QGraphicsPathItem Doubt

[arjunasd]

Hi all

I am having a QGraphicsPathItem which is selectable. I am able to select the item by clicking the area defined by its path. But I would like it to be selectable by clicking any point within its bounding rectangle.

For example, if my shape is circle, I want it to be selected if I click on any point its bounding rectangle.

Any suggestion for how to do this?

Thanks
Arjun

[Gopala Krishna]

Reimplement the contains function by deriving a class from QGraphicsPathItem like this

class MyPathItem : public QGraphicsPathItem
{
public:
     MyPathItem(const QPainterPath & path, QGraphicsItem * parent = 0 ) : QGraphicsPathItem(path,parent)
     {}
 
      bool contains( const QPointF & point ) const
      {
             return boundingRect().contains(point);
       }
};

class MyPathItem : public QGraphicsPathItem
{
public:
     MyPathItem(const QPainterPath & path, QGraphicsItem * parent = 0 ) : QGraphicsPathItem(path,parent)
     {}

      bool contains( const QPointF & point ) const
      {
             return boundingRect().contains(point);
       }
};

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[arjunasd]

One more doubt.

I have the QGraphicsPathItem and its bounding rectangle. I want to change the Pen that draws the bounding rectangle when the item is selected. I dont have the paint function. I just use the default implementation as of now.

How to set the pen for drawing the bounding rectangle when the item is selected. Is there a way to use the default implementation and still achieve this?

Thanks
Arjun

[Gopala Krishna]

Oh you mean the bounding rect is part of the painterpath ? If thats the case you can't achieve what you wanted. You can draw the bounding rect separately. Then you can control its pen like this

MyPathItem::paint(QPainter *p, QStyleOptionGraphicsItem *o, QWidget *w)
{
     QGraphicsPathItem::paint(p,o,w);
     if(o->State & QStyle::State_Selected)
         p->setPen(selectedPen);
     else
         p->setPen(unselectedPen);
     p->drawRect(boundingRect());
}

MyPathItem::paint(QPainter *p, QStyleOptionGraphicsItem *o, QWidget *w)
{
     QGraphicsPathItem::paint(p,o,w);
     if(o->State & QStyle::State_Selected)
         p->setPen(selectedPen);
     else
         p->setPen(unselectedPen);
     p->drawRect(boundingRect());
}

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[arjunasd]

Oh you mean the bounding rect is part of the painterpath ?

No. The bouding rectangle is not part of the painterpath. Its just the QRectF returned by the boudingRect fucntion.

The default paint implemnetation draws it with black pen and dotted lines. I want to chnage this behaviour. So, can I just draw the bounding rect with the new pen over the old one? or can I do it differently?

Thanks a lot
Arjun

[Gopala Krishna]

In this case , the solution above involving paint event is what you need

[Gopala Krishna]

BTW i had a look at the source code of QPainterPathItem and actually that draws the bounding rect. So the above solution will be drawing the bounding rect twice
You can use this hack instead

MyPathItem::paint(QPainter *p, QStyleOptionGraphicsItem *o, QWidget *w)
{
   QStyle::State back = o->state;
   o->state &= ~QStyle::State_Selected;//Removes selection flag
   QGraphicsPathItem::paint(p,o,w);
   o->state = back;
   if(o->state & QStyle::State_Selected)
      p->setPen(selectedPen);
   else
      p->setPen(unselectedPen);
   p->drawRect(boundingRect());
}

MyPathItem::paint(QPainter *p, QStyleOptionGraphicsItem *o, QWidget *w)
{
   QStyle::State back = o->state;
   o->state &= ~QStyle::State_Selected;//Removes selection flag
   QGraphicsPathItem::paint(p,o,w);
   o->state = back;
   if(o->state & QStyle::State_Selected)
      p->setPen(selectedPen);
   else
      p->setPen(unselectedPen);
   p->drawRect(boundingRect());
}

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[arjunasd]

This is what I wanted. About how to avoid painting the bouding rect twice. Thanks man.

Arjun