Qt 5.11 | Qt Widgets | Elastic Nodes Example | node.cpp Example File

Qt 5.11.3 Reference Documentation

# node.cpp Example File

graphicsview/elasticnodes/node.cpp

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      #include "edge.h"
      #include "node.h"
      #include "graphwidget.h"

      #include <QGraphicsScene>
      #include <QGraphicsSceneMouseEvent>
      #include <QPainter>
      #include <QStyleOption>

      Node::Node(GraphWidget *graphWidget)
          : graph(graphWidget)
      {
          setFlag(ItemIsMovable);
          setFlag(ItemSendsGeometryChanges);
          setCacheMode(DeviceCoordinateCache);
          setZValue(-1);
      }

      void Node::addEdge(Edge *edge)
      {
          edgeList << edge;
          edge->adjust();
      }

      QList<Edge *> Node::edges() const
      {
          return edgeList;
      }

      void Node::calculateForces()
      {
          if (!scene() || scene()->mouseGrabberItem() == this) {
              newPos = pos();
              return;
          }

          // Sum up all forces pushing this item away
          qreal xvel = 0;
          qreal yvel = 0;
          foreach (QGraphicsItem *item, scene()->items()) {
              Node *node = qgraphicsitem_cast<Node *>(item);
              if (!node)
                  continue;

              QPointF vec = mapToItem(node, 0, 0);
              qreal dx = vec.x();
              qreal dy = vec.y();
              double l = 2.0 * (dx * dx + dy * dy);
              if (l > 0) {
                  xvel += (dx * 150.0) / l;
                  yvel += (dy * 150.0) / l;
              }
          }

          // Now subtract all forces pulling items together
          double weight = (edgeList.size() + 1) * 10;
          foreach (Edge *edge, edgeList) {
              QPointF vec;
              if (edge->sourceNode() == this)
                  vec = mapToItem(edge->destNode(), 0, 0);
              else
                  vec = mapToItem(edge->sourceNode(), 0, 0);
              xvel -= vec.x() / weight;
              yvel -= vec.y() / weight;
          }

          if (qAbs(xvel) < 0.1 && qAbs(yvel) < 0.1)
              xvel = yvel = 0;

          QRectF sceneRect = scene()->sceneRect();
          newPos = pos() + QPointF(xvel, yvel);
          newPos.setX(qMin(qMax(newPos.x(), sceneRect.left() + 10), sceneRect.right() - 10));
          newPos.setY(qMin(qMax(newPos.y(), sceneRect.top() + 10), sceneRect.bottom() - 10));
      }

      bool Node::advancePosition()
      {
          if (newPos == pos())
              return false;

          setPos(newPos);
          return true;
      }

      QRectF Node::boundingRect() const
      {
          qreal adjust = 2;
          return QRectF( -10 - adjust, -10 - adjust, 23 + adjust, 23 + adjust);
      }

      QPainterPath Node::shape() const
      {
          QPainterPath path;
          path.addEllipse(-10, -10, 20, 20);
          return path;
      }

      void Node::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *)
      {
          painter->setPen(Qt::NoPen);
          painter->setBrush(Qt::darkGray);
          painter->drawEllipse(-7, -7, 20, 20);

          QRadialGradient gradient(-3, -3, 10);
          if (option->state & QStyle::State_Sunken) {
              gradient.setCenter(3, 3);
              gradient.setFocalPoint(3, 3);
              gradient.setColorAt(1, QColor(Qt::yellow).light(120));
              gradient.setColorAt(0, QColor(Qt::darkYellow).light(120));
          } else {
              gradient.setColorAt(0, Qt::yellow);
              gradient.setColorAt(1, Qt::darkYellow);
          }
          painter->setBrush(gradient);

          painter->setPen(QPen(Qt::black, 0));
          painter->drawEllipse(-10, -10, 20, 20);
      }

      QVariant Node::itemChange(GraphicsItemChange change, const QVariant &value)
      {
          switch (change) {
          case ItemPositionHasChanged:
              foreach (Edge *edge, edgeList)
                  edge->adjust();
              graph->itemMoved();
              break;
          default:
              break;
          };

          return QGraphicsItem::itemChange(change, value);
      }

      void Node::mousePressEvent(QGraphicsSceneMouseEvent *event)
      {
          update();
          QGraphicsItem::mousePressEvent(event);
      }

      void Node::mouseReleaseEvent(QGraphicsSceneMouseEvent *event)
      {
          update();
          QGraphicsItem::mouseReleaseEvent(event);
      }