- Qt 5.5
- Qt Widgets
- Elastic Nodes Example
- node.cpp Example File
- Qt 5.5.1 Reference Documentation

# node.cpp Example File

graphicsview/elasticnodes/node.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
    ** met:
    **   * Redistributions of source code must retain the above copyright
    **     notice, this list of conditions and the following disclaimer.
    **   * Redistributions in binary form must reproduce the above copyright
    **     notice, this list of conditions and the following disclaimer in
    **     the documentation and/or other materials provided with the
    **     distribution.
    **   * Neither the name of The Qt Company Ltd nor the names of its
    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
    **
    **
    ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
    ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
    ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
    ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
    ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
    ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
    ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
    ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
    **
    ** $QT_END_LICENSE$
    **
    ****************************************************************************/

    #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::advance()
    {
        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);
    }