How PixmapItem in MainWindow:
main.cpp:
Qt Code: 
  1. #include <QApplication>
  2. #include "diagramwindow.h"
  3. int main(int argc, char *argv[])
  4. {
  5.     QApplication app(argc, argv);
  6.     DiagramWindow view;
  7.     view.show();
  8.     return app.exec();
  9. }
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graphwidget.h:
Qt Code: 
  1. #include <QApplication>
  2. #include "diagramwindow.h"
  3. int main(int argc, char *argv[])
  4. {
  5.     QApplication app(argc, argv);
  6.     DiagramWindow view;
  7.     view.show();
  8.     return app.exec();
  9. }
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graphwidget.cpp:
Qt Code: 
  1. #include "graphwidget.h"
  2. #include "node.h"
  3. #include <QtGui>
  4. GraphWidget::GraphWidget(QWidget *parent)
  5.     : QGraphicsView(parent)
  6. {
  7.     QGraphicsScene *scene = new QGraphicsScene(this);
  8.     scene->setSceneRect(-200, -200, 400, 400);
  9.     setScene(scene);
  10.     setRenderHint(QPainter::Antialiasing);
  11.     setWindowTitle(tr("Elastic Nodes"));
  12.     Node *node4 = new Node(this);
  13.     centerNode = new Node(this);
  14.     Node *node6 = new Node(this);
  15.     scene->addItem(node4);
  16.     scene->addItem(centerNode);
  17.     scene->addItem(node6);
  18.     node4->setPos(-50, 0);
  19.     centerNode->setPos(0, 0);
  20.     node6->setPos(50, 0);
  21. }
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node.h:
Qt Code: 
  1. #ifndef NODE_H
  2. #define NODE_H
  3. #include <QGraphicsPixmapItem>
  4. class GraphWidget;
  5. class Node : public QGraphicsPixmapItem
  6. {
  7. public:
  8.     Node(GraphWidget *graphWidget);
  9.     enum { Type = UserType + 1 };
  10.     int type() const { return Type; }
  11.     QRectF boundingRect() const;
  12.     QPainterPath shape() const;
  13.     void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
  14. private:
  15.     GraphWidget *graph;
  16. };
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node.cpp:
Qt Code: 
  1. #include <QGraphicsScene>
  2. #include <QGraphicsSceneMouseEvent>
  3. #include <QPainter>
  4. #include <QStyleOption>
  5. #include "node.h"
  6. #include "graphwidget.h"
  7. Node::Node(GraphWidget *graphWidget)
  8.     : graph(graphWidget)
  9. {
  10.     setFlag(ItemIsMovable);
  11.     setFlag(ItemSendsGeometryChanges);
  12. }
  13. QRectF Node::boundingRect() const
  14. {
  15.     return QRectF(-24,-24,48,48);
  16. }
  17. QPainterPath Node::shape() const
  18. {
  20.     path.addRect(-24, -24, 48, 48);
  21.     return path;
  22. }
  23. void Node::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *)
  24. {
  25.     QPixmap pixmap = QPixmap("Hub.png");
  26.     painter->drawPixmap(-24,-24,pixmap);
  27. }
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What can be?