Elastic Nodes Example | Qt Widgets 5.13.0

Qt 5.13 | Qt Widgets | Elastic Nodes Example

Qt 5.13.0 Reference Documentation

# Elastic Nodes Example

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

      #include <qmath.h>
      #include <QPainter>

      Edge::Edge(Node *sourceNode, Node *destNode)
          : arrowSize(10)
      {
          setAcceptedMouseButtons(0);
          source = sourceNode;
          dest = destNode;
          source->addEdge(this);
          dest->addEdge(this);
          adjust();
      }

      Node *Edge::sourceNode() const
      {
          return source;
      }

      Node *Edge::destNode() const
      {
          return dest;
      }

      void Edge::adjust()
      {
          if (!source || !dest)
              return;

          QLineF line(mapFromItem(source, 0, 0), mapFromItem(dest, 0, 0));
          qreal length = line.length();

          prepareGeometryChange();

          if (length > qreal(20.)) {
              QPointF edgeOffset((line.dx() * 10) / length, (line.dy() * 10) / length);
              sourcePoint = line.p1() + edgeOffset;
              destPoint = line.p2() - edgeOffset;
          } else {
              sourcePoint = destPoint = line.p1();
          }
      }

      QRectF Edge::boundingRect() const
      {
          if (!source || !dest)
              return QRectF();

          qreal penWidth = 1;
          qreal extra = (penWidth + arrowSize) / 2.0;

          return QRectF(sourcePoint, QSizeF(destPoint.x() - sourcePoint.x(),
                                            destPoint.y() - sourcePoint.y()))
              .normalized()
              .adjusted(-extra, -extra, extra, extra);
      }

      void Edge::paint(QPainter *painter, const QStyleOptionGraphicsItem *, QWidget *)
      {
          if (!source || !dest)
              return;

          QLineF line(sourcePoint, destPoint);
          if (qFuzzyCompare(line.length(), qreal(0.)))
              return;

          // Draw the line itself
          painter->setPen(QPen(Qt::black, 1, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));
          painter->drawLine(line);

          // Draw the arrows
          double angle = std::atan2(-line.dy(), line.dx());

          QPointF sourceArrowP1 = sourcePoint + QPointF(sin(angle + M_PI / 3) * arrowSize,
                                                        cos(angle + M_PI / 3) * arrowSize);
          QPointF sourceArrowP2 = sourcePoint + QPointF(sin(angle + M_PI - M_PI / 3) * arrowSize,
                                                        cos(angle + M_PI - M_PI / 3) * arrowSize);
          QPointF destArrowP1 = destPoint + QPointF(sin(angle - M_PI / 3) * arrowSize,
                                                    cos(angle - M_PI / 3) * arrowSize);
          QPointF destArrowP2 = destPoint + QPointF(sin(angle - M_PI + M_PI / 3) * arrowSize,
                                                    cos(angle - M_PI + M_PI / 3) * arrowSize);

          painter->setBrush(Qt::black);
          painter->drawPolygon(QPolygonF() << line.p1() << sourceArrowP1 << sourceArrowP2);
          painter->drawPolygon(QPolygonF() << line.p2() << destArrowP1 << destArrowP2);
      }