diagramscene.cpp Example File

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 #include <QtGui>

 #include "diagramscene.h"
 #include "diagramitem.h"

 DiagramScene::DiagramScene(QObject *parent)
     : QGraphicsScene(parent)
 {
     movingItem = 0;
 }

 void DiagramScene::mousePressEvent(QGraphicsSceneMouseEvent *event)
 {
     QPointF mousePos(event->buttonDownScenePos(Qt::LeftButton).x(),
                      event->buttonDownScenePos(Qt::LeftButton).y());
     movingItem = itemAt(mousePos.x(), mousePos.y());

     if (movingItem != 0 && event->button() == Qt::LeftButton) {
         oldPos = movingItem->pos();
     }

     clearSelection();
     QGraphicsScene::mousePressEvent(event);
 }

 void DiagramScene::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
 {
     if (movingItem != 0 && event->button() == Qt::LeftButton) {
         if (oldPos != movingItem->pos())
             emit itemMoved(qgraphicsitem_cast<DiagramItem *>(movingItem),
                            oldPos);
         movingItem = 0;
     }
     QGraphicsScene::mouseReleaseEvent(event);
 }