How to insert pointer in QGraphicsItem so when they get selected pointer will be accessed?-CodePudding

I am having a boost graph of a design. Traversing through boost graph, I am getting co-ordinates of rectangle and polylines. Through that co-ordinates I am drawing rectangle and polyline on QGraphicsView.

Now I want to select rectangle/polyline through scene with mouse click and should be able to print it's name and other property. It's name and other properties are in the boost graph node. But I dont want to interact boost graph again.

So when I was drawing rectangle/polyline through boost graph co-ordinates, I should be able to store some pointer of boost graph node on rectangle/polyline so when I will click on rectangle/polyline, then through that pointer I can access it's name and other properties.

Question is Is this possible ?
I tried but got run time errors.
one of the boost graph class.

class schVertexProps
{
public:
    explicit schVertexProps(std::string moduleName = "",std::string name = "",
                            SCH_VERTEX_TYPE type = SCH_VERTEX_TYPE::SCH_INST_VERTEX,
                            long crossRefPtr = 0,int vertexLevel = -1,int xPos = 0.0,
                            int yPos = 0.0,schSymbol* symb = nullptr)
                          : _moduleName(moduleName),
                            _name(name),
                            _type(type),
                            _crossRefPtr(crossRefPtr),
                            _vertexLevel(vertexLevel),
                            _xPos(xPos),
                            _yPos(yPos),
                            _symb(symb){

    };

Among all above parameters, I want to store only _crossRefPtr ( it is basically a pointer, but store as long, while using it will be type cast )

 rect = new guiSchematicRect();
    while(true)
    {    
       // traversing through boost graph
       for(auto iter = verts.begin();iter != verts.end();  iter)
      {
        // getting co-ordinates of rectangle     
          QGraphicsRectItem* rectItem = rect->createRect(co-ordinates of rectangle);
          rect->_boostRefPtr =  iter->_crossRefPtr;  // trying to store _crossRefPtr  
      }

      // code somewhat similar for polyline
    }

guiSchematicRect.h

class guiSchematicRect : public QGraphicsRectItem
{
   ........
  QGraphicsRectItem* createRect(QRectF& rect);       
  long _boostRefPtr;
}

And when I will click on rectangle on scene through mouse I am doing like this:

if(_scene->selectedItems().count() != 0)
    {
        foreach(QGraphicsItem* currentItem, _scene->selectedItems())
        {
            QGraphicsRectItem* rItem = qgraphicsitem_cast<QGraphicsRectItem*>(currentItem);
            if(rItem)
            {
                guiSchematicRect* r = reinterpret_cast<guiSchematicRect*>(rItem);
                if(r)
                {
                   // I am assuming _boostRefPtr has address of Instance (rectangle)
                    Instance* i = reinterpret_cast<Instance*>(r->_boostRefPtr); 
                    qDebug()<< i->Name();
                }
            }

But aobve way is wrong. Getting run time errors ( Showing Verbose stack trace)
So the question is :

How to store pointer on QGraphicsItem so that, once they get selected, that pointer will be accessed ?

CodePudding user response：

Use Qt's dynamic properties, check QObject::setProperty. It should do the trick.

But AFAIC, I would have used a double QMap to associate directly <graph_node, QGraphicsItem> AND <QGraphicsItem, graph_node> - so you can search quickly for both associations, and both in O(log2(n)) complexity. You can store this either as a static part of your graph (better) or standalone (not the best idea). Obviously, if your graph is already in O(log2(n)), you don't need this map and you need only the <QGraphicsItem, graph_node> one.