- Qt 5.5
- Qt Widgets
- Diagram Scene Example
- arrow.cpp Example File
- Qt 5.5.1 Reference Documentation

# arrow.cpp Example File

graphicsview/diagramscene/arrow.cpp

    /****************************************************************************
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    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
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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);
        }
    }