Settings::snapSize();
      newPos.setX(floor(newPos.x()/s)*s);
      newPos.setY(floor(newPos.y()/s)*s);
    };
    //check collision 
    saScene* m_scene=static_cast<saScene*>(scene());
    QList<QGraphicsItem*> sl=m_scene->collidingItems(this,Qt::IntersectsItemBoundingRect);
    qDebug()<<"newpos:"<<newPos<<" oldpos:"<<oldPos;
    if(sl.count()==0)//no collision
    {
      emit itemPositionChanged();
    }else //collision 
    {
      newPos=oldPos;
    };
    oldPos=newPos;
    return newPos;
  };
  return value;
}

QVariant saItemSteelNode::itemChange(GraphicsItemChange change, const QVariant &value)
{
  double s;   
  if (change == QGraphicsItem::ItemPositionChange) {
    QPointF newPos = value.toPointF();  
    if(Settings::snapOn()==1)
    {
      s=Settings::snapSize();
      newPos.setX(floor(newPos.x()/s)*s);
      newPos.setY(floor(newPos.y()/s)*s);
    };
    //check collision 
    saScene* m_scene=static_cast<saScene*>(scene());
    QList<QGraphicsItem*> sl=m_scene->collidingItems(this,Qt::IntersectsItemBoundingRect);
    qDebug()<<"newpos:"<<newPos<<" oldpos:"<<oldPos;
    if(sl.count()==0)//no collision
    {
      emit itemPositionChanged();
    }else //collision 
    {
      newPos=oldPos;
    };
    oldPos=newPos;
    return newPos;
  };
  return value;
}

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[hayzel]

I solved the problem finally with the code:

QVariant saItemSteelNode::itemChange(GraphicsItemChange change, const QVariant &value)
{
  double s;   
  if (change == QGraphicsItem::ItemPositionChange) {
    QPointF newPos = value.toPointF();  
    if(Settings::snapOn()==1)
    {
      s=Settings::snapSize();
      newPos.setX(floor(newPos.x()/s)*s);
      newPos.setY(floor(newPos.y()/s)*s);
    };
    //check collision with other nodes
    QPainterPath p;
    p.addEllipse(newPos,diameter/2.0+1,diameter/2.0+1);
    QList<QGraphicsItem*> sl=scene()->items(p);
    sl=saScene::refineItems(sl,saItemSteelNode::TypeSteelNode);
    sl.removeAll(this);
    if(sl.count()>0)//collision
    {
      newPos=pos();
    };
    emit itemPositionChanged();
    return newPos;
  };
  return QGraphicsItem::itemChange(change,value);
  return value;
}

QVariant saItemSteelNode::itemChange(GraphicsItemChange change, const QVariant &value)
{
  double s;   
  if (change == QGraphicsItem::ItemPositionChange) {
    QPointF newPos = value.toPointF();  
    if(Settings::snapOn()==1)
    {
      s=Settings::snapSize();
      newPos.setX(floor(newPos.x()/s)*s);
      newPos.setY(floor(newPos.y()/s)*s);
    };
    //check collision with other nodes
    QPainterPath p;
    p.addEllipse(newPos,diameter/2.0+1,diameter/2.0+1);
    QList<QGraphicsItem*> sl=scene()->items(p);
    sl=saScene::refineItems(sl,saItemSteelNode::TypeSteelNode);
    sl.removeAll(this);
    if(sl.count()>0)//collision
    {
      newPos=pos();
    };
    emit itemPositionChanged();
    return newPos;
  };
  return QGraphicsItem::itemChange(change,value);
  return value;
}

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