AddPickList Of vtkPicker Will Not Check Adding The Same Object Repeatedly

The interface vtkAbstractPicker::AddPickList is used to add an object to the bottom of the list. But it will not check adding the same object to the list. So the number of items in the pick list will increase if we add the item multiple times.

Source code for the interface:

// Add an actor to the pick list.
void vtkAbstractPicker::AddPickList(vtkProp* a)
{
  this->Modified();
  this->PickList->AddItem(a);
}


// Add an object to the bottom of the list. Does not prevent duplicate entries.
void vtkCollection::AddItem(vtkObject* a)
{
  vtkCollectionElement* elem;

  elem = new vtkCollectionElement;

  if (!this->Top)
  {
    this->Top = elem;
  }
  else
  {
    this->Bottom->Next = elem;
  }
  this->Bottom = elem;

  a->Register(this);
  elem->Item = a;
  elem->Next = nullptr;

  this->NumberOfItems++;

  this->Modified();
}


int GetNumberOfItems() { return this->NumberOfItems; }