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    41 

    42 #include <QtGui>

    43 

    44 #include "arrow.h"

    45 #include <math.h>

    46 

    47 const qreal Pi = 3.14;

    48 

    49 //! [0]

    50 Arrow::Arrow(DiagramItem *startItem, DiagramItem *endItem,

    51          QGraphicsItem *parent, QGraphicsScene *scene)

    52     : QGraphicsLineItem(parent, scene)

    53 {

    54     myStartItem = startItem;

    55     myEndItem = endItem;

    56     setFlag(QGraphicsItem::ItemIsSelectable, true);

    57     myColor = Qt::black;

    58     setPen(QPen(myColor, 2, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));

    59 }

    60 //! [0]

    61 

    62 //! [1]

    63 QRectF Arrow::boundingRect() const

    64 {

    65     qreal extra = (pen().width() + 20) / 2.0;

    66 

    67     return QRectF(line().p1(), QSizeF(line().p2().x() - line().p1().x(),

    68                                       line().p2().y() - line().p1().y()))

    69         .normalized()

    70         .adjusted(-extra, -extra, extra, extra);

    71 }

    72 //! [1]

    73 

    74 //! [2]

    75 QPainterPath Arrow::shape() const

    76 {

    77     QPainterPath path = QGraphicsLineItem::shape();

    78     path.addPolygon(arrowHead);

    79     return path;

    80 }

    81 //! [2]

    82 

    83 //! [3]

    84 void Arrow::updatePosition()

    85 {

    86     QLineF line(mapFromItem(myStartItem, 0, 0), mapFromItem(myEndItem, 0, 0));

    87     setLine(line);

    88 }

    89 //! [3]

    90 

    91 //! [4]

    92 void Arrow::paint(QPainter *painter, const QStyleOptionGraphicsItem *,

    93           QWidget *)

    94 {

    95     if (myStartItem->collidesWithItem(myEndItem))

    96         return;

    97 

    98     QPen myPen = pen();

    99     myPen.setColor(myColor);

   100     qreal arrowSize = 20;

   101     painter->setPen(myPen);

   102     painter->setBrush(myColor);

   103 //! [4] //! [5]

   104 

   105     QLineF centerLine(myStartItem->pos(), myEndItem->pos());

   106     QPolygonF endPolygon = myEndItem->polygon();

   107     QPointF p1 = endPolygon.first() + myEndItem->pos();

   108     QPointF p2;

   109     QPointF intersectPoint;

   110     QLineF polyLine;

   111     for (int i = 1; i < endPolygon.count(); ++i) {

   112     p2 = endPolygon.at(i) + myEndItem->pos();

   113     polyLine = QLineF(p1, p2);

   114     QLineF::IntersectType intersectType =

   115         polyLine.intersect(centerLine, &intersectPoint);

   116     if (intersectType == QLineF::BoundedIntersection)

   117         break;

   118         p1 = p2;

   119     }

   120 

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

   122 //! [5] //! [6]

   123 

   124     double angle = ::acos(line().dx() / line().length());

   125     if (line().dy() >= 0)

   126         angle = (Pi * 2) - angle;

   127 

   128         QPointF arrowP1 = line().p1() + QPointF(sin(angle + Pi / 3) * arrowSize,

   129                                         cos(angle + Pi / 3) * arrowSize);

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

   131                                         cos(angle + Pi - Pi / 3) * arrowSize);

   132 

   133         arrowHead.clear();

   134         arrowHead << line().p1() << arrowP1 << arrowP2;

   135 //! [6] //! [7]

   136         painter->drawLine(line());

   137         painter->drawPolygon(arrowHead);

   138         if (isSelected()) {

   139             painter->setPen(QPen(myColor, 1, Qt::DashLine));

   140         QLineF myLine = line();

   141         myLine.translate(0, 4.0);

   142         painter->drawLine(myLine);

   143         myLine.translate(0,-8.0);

   144         painter->drawLine(myLine);

   145     }

   146 }

   147 //! [7]