Qt 5.9 | Qt Widgets | Diagram Scene Example | arrow.cpp Example File

Qt 5.9.9 Reference Documentation

# arrow.cpp Example File

graphicsview/diagramscene/arrow.cpp

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      #include "arrow.h"

      #include <math.h>

      #include <QPen>
      #include <QPainter>

      const qreal Pi = 3.14;

      Arrow::Arrow(DiagramItem *startItem, DiagramItem *endItem, QGraphicsItem *parent)
          : QGraphicsLineItem(parent)
      {
          myStartItem = startItem;
          myEndItem = endItem;
          setFlag(QGraphicsItem::ItemIsSelectable, true);
          myColor = Qt::black;
          setPen(QPen(myColor, 2, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));
      }

      QRectF Arrow::boundingRect() const
      {
          qreal extra = (pen().width() + 20) / 2.0;

          return QRectF(line().p1(), QSizeF(line().p2().x() - line().p1().x(),
                                            line().p2().y() - line().p1().y()))
              .normalized()
              .adjusted(-extra, -extra, extra, extra);
      }

      QPainterPath Arrow::shape() const
      {
          QPainterPath path = QGraphicsLineItem::shape();
          path.addPolygon(arrowHead);
          return path;
      }

      void Arrow::updatePosition()
      {
          QLineF line(mapFromItem(myStartItem, 0, 0), mapFromItem(myEndItem, 0, 0));
          setLine(line);
      }

      void Arrow::paint(QPainter *painter, const QStyleOptionGraphicsItem *,
                QWidget *)
      {
          if (myStartItem->collidesWithItem(myEndItem))
              return;

          QPen myPen = pen();
          myPen.setColor(myColor);
          qreal arrowSize = 20;
          painter->setPen(myPen);
          painter->setBrush(myColor);

          QLineF centerLine(myStartItem->pos(), myEndItem->pos());
          QPolygonF endPolygon = myEndItem->polygon();
          QPointF p1 = endPolygon.first() + myEndItem->pos();
          QPointF p2;
          QPointF intersectPoint;
          QLineF polyLine;
          for (int i = 1; i < endPolygon.count(); ++i) {
              p2 = endPolygon.at(i) + myEndItem->pos();
              polyLine = QLineF(p1, p2);
              QLineF::IntersectType intersectType =
                  polyLine.intersect(centerLine, &intersectPoint);
              if (intersectType == QLineF::BoundedIntersection)
                  break;
              p1 = p2;
          }

          setLine(QLineF(intersectPoint, myStartItem->pos()));

          double angle = ::acos(line().dx() / line().length());
          if (line().dy() >= 0)
              angle = (Pi * 2) - angle;

          QPointF arrowP1 = line().p1() + QPointF(sin(angle + Pi / 3) * arrowSize,
                                          cos(angle + Pi / 3) * arrowSize);
          QPointF arrowP2 = line().p1() + QPointF(sin(angle + Pi - Pi / 3) * arrowSize,
                                          cos(angle + Pi - Pi / 3) * arrowSize);

          arrowHead.clear();
          arrowHead << line().p1() << arrowP1 << arrowP2;
          painter->drawLine(line());
          painter->drawPolygon(arrowHead);
          if (isSelected()) {
              painter->setPen(QPen(myColor, 1, Qt::DashLine));
              QLineF myLine = line();
              myLine.translate(0, 4.0);
              painter->drawLine(myLine);
              myLine.translate(0,-8.0);
              painter->drawLine(myLine);
          }
      }